View Full Version : New '60s Philco Roundie


Hagstar
09-29-2016, 08:13 AM
Well in June I saw this with a SOLD sticker at our local recycle store. At the time I wasn't much impressed but after posting on Facebook about it I decided to frequent the store two or three times a weeks the rest of the summer- like lightening was going to strike twice (we had 2 stations only part color here in the early '60s). But then what reappeared last Fri. but this same early '60s Philco roundie with amp and original turntable (I had thought it was just storage, didn't look at it closely due to the SOLD sticker in June). They had determined to put it aside and research it but decided it was rare but not too valuable. SO they suggested $50- and it's mine now.

They informed me the possible collector interest was well known to them for anything odd like this. I never ever see color sets this old in the "field" here, they are rare enough in NYC or Boston areas where stations were plentiful.

I'm told this uses transistors in the signal chain and isn't a CTC clone, and is a 1966 product? The yellow edge makes me suspect a Zenith-made CRT. Any info before I begin tearing into it (possibly mid-Oct) would be appreciated. 6813931 is what is marked as a model number as far as I can tell.

Electronic M
09-29-2016, 09:55 AM
Awesome score!

Philco had loss leader roundys into the early 70's IIRC. I think that is post 1968 as the control layout looks newer than the 1968 models to me....It is real odd that it is in a combo since I thought Philco only sold them as cheap stripped models primarily in metal cabinets by then.

It definitely has a Zenith style cat...You can cut those off hot or cool with a guitar string, peel the glue, clean and reattach the glass. I have a good removal vid on my photobucket account (that I've posted a few times).

DaveWM
09-29-2016, 10:03 AM
If its the late model with the SS tuner, it will make a nice pic assuming the CRT is good. Weak spot is the HV fly, runs very hot, uses some pulse feed back to regulate the HV, rather than the more traditional shunt tube. They touted it as very high power 27kv for a nice bright picture which it does have.
Not sure why but mine has the best dynamic convergence of any set I own, think others here have the same experience.

miniman82
09-29-2016, 05:52 PM
Yup, same experience here. I've had many roundies, none have had better convergence than the Philco. So close, I'd call it nearly perfect. No fringing what so ever.

Hagstar
10-01-2016, 03:31 PM
Awesome score!
It is real odd that it is in a combo since I thought Philco only sold them as cheap stripped models primarily in metal cabinets by then.

Here's an illuminating ad-

tom.j.fla
10-01-2016, 03:43 PM
Have a combo in storage with date code 11 71 so sold as 1972 model. Has bright deep color and is a hybrid with that PITA color decoder chip. When stored was working and looked like it was just unboxed. All the best Tom.J

EdKozk2
10-01-2016, 09:59 PM
Hagstar,
Did you look insde the set to find a chassis number ? That way you can get the correct Sam's folder. There seem to be many variations of this model from June of 1964 onward. The crt may be a 21FJP22. I am curious too. Nice find.
Ed

zenithfan1
10-02-2016, 04:32 AM
All this talk of perfect convergence makes me wanna get my Philco roundie going. Yours is a great looking set btw.

Electronic M
10-02-2016, 12:02 PM
Here's an illuminating ad-

Going by the control panels (same as my 1965' philco roundy) in that ad, that ad is from circa 64'-66' a time when I'd still expect roundy combos to be a common product.

The set the OP posted looks to be 1968-73 based on control panel aesthetics.

Hagstar
10-02-2016, 02:45 PM
Well I took the back off (chassis #7MT808) and tested the 21FJP22, red was low even running the filament an hour. But after the lowest level of rejuvenation it popped right up to balance with the other guns at the lower end of the green scale.

Here are some photos. At this point I take it I should remove all scanning related tubes, apply power ramping up to line voltage slowly looking for trouble, then reawaken horz then vert oscillators? What I did with my CTC4 was replace every 'lytic and paper cap before applying power but this is obviously mostly "brown dip" caps. Thanks for the feedback so far!

