View Full Version : 1968 Motorola works in a drawer


maxhifi
06-27-2016, 12:12 AM
Just picked this up today, picture tube tested weak at first but after about ten minutes came up good on all three colours and even decent tracking. Worth a restore? It does make a raster.

MRX37
06-27-2016, 09:00 AM
I'd say so yes, and it probably doesn't need much.

maxhifi
06-27-2016, 01:04 PM
I like how the chassis is similar in form factor to a desktop PC. The 25ZP22 has quite a cateract, something needs to be done about it. I am a bit gun shy about the process, but have read all the tutorials and watched all the YouTube videos. Am thinking the guitar string method is the way to go.

The chassis being solid state, and so old, really makes it seem like it would have been progressive and modern when released. Mind blowing how much progress was made in the 22 years separating the 630 RCA, and this all silicon all transistor chassis.

maxhifi
07-31-2016, 07:34 PM
This tv is coming together, cabinet refinished, cataract fixed on tube.. Just put in a huge Order for capacitors at mouser, all 105 degree nichicon. Also SAMS says the CRT crosses to a 25XP22 RCA, which is awesome because the one in my CTC38 tests as new.

sampson159
07-31-2016, 09:57 PM
my dad said these sets were a marvel of electronic design and manufacturing back then.its just that the crts were pretty bad.please post pictures for all of us to see

maxhifi
08-01-2016, 12:01 AM
Right now it's in a million pieces, the cabinet is at my folks place, chassis and tube here. I had attempted to refinish and was unhappy with the result, so took it to my Dad. He really woke it up, he's got a lot more finesse than I do when it comes to wood finishing. Once I get it all back together I will post photos, and no doubt some technical questions too.

walterbeers
08-01-2016, 09:19 PM
Those Quasars, all solid state 1968 works in a drawer were quite advanced for it's time. Good idea, but there were a lot of problems with those small orange electrolytic's, and of course the contacts to the boards were always getting loose and dirty causing problems. Our neighbor next door had one of those and had it as their main TV for many years, and of course I repaired it several times. I think I changed out a couple of boards with rebuilt's, and I remember changing out small electrolytic's as well. Always had a good picture, but a few years before they gave up on it, the CRT was getting on the dull side. They bought an RCA console, (not sure what model, maybe something like a CTC168-CTC1##), which is still in use, on cable with a DVR, in which our neighbor still records her soaps and watches them on the console CRT RCA. Unfortunately the Quasar got junked, without me knowing about it years ago. Wish I could have got a hold of it back then. I remember it had a solid state HV rectifier in place of a 3A3, which never did go out.

maxhifi
08-02-2016, 11:28 AM
Hmm that's all very encouraging info. I am doing a bulk replacement of all the electrolytic capacitors. I have repaired a fair bit of audio equipment from the mid sixties and the small low voltage capacitors are often bad. When I got the tv I plugged it in and got a raster, so I am reasonably confident the fly back and deflection yoke are okay. My picture tube did come up to testing good after about ten minutes. If it ends up being bad I have an RCA tube I can put in, but considering all the work to remove the cataract I have high hopes for the Motorola tube!

centralradio
08-02-2016, 01:51 PM
These are great sets.My parents had a 19 inch Quasar from the early 1970's that the pix was so superb that made the other sets look bad.The only issues with these sets were the plug in circuit board connections gets loose and we had to whack the side of the set like Fonz did with the juke box on Happy Days to get it going.We had the set in the shop a few times and me fixing it in its almost 20 years of use. Mostly clean the board connections and replace the horz and the power modules which probably fried do to the loose connections. I still have the set here and some day i will bring it out and restore it.Also I have my grandfathers 13 inch Quasar which was bought around the same time as the 19 inch set.I will look into that too.

holmesuser01
08-04-2016, 09:11 AM
I've got a 17" version of this set in my garage. It's got all the modules and has 4 tubes. It's a good set. I fixed a broken power switch when I received it, and the owner never came to pick it up. (I hate that.)

