Zenith 25DC56 console TV acquired!
 

Well, it all worked out. I went to that estate sale today and picked up this Zenith for a whopping $20. It's got its problems though. There are numerous wiring problems involving the flyback and the tripler. The CRT socket is also melted. Other than that, it's not too bad. It has the original tube which is a 25VBQP22. I do like this TV quite a lot. I plugged it in for a few seconds - there is audio, but no HV.

Congrats on the pickup!

About three hours later, and I finally got the set cleaned up. If two words could describe the set as found, they would be HEAVY and DISGUSTING. It's still heavy, but cleaning it up made a world of difference.

Here is the 25DC56. If you look near the flyback, you can see some loose wiring and on the tripler there is some very thin wire that's barely holding on.

That is a good looking set and it looks like new after you cleaned it! Good luck restoring it and I look forward to seeing your progress.

Thanks, Radiotronman. I'm going to call up my friend Danny and ask for his consensus on the melted socket and no HV. I'm really looking forward to watching this set. I've been wanting a delta gun Zenith for quite a while now.

Yep they are as ever. When i had a service call it was to an apartment and seams like it was on the top floor. if I had to take it back to the shop for bench work i had to take it down 4 or 5 flights of stairs. they are greats sets loved them they were and still are the best chassis ever. <y back harts thinking about it lol. i happy for you good luck with it.

if i was you i would find and spare Tripler and focus divider.

Oh boy. If I had to carry this thing down five flights of steps, I'd find another job. By the time I got it to the truck (with the help of two other men,) I was exhausted. And I'm 6'5".

On the socket pic the melt down is at the focus pin(9) and on the flyback pic i see 2 of the nasty white 22-5001 safety caps, check them 1 or more or open to cause that kind of damage to the socket. Check H.O.T.,damper diode, video output transistors and video driver transistor to start. When the safety caps open H.V. skyrockets also check the CRT as it may be ruined. Hopping for the best,Tom

Thanks for the information. I really hope the CRT is still good. What I'll probably do is replace those blown caps and replace the CRT socket. That much I can handle. Anything more than that and I'll probably need help. I'm going to the radio club this Saturday - I was told that there are some CRT testers there that they want to get rid of.

this will be an easy restore for you.a little solder here and there and your in business.dont worry,crt will be like new

I sure hope so. I don't have a test pattern generator to do any convergence or purity or anything. I'm going to take a look at those capacitors and replace them and replace the CRT socket, and hopefully, I'll be in business.

I've been informed that you have to replace those white safety caps with proprietary caps. I didn't know there was a such a thing as proprietary capacitors, but OK. I'm taking the chassis down to the radio club this weekend to give it a thorough cleaning.

Yes you MUST. There are 2 on the flyback & 3 more under the chassis.
They are 22-5001 Zenith OEM. If you cant find them check with
findemkeepem (sp?) he can point you to the RIGHT substitute.
You can use almost any socket. The only difference in Zenith
sockets I ever found is lead length & push on connectors.
The tripler has been changed & focus divider deleted. If you change
it back USE OEM. IIRC the divider is NOT the common 800-616 kit.
Check with someone with a parts book for subs. IIRC its 63-9898
but its been years.

Here is the scenario...
One or more caps opened & the HV & focus went up. That
caused the socket to arc, the divider to crack or melt then
finally the tripler to burn or open. A butcher moused the set
but left it with bad caps so it happend again. Now odds are the
tripler is gone again.

73 Zeno:smoke:

I talked to Danny yesterday, and he told me that he had some proprietary capacitors he would give me the next time I go over there. I'll guess I'll also replace the tripler. Anyone know the part number of the tripler? Do y'all think the horizontal output transistor is still any good? I checked my tripler inventory, and I have four of them. ECG533, ECG534, ECG535, and ECG550.

Do you have a DVD player? Can you burn a DVD?

If yes then here's your test pattern generator:
http://techpreservation.com/dvddl/testdisc.htm

I'm not too concerned with test patterns right now. My main concerns are those three safety caps, the CRT socket and the tripler. When I get a raster, I'll proceed from there. I can't burn a DVD anyhow - all that computer hogwash confuses me.

I don't remember seeing a value on the replacement caps, only a Zenith part number. IIRC, they were a carefully selected value, with a close tolerance.
I never subbed Zenith HV parts, as Zenith had one of the oldest and best distributors located in Milwaukee. It was very seldom, that they had to order anything. Their stocks were that complete! :thmbsp:

Those Caps. are .0018mf @ 1.6KV.

What I've done B4 is replace all 5 caps. with one 800-616 ( .01mf @ 1.6KV )

Ed

I was thinking about that very thing myself! :thmbsp:
I haven't worked on one of those sets for probably 30 years and of all the Zeniths I have, I don't have one of that model. :sigh:

I really don't see what's so special about the 22-5001 special cap. I mean it's just a capacitor - I didn't know it was that critical. If I used a .0018 with at least a 1.6 KV rating - what difference does it make? I took the 25DC56 out of the cabinet today. I'm going to take it to the radio club and clean all the controls and whatnot. I'm also supposed to get a CRT tester.

Some discussion of the safety cap issue here:

http://www.videokarma.org/showthread...nith+capacitor

jr

Interesting thread. I'm glad I learned that polyester caps can't handle the high voltage pulses. Polypropylene it is. I can't wait to get this TV fixed - I already know where I'm going to put it. I'm keeping my fingers crossed that the CRT checks good. Assuming I get a tester tomorrow.

