How big is the sync pulse at the plate of V20 (pin 2)? Any chance that C306 or C307 are accidentally too large in value? Like a .01 in place of a .001 uF? Certainly looks like the sync separator is working; it may simply be that the pulse making it to the vertical oscillator is too small. Incorrect values on those capacitors (or the associated resistors) might be a culprit.

C306 and C307 are correct values.
I moved the Speakers 220 ohm connection from the 275v B+ to the 265 B+ and the Vertical Hold synced. But, when the audio is turned up it jitters the video.

I'm wondering if the issue is a) something to do with the AC to DC circuit, or b) something about the speaker transformer loading the circuit.

Noted that the Damper tube is a 25AX4 while the SD states that it should be a 25W4. Thought hmm. Noted that the 25AX4 has more pins than the 25W4. Still swapping a 25W4 did not help.

Carl

I seem to remember that the 6AX4 was an improved type over the 6W4 (and by extension, the 25V versions as you have) - something about better insulation between the cathode and heater? (especially given this tube's typical role as a damper tube)

It looks like there is an intermediate B+ voltage developed somehow and that this is bypassed to ground by C278 (if that part of the schematic matches what is in your set). Check that line and also the various B+ lines with your scope and see if you see audio on any of them with the volume turned up. Set the scope to AC coupling so that you can use a sensitive scale. Also, it sounds like there is too much ripple on the 275 volt B+. Perhaps you got a bad batch of electrolytics in the power supply.

I have seen shorts, or, leakage problems on primary of audio output transformers to ground.
Insulation breakdown.
Any chance, does transformer get warm after playing awhile?
If so, there's your problem...
Bill Cahill

Tom, Bill ... thanks again.

Tom, I checked the B+ supplies and no audio even at maximum.
C278 ... I can't find on the Schematic.

Bill, I ohmed the Speaker and there is no short to ground.
On the Secondary, one lead is to the frame.
I removed the speaker and isolated it from the chassis - but no improvement.


I did find a discrepancy on V16 - there was a 680 ohm and a 15K resistors where the Schematic called for 33K and 68K. I replaced those ... still no joy.

I put my Scope on the 25L6 Audio Output Tube and B+ 265v:

Top waveform: Grid, pin5 V19 - 50mv/div
Middle waveform: Plate, pin3 V19 - 500mv/div
Bottom waveform: 265V B+ - 100mv/div

All probes were x10 - so I got 1.2 volts ripple on 265V B+.
Time base is 5ms/div - 60hz waveforms.
The volume control was full minimum - looks like the tube is amplifying the 60hz ripple - giving a 7v hum on the plate - or is that the 60hz Vertical Sync pulse we are sending into the Audio Amp - hmm.

Had some difficulty adjusting the picture.
This is about as good as I can get it centered:

Tom, you were right about not putting too much faith in the Sencore CR70 Cutoff test - this tube still looks pretty good even if it failed that test.
The Focus Coil has a much bigger diameter than the 10BP4. I assume that is the way its supposed to be.

Carl

This may or may not be a case of looking at different schematics. Lets try it this way. Look at your schematic and find the 6SQ7 1st audio tube. Find the line that is connected to pins 3,4 &5. That is the line I am thinking of. Follow it around the schematic. On the one I am looking at it runs around to the side and then up to the top. Over a little I see a 150 mf electrolytic. Scope that line to see if it has audio on it at full volume and see if that electrolytic is there and connected in the set.

On that 6SQ7, pins 3,4,5 do not have audio on it even at max setting.

Here is the Schematic I have for the "W" version of the GE 805:
http://cerant.com/TV%20GE%20805%20-%201 ... /SD/SD.PDF

Those two little circuit boards make tracing circuits very difficult.
I now know what you guys were talking about when you warned me about these TVs.

Carl

Ah, that is a little different all over. And I see that the cathode of the 1st audio goes to ground in this version.

Well, you have audio showing up where it should not be. And it sounds like you have 60 HZ getting into things too. If the coupling is not through the B+ (you might scope the 150 volt line and the 275 volt line), there is another possibility. If there is a poor connection in the ground wiring, some points that should be ground might not be. Pick one point to connect your scope ground to and then look at the grounds at several places. Such as, the ground ends of the power supply filters, the ground end of the focus coil, the ground end of the 180 K resistor below the cathode of the audio output, the ground end of C354 (bypassing the focus coil), the cathodes of the video amps & any other place that you think to check.

After that, call the witch doctor.

SOLVED!!

Well Tom, I finally figured out what the problem was.
I highly suspected it had to be something dumb and it was.
I'll go sit in the corner and put on my dunce hat:-)

When I stuffed the two Electrolytic cans with capacitors, I did the middle can correctly.
When I stuffed the Electrolytic can on the side of the chassis (C358, C354, and C297), I wired all the negative leads together but did not feed a wire down to the bottom for the common. For the hum I was getting in the speaker, I previously paralleled a capacitor across C358. So, the symptoms were entirely because of C354 and C297 not being in the circuit. In essence, these two Electrolytic capacitors were out of the circuit - in the Vertical Output and Focus circuits. Your last post to check the Electrolytic piqued my curiosity.