Dude111
08-04-2016, 01:22 PM
Good luck buddy :)

maxhifi
08-07-2016, 01:15 AM
Some progress.... Lots of screwing around to get plastic bezel to sit tight to CRT, looks good now. Improved since attached photo.

TVTim
08-07-2016, 08:57 PM
Lookin' good!

Dreamsbeard
08-07-2016, 09:03 PM
Looking good indeed! What did you use to refinish the cabinet?

TUD1
08-08-2016, 12:10 AM
That set looks very good. Great job refinishing it. I just got the exact set today at an estate sale. I just used Gojo on mine, and I'm satisfied with it.

maxhifi
08-08-2016, 12:36 AM
Looking good indeed! What did you use to refinish the cabinet?

What I did, was sand it with 100, then 220, and finish with Danish oil. It looked awful, like a car with a $300 paint job.

I turned it over to my dad, He used a scraper to flatten out the grain, then used a bunch of tricks to get it really smooth, followed by oil for color and then polished beeswax. It looks like furniture again. Don't quote me on the process, but I am really happy with the result. I can get specifics if you like, the finish really suits the style of furniture. I want this one to be living room quality.

I'm more an electronics guy than a furniture guy. My big victory so far is its my first cataract removal.

maxhifi
08-08-2016, 12:42 AM
That set looks very good. Great job refinishing it. I just got the exact set today at an estate sale. I just used Gojo on mine, and I'm satisfied with it.

Hopefully we can learn from each other. I'm going for a total re-build, I want it to work perfect. I like how this set has tons of adjustments, I like to be able to dial things in really precisely. I hope the color is accurate once it's all set up. For example my ctc 38 has no centering pots, and this tv does.

Trance88
08-08-2016, 04:48 AM
Some progress.... Lots of screwing around to get plastic bezel to sit tight to CRT, looks good now. Improved since attached photo.
This is like my dream vintage TV console style with the cool little peg legs. Looks amazing!!!

TUD1
08-08-2016, 12:08 PM
I find it interesting that these have to separate controls for tint. They have one wheel for tint, and a slider for hue.

zeno
08-08-2016, 03:49 PM
I find it interesting that these have to separate controls for tint. They have one wheel for tint, and a slider for hue.

Dont remember on Motos but Admirals had a control that changed
the grey scale for a "warm" or "cool" picture. Always center it
before grey scaling.
73 Zeno:smoke:

zeno
08-08-2016, 03:52 PM
Your father sure has a touch with wood. Wish I did !!
This will be a show piece when done.

73 Zeno:smoke:

Dude111
08-11-2016, 01:33 AM
Good job buddy,your giving her the respect she deserves :)

Please give her a good wipe for me,give her a pat;tell her I said hello!!

Dreamsbeard
08-13-2016, 11:37 AM
What I did, was sand it with 100, then 220, and finish with Danish oil. It looked awful, like a car with a $300 paint job.

I turned it over to my dad, He used a scraper to flatten out the grain, then used a bunch of tricks to get it really smooth, followed by oil for color and then polished beeswax. It looks like furniture again. Don't quote me on the process, but I am really happy with the result. I can get specifics if you like, the finish really suits the style of furniture. I want this one to be living room quality.

I'm more an electronics guy than a furniture guy. My big victory so far is its my first cataract removal.

Of course I would like the specifics! :P And I'm sure a lot of VKers would be interested in that also. Well all came across some less than stellar looking cabinets that would need a good refinishing.

I would say that cataract removal is very ballsy and especially if you did it with the heat gun...

maxhifi
08-13-2016, 12:09 PM
Of course I would like the specifics! :P And I'm sure a lot of VKers would be interested in that also. Well all came across some less than stellar looking cabinets that would need a good refinishing.

I would say that cataract removal is very ballsy and especially if you did it with the heat gun...

I will ask my dad next time I see him :)

Cataract procedure was as follows:

Remove yoke, convergence coils, purity rings (in opposite order!)

