Well, I must say the mover could not have come at the worst time.. 7am without notice woke up by the mother saying this thing is not coming in the house.. And not to mention it was damaged during shipping.. The whole bottom is particle board and one of the legs failed during shipping.. The mover gave me half my money back... Looks like the whole bottom is just going to have to be replaced with plywood..

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8916.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8922.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8925.jpg

On the upper note, the pic tube came up right away, with blue a little weak, but seems to be climbing:
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8942.jpg

Lovely find! Particleboard is a terrible product when used as part of the structure in heavy pieces like this. I have seen heaps of sets with a particleboard cabinet, and with the bottom of the set giving out and buckling around the legs - Definitely not safe for shipping with the legs attached.

Had to remove the whole chassis.. Looks like a cap has exploded entirely.. Probably got struck by lightning, I thought that was a fuse of sorts until I saw reminisce of a film cap.. I did try and power up on a variac, with ohm meter before I work the chassis out and at 60 volts it started to spark, meter was only reading .4 amp.. Has to just disconnect everything, some wires I don't know what goes where.. Have no choice other than to remove everything and then see what can be done with the cabinet.. If I would have left everything in, it would have just falling completely apart and I don't want pic tube to get damaged.. Now don't know where to go with the cabinet.. I'm not an expert at wood work..

Talk about 60 years of nicotine.. Wires are all slimy and the stuff just sticks to your hands and don't want to come off..

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8945.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8959.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8958.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8955.jpg

Red is looking better
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8963.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8968.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8971.jpg

Pic Tube = Spirit of 76 rebuilt of sorts
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8966.jpg

some epoxy should be able to fix that particle board, would be better to remove it, then put some wax paper down on the floor so the epoxy does not run everywhere. Have some would shaving handy to fill in voids from missing bits.

the slime is typical of magnavox, rubbing alcohol and ebow grease will get it fairly clean.

Pots tend to be noisy, lots of action behind those vert mount boards, easy to short wires out.

RCA clone but for the silly swap of the fly and power trans. Like rca the fly is the weak spot unless already replaced with a better one.

good chance it will work as is, since the safety cap is blown, may as well get it out of there, but the rest of the caps are from an era that was pretty good.

Oops I went ahead and used wood glue, and got it outside with cinder blocks piled on top.. I cut out that interlock cap like I did with the GE, have the chassis on the variac with the HV output tube removed, and the tubes are coming up slightly.. I did 30v at first for 15mins and now at 60 volts..

wood glue is fine, I just prefer thin (30min) epoxy since is can be more of structural element (esp if wood shavings are mixed in). Its a bit messy but works fine. You may need to backup the repair with some 1/4" wood triangles under the leg mounts, do them in all 4 corners of course to keep the height correct, and make them large enough to distribute the load.

I may go over the part that's glued with either a thin piece of wood or a metal flat strap that's rectangular.. And i'll bond that to the area with epoxy for even more support.. I hooked the speaker up to chassis and heard normal fuzz noise.. Tried to tune to a channel but don't hear noise to the sound of the tuner as I change channel.. Bump it up to 120 volts from 100 and heard and saw a pop near the power transformer.. Was drawing around the normal 1.3 amps.. All the filter caps stay cold..

should be more like 3.0 amps, guess is the HV is not working as that draws a lot of power. oh, maybe still no horz out tube installed then the 1.3 makes sence.

Another option would be to take that board to a wood working shop and ask them to make another one just like it out of plywood.

Another option would be to take that board to a wood working shop and ask them to make another one just like it out of plywood.

I've thought of that too, but If the original can't be fixed.. I'll do that..

Whats the best solution to remove gunk and tar from the wires and PC boards.. I've been using rubbing alcohol, but I wonder if there is something better to use?

I know spatsbear on youtube puts the whole chassis of his sets in the dishwasher, but I not going to do that seeing how I don't even have a dishwasher..

I've got a station tuned into it now.. So looks like another simple fix.. Tuner is dirty, and the little plastic gears for the fine tuning are popping out, so not sure if I can fine tune a channel in..

Don't remove it. at least until after you have base lined the set to determine the current operating status.

After that, if you want to clean it, rubbing alcohol is good for the slime on the wires, q tips are good for cleaning the pcb. Just remember that the parts are very old so any cleaning has to be done gently, and generally is not needed for the set to operate.

I am amazed your TV's CRT is still as strong as your tester says it is. I saw the date code on the tube, January 1976, so that CRT is probably a replacement. However, I would not expect a 39-year-old CRT to test good on all three guns, unless the TV was used very, very little or else it has been rejuvenated once.

BTW, particleboard cabinets were replacing real wood ones by the mid-'70s, although the trend may have started some time earlier. The stand (actually a modified utility cart) my home entertainment system is on is made of particleboard with some sort of fake woodgrain covering. That doesn't surprise me, as I bought the stand in the mid-'80s; by then just about everything was being constructed of this cheap material, a trend that continues to this day. My desk is made of the same stuff, and it is showing its age (I got it in the early 1990s).

One option is to set it in the driveway and hose it down with the garden hose, and maybe a paint brush and some soap for the PCB. I've hosed down a set before and had it go well. The key is to let it dry thoroughly. Here in the Wisconsin coolness it means waiting like three days to a week, but in the scorching Florida sun (I used to live there so I know) I'd reckon that if you give it 3 hours of even sun exposure on the top of the chassis, flip it and do the same for the bottom, and repeat until thorough inspection finds no moisture it will be fine. Word to the wise before you soak it get pictures of any and all paper labels on the chassis.

You can also put rubbing alcohol (isopropyl alcohol) in a spray bottle and use a paint brush or toothbrush to loosen the dirt. Turn the chassis on its side and work from the top down.

Phil Nelson

I would be extremely careful around those PC boards, as they get brittle with age. I had a Silvertone (RCA CTC12 clone) roundie color TV in the early '70s that worked fairly well, until I tried to replace a tube on the video output panel. The tube socket broke out of the board, :no: ruining the set (I was in no position at the time to repair the board). I've been wary of PC boards ever since.

Making some progress on day one:

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8977.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8980.jpg

Cleaned the chassis with some electrical contact cleaner the boards look better, but still need to go in with a Qtip..
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0123.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0111.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0107.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0118.jpg

Fine tuning gears.. Not sure if that green plastic brook.. It sorta flops around with fine tuning, though it does turn the gears, but not sure if its turning the inside parts...
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_8989.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0137.jpg

The two 'fingers' that slide inside the tuner are broke off and gone.
Maybe somebody with a stash of old tuners could come up with a good slider assembly to donate. (It comes with the gears attached.)

If anyone has an extra slider assy I would be interested..