DaveWM
10-02-2016, 04:47 PM
no need to recap, just give it a slow start with the horz out and vert out tubes pulled, power up slow, monitor the B+, stop the variac when it gets to about 375v, check cans for heat, if all good plug in the sweep tubes, monitor the horz out cathode for current and do a full power startup. Don't be surprised if the cathode current is somewhat high, like 230ma IIRC. get it as low as you can but be warned the fly runs hot. upping the contrast makes it run hotter IIRC. Lowering the HV will lower the cathode current, but may end up with not enough horz sweep. Its a bit of an odd ball with the feedback HV regulation.

here is a video

https://www.youtube.com/watch?v=1vKzh33VaWI

Hagstar
10-02-2016, 05:44 PM
I take it I should pull the chassis to measure the horz output current? Or is there some sort of fitting, there appears to be such to the right of HO tube? Normally I'd make a test adapter but I have no Compactron stuff....SAMS not here yet.

John H.

EdKozk2
10-02-2016, 11:39 PM
I found your TV chassis # 17MT80B in Sams 885-2. The set is dated May of 1967. The Sams' shows 220ma on the cathode of the 6KD6 horizontal output tube. The HO cathode is tied directly to ground. Grid #3 is also connected to the cathode. I didn't see any test point .

DaveWM
10-03-2016, 07:49 AM
you can get test sockets for checking HO current, plug the socket in, the tube into the socked. It has test leads coming out that you hook the meter up to.

On mine I installed a small fuse holder with a 275ma fuse. Not sure I would bother doing that again, just something to make it easier to test really.

BTW there are LOTS of ideas on how to deal with 1st start ups. Some go with just plug in and watch for smoke to the more detailed monitoring of everything with very slow startup. Not saying there is a correct way, just different. IIRC the issues I ran into was some cracked solder joint on the color pcb where some high power resistors were. They stand off from the board quite a bit I presume to keep from cooking the pcb, you could tell they were a bit loose just by touching them. There were also some loose feeling sockets on some of the compactron tubes in that same area.

Hagstar
10-03-2016, 08:50 AM
I may go with a simplified start up procedure as I strongly suspect the recycle store already powered this up, can't even be sure they used a variac.

Thanks again, will report.

Electronic M
10-03-2016, 10:20 AM
Sometimes H out tube current test points are there but not indicated on the schematic.
If not present I like to add one as well as protection by placing an above chassis fuse holder in series with the H out cathode...The right fuse will protect it, and I can pull the fuse and replace it with a current meter to check current whenever I feel like it without need to pull the chassis to check.

DaveWM
10-03-2016, 10:41 AM
I may go with a simplified start up procedure as I strongly suspect the recycle store already powered this up, can't even be sure they used a variac.

Thanks again, will report.

Right that's a good point, its often already been started cold full power. Sometimes you will find one with a badly disintegrated plug that clearly not been used in years.

Findm-Keepm
10-03-2016, 10:49 AM
you can get test sockets for checking HO current, plug the socket in, the tube into the socked. It has test leads coming out that you hook the meter up to.



Pomona 2712, 2712A and EBY Cath-2 (interrupts pin 2) will work.

I don't have a GC/Walsco catalog that shows the one for the 6JS6/6KD6, but they probably made one.

DaveWM
10-03-2016, 10:59 AM
ok now I remember, the HV is controlled by a horz bias pot which directly bias's the Horz out. So you adj the HV to about 25kv with that pot. The regulation takes place from feedback from the fly. The problem I ran into was the excessive heat (to the point of severe wax melting and even smoke) so adj the bias down to get the heat down resulted in under scanning of the crt. That was resolved with a HV disc cap across the yoke horz windings. Pretty mickey mouse fix that maybe was not the right thing to do. Perhaps it needed a new fly.. whatever just don't leave the set alone (good idea for any 50 year old color tube set). I think I adj to about 23kv

DavGoodlin
10-03-2016, 12:00 PM
ok now I remember, the HV is controlled by a horz bias pot which directly bias's the Horz out. So you adj the HV to about 25kv with that pot. The regulation takes place from feedback from the fly. The problem I ran into was the excessive heat (to the point of severe wax melting and even smoke) so adj the bias down to get the heat down resulted in under scanning of the crt. That was resolved with a HV disc cap across the yoke horz windings. Pretty mickey mouse fix that maybe was not the right thing to do. Perhaps it needed a new fly.. whatever just don't leave the set alone (good idea for any 50 year old color tube set). I think I adj to about 23kv

Sylvania used feedback from the fly to regulate pulse amplitude to the HOT grid on this on their later tube and hybrid chassis. Didn't Motorola do it also?