Remove CRT, (from front on a Moto) place face down on old sleeping bag then remove x-Ray shield, degaussing coil, mounting hardware.

Everything removed was photographed before removal so the orientation not lost. Dirt not cleaned off neck of tube to allow easy repositioning of various parts.

Worm gear on band photographed so that I knew how tight to make it after process.

Next step put a bunch of rocks in the bottom of a large garbage can, and put bare tube into it facing up. Wrap tube in black plastic garbage bags, and let sit in the sun for several hours.

Once it got good and hot I removed tape from around the edge and I used the "guitar string" method to slice it off. Basically just attached a guitar string to two 6" dowels (sticks our clematis came with cut up) used as handles. Slice off the safety glass like as if it's a cheese knife. This part was surprisingly easy.

Then clean off the old silicone (a nasty mess, I used acetone alcohol, water, windex, fingernails, plastic scrapers and plenty of elbow grease)

After everything is clean I affixed the safety glass with four pieces of double sided tape, siliconed around the edge, and then when that was dry taped it with book binding tape.

After than assembly was reverse of disassembly (got that phrase from Haynes :)

Note: to prove I am not bold

I did this on days ranging from 25-30 degrees Celcius (Hot!), and wore steel toe boots, and Arctic arc flash rated coveralls and winter jacket zipped up to my chin to cover my neck (heaviest stuff I own, from working in a diamond mine) along with a face shield and safety glasses and heavy leather gloves

After each major step I took a break and let it sit for a while to ensure its stable

Would definitely do this again.

Note guitar string method works only for green type cateract, the heat gun is for RCA tubes.

Thanks to all past and present members here for getting this down to a science before I attempted it :)

Electronic M
08-13-2016, 11:48 PM
The Zenith method is pretty tame and reliable. I've done it perfectly all three times attempted...In contrast 2 of three RCA operations ended in destruction of the CRT for me (the most recent was last weekend :sigh: ). The middle one a few years ago I got lucky and only ruined the safety glass and put a small nick on the face of the CRT chipping the rest of the glass off. I think I'm at the point where if I did another RCA I could be successful with it....I get better every time, and the last one would have been the best yet had the screen not cracked at the cusp of getting the last of the glass free.

maxhifi
08-21-2016, 08:44 PM
About half done the recap... Plastic case electrolytics are about half bad, some
Open, some short, some way low value. film caps all good both value and leakage wise on borrowed sprague telohmike. Will leave film caps alone for now as all I have tested are in tolerance and behave as new caps on leakage test.

Took apart front panel and cleaned it up, this tv is great!

Photo is convergence/vertical board, with bad caps beside it

Put new grease under horizontal outputs, will do same with vertical and audio out

maxhifi
08-28-2016, 10:55 PM
Got her all back together today.

Powered up and got a nice screen filling raster. Picture is very sharp but couple issues, red blooms like crazy when colour is turned up, and colours are all wrong. Convergence is also off. Will do a set up and the fix colour problems.

Am having problems with the first step.. Static centre convergence. . Use the blue lateral magnet to adjust blue and the disk magnets to adjust red and green. Only what disc magnets? All I see are the purity rings.

maxhifi
08-28-2016, 10:56 PM
Here's the front view

Electronic M
08-28-2016, 11:20 PM
Got her all back together today.

Powered up and got a nice screen filling raster. Picture is very sharp but couple issues, red blooms like crazy when colour is turned up, and colours are all wrong. Convergence is also off. Will do a set up and the fix colour problems.

Am having problems with the first step.. Static centre convergence. . Use the blue lateral magnet to adjust blue and the disk magnets to adjust red and green. Only what disc magnets? All I see are the purity rings.

You know what the convergence clover looks like right? The disk magnets are near the tip of the petals...They are like a thick ferrite penny laying down on the petal tips....Or think of them like the knobs on 60's transistor radios where only the rim protrudes from the cabinet.

maxhifi
08-28-2016, 11:50 PM
Thank you! So adjust by rotating? I took a close up pic of the ones on my set. I've not seen this style before, on my other TVs they were more obvious.