Here's more progress:

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_9005.jpg

Betron is liking this pic tube even more so, only at 5volts
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/IMG_9004.jpg

Ive got a bunch of these. If this is what you need I'll mail you one, but i'm not sure what part broken on yours, do these look the same?
http://i.imgur.com/Fcf8xYY.jpg

Those outside the box does, but I don't know what it looks like on the inside.. I suppose I could crack open the tuner and see... They mentioned something about fingers that slide inside the tuner...

I just looked and I see the hole where the gear goes in, but nothing behind it.. There is a metal piece thats sorta coiled a little around the shaft, one end going into the tuner and looks to have two other feet that aren't going anywhere, maybe that is suppose to force the gears to make contact?

Is that a Standard-Kollsman tuner?

If you need the FT gear, it is not too hard to find. The fingers OldCoot refers to are on either side on the gear slider assembly, just out from the tuner shaft and click into slots in the tuner sheetmetal.

Standards usually had a 6HB7 tube and were used in GE and Mags, not known for good fringe reception IMAO.

Oak tuners were used in Motorola and some others, also not real good in comparison to Zenith and RCA

Looking at reference photos from my previous GE roundie restore, it looks to have the same thing pretty much

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/GE%20Color%20Roundie%20TV/DSCF3157.jpg

I'm looking at the springy thing with feet that's around the shaft, looks like it's suppose to apply some tension on that plastic gear assy.. Looks like it could have been knocked out of place during shipping, especially seeing the condition of the cabinet.. I'll look more into it Monday when I have more time to look into it

I took out the whole clunker and removed the gear assy, I ended up breaking one the of the teeth, the little gears that are attached on each side and goes through and turns the mechanism is very wobbly, So I think there were issues already with it.. I'm going to need a spare from you.. I'll take a few if you don't mind parting with a few..

I put the clunker back in and powered the chassis up again, and still working fine and still can hear audio coming in from a channel.. First time removing one of these clunkers..

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0145.jpg

pm sent

Thanks Paul..

Finally got the cabinet in the house, hooked up pic tube and HV, and was greeted with a pic.. Black bar at the bottom convergence is way off it looks like.. Haven't checked any of the tubes yet.. But I'm getting good results so far..

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0165.jpg
http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0169.jpg

I left it running for a while, and the original flyback in it started to smoke.. Screen went dead.. I left the room and started to smell a burning smell... These things smell like burning firewood with an odd stench, I thought the house was on fire..

Waited a while and powered back up, and probed the HV and it goes up to 5000kv before falling.. I removed the HV cover and poked around, there's wax drippings and I felt around the donut and felt a bump on the bottom of it.. I heard Shango on Youtube, chisrtv i think on here, is able to fix these, if so, let me know how much you want and I'll mail it to you... I've also got three Thordason flys for CTC15 which I assume will work in this unit.. Still rather have the original repaired if it's repairable..

Never leave the room with a set on. You want to be able to jump at the power switch if things go noticeably wrong.

I hope you did not kill the fly.

I was probably cooking for a good minute before I realized.. There's no obvious marks on the Donut other than the bump on the bottom which was probably there before... Perhaps maybe it took out a tube instead? Tested the 6BK4C 6BK4B in the HV section and fails grid emissions and the 3CU3 is weak... Does anyone know how to get a hold of shango066 from Youtube?

I just looked at my NOS Thordason Flybacks which are FLY-277.. They call for Magnavox Part numbers 361046-1 and 906152-501.. The Sams photofact lists the Magnavox part #361084-1(B) which calls for Thordason FLY-305 which I don't have.. So unless I either #1 have someone fix this one, or #2 find a Thordason FLY-305 I guess the project would end right now... I called Moyers and they are looking in their warehouses...

yes the 361084 is the magnavox number and i have a fly 305 new in box for the maggie combo i have. if you need the fly why dont you take this combo i have here with the fly for 250.00, it has been for sale but i need the fly with the set but if i didnt have this combo then i wouldnt need the fly. need to downsize here alittle, not much room and besides your chassis is and looks exactly the same as mine, a spare chassis helps and this combo works fine, even the flyback.

yes the 361084 is the magnavox number and i have a fly 305 new in box for the maggie combo i have. if you need the fly why dont you take this combo i have here with the fly for 250.00, it has been for sale but i need the fly with the set but if i didnt have this combo then i wouldnt need the fly. need to downsize here alittle, not much room and besides your chassis is and looks exactly the same as mine, a spare chassis helps and this combo works fine, even the flyback.

Last combo he had almost got parted for space reasons (but another member saved it), and earlier in this thread I seem to recall his mom telling him "this is not going in my house" about that little table/legged console...So I doubt he will take you up on this.

If the HV on your set is good, and the fly in it don't look too cooked then I don't see why you would need a spare flyback. Sure it is nice to have a spare fly, but if you dip the horizontal current, add a 125mA (or other appropriate value for the given design) HO tube cathode fuse, and maybe open the HV cage some (or add a fan) to increase air flow the fly should last for a very long time.

Tom is right.. Thanks..

I did a little more poking around and I'm not sure if the flyback in mine is dead.. It sure doesn't hurt to have a spare.. I measured cathode current and it's suppose to be at 200ma, It doesn't stabilize and is way up past that, even turned the slug in the osc coil, gives me wacky readings between 220ma to well over 300ma, and meter just keeps climbing, flyback was getting warm while doing all this.. I tested the Horz osc tube and it's weak, looks like there has been caps replaced on the sweep board before...

What is the HO tube grid voltage relative to specification? If it is not as negative as it should be by a decent margin then your H osc. is dead or not functioning correctly. I'd order a new osc. tube if the old one is weak. Sometimes a weak tube will work as an osc., but it is at high risk of sudden random failure and when the osc. fails if let run too long damage to the HO tube and or fly usually result.

I'm getting -72 DC volts at pin 7.. Sams calls for -120.. Someone must have replaced or removed the Horz osc, one or two of the solder pads have been burnt off and jumpered from the horz osc..

Good luck, I hope the fly is good. The tuner gears are in the mail.

Thanks Paul..

I've just tested of the resistors on the sweep board.. There are alot of them that are way out of spec.. Not sure if it's because they are still in the circuit... Flyback area still has that burnt wood smell, smells like wood that was burnt and wet afterwords, sorta like a wet burnt smell I wanna say.. I wonder if that's a combination of the wax paper on the fly and the nicotine that was burnt..

I'm getting -72 DC volts at pin 7.. Sams calls for -120.. Someone must have replaced or removed the Horz osc, one or two of the solder pads have been burnt off and jumpered from the horz osc.. Sams and the printed boards are incorrect from each other...

The osc. signal is definitely not properly reaching the HO grid. Test and or replace all suspect parts in the osc, and all parts from it leading to the grid of the HO Tube.

A near 50% positive increase in the HO grid voltage is the main cause of the problem. The HO tube is going to conduct way too much current until it's grid drive signal is made right....I recommend removing the top lead and disconnecting the screen grid (not the control grid) lead from the socket of the H output tube. until you can get the grid voltage back in the ballpark.