Ill make sure to copy these notes into my "Philco Color TV service manual" a Tab book by Robert L Goodman. I have a 19" chassis version of this set and its fly runs hot.

Few color TVs had a tuning meter or tuning eye tube. The OP's model might have the tuning eye tube. Only GE had a tuning device on their 1967-68 color sets and Westinghouse had that on-screen bar graphic on that one-shot chassis before they quit making Tvs. otherwise, I never saw visual tuning devices on an RCA, Zenith, Mag etc

Hagstar
10-03-2016, 04:29 PM
This little terminal board with jumper seems like it may very well be a test point. Seems I will add a fuse in place of jumper if so.

Electronic M
10-03-2016, 04:33 PM
Probably is the jumper (some continuity tests/circuit tracing should tell you for sure)...The picture is blurry enough that bigfoot ought to be in it. :D

Hagstar
10-04-2016, 07:30 PM
Few color TVs had a tuning meter or tuning eye tube. The OP's model might have the tuning eye tube.


I noted tonight on first fire up there is indeed an eye tube. No heating of filters, swear I hear horz sweep running yet no high voltage. The 6KD6 and most of the other tubes are Philco brand and look tired, I happen to have saved a couple NOS I came across for no other reason than they are pricey :)

The radio works, and phono cartridge but no motor action. But the whole combo looks remarkably unmolested, although as yet the TV chassis is filthy. SAMS is coming, today I got a Goodman Philco service manual from 1970.

John H.

philcophan
10-06-2016, 09:56 AM
Nice find, John!!! My personal opinion, in those days, is that Philco sets produced THE most perfect flesh tones, hands down, of ANY set out there...!!! I lusted after one as a kid, but it just wasn't in the cards... one day...

Jim

DavGoodlin
10-06-2016, 01:13 PM
Nice find, John!!! My personal opinion, in those days, is that Philco sets produced THE most perfect flesh tones, hands down, of ANY set out there...!!! I lusted after one as a kid, but it just wasn't in the cards... one day...

Jim

Much of Philco advertising and shop signs had a butterfly to highlight this. Ads invite you to "take the face test" and compare fleshtones. :thmbsp:

These use some 6BL8s instead of all 6GH8s, though there is lots of both in there. The "SS" on the front refers to the tuner and IF strip only, mine had good reception before DT but it hates signal from the set-top box.

Worked on one of these wayyy back in HS VoTech and it did look good when we sent it on to a needy family IIRC. These were also loss leader sets for like $299, yes?

Can you get a neon lamp to light holding it near the 6KD6 cap? Watch for a shorted 3AW2 also, pull the cap then look for arcs. Hope its not the Fly. Think I have a leftover diagram for a replacement fly

Steve D.
10-06-2016, 02:28 PM
The Philco "Butterfly" & "Face Test" ads:

-Steve D.

Hagstar
10-06-2016, 06:07 PM
. Hope its not the Fly. Think I have a leftover diagram for a replacement fly

Why for me is it always the fly? It sure don't look healthy, and indeed reads open. Tripler time again perhaps. BUT my old pal Shango066 on youtube claims one can easily substitute another fly. 3AW2 is shattered at base, note soot.

The horz. output section seems to be intact but fly "tire" is open. But there's no horz. output voltage either so without a high voltage fuse what's also blown up I wonder?

Electronic M
10-07-2016, 07:37 AM
A good place to start is by measuring base voltages on the H output tube. If the osc. is dead or malfunctioning(manifested in grid voltage), the screen bias network is damaged, or the cathode ground wire is open, then the output tube will not drive the fly properly. I'd change the HV rect and try to get the H out tube workin right. HV has a funny way of re-welding closed or bypassing small opens, and you might get lucky.
I'd be more concerned if it failed a ring test (granted you need the HV winding to ring it IIRC), or windings other than the HV were open.