Update: figured it out. Convergence procedure went well as did grey scale. Purity was difficult but found a decent compromise.

Set makes a great monochrome picture, but colour is kind of weird, tends to smear across the screen when there's a block of one colour, almost like a shadow. Picture a bit jumpy after convergence procedure as if one of the convergence pots was dirty.

rcaman
08-29-2016, 07:29 AM
Smearing as you describe is most always a weak crt in a solid state set.
steve

Electronic M
08-29-2016, 07:38 AM
Smearing as you describe is most always a weak crt in a solid state set.
steve

Can also occur if color level is too high, or fine-tuning is mis-adjusted.

holmesuser01
08-29-2016, 08:16 AM
Did you take the parts off of the CRT while you were working?

maxhifi
08-29-2016, 09:24 AM
Yep all parts were taken off the CRT to remove the cateract. I marked their positions and put back as close as possible. I tried it this morning and now it seems like the blue horiz amp pot has developed a dead spot, exactly where it needs to be. Will have to continue on it later.

maxhifi
08-29-2016, 10:57 AM
Can also occur if color level is too high, or fine-tuning is mis-adjusted.

When it is a monochrome picture (intensity all the way down, or in a middle to low position) there is no smearing regardless of brightness setting. It doesn't bloom like a weak crt in monochrome set, but rather smear the colour way past where it should be. I wanted to make a photo this morning (this is really hard to describe but easy to photograph!) but issue with convergence pot came up and needs to be dealt with first.

Tube does test good on all three guns with good colour tracking and cutoff

Worst case I can use the new testing 25XP22 in my RCA ctc38 , the Motorola is a much nicer TV and deserves a good tube. The sharpness of the picture is wonderful.

old_tv_nut
08-29-2016, 07:43 PM
I find it interesting that these have to separate controls for tint. They have one wheel for tint, and a slider for hue.

I know that Moto tube sets had the separate tint control because of the super-simplified DC-coupled single tube chroma section, but I didn't remember one on the solid state sets.

http://www.videokarma.org/showthread.php?t=93056

zeno
08-30-2016, 07:23 AM
Smearing is almost always CRT. If it only the red & only
with the color turned up even more so BUT it should
also smear some on a hard driven B&W pix.
Only other thing is the 200V that feeds the 3 color output
transistors. If the 200V isnt clean you can get smearing
& a lot of other symptoms, often subtle. Check
any 'lytics on it.
For blue pot you can add a 2W resistor in series with it.
About half the value of the pot. This will move the setting
away from the bad spot. Then you can scare up a replacement.

73 Zeno:smoke:
LFOD

maxhifi
08-30-2016, 10:01 AM
Smearing is almost always CRT. If it only the red & only
with the color turned up even more so BUT it should
also smear some on a hard driven B&W pix.
Only other thing is the 200V that feeds the 3 color output
transistors. If the 200V isnt clean you can get smearing
& a lot of other symptoms, often subtle. Check
any 'lytics on it.
For blue pot you can add a 2W resistor in series with it.
About half the value of the pot. This will move the setting
away from the bad spot. Then you can scare up a replacement.

73 Zeno:smoke:
LFOD

It also does it on blue. The effect is stronger on blue than red, and it only smears to the right, the left edge is sharp. Actually it's interesting you mention the three video output transistors, their load resistors look a bit heat stressed, and this PCB has clearly seen some repairs in the past. I did a bunch of re-soldering and repaired a trace on it but changed no parts during the recap. I will check the supply voltage and all the voltages on those transistors, if one was saturating would it have a smearing effect?

Thanks for the advice regarding the blue pot, that should be enough to get me going!

maxhifi
09-01-2016, 12:22 AM
So as it turns out the 150 ohm blue pot was open in a couple spots. I found a 400 ohm pot in a junk zenith chassis and installed it. Convergence isn't perfect with the wrong value pot but it will do for now (see image). With the 150 ohm pot the right side of the picture looked a whole lot better.