Are you still suspecting the horz osc coil is still the suspect? or should I test and replace all caps and resistors in between? I'm going to order up all the caps on that board and replace them anyways seeing how there's a problem, and there are a few resistors in between that are giving wacky results.. I'm still waiting for the tubes as well..

a few things..

what are you using to check the voltages, a VTVM is best.

have you tried a known good osc tube 6FQ7

Note the grid circuit includes a voltage divider as part of the horz hold. Since the grid is too positive a good start would be to check the parts in that circuit,mainly the 22k resistor to ground from one side of the horz hold pot.

I would be scoping the cathode and check the free running freq (no signal) to see if its in the ball park.

Using a regular ohm meter.. Klein tools to be exact..

I'm waiting for a few spares as for tubes.. I checked that 22k resistor and it's within spec..

I'm going to order up the caps and the resistors that are out of spec and just start replacing.. Only a couple of resistors that check way off, but those are probably the ones that give a proper readings out of circuit..

interesting so the you lifted the 22k for testing? its in circuit as well.
did you use the sams to check the pin resistance readings?

Be careful of the 6CG7/6FQ7 you use. The RCA side getter (clear top) types are controlled warmup time just for horizontal circuits. RCA made it to get drive to the HOT as fast as possible and to make sure the oscillator was stable and gave a locked in picture when the HV came up.

That voltage you posted was the H output grid voltage right? Normally I use 'HO tube' to refer to the output and 'H osc.' to refer to the oscilator.

If the H out tube grid is not as negative as it should be by more than ~15% the osc. and the parts coupling it to the output tube are automatically suspect.

My approach would be to replace any resistors that are out of tolerance, change the caps, make sure the osc. coil ohms out similarly to the values in the sam's and that it don't look damaged, and perhaps most importantly get a strong osc tube in there.

It's the grid off the 6FQ7 that I did the voltage check which is a tube that needs to be replaced.. I tested the 6JE6 horz output tube and it tests very strong... The horz osc coil also appears to look fine...

It's the grid off the 6FQ7 that I did the voltage check which is a tube that needs to be replaced.. I tested the 6JE6 horz output tube and it tests very strong... The horz osc coil also appears to look fine...

Please test the voltage at the grid of the H output tube.

Im getting -45.. Sounds about right.. Suppose to be -55 according to the Sams.. Realized i had to put the HV tube back in to get a correct reading.. Didn't let sit running for long seeing how I don't have pic tube connected..

That is almost 20% high which I'd consider a bad thing. Definitely work on that H osc.

Received the fine tuning gears.. Thanks a bunch Paul.. What type of grease would you all recommend to buy?

Also received some of the tubes including the 6CG7 [6FQ7] So I'll do some voltage checks probably tonight and see if there is any difference with a good tube..

I fixed the tuner, put the gears back in, had a hell of a time getting the tension spring in place seeing how I never saw what it looked like in place, so now its in perfect to where you push in to fine tune..

Now with the Horz osc issue.. I put in the new tube, and the voltage is now +2.6 at the grid of the osc tube.. Checked voltages at the HV output tube and meter just jumps around.. Doesn't make since, notice the HV output tube was glowing bright.. unplugged the unit, luckily I didn't kill the tube... Third time powering up the damper tube next to the HV tube started the glow bright...

pin 7 resistance to ground horz osc tube.

194K cold.. After power up it starts falling from being open and takes about 10min until it falls to 194k..

194K cold.. After power up it starts falling from being open and takes about 10min until it falls to 194k..

I dont understand what you mean about after power up etc...

is it 194k to ground with the set turned off?

what is the resistance from pin 6 of the horz osc to the output from the doubler diode (the one that supply the B+).

meaning I hooked up my ohm meter after power off, and the meter drops as for resistance for a while until it stay steady at around 194k, and it's to ground from pin 7 on the horz osc tube..

Not sure where the doubler diode is..

ok well that does not mean anything other than caps discharging. You always measure resistance on a chassis after B+ has been off long enough to discharge, same as you always read resistance after having hooked up to let is stablize just in case there is a cap in there. you should also reverse polarity when reading resistance if it reads an odd amount when comparing to the resistance chart.

what was the pin 6 to B+ double reading?

Ok, well I get 194k between pin 7 of horz osc tube to ground..

I'm not sure where to hook to B+ to measure..

there are two diodes in the power supply one has a connection to the ground, that is X1, it connect to X2, find the other side of X2 that is where you read to instead of the ground, see the Sams resistance pin reading charge, see the table explaining the symbols. some readings will be noted with symbols that tell you to read not to ground but some other place like the output of X2.

pin 6 of V11 read to the output of X2, should be 60k

sometime polarity or adj pots will effect these, sometimes sams is just wrong, sometime there are big variance and it does not matter, but its a starting point, after you narrow down the offending stage. A scope is a better tool for diagnosis, but you can do a lot just checking parts if you know where to look.

most of the time its going to be an open plate load resistor, a bad solder joint, a broken wire, this is why I discourage excessive cleaning and handling (wire and solder joint issues).

the number one thing to do is to wiggle the tubes in the circuit. poor contacts due to heat cycling is a big problem. cleaning the pins is a solution but I prefer to not mess with it until I have a base line run.

Ok I think I see what you are talking about on the sams.. Give me a few to figure out to list reading..

62.5k on the side of diode X2 assuming im measuring on the right side of that diode which is coming off one of the filter caps, to pin 6 on horz osc tube..

that sounds good, try wiggling the tube, try another tube, grid emissions can be an issue, best practice is to use a known good tube.

you can often just look closely and see the problem.

check resistances of coil L36 all terminals

dont forget to wiggle the tube when the set is on.

I try and measure the voltages at pin 7 of the osc tube.. Each time I power off and on again and measure again, I get a totally different readings..

Update: seems to be stabilizing at +28 volts..

I've wiggled tubes and all that too.. There's 5 different terminals coming off the horz osc..

if if the tube is getting +28v at the grid the tube or some part will be quickly distroyed, assuming B+ is still getting to the plate and the cathode is still connected to the ground thru the coil, check pin 8 per the sams.

I've wiggled tubes and all that too.. There's 5 different terminals coming off the horz osc..

thats right and resistance readings are on the sams.

you should confirm the circuit ground states are good, and watch this video, I have seem flakey tube sockets on other sets as well

https://www.youtube.com/watch?v=y4vkDchJRyI

Sams shows 23.5 ohms between 5 and 3, and 57.5 between 4 and 5.. None of the terminals are in order or labeled on the pc board for the osc coil, and the only one I can ID is the one going to ground.. I've measure between the 4 terminals in every way and I don't get anything at 23.5 ohms or 57.5 ohms.. I get 25 ohms between two of them and 65 ohms between another two, is the closest thing I can get.. I checked for continuity at the pin and the solder joint for each pin while tube is still in socket, probe of my ohm meter is thin enough... The new tube that I replaced is good but at the lower end, and it passes shorts and grid emissions..