DaveWM
10-07-2016, 11:02 AM
Why for me is it always the fly? It sure don't look healthy, and indeed reads open. Tripler time again perhaps. BUT my old pal Shango066 on youtube claims one can easily substitute another fly. 3AW2 is shattered at base, note soot.

The horz. output section seems to be intact but fly "tire" is open. But there's no horz. output voltage either so without a high voltage fuse what's also blown up I wonder?

how are you checking the open on the fly? IIRC that is a little funky, like the tire HV is isolated from the rest of the windings with some high resistance power resistors. Start from the anode of the focus rectifier (pin 6 of the fly) to the plate lead for the HV tube. 540 ohms

Hagstar
10-09-2016, 12:04 AM
Start from the anode of the focus rectifier (pin 6 of the fly) to the plate lead for the HV tube. 540 ohms

This reads a steady 109 megaohms.

John H.

rob Cashin
10-10-2016, 07:45 AM
How did you make out on powering the set up?

Hagstar
10-10-2016, 09:33 AM
How did you make out on powering the set up?

The flyback has been cooked to open, see previous posts. Waiting for tubes for more testing.

John H.

miniman82
10-10-2016, 10:38 AM
Take the tire off and see if the break is near the surface, if it is you might be able to repair it. If not, like you said you can always do the tripler mod.

DavGoodlin
10-12-2016, 09:09 AM
The HV rect plate lead broke off of a 1955 GE flyback because it was super stiff and I was not careful pulling it off, where the 1B3 was outside the fly "can".

Wax was already crumbling off the tire so I was able to make a connection just a few turns short, use an exacto knife and hyper-eutectic solder. Shmutz with black RTV when done. I wish you good luck.

Radiotronman
10-17-2016, 10:05 AM
I've got a Philco roundie too and believe they have the most comparable picture to more modern sets. Great find and I wished mine had the eye tube. The mIssing control door seems to be common on these sets too.

Hagstar
10-30-2016, 01:23 PM
Brought this Philco white elephant in from van finally and fired up by degrees with variac. Like in another thread- http://www.videokarma.org/showthread.php?t=253593 - my focus coil is blackened and began to mildly smoke. BUT I ordered a new Workman replacement from Talon (edit- not Frontier Electronics)!

WHY do these burn up is what I want to know.....

Findm-Keepm
10-30-2016, 03:12 PM
Link to Frontier? My CTC16 smoked it's focus coil, and is now using my only replacement....I'd like to order one too.

Edit: My CTC16 set had a bad focus rectifier causing the focus coil to burn up, so I replaced it with a solid state one, but you never know...

Hagstar
10-30-2016, 03:35 PM
Talon not Frontier sorry, and I seem to have purchased the only one but Playthings of the Past has a ctc15 one and a couple others.

http://www.talonix.com/shop/category.aspx?catid=34

Hagstar
10-31-2016, 12:56 PM
Answering my own question- per a Philco repair manual focus coils on these models may have two "sharp" positions and using the wrong one may cause overheating.

Hagstar
10-31-2016, 01:45 PM
And NOW Moyer Electronics is sending me a $50- NOS flyback!!!!! :banana: Already ordered a cheap tripler BUT this is much better.:yes:

DavGoodlin
11-01-2016, 04:18 PM
And NOW Moyer Electronics is sending me a $50- NOS flyback!!!!! :banana: Already ordered a cheap tripler BUT this is much better.:yes:
Way to go! - :thmbsp:

Hagstar
11-06-2016, 01:39 PM
The new focus coil is installed the Philco- no more burning there, old flyback still in. But though screen of the horz. output tube is fed the right voltage of B+ once the tube *warms up* it plummets to like 70 volts from 260 even though cap plate lead is off. Grid input voltage is a little off specs at -55 (listed as -60). Another mystery.

kvflyer
11-06-2016, 02:49 PM
The new focus coil is installed the Philco- no more burning there, old flyback still in. But though the horz. output tube is fed the right voltage of B+ once the tube *warms up* it plummets to like 70 volts from 260 even though cap plate lead is off. Grid input voltage is a little off specs at -55 (listed as -60). Another mystery.