Then I tried some tests to check the smearing. It's worst on blue, so I measured voltages on the collectors of the video output transistors. They are way low, blue was only 100 volts and red and green around 125. The collector load resistors quite charred. When I swapped the connections between colours the smearing changed colour to whichever gun was connected to the blue transistor. (Yes!)

I think the collector load resistors are way high in value, not sure what's the root cause of looking burned though. Thank goodness it isn't the tube! Will pick up some parts and keep digging!

DavGoodlin
09-01-2016, 09:27 AM
It's great to see one of these fine machines dialed in right. Loved to work on them, few that I saw.

Makes me want to dig out my 1972 Quasar (the last WID?) and swap the tuner, which took it out of service and got it buried..

maxhifi
09-01-2016, 09:47 AM
It's great to see one of these fine machines dialed in right. Loved to work on them, few that I saw.

Makes me want to dig out my 1972 Quasar (the last WID?) and swap the tuner, which took it out of service and got it buried..

Mine has quite a ways to go before it's dialled in right, the components seem less bulletproof than an RCA or Zenith of the era.

Is yours a console too? I think it's a worthy project, I am definitely enjoying mine.

Kind of makes me want to get some AR-3 speakers since the styling is so similar!

DavGoodlin
09-01-2016, 01:53 PM
Mine is a TS938 dated 2M72 and very similar to the one RadioTVnut posted in the rectangular color, in the same walnuty legged cabinet.
Instead of the 4-5 tube hybrid, mine has a SS sweep section and switched power supply module that was tricky. It has a 2-button clicker remote and no selector knob but a preset channel drum behind the door with 18 positions, 6 were for UHF and 6 was not enough in this area believe it or not :) but I had a VCR on it.

It moved with me twice since I got it in the mid 80s and used it in my room until the VHF tuner crapped out. Ill post a link as I put a picture on VK somewhere but the ad below shows the general arrangement. Loved that advertising they used ;-) but the tuners, MEH - not quite a Zenith!

I think many of these survived into the 80s and 90s simply because the TV repairmen liked working on them and the customer thought the drawer was cool as S**T 192329

maxhifi
09-02-2016, 01:28 AM
I adjusted it to exaggerate what I called smearing. This image should be monochrome. The video output voltages seem find and the CRT checks firmly into good..

It seems like solid blocks of red or blue will smear, while green doesn't at all. Definitely most noticeable in high contrast scenes.

I can adjust it to be totally watchable and reduce this effect but then it comes back when the contrast of a scene is high and saturated colors are present. I.e. Text or brightly colored clothes.

DavGoodlin
09-02-2016, 10:12 AM
Its been a while since Ive had a problem like this but it IS similar to how mine would behave under high-contrast and never happened with green IIRC. My 25V-crt was good and balanced but not like new.

So, it may be a CRT fault that is bore out by how fast the blue and red need to cut off. The white parts of the picture occur when all three CRT grids are as positive, and cathodes as negative as they get. It is probably not a demodulator issue, but its after that stage is the R-Y and B-Y possibly "ringing " as opposed to switching. In bit parlance, it needs to be de-bounced.

One book that may offer insight is the Tab Book - Motorola Color Service Manual by Forest H Belt. Ill check and see if this is discussed...

maxhifi
09-02-2016, 10:26 AM
Its been a while since Ive had a problem like this but it IS similar to how mine would behave under high-contrast and never happened with green IIRC. My 25V-crt was good and balanced but not like new.

So, it may be a CRT fault that is bore out by how fast the blue and red need to cut off. The white parts of the picture occur when all three CRT grids are as positive, and cathodes as negative as they get. It is probably not a demodulator issue, but its after that stage is the R-Y and B-Y possibly "ringing " as opposed to switching. In bit parlance, it needs to be de-bounced.

One book that may offer insight is the Tab Book - Motorola Color Service Manual by Forest H Belt. Ill check and see if this is discussed...