I cleaned the volume/power switch with a little WD40 and the power switch is flaky..

pin 8 to ground resistance is?

check pin one
voltage and resistance per sams on the horz osc. Do this with the horz out tube removed from the socket to avoid damage.

Had to take a break from the project due to weekend jobs.. I'm back on it..

Pin 8 to ground is 50ohms
Pin 1 to ground is 22.5k
Pin 1 voltage is at 25VDC

Replaced alot of the caps and a few resistors and still no change..

Doing B+ source checks on the sweep board I'm getting around 435 on the 405 and 410 voltage test points.. It's slightly high for both, but is it still normal?

265 volt check point seems to be right dead on..

Come to find out it's the osc coil, I was able to get -120 at pin 7, then when I started touching the osc coil, the meter started jumping over over the place.. I've got a replacement coming from Moyers..

There was a bad solder joint on the old Horz Osc Coil.. Was able to get the voltages at -114 at pin 7 and -55 volts at the Horz output tube... Still I can't get the MA in the ballpark.. I can't get it under 240ma.. It also jumps around into the 300ma range when adjusting the horz hold control.. I replaced the old coil with the new one and makes no difference... I think the flyback is toast, I replaced shunt tube and other tube and hv only comes up to around 5000v..

Could there be an HV arc or short loading it down?

I'm not sure.. Don't know where to go to from here other than letting my friend Dave figure it out..

Well I posted results from what DaveWM asked a week ago.. He hasn't replied back to this thread.. I'm all ears.. I don't know where to go from here.. Tying to learn this stuff and if I can't fix it, than really is no point in having it.. My friend is not going to be around forever and if I can't keep these things going into the future than they will just be static items that are useless..

does the eff coil have a sharp peak?

did you go thru the horz sweep circ adj per the sams?
if so how is the shunt tube current (voltage drop across the 1k resistor, confirm the resistor value as well).

does the HV regulate well? (HV should hold constant while adjust raster brightness.

check the horz hold pot for continuity

is the line voltage 117v?

try subbing other sweep tubes esp the 6JE6 and the 3A3.

do you have the correct damper tube? make sure its a 6DW4 and not some 6C somthing

check the screen voltage and current of the 6JE6

does the focus coil look ok? (not burned up).

The focus coil looks fine.. The 6JE6 tests very strong.. I don't have another tube to put in it's place to see if there is any change.. I would have to order another one off eBay to do that.. The damper tube in it is a 6CJ3.. According to the sams, it's suppose to be a 6DW4.. But supposedly those are both the same tubes... Doing an eBay search most auctions list those tubes under both set of numbers.. There is no picture and HV only holds at 5000kv as I said in a previous post..

As for doing voltage checks and measuring across the pot, I will take the chassis back out tonight and do all of that..

maybe its a similar problem i had with my sivertone, after checking voltages at the 6bk4 shunt come to find out there was a shorted ceramic disc in the IF section that affected the bias voltage of the shunt tube and kept the hv from rising up to where it belongs. after checking the hv adjust pot and all other related voltages come to find that the shorted ceramic cap was in the shunt tube heater string that only would have affected the crt heater, shunt tube heater, and one other that i dont remember at this point because it took years to find this problem and i dont want to look back on it because it took so long to figure out. and let me point out that i would have never have found this problem if it was not for daveWM . so if anyone is going to get to an unusual problem with one of these sets it will be daveWM. take your time and be sure to check even everything even if something dont seem related and you will probably be surprised at what you may find as the culprit all along.like me i never would have thought that a tiny .001 cap would have caused the problems i had for so long. over the 4 years i had this silvertone i replaced so much, caps, resistors, done it all.

tube substitutions are the way to go with sweep circuits not tube checkers.
if you have another working roundie use those tubes.

you may be running off frequency, a scope or freq counter would tell you that.

try unpluging the shunt tube plate cap (HV there so hang out away from anything to prevent arcing). see if voltage comes up.

make sure yoke is plugged in correctly.

https://www.youtube.com/watch?v=CiaDjKUw0nU

this should be checked on ALL vintage tv's, it is now something I do routinely.

This is a preventive maint kind of thing, as it detects a defect that can destroy shunt tubes and CRT's if there is a problem.

Ok, I got the chassis out up on the table, and I'm getting only 244v at the HV regulator tube on pin 5, assuming it's the shunt tube, on the pin where the 1.5meg resistor is.. It's suppose to be 400v..

I'm measuring 0455v where the 1k resistor is on (R139) under the same tube which is HV regulator tube.. I cut the one side to measure the 1k resistor and it's only 181ohms on the meter.. Bad resistor.. Sams says voltage should be 410v, and the same on the other side of the resistor, but meter shows it a bit higher on the other side..

Adjusting the Horz EFF coil has made the current go down to around 197 - 205 ma under the HV output tube... I replaced the the 1k resistor and voltages go down to where they should be under horz reg tube..

Perhaps maybe the EFF coil could be an issue too seeing how it's right next to where the cap exploded..

Still under horz reg tube the voltages are still low at pin 5.. and HV probe at anode still shows only 5000kv

Here's the screen voltages:

Pin 4 340v
Pin 13 360v
Pin 5 345v
Pin 6 around 140-150 should be 200v
Pin 12 the same as pin 6
Pin 2 again same as pin 6 and 12
Pin 7 630v should be 960v
Pin 11 600v should be 980v
Pin 3 597v should be 860v

Voltages are being checked without the convergence board hooked up if that matters.. Please read previous posts as its started another page and I posted other posts..

pin 5 is the ref voltage from the voltage divider off the boost.

Clearly the boost is low as it should be in the 800v range (the voltage divider of the 1.5 meg resistors and the HV adj pot sets up the 400v that should be there.

the low voltage on the pin 5 means the shunt is completely cut off, so its doing nothing (the HV adj is prob not having any effect).

I would look at the .068 caps off the eff coil, leakage there could pull down the boost voltage.

check the resistance reading of the yoke as well for the horz windings.

with the horz tube out of the socket, read the DC voltage at the plate lead (the one that says "do not measure") again WITH THE HORZ TUBE OUT OF THE SOCKET.

the 1k resistor in the cathode of the shunt must have gotten very hot at some point and carbonized to that that low (181 ohms). This means something bad wrong happened in the shunt circuit at some point. could have just been a shorted tube, but hard to say.

Did you ever read the DC voltage to ground of the filaments of the CRT?

I checked both caps that are .082 and .068 off the EFF coil and they are good and no leakage according to my cap checker, even checked a new one with one in comparison...

If you mean the ohms in between the two yellow wires and two wires that are blue and red.. I get 00.8 ohms between them.. I don't have the yoke hooked to it...