Grid emission? High power tubes are suspect.
Do you have a new Horizontal Output Tube?

DaveWM
11-06-2016, 05:00 PM
check the HV setup pot. It bias the H Out tube, so it setting will directly effect the voltage reading.

Hagstar
11-07-2016, 03:40 PM
I have the answer- massive arc-over of the high voltage insulating cup under the high voltage rectifier. Ordered a new one.

Electronic M
11-07-2016, 05:19 PM
I have the answer- massive arc-over of the high voltage insulating cup under the high voltage rectifier. Ordered a new one.

Sometimes that can be fixed. I had a zenith color port set that arced through the bottom of the cup. My solution was to drill out the carbon arcing path then use Permatex gray silicone to fill in the hole...It worked well and was almost a free repair.

Hagstar
11-07-2016, 06:28 PM
This cup though was toast. I cleaned it with every solvent but carbon is deeply incorporated into the plastic over a lot of it.

We do have a cause of death here- severe arcing over the insulator cup blackened the whole bottom of the cage and overloaded the flyback system.

Hagstar
11-09-2016, 09:05 AM
I find fixing vintage stuff there are these days that seem like weeks waiting for parts to come. This thing wanted to wake up but the old HV cup is like poison- catnip for anything that wants to arc.

I need the parts to come soon before I lose momentum. My CTC4 was on the bench a year like this.

Findm-Keepm
11-09-2016, 12:17 PM
Sometimes that can be fixed. I had a zenith color port set that arced through the bottom of the cup. My solution was to drill out the carbon arcing path then use Permatex gray silicone to fill in the hole...It worked well and was almost a free repair.

+1 - works every time. The Silicone Rubber has a higher volts/mil rating than the plastic in the cup - the cup will go before the patch!

RTV3145 is the best for HV applications - it's electronic grade, self wets, and cures in 6 hours or less. Navy avionics owes it's success to RTV3145 - it solved many arcing problems in F-14 (AWG9) radar power supplies, sealed chaff buckets, and I used it to cure arcing in a Conrac monitor used in the CATIIID bench that troubleshot modules. Great stuff.

DavGoodlin
11-09-2016, 02:05 PM
+1 - works every time. The Silicone Rubber has a higher volts/mil rating than the plastic in the cup - the cup will go before the patch!


+2 a similar repair is still holding in a 16" Zenith color portable.:thmbsp: There was a full metal cap behind the HV rect cup, drilled out the pinhole the arc made and plugged and coated the cup bottom with black RTV.

Hagstar
11-09-2016, 04:09 PM
In this case though the entire cup is baked to a light brown color with spider webs of carbon deep in the plastic. Discharge paths cover most of the area around it in the cage.

Hagstar
11-17-2016, 07:11 PM
HOUSTON WE HAVE RASTER :rockon: https://youtu.be/QniUxBgu3CY

John H.

Tony V
11-17-2016, 08:14 PM
That's awesome news! Congrat's!

Electronic M
11-17-2016, 11:07 PM
Sweet! Looks like it is only an evening of adjustments away from a good picture.

zenithfan1
11-18-2016, 07:50 AM
Nice! :D :banana:

Hagstar
11-18-2016, 09:07 AM
It looks like the set was fired up in a basement or garage with the copious dust I removed on it plus some moisture from a quick warm up. It had some latex paint rings characteristic of a Garage Period. My TV mentor Keith Park killed a TV once powering it up as a kid in the garage- an arc from the anode hit the cold glass.....boom.

John H.

Hagstar
11-19-2016, 02:58 PM
Odd symptom- high voltage takes 90 sec to appear at all, then over next minute or so builds but only to 21 kv. I am replacing 3.8 and 1000 ohm resistors under rectifier.

Interesting to note this was built at the factory with a rebuilt CRT. Philco got a lot of flak for this as I recall.

Hagstar
11-22-2016, 05:53 PM
Fixed high voltage issues. Just rough convergence so far but finally an okay picture :yes: My next puzzle is that the AGC doesn't work though the pot seems to measure and function normally. Only just the right fairly weak signal makes an image, it overloads at the drop of a hat.

https://www.youtube.com/watch?v=Uj-wk-OtwzE

John H.