Thank you! I need to check eBay for that book! Also, I can add a bit more information now. The G1 voltage is derived from a voltage divider off 230V B+, with a 27k resistor in series with a 10k resistor. I woke up this morning and decided I had to check G1 voltage, and It is 0V. The 27k resistor must be open. Not sure how this is related to other problems, but I can't imagine it helps the CRT to work properly. Will try a new resistor after work (no time for working on TVs this morning!)

old_tv_nut
09-02-2016, 11:51 AM
As stated above, this is due to the video output transistor in that color saturating, that is, driven to the point where the collector-emitter voltage goes to zero or minimum possible. There may be a video drive limiting adjustment somewhere or a bias or G2 adjustment that will improve it. It can occur if the particular CRT (due to either original tolerances or age) requires cutoff voltages that then make the video outputs be run at low collector voltages. Referring to service info that shows the scope traces at the cathodes can tell if the outputs are biased lower than usual even though the video B+ is normal.

[Edit: oops - I just saw your post about G1 being low. This will definitely cause this problem, because the cathodes now must be lower also so that the CRT is not cut off.]

maxhifi
09-02-2016, 12:02 PM
[Edit: oops - I just saw your post about G1 being low. This will definitely cause this problem, because the cathodes now must be lower also so that the CRT is not cut off.]

Probably I should have checked this up front, chalk it up to a lack of experience. It also makes sense logically to me because the brightness control has to be in the top 1/3 of its range to produce a picture at all. I guess the low bias on G1 is requiring the video outputs to be driven into clipping to get a picture, and the effect is more noticeable with saturated colors. Will be interesting to see what happens when G1 is at the correct 94 volts instead of stuck at 0. Also not sure why the resistor went open (if it indeed is open and not a shorted G1 or shorted 10k resistor)

As an aside I find it interesting the video amplifiers are just wide open transistor stages with no negative feedback to control gain or improve linearity. This really is an early model solid state design.

Electronic M
09-02-2016, 12:16 PM
TVs ain't HiFi audio amps....Feedback is rare (ignoring AGC, and sweep oscilators).

maxhifi
09-02-2016, 12:23 PM
TVs ain't HiFi audio amps....Feedback is rare (ignoring AGC, and sweep oscilators).

How about in more modern stuff based on ICs? Any sort of op amp would
Never be run open loop. I ought to study some schematics of some newer stuff just for education purposes.

This Moto is my first foray into solid state TV repair, everything TV related
I've done prior has been tube based.

Electronic M
09-02-2016, 03:56 PM
1978 is about my cutoff on how new a set I'll fix. Can't tell ya if and how the newer SS stuff works.

old_tv_nut
09-02-2016, 03:59 PM
I think you are more likely to find CRT drivers with feedback in computer monitor designs. Usual TV drivers were class A resistive loads, with large power dissipation. Like tube video outputs, they were run with the maximum gain possible to reduce the need for multiple earlier stages. Transistor sets, especially once video ICs were introduced, still commonly used class A outputs, only now there were three for R,G, and B. Push-pull outputs were also developed ( I remember them in European sets)- much less power dissipation, and less hefty transistors could be used, but the CRT arc protection had to be better to avoid frying the smaller die. The class A outputs would get quite non-linear at high frequencies and large signals due to the capacitive loading of the CRT, but it didn't make much difference for a 3 or 4 MHz bandwidth video signal - just put in emitter peaking capacitance to get enough amplitude and don't worry about the shape of a 4 MHz sine wave. Computer monitors needed more bandwidth, and hence more complex design; also compromises like even more output current and dissipation, less output swing, etc., etc.

The above is my partial knowledge and memory of the status of things in the mid 80s, so I am sure there is more to learn.

maxhifi
09-02-2016, 06:37 PM
So new resistor installed and the problem is 90% fixed. g1 is at 95 volts as per spec m. Still a bit of bleeding on very saturated colours, like fine block letters on a black background, but the picture is genrally superb. Way better than my RCA CTC38.