Which pins are the firmaments to test?

Which pin on the HV output tube to measure I see where it says do not measure but not sure which pin..

The EFF coil was adjusting strange I thought.. it's a position in the middle where it can stay below or around 200ma, if I start adjusting either way, it starts going up..

crt pin 1 to ground. what is the DC voltage

the yoke resistance is given in the sams, check where the horz wires plug in.

you need to disconnect the yoke to check the resistance readings, otherwise the yoke should always be attached when running the set with the sweep circuits active.

Pin 1 to ground is around 195vdc... Trying to figure out the yoke resistance.. Looking on the sams, and I still can't figure that one out..

Still not sure about the horz output tube.. Shows the lead going to the flyback section where it says to "do not measure", but I don't see any wire going to the fly section from the HV output tube..

I can't have everything hooked up when doing voltage checks, I leave everything in the set, and remove the chassis/tuner/controls/ and set up all that in a different room on a table to work on.. As there is no room.. Yoke stays on pic tube in the set..

I'm following the sams and it says there is a 1240v boost point on the convergence board which is tied into the other higher voltages I listed that are low.. Now I'm measuring without the convergence board hooked up.. Is that why?

Update: I tested voltages with everything hooked up, and I checked pin 7 for voltages and it's even lower.. I noticed the shunt tube filament came up..

horz windings of yoke should be around 6.6 ohms per sams (disconnect red and blue leads before checking)

HV readings (currently at 5kv) was that taken with the yoke connected or not connected?

HV will not work if yoke is not connected.

well you may get 5kv with the yoke out, if your lucky. sounds like the headache i had with that silvertone hv problem. BTW its still working great , whites are white, lol..

I tried it both ways and HV was the same.. I disconnected the red and blue wires and put the the probes of the meter where the blue and red wires would go and my meter reads 007.5 ohms..

No change with the yoke connected and not connected huh, that is odd.

I suggest you do some continuity checks from the yoke leads back to the set, something is not right. I think the yoke is not in the circuit.

what is the ohms of the leads?

also check while working the horz pos pot back and forth.

00.72 ohms between the blue and red wires.. It does change slightly moving the horz centering pot, if that's the one you are talking about..

These long things.. I'm not sure what they are.. I figure they are a resistor of some sort, or a fuse.. The black long thing and the bumble bee colored black/yellow thing.. I measure them with my ohm meter and they measure open.. I get no continuity out of either of them on both continuity beep mode or regular resistance mode....

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0355.jpg

focus rectier (long black), the other is a 66meg resistor, not part of the problem.
Could be the horz osc is WAY out of tune.

.72 ohm seems low given the values in the sams.

Hmmmm... So what would the problem be?

well you could start by check the various winding resistance per the sams, yoke disconnected of course on the fly.

I'm not able to follow in between which wires to measure... I'm able to follow a schematic slightly, but alot of times, I'll see where a cap and resistor that are connected to each other than when I look for the resistor and cap number on the sams and then follow the schematic they are far away from each other on two totally different circuits and connected to other things..


Here's the pic of the wires coming out of the flyback:

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0186.jpg

the sams has a term guide for the fly printed right next the the fly on the schematic.

None of this tells me anything:

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0364.jpg

These long things.. I'm not sure what they are.. I figure they are a resistor of some sort, or a fuse.. The black long thing and the bumble bee colored black/yellow thing.. I measure them with my ohm meter and they measure open.. I get no continuity out of either of them on both continuity beep mode or regular resistance mode....

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0355.jpg i dont want to stick my nose in here but the focus coil looks done, they do get warm but not hot enough to burn the cover over the coil . i do know that if the focus coil is run to far one way they burn right up since i burned a new one i had just got from moyers. that looks like an issue.

None of this tells me anything:

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0364.jpg t4 is the guide look at the marks on the fly compare with the schematic it shows where they go either by letter or number whatever is there. and that fly may be old but it looks like it got really hot, could be a short in the primary that now spread to the donut.

P to chassis ground gives me 2.6megs if im measuring correctly.. But I think I'm suppose to measure in between wires going into the donut..

example Plate lead of 3a3 to plate lead of 6je6 is 635 ohms

p to C2 5.5

agree with timmy, check the focus coil use the term guide, shorted focus coil could account for the low reading from the blue and red yoke wires.

shorting the yoke also would explain why it has no effect.

Good eyes there Timmy, I think you got it.

P and C2 are labeled at the same terminal and are connected together.. Look at the pic above.. Unless they mean C2 being the wire on the back side connected to the top of centering pot.. If so, than I'm getting 6.5ohm

P and C2 are labeled at the same terminal and are connected together.. Look at the pic above.. Unless they mean C2 being the wire on the back side connected to the top of centering pot.. If so, than I'm getting 6.5ohm

check the focus coil

Focus coil, three terminals being used, one outer one connected with a resistor to the middle... Measuring the two outer ones, I'm getting 1.4 ohms as I'm turning the control there is no change other than the meter bouncing back and forth from 1.4 to 1.5 ohms.. And the slug keeps turning, there is no end in either direction..

L41 is the focus coil check the terminal guide 1234 and compare with the coil on the sams and check the ohms 28.5 x2 and a 42.5 but you may have to clip one end of the resistor thats there. really high ohms its bad really low ohms its bad it should be at a happy medium. turning the coil stick wont change anything but disconnect what is on it to get an accurate reading , it is a pain in the ass.

Indeed you are right timmy.. I suppose I should just remove the whole flyback assy at this point, and take reference photos of what is connected to other parts of the chassis before I do?

or even right down the color wires and where they go to each terminal the fly is marked but there is a red one for the centering pot write that one down too as well as others including the little one on the back side of the primary by itself.

what ever you find on the fly thats bad like the centering pot or resistor dont worry about it the new fly has it on there with the exception of the focus rectifier, and the focus coil, and the 66 meg resistor.

I would not write off the fly too quickly I have crustier ones that have leaked more wax still working, and have had non-fly related HV drops like that (mine were caused by a weak damper that would test good unless you held the test button for a round a minute, then it would sag into the bad range).

That's exactly what I'm trying to do, is not write it off too quickly and have the one timmy is sending me as a spare for backup, hoping this one is still good.. But I wonder if I should just take the whole fly assy out and do checks on it that way, or should I just leave it in the chassis?

you can check the focus coil with out removing anything.