Hagstar
11-24-2016, 12:03 PM
Thankful today for this forum- our little corner of the world for our bizarre specialty.

Does anyone know WHY Philco put over 100 volts on the early transistors in my set- in a signal chain where such voltages are dangerous and not needed it seems?

Hagstar
12-30-2016, 07:11 PM
Clues appreciated on the add warmup problem here- see video notes- https://www.youtube.com/watch?v=rLD2Pqtoo-g&feature=youtu.be

Hagstar
12-31-2016, 01:59 PM
Electrolytics are all OEM in this set, no heat or current excess but I will now replace them.

Electronic M
12-31-2016, 05:43 PM
Look at tube heaters as it does it's warmup cycle. I had a RCA set that lost green during warmup and intermittently with long cycle time. It was a bad socket...Also reflow solder on ground stakes on the PCBs...They get flaky and are heater and signal/B+ ground so if one or more open even temporarily they can cause REAL odd problems

Hagstar
02-18-2017, 10:16 PM
Well after months of head scratching and breaks for other projects I finally solved the slow start and AGC issues. I did a full 'lytic recap but I think the starting issue was a cold solder joint or two, fixed a few. After checking everything else replacing the pulse gate transistor brought back AGC voltage even though it seemed to test fine in place (this set is solid state front end, color and sweep all tubes). An NTE123A as OEM however did not last long in circuit- this transistor is where the hybrid part happens- the noise inverter tube provides a static 160 volts across the transistor with 35 volt peak sync pulses so it has a hard life. I swapped it out for a video driver NTE 128 transistor and voila, almost normal picture and proper AGC action.

Steve D.
02-19-2017, 01:29 AM
Just found this Philco roundie ad from Aug. 1967. Promoting it's under $300.00
color TV.

Hagstar
02-21-2017, 11:11 PM
Built December 5, 1966

Success! The Philco stereo phono/AM/FM receiver section is in and sounds great relatively speaking of course. Also last week I managed with the invaluable help of Chris Cuff's videos to clean and tune up the Philco badged Voice of Music record changer model 100C. The receiver's volume issues turned out to be simply dirty pots. I remembered low voltage modern circuits are like that. Either adding metal cabinet extension speakers (it has RCA jacks for them) or adding better speakers would be good as the 4 GE2 transistors manage to overwhelm the speakers which appear to be 2 oz magnet single 8" cone. The TV just uses the usual little speaker and can't play thru the hifi, could be arranged with some sort of switch box.

I had to repaint the top of the main tuning cap housing due to rust but otherwise I just cleaned it with brake cleaner, DeOxit for the pots, bits of lube for pot shafts and dial drive. Oh and a resistor and LED tuning light was added to replace dead OEM bulb (lower left).

December 5, 1966 (Monday)
In a case frequently cited as an example of the phenomenon of spontaneous human combustion, Dr. John I. Bentley, a 92-year old retired physician and surgeon, was found dead in his home in Coudersport, Pennsylvania. An Associated Press report noted only that he was "found dead in his Potter County home Monday, apparently the victim of a fire" and that "His clothes and the floor were partially burned." [17] The facts were more gruesome, because a meter reader found only a pile of ashes, and that the only identifiable portion of him was "his lower right leg, still clad in its bedroom slipper, and his walker, which strangely enough suffered little damage", as seen in a famous photograph of the death scene.[18] Some authors have blamed spontaneous combustion [19] Other authors point out that the leg as "lying at the edge of a hole about two and a half by four feet that had burned into the basement" and that Dr. Bentley was a pipe smoker who had previously been burned from dropping matches, or hot ashes, onto his clothes. A plausible theory was that Bentley had accidentally ignited his robe, attempted to douse the flames with water from a pitcher, ignited the linoleum floor the hardwood flooring and wooden beams beneath it.[20]
The United States Supreme Court ruled unanimously that Julian Bond had been improperly denied a seat in the Georgia House of Representatives after winning two elections to the state legislature. The Court concluded that the basis for the disqualification Bond's criticism of American policies in the Vietnam War) had been a violation of Bond's right to free speech. "Legislators have an obligation to take positions on controversial political questions," Chief Justice Earl Warren wrote, "so that their constituents can be fully informed by them," and added that the denial of the seat "violated Bond's right of free expression under the First Amendment".[21] The House would, reluctantly, administer the oath of office to Representative Bond, along with all the other members, on January 9, 1967.[22]
The successful musical I Do! I Do! opened on Broadway, at the 46th Street Theatre, and would run for 560 performances. The entire cast was limited to two actors, and only one set, as the play followed the course of a 50-year marriage. Mary Martin and Robert Preston were the first to perform the roles of Agnes and Michael Snow.[23]
Buffalo Springfield's self-titled debut album was released.