Lot of hair pulling and studying the circuit in this GE 805.
Though it was a dumb mistake, I learned a lot.

Thanks everyone who helped me with this.

Carl

Two posts at the same moment again! Good that you got it fixed!

Thanks. I remember suspecting the Electrolytics and put my Capacitor Meter on them.
I did not get a reading but dismissed it because it was connected in the circuit and I did not want to take the time to disconnect leads to test.

Carl

Good detective work! Missing or incorrectly sized electrolytic capacitors can have surprising and hard-to-track down effects. Hum is the obvious problem, but stuff like poor vertical stability can also result. I had a problem with a Philco Predicta with vertical problems that I traced to an incorrectly sized electrolytic that I accidentally put in. (You would think I would have remembered that in this case and mentioned it sooner, but it only comes to mind now that you've mentioned a similar story.) Nice to see a definitive fix, and we've all learned a few interesting things to keep in mind for the future.

I think the next time I re-stuff an Electrolytic can capacitor, this event will be on my mind:-)

Carl

Now, please adjust your width, linearity.
One side is about right. Damper.
Other side is stretched. Horiz. Output.
Note not all the pattern is showing on Horiz. side of picture.
Vert. may also be just a tad stretched. Centering looks perfect.

I told you these sets were the tv from hell!
Bill Cahill
Congrats. You are now as insane as I am........

Bill ... I remember you telling me and you were right on.
I believe you.

I'm going to the ETV Convention and on the look out for a Muntz!!

What are some 1950's TVs that are relatively straight forward and play well?

Carl

Mid to late 50's power transformer RCA.
Late 50's power transformer Admiral.
Some of your worst nightmares follow;
Olympic.
Crosley.
Silvertone.
Airline.
Zenith.
GE.
Air King.
Pacific Mercury.
Anything else odd ball.

Sets to skip. SERIES STRING anything.
Skip GE M4-M6 tv's. Yoour worst nightmare!
Zeniths like to eat yokes, and, flybacks.
I do like one odd ball, that you would never find a schematic for.
deforest Sanabria. Made by American Television companny.
Why? Simple, cheap chassis.
Oh. Skip later Emersons. Just crummy.
Also skip Sonora tv's.
I love the remote control power transformer Admirals.
Some of the Magnavox tv's were also good.
Skip Sentennel. Junk.
GE actually made one deluxe 25" color console tv with power transformer, and, sliding tambour doors that was actually EXCELLENT!
Sylvania made both good, and, bad tv's.
Actually, most did.
But, Silvertone STUNK!
You don't want a slim Admiral portable from about 1959. Manny problems, and, picture tubes are never good.
Same with the Philco "seventeener" series.
Some other Philcos o.k., but, troublesome.
Alot of the tv's with those miserable horizontal diodes are a nightmare.
GE portables of 60's like to eat flybacks, yokes, tubes, electrolytics, and, get lots of poor connections.
The GE Porta Colors are a tech's worst nightmare.
Skip most hybrid tv's, though the RCA hybrids aren't bad.
Muntz is so cheap it's fun.
OH. Skip hallicrafters. Especially early ones, including the 7".
That one has big design flaws with hv osc. coil.
Same with Philco bakelite 7" sets with hv transformer. It's always bad, and, has design flaws.
Is that a good start???
I like the early RCA tv's, though the ones from 40's are a nightmare, and, some of those power resistors are very difficult to find.
Yes, that includes 621, 630 TS, 721 TS, 641 TV,
and, 8TS30.
Great sets, but, power supply nightmares.
Bill Cahill

Looks like everything I've worked on is on your crap list:
- 1950 16" Zenith Porthole - transformer
- 1951 19" Zenith Porthole - transformer
- 1949 7" Emerson 639 - series filaments
- 1949 10" GE 805 - series filaments

Got to admit, much of the debug problems I had with the GE 805 were my doing.
But, I don't like those under chassis wiring boards - they suck.

The Emerson 639 was tight to recap.

The most enjoyable TV so far was my first one - the rusty Zenith Porthole.

All of these, I think, are not really reliable and will soon be back on the workbench even though they have been totally recapped.

Looking for another, different, TV adventure. I'll take your list with me to the ETV as a reference. Thanks

I was hoping that the GE 805 would be a quick recap and back working again. I wanted to use the Sencore VA62 mod, that a fellow on Videokarma came up with, and use the GE 805 as my first attempt to do a TV alignment. The GE 805 sapped my energy and I'm tired of fooling with it. Need a change of scenery.

Carl

Get an early Admiral. Fun sets.
I'm still working on my 16" double D, but, I like them. I think the 7" Admiral would also be a pleasure.
I like the early Rect. from 16" to 21".
The 16" round tube Admiral, while having been jury rigged, has been one of my favorite sets.
Sorry for myopininls on others. You asked...
I can say these things from over 45 years experience.
Alot of these sets were trouble when new.
Bill Cahill

Hey, don't feel bad. I'm trying to get an RCA 1950 19" with doors. KCS 49.
My worst nightmare may be returning.....
Get an Airline 7". Also easy set.
How about a nice Spartan?
Bill Cahill