Ok, I'll do that later on if I can squeeze it in..

and if it does test shorrted (very likely) you can replace it without removing the fly. the less you mess with the fly wiring the better. Its not that hard, but try to find an exact replacement focus coil (assuming its bad) as it makes hookup a bit easier.

it will take a min to test.

test it in circuit, no need to take apart, you are looking for VERY low ohms for a short. leave the resistor in, leave it wire, just look a the schematic ID the terms and check. Do disconnect the yoke.

oops you may have to disconnect term 4 or 2 which ever is easier

I've measured between terminals 1 and 2 so far and I'm getting 14.5ohms.. That's with everything connected.. Suppose to be 28.5ohm assuming I'm doing it correctly.. I'll measure the other side, removing the resistor.. Should I disconnect everything from the focus coil that's going to other components?

just disconnect 2 for now, just clip the wire from it to the fly, the coil form will break if you work it too much, you can jump in back in if it test ok.

1 and 2 are exactly 28.5 like the sams says..

ok now 1 to 3 and 1 to 4

1 to 3 42.9 ohm
1 to 4 28.5 ohm

Looks good to me..

4 to 2

56.2ohm

darn. if you have another roundie RCA style handy that is working get a reading of the Blue and Red leads to see if they are also .7 ohms

I can do that with a ctc15..

With an RCA CTC15 I get 008.4

I measured again on this chassis and the meter is bouncing from 007.8 to 8.0

I thought you said it was .7 before?

Just looked back, and yes I must have made a typo... But assume it's normal then.. So I don't know what to do next..

get Dave to take a look at it. If it was mine I would put a TV analyst plate drive to the fly and start there.

my mistake you can leave the 100k resistor in place to check ohms. if you look at the flyback it appears the wax is running out of the ends of the primary coil but typically it would run out of the middle of the donut. but there is nothing wrong with ruling out a bad fly or not. but just comparing ohms on the flyback if close rules out a bad primary but not the secondary since hv leaks in the donut takes that part out.

The flyback got toasted in this set.. We replaced with timmys flyback and I've got HV...

:thmbsp:oh ok thats great hv is always a good thing, you got 23.5 kv on the anode and about 190ma on the coil ? if you got that then it looks like your in business now.

I received my tube order for this set.. I still haven't replaced the electrolytic cap on the sweep board.. But there is a vertical bar of about an inch or two on the top and bottom of the screen, and if I adjust the width to fill the screen, it just stretches the images.. With my Leader pattern generator I can get a round circle with the screen not fully blown up, but with it blown up I get an oval shape.. I did check all the resistors that are 1.5meg and up in the vertical circuit and they seem to be in reasonable spec.. The sharpness and contrast controls do nothing.. And it appears to be too much contrast on the screen that I can't adjust.. I measured the sharpness pot and it measures something like 3 ohms and it doesn't change as I adjust the pot.. The contrast pot, however does seem to be fine and the ohms does go up/down as I adjust the pot...

Look for tin whiskers shorting the sharpness pot.

None of the pots seem to have that issue, I sprayed them with contact cleaner too.. Also there is a slight hum in the speaker, when volume turned down, it's noticeable... Almost all tubes were bad in the audio circuit, and with the bad tubes, seem like the hum was a bit more louder at times at times, I was able to hear change in the noise as if there was a short, now seems to be steady with the new tubes.. There was very little color with the bad tubes in the color circuit, now with the good tubes installed the color can be turned up so much that everything just blurs out.. But it also has problems with the color, very noisy picture and the more intense the color is, the more worse it gets, color all the way down to a B/W picture, the noise is gone.. I know all CRT TVS have this and usually can be minimized by tuning it the set, but this just can't it's pretty bad.. Here's a video to show it.. There's multiple issues, but would like to start with the color issue first than work my way to the rest of them.. As you can see who ever put this rebuilt crt in didn't put it in correctly as you can see the numbers in the phosphor and then which you call it thing that should be down under the bezel, but I noticed the anode connector on the back is about in the same spot as any other tv, so turning the crt would only turn the anode connect more of a downward position, but perhaps maybe I could turn the tube around to where the upper part of the bezel hides that and the anode connector will be on the same side of the HV cage?..

https://www.youtube.com/watch?v=7ALjbvsxsnY

Anybody???

needs a good setup,

HV set, degauss CRT, rough center converge,purity setup,full converge center/dynamic,grey scale.

then take a look at it. worminess looks like fine tuning. focus poor do to convergence.

I know it needs to be degauss.. I'm not worried about that right now, as space right now is an issue.. The worminess is what I can't get to go away.. I've adjusted the fine tuning, and it doesn't fix it.. HV is set all the way up, if that's what your talking about..

Purity was way off, had to adjust the yoke and the purity ring alot to get red in the middle, it was way off to the side.. I also did convergence and got it much better in the middle, all this seemed to minimize the worminess.. But the contrast is way too much.. I'll have to take the chassis out and follow the contrast pot leads and make sure none of them broke off..

does the contrast control not reduce the contrast?

It doesn't.. Not sure if you read the previous post on it.. But the pot seems to be good, but there is no effect when adjusting the control pot.. There is issues with the sharpness pot too..

check for a shorted cap, its in one of the cans, you will see the pot wire go to it, prob 100uf of something big like that, low volt, prob 50v

sub in a new 12GN7.

back of the AGC just a bit (adj clockwise till you lose sync, then back off till sync is normal is the typical adjustment. Make sure the AGC is work like this. You should be able to adjust from no pic at all (washed out) to a dark pic and then loss of sync.

I adjust the AGC control and all it does is make the pic bright or dim...

I'm probably going to replace all the filter caps, So after I restuff all the cans and caps on the sweep board, I'll see what improvements there are between the controls and the vertical width.. This thing has like 4 cans and one cardboard can and a non polarized electrolytic in it somewhere and also an electrolytic in the audio circuit.. I guess I might as well replace them all..

you would be better off diagnosing the problem and correcting the issue.
This era set rarely needs shot gun replacement of parts.

The contrast issue sounds like a video out tube since the other areas (sync/audio/color) are fine. Lack of hum bars in the pic indicates the B+ is prob ok. I typically look at the B+ voltage and scope the ripple to determine the condition of the B+ supply.

if a new video out tube does not clear it the next logical area to look into is the cathode bypass cap on the video out. disconnecting the cap would confirm this, bridging would not help since is seems to be shorted not open (open would be too little contrast).

The issue I have with shot gun replacement is two fold, often it simply is not needed the caps are fine, but more importantly is when used as a way to correct a problem you end up not learning much (what happens if the contrast problem returns? shotgun recap again?).

So best approach is to bone up on what the clues are from the set and learn the various circuits and how they function. Then with some decent test equipment you can trouble shoot and pin point the offending part or parts.

So back to the orig suggestion, try a new video out tube, if no change disconnect the video out cathode bypass cap, test the contrast control, test the bypass cap, replace if bad.

This take much less time to do than a restuffing of caps. One last problem is mass replacement of parts can create tough dogs out of pushovers IF an incorrect part value is used in the replacement. Not impossible to do. It one reason why unmolested sets tend to be more desirable than "restored" sets, unless of course the work was done correctly and the set is currently working.

Work one issue at a time, get the contrast fixed move to the vert, vert problems are tube/bypass cap/feedback cap/plate load resistor on multivibrator.