I took the tuner out of the set and used up the last of my tuner cleaner on it. Not the Tun-O-Wash - but my newer Radioshack stuff. Even being a gold tuner, it was still very tarnished.

Good news! The picture tube checked good on my new RCA WT-115A. All three guns checked right around the same.

We also replaced the white safety caps with .002 at 1600 volt Sprague Orange Drops. Everybody there seemed to think that those caps would be just fine in there. If they're not - I'll just have to take them out again.

i just aquired a flat chassis today.had high voltage with a vertical collapse.cleaned the module and controls,voila!a working set with a beautiful crt.the cabinet is a mess but the set will also require a tuner rebuilt and full restore on the cabinet.the crt delivered a fine,razor sharp pic today.it was a trade from fellow vker Os X.i couldnt make the etf today but we made some nice trades.i got a nice bugeye zenith with stand and a zenith full tuber that needs some help.all told,good day and met a really nice fellow

Nice! I always find it fascinating with both radios and TV's that the set with the cabinet in good shape will almost always have a chassis in bad shape, and a set with a very poor condition cabinet will have a chassis in good shape - usually working out of the box. I find this phenomenon to be very consistent. Take my Zenith Chromacolor for example - the cabinet is in near mint condition, but the chassis has suffered a meltdown.

Orange drop style caps were the better and later safety cap option.

Good. I was informed that even though the new caps are only 200 picofarads higher than the original, it could still affect the horizontal deflection. I guess we'll just have to wait and find out. I'll also be deleting the instant on feature.

Thanks for the link for the video DVD test patterns. My color bar generator has seen better days, and this make's it so easy to display several different patterns for convergence and purity, along with resolution patterns.

Dont worry about the instant on. If all tube chassis I would delete it.
If you are worried about the CRT keep in mind most Zeniths from
this era had it & the CRT's are the longest lasting of any ever
IMHO. Not much heat generated & not a lot of power used.
In theory & my opinion keeping the CRT warm eliminates most of
the hot/cold cycle & expansion / contraction that kills things.
All tube sets especially built on PCB's suffer from extreme drying
out of everything & risk of fire. Thats why cats love to sleep on them !

73 Zeno:smoke:

I admit that the CRT's life was a factor in my decision, but that's not really my main concern. I just want the longest warm up time because I'm weird that way.

well my flat chassis bit the dust after 3 days.big snap and suddenly i had a very small picture.safety cap blew.set was changed over to a tripler without focus block.they didnt change out the white caps.it has a replacement oval shapped capacitor.i ordered 6 spraque orange drops nos from ebay.4.00 plus 2.00 shipping.they got here yesterday.installed and its back!completely disassembled and cleaned every inch of the tuner,deoxit on every control and module.hit the switch and ..............................it works!tuner locked solid,full screen and once again,the patented zenith look.it got about 5 hours of viewing today and was flawless.i did have to readjust twice.seems the crt is slowly getting brighter.second adjustment held about 4 hours.i will post pics.cabinet is not too bad after a very close inspection.i have an avanti with a like new crt and a decent cabinet or should i wait until i find donor modules?will post pictures tomorrow

If you want long warm-up time a SS set is NOT the way to go. Even with no instant-on...a picture will be watchable on most within 15 or so seconds...and at full output by 30-40 seconds..

I'm used to solid state sets' warm up time. It's still a mighty nice TV though. It will be the centerpiece of my room when the chassis is fixed next month.

Concerning your loss of HV, you can disconnect the lead at the tripler that comes from the flyback. Then, move this lead away from anything that it can arc to. Then, power up the set and if HV is getting to this point, you'll be able to draw an arc to a screwdriver, when you bring the screwdriver blade close to the end of the lead. If you get the arc, that means everything up to that point is good and your tripler is bad.

If you don't get the arc, that means no HV is getting to the tripler and there are a number of things that can cause this. Two common things are loss of B+ voltage to the horizontal output stage and loss of horizontal drive to the base of the horizontal output transistor. No horizontal drive can be caused by a defective horizontal oscillator module, no B+ voltage going to said module, or an open winding on the horizontal driver transformer. There are other things that can cause it; but, these are most common.

If you're getting no B+ voltage at the horizontal output transistor (should be around 120V-130V), the most likely cause is either an open winding on the flyback or an open power resistor that feeds voltage to the flyback.

The horizontal output transistor is likely still good because when they fail, they usually short and when that happens, the circuit breaker will trip.

While you're in there, that sloppy connection to the tripler needs to be redone and it would be a good idea to seal this connection with RTV (once the set is fixed).

Don't anyone forget abut the "interlocks", on one of the b+ line--I think the 24V. line..that runs THROUGH the modules. if one of these gets a bad connection...NO HV or Sound..

I discovered this the "hard way" nearly 30 years ago..when working on a flatty...it had this problem...

I used a remote power switch, the kind often sold around Christmas time used to turn on lights. Just plug the set in, leave the power switch on, use the remote to turn it off and on. I looked a the circuit that powers the filament, did not look like something I wanted to defeat, but also rarely watch the TV so did not want the filaments left on all the time.

I took the chassis to Danny when I was there the weekend before last. When we where testing it, two if the filter caps opened up and caused no sweep whatsoever. I think he's almost got it all sorted out. I will pick the 25DC56 up on June 11.