DavGoodlin
02-22-2017, 09:04 AM
Ah yes, last of the US-built solid state radio chassis. Philco would later shift this work to Taiwan, still a decent product but not so easy to work on. Nice work.

Hagstar
02-22-2017, 02:13 PM
I noted in my Philco manual that later hybrids used a low voltage not high voltage transistorized TV AGC system- I bet they had plenty of trouble with the pulse gate transistor.


Still odd the used video output tube works but a new one creates only a very dark picture. This chassis controls brightness via the video amp.

BigDavesTV
02-24-2017, 01:06 PM
Here's a few shots of my '67 Philco Roundie, that I bought from the original owner. He bought it new and put it into service in November, 1967. He had a custom laminated glass cut and edges polished, for the top of the set, to protect it's finish! The way I have it displayed, is the way I found it, with a "condensed operating instruction sheet" under the right-front corner of the glass, with a note written on it in his pen. This TV was still connected directly to an outdoor antenna (no D/A converter box at all), so it must have had occasional use up until the 2009 changeover, as we have no analog stations on UHF, or VHF whatsoever, here. Every tube in this set was the original, I had to replace, IIRC, 3 color circuit tubes, I believe all three were 6GH8A's (no surprise:). New 3.58 crystal, new Vert. HT. pot, to replace the broken one that he likely tried to adjust, at some point, with the wrong tool! CRT is original 21FJP22A Philco, and I had to perform a mild gun-cleaning restoration, it's cataracted and somewhat "tired" but will do for now.

Hagstar
02-24-2017, 06:25 PM
I do have a vexing issue still with the AGC that I don't understand. Originally I had no AGC voltage at all. After changing the two AGC diodes and both gate and amp transistors I do have voltage of 3-6 volts depending on AGC control setting. BUT there's an 8 volt zener that spills voltage into the tuner AGC line and I never get voltage that high. A high signal input from the test equip. increases voltage from 5.5 to 6 volts, that's it. BUT the schematic calls for around 5.5 normal with signal so I'm not sure what's right. The service manual for similar models says I should be able to get 2-14 volts....

Pulses controlling the AGC gate from the coil on the new flyback are weak on the positive side through the diode but strong on the negative side....

Electronic M
02-24-2017, 07:20 PM
It's hard to read the schematic well enough to tell, but two thoughts come to mind: 1.) the zener may be meant to keep the tuner signal under 8 volts in the event of AGC failure to protect the tuner. 2.) they are using the fixed voltage drop off the zener to increase the DC voltage level going to the tuner relative to the IF AGC bus.

Once you start looking at SS gear schematics you start to find all sorts of clever ways to take advantage of the new properties of SS devices.

Hagstar
02-24-2017, 09:03 PM
No the zener serves a delay function to prevent any real AGC voltage on the tuner until signal strength gets high per the manual.

Another clue- if I add a 9 volt battery to the pulse gate terminal that brings more voltage into the gate transistor collector and tap the connection I can see it shoot up to 10 or more volts. The HOT winding is so simple but for some reason I'm only getting a pulse of a few volts here instead of the 30-35 expected.

sampson159
02-24-2017, 09:08 PM
my dad bought a philco roundie back in 1964-65.sun tv and spanky mcfarland was there to help promote the products.philco ford with the blue tuning bars.set had a great picture,actually as good as the zeniths and rcas.we had that set for years,with very little trouble.sold it to a neighbor and they had it for years.i hit the crt a few times and it would hold up for about a year before it would fade.never another problem.the chassis ran on original everything for almost 25 years