I'll pull out the chassis sometime early this week and go by your directions, and see if I can find anything...

before you pull the chassis do the easy thing 1st try a new video out tube. I always start with the easy possible 1st even if its not the likely problem. Also use the sams to check the pin resistance.

I've ordered a few of the 12GN7 tubes, so I will be waiting for those to arrive before I will be moving on..

I just tested the 12GN7 and it fails grid and shorts.. I thought I tested it before and it tested fine... I guess I'll see what happens when the other tubes arrive...

I know it needs to be degauss.. I'm not worried about that right now, as space right now is an issue.. The worminess is what I can't get to go away.. I've adjusted the fine tuning, and it doesn't fix it.. HV is set all the way up, if that's what your talking about..
I'm working on a similar set, a Sylvania 580 (CTC15 clone). The alignment instructions for the 4.5 mc trap (a single slug-coil) right after the video detector diode say to put contrast at max, fine tune into the worms/beat then adjust the slug for minimum interference.

I received my 12GN7 tubes today.. There are 3 of them, and my B&K 747B tester tests them all in the weak range.. I'm not sure why.. If it's really my tester, or all these tubes are weak.. The eBay auction stated them all being strong.. one goes up around the "?" range, and I used that tube.. I get better color and the picture in all looks better, but I still can't adjust the contrast.. The worminess seems to be at the normal minimal..

with one of the tubes, After being on for a few minutes, I noticed the color becomes out of sync...

not able to adjust contrast, look for that wire coming off the contrast pot that goes to one of the sections of a can, 100uf 50v or something like that. Disconnect that, you should lose most of the luma content (looks like very low contrast). then try hooking a good 100uf cap to that wire (pos, neg to ground), see if that fixes the contrast control.

Tube testers are not much good but for testing short/grid emissions/and totally dead tubes. Don't put much faith in them, better to do tube subs with known working tubes.

I'll try that either later tonight, or another night when I've got more time...

Thanks..

I managed to squeeze some time in.. I removed the chassis, sat it up on the table, I snipped the wire going to the electrolytic and connected a 100uf 50v cap to the wire, and the ground to one of the terminals that go to ground, put the chassis back in the cabinet, hooked everything back up, and there is no change.. Contrast control still does nothing..

did you try it with the cap disconnected? do some resistance check for pin 1 of the 12GN7 see what the sams say is should be. Make sure the control effects the resistance readings.

I did try it with the cap disconnected and the color looked weird.. I'll do some readings when I have time to pull the chassis out again and set on the table to where I can access it much better.. Am I able to check resistance with the tube out?

the color should have been correct, just very washed out. if it goes from very washed out to too much (cap out/cap in) then is sounds like the control is not working, check the pot, look also for any shorts, sometimes the output terminals from a pot can get moved around during chassis removal, resulting in shorted term to ground. its always best to check tube pin resistance readings with the tube installed. Depending on how its wired, an open pot ground may have the same effect. check to make sure its functioning AND the ground lead is not open.

The color did look washed out, but look like it also wasn't in sync correctly.. I'll check all this soon, when I have more time.. Thanks..

sync should not be effected. could have be a co incidental. My bet is on a bad pot (crack in element) or bad ground.

I measured resistance, Easier than I thought, I didn't have to pull the chassis out.. Not sure which one is pin 1, but I measured the two outer pins, one measures at 196ohms, and the other outer 000.6ohms, and they don't change adjusting the contrast pot..

The sams doesn't show any measurements on the schematic out from pin 1, just shows voltages

The pot according to the sams is a 600ohm, I measured acrossed it, and it doesn't go near it while adjusting..

disconnect the pot enough to be sure and isolate it, then check the two outside terms and confirm 600ohms (no breaks in element) and then the wiper to each outside, checking for correct action (0-600 ohms).
an analog meter is the best tool for this.

the pot is setup as a variable resistor, so IF its broken you MAY be able to swap the wiring around to get it to work.

I measured the two outer terms with everything still connected and it only stays at 196ohms when adjusting.. I assume the pot is bad.. Still with everything connected, I would think there would be change as I adjust the pot..

best to take off at least 2 wires if 3 are on the pot to get an accurate reading. to find out if the pot works you have to use one end term and the middle term then rotate and see if ohms change.

Oops I was doing this all wrong.. I disconnected the wires, I get 736 ohms out of each end, and it goes down to about 00.2 ohms on the lower end from wiper to each end.. So I assume the pot is good..

hmmm very odd, the pot checks out, you need to review the wiring and make sure nothing is shorting and all is hooked up correct. The washed out look is correct (degenerative feedback) the cap bypasses the cathode eliminating the degenerative feed back. this is a very simple circuit, should not be that hard to make work. IF you get the washed out pic AND you get the over contrast then the pot/cap have to be an issue.

I disconnected the green wiper wire that goes to the filter cap that's suppose to give a washed out look when disconnected, and really no change in the picture, I touch it on the terminal while the set is on, to see if there is sudden change in picture and it seems to make it slightly brighter or add a slight more contrast when connected.. Odd how it didn't give that washed out look this time, but I also disconnected the wire from the contrast pot this time instead of from the filter cap leaving the 100uf cap connected to wire and removed from ground the last time..

the way it works is the pot outside fixed resistance is in the cathode to ground circuit of the video amp, its in p with a fixed 220 ohm cathode resistor. This allows for a voltage drop across the resistor and pot when the video out tube conducts. The result is the cathode of the tube has a positive voltage with respect to the ground. This sets the bias of the tube (control grid to cathode). Proper bias is needed for the tube to work as designed.

the Cap is connected in such a way (neg to ground/pos to wiper) so when the pot is fully CCW (least contrast, least gain) the wiper is at ground so the cap does nothing. As you turn CW the cap is introduced into the cathode circuit, acting as a bypass to the ac signal generated by the tube conducting a normal video signal. With out the cap there is neg feedback (strong signal, more voltage drop, more voltage drop higher cathode voltage, higher cathode voltage greater bias off of tube. With the cap in place the bias is held constant for max gain (most contrast) of the tube.

Looking at the schematic.. The circuit only consists of 2 ceramic disc caps and two resistors, plus the 100mfd cap off the filter cap which isn't the problem.. I don't know what else it would be other than possibly one of the resistors, or one of the caps which is probably unlikely..

I checked the two resistors in the circuit which are rated at (R67) 220 and (R68) 270 ohms.. I get 229 out of the 220 rated resistor, and 195ohms out of the 270 ohms rated resistor.. Testing them in circuit, the one is off by alot, but could be due to being in circuit, and even if it is way off like that, I would still think there would still be contrast control..

doubt the ceramic are an issue, and the resistor values are not critical.

The clue is if you disconnect the can cap and the contrast gets super weak then it pretty much has to be something screwy with the pot/100uf/wiring.

you can check other things but that seems to be the case to me.

I don't know how to proceed other than to check pin one on the tube socket and check for continuity each end of the wires or just replace the pot if I can find a equivalent part.. The sharp control is also another issue, the wiper and one of the end terminals are bent into each other on that pot and soldered to each other and goes to ground, pot measures very low ohms and meter doesn't go up/down at all the way it's set up, but according to the sams, this is the way that pot is..

http://i1220.photobucket.com/albums/dd458/vintageceilingfans/Magnavox%20Roundie%20TV/DSCF0382.jpg

no reason to replace the pot if it check out.

Well it seems to be a Maggie problem with contrast because the contrast on my 65 is not the greatest but I decided to leave it alone.

lets recap the contrast problem as stated.

Too much contrast, contrast control does nothing.

Disconnect the 100uf cap in the contrast control circuit, contrast goes very low
colors get "weird" (not sure of what that means or if related).

My conclusion is since there are only two things in the contrast control a pot and a large cap, and deactivating the contrast by removing the cap effectively puts the contrast at the other extreme, then the problem HAS to be the cap/pot/wiring one of those are a combo.

I'll try the 100mfd cap again, this time I'll tack it on a short wire from the pot control instead of going under the chassis..

It's the 100mfd cap... For some reason now it's working.. Last time I tried it didn't work.. Possibly due to the fact I rigged it under the chassis last time, and perhaps maybe when I put the chassis back in the set something may have came loose..

Should I go ahead and just restuff the can? infact I might as well restuff them all..

if you have a cap tester you could test the others (old school eye tube type to check for leakage).

IF it checked fine I would leave it and just not use the 100uf in the can. IF any others tested bad (leaky or weak) then I would go ahead and restuf.

Am I able to test the cans while they are still hooked up, or does the wires need to be removed to test?

I was looking into the sharp control circuit, I changed out the 6GHA which had a 6LM8.. Now video went away, it's just a grey scale screen.. I inserted the original tubes, and same thing..

Am I able to test the cans while they are still hooked up, or does the wires need to be removed to test?

need to be removed for testing leakage

Well I give up on the damn thing... All I did was remove and exchange the third video IF tube and the 6G8H video amp and the other 6G8H on the sweep board... I wiggled wires around, and checked the tube sockets, wiggled tubes to see if any change and nothing changes.. I can't get video back.. I get nothing but a grey scale screen with moving retrace lines..

Here's an example: The flickering is the camera..

https://www.youtube.com/watch?v=o7847FdbnBY

its best to only do one thing at a time on a working set. That way if something goes wrong its easier to find the problem.

I looks like no signal getting thru the video since the audio is working.

1st is the tube lighting up? sometimes pcb grounds can crack, Need to be gentle when removing tubes. I use a spray lube/contact cleaner on tube before removing just aim around the base and let it set. this way the tube comes out easy and less likely to flex an old pcb.

If it was mine I would start with signal injection at the grid of the video out and work back. OR scope the signal begining at the output of the video diode.

if you lack the equipment for the above you need to do voltage test and see if the video tubes (video amp and video out) have correct voltage.

as to why this would happen, hard to say, most likely a flakey pcb or if you inserted a shorted tube then maybe smoked a plate or screen resistor.

It's something not making a connection, because it has happened one or twice before when messing with those tubes, I remember powering off, wiggling tubes and wires, and powering back on and the problem went away.. This time it's not.. I moved on to the sharpness control seeing how I already know what the problem is with the contrast... All tubes are lighting, I took the 6GH8 out from the sweep board and powered on and seems like no change.. I have to go to work so I have to look into this probably on Monday, is when I have free time..

Circuit board traces under the tube sockets probably the video output tube or more likely others. All my sets had broken connections on several sockets but you have to look closely for them . Best thing to do is resolder every tube socket and mark it off your list of problems.

what timmy is describing is shown on one of my videos working on a predicta. a tube socket extender with the test points is ideal for finding such issues. Agree using your eyes and a magnafiy glass is a good start.

I've seen Shangos recent predicta video where he actually zooms in real close to and it shows a break in the tube socket connection.. I've checked the 3 sockets that I pulled the tubed from before this problem occurred... I check with a mag lite, magnifying glass and poked in each hole with a small wire.. All of them are solid.. I'll go under the board where I have to remove the bottom metal plate, which I already did once, and this time I'll just reflow the tube sockets as timmy says.. The wire that goes to the sharp control was broken lose and the inner wires were touching each other.. But I don't think that's the problem.. I don't think anything like a resistor got burned out or else I would have smelled something or saw something cooking, unless a resistor burnt out without noticing any symptoms..

Should I spray WD40 and contact cleaner in the sockets pin holes?

I'm getting 125v at the 6EJ7 3rd video IF, sams says its suppose to be 180v, I pull the tube out of socket and the voltages jump up to about 180v.. I'm getting 150v at the 6GH8 second video amp which is about right... I get 51v at 6GH8 sync sep, suppose to be 85v.. I'm doing the test with the chassis out of the cabinet and the HV tube removed..

audio is after that tube so its not the problem.

inject a composite video signal at test point B

I reflowed tub sockets, no change.. I attached an alligator clip to test point B which is between L10 and the tube socket and touched a coax cable to it, and i can't get anything.. Not sure if I'm injecting the signal right.. all it does is make horizontal bars on one side of the screen..

what was the source of the composite video signal?

I tried cable TV, and I also tried my B&K pattern generator in IF mode...

you need to use the video, no an RF or IF modulated carrier wave.

So something like an RCA video output from something like a DVD player?

yes the video out may work. you should isolate it with a .1 uf cap to protect against any DC potential.

what model BK is it? a 1076 or 1077 would be ideal.

I used a B&K 1248 digital I.C. color generator

I connected the video output from a DVD/VCR player and was able to get a picture.. The colors were off and the horz and vertical are wacky, but I was able to see the menu screen of the player...

Well then its prob before that point then.

since you are getting audio, then the prob should be somewhere between the plate of the 3rd IF tube and the test point B.

Of course it could be an AGC voltage that is off, allowing audio but not video.

I would try clamping the AGC with a variable DC supply to see if that brings it back.

if it was mine I would use my 1076 BK analyst to inject starting at the plate of the 3rd IF and look for signal loss going back.

It looks like something beyond my capabilities.. So I guess I'll hand it over to Dave, and let him finish the rest of the restoration..

Before you do that, futz around with the AGC pot, and try a new AGC tube.

That's a good idea.. Is it the 6GH8A V23 behind the AGC control?

V6 keyed agc, not the one by the agc control.

That's the one I suspected in the beginning.. I already tried replacing that one, I even pulled it out and powered on and there was no change... The agc pot I did adjust numerous times.. I notice the sharpness pot when adjusting, puts purple color streaks all over the screen...