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  #16  
Old 02-08-2013, 09:23 AM
dieseljeep dieseljeep is offline
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I see the part location diagram shows two different chassis. I remember that 25DC57 was a real dog! It had that troublesome voltage regulator. I don't remember seeing many of that model around. The 25DC56 seemed to be more common and a lot less grief.
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  #17  
Old 02-08-2013, 09:58 AM
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DavGoodlin DavGoodlin is offline
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Forget that negative "TV guy" assessment...this IS the best TV made.

Does this set have the black slate on top? I intercepted a trade-in like yours in 1985 and my parents used it as a daily set until 2003 or so, wanting a remote, they got a Sony 27" CRT Wega. It lived in my garage for a while but I parted it out due to the worn-out CRT (only after I rejuvenated it in '85!) and a pile-on of other issues. Had I been on VK then, I'd have kept it but I have the cabinet top yet

The low voltage regulator issue in ours was a zener diode but it took me a while to figure that out because it looked like a hum-bad capacitor. The undiagnosed intermittent vertical shrink was probably the service switchbut I was young then and kept cleaning the module pins and size/lin pots.

If you have a shorted HO Transistor, its easy to tell. Just set your multimeter on "diode test", put black probe on chassis and red on the (121-831) HOT case (the collector), it should read open but if you get the beep, its probably shorted. reversing the leads will read the damper diode, usually OK.

Never saw a fly go on these, but the "22-5001? white critical cap fails - HOT shorts" always the issues I saw. just my 2c

We'll help you fix and keep it.
Minor, inexpensive repairs will keep yours alive indefinetly!
Like Bryan said, we has parts. just find which one is bad.
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  #18  
Old 02-09-2013, 12:12 AM
StratLou StratLou is offline
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You guys are unbelievable. Thank you for the many words of encouragement and offers of assistance. I mentioned it to Mom and she was quite impressed as well and feel she may be on board to give it a shot. She is definitely not wishing to go for a "smart" tv that's for sure. It's not her main tv so she doesn't mind if it takes a while as I know it will due to the learning curve involved for me.
I guess the first things would be to ask if anyone has any idea where to find a schematic, how to check which of the 2 chassis I'd be working with, and what diagnostic equipment I'd need exactly to perform the tests. I may have 1 or two and may be able to obtain the rest, maybe. Thanks for being patient with me on this, guys, and for the continued guidance and assistance.
DavGoodline: Yes, it has the black slate on top!
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  #19  
Old 02-09-2013, 07:56 AM
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hi_volt hi_volt is offline
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The guy who looked at your set obviously didn't want to work on it. It would have been nice if he would have just been honest with you and said that, instead of putting on the show he did. I've never learned the fine art of diagnosing electrical problems (other than intermittents) by tapping the circuit with the back end of a screwdriver

I agree with the other posters. If the set had a good picture the last time it was turned on, the likelihood that your CRT has gone bad is pretty low, and you should be able to fix the set. These were great sets, and should last a long time once you fix it. I vote that you give it a shot.
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  #20  
Old 02-09-2013, 09:39 PM
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You need to pinpoint the exact model or chassis number. According to the Sams Photofact index, early production chassis 25DC56 is in folder 1312-3, late production 25DC56 is 1375-3 and 25DC57 is 1315-3. I don't have spare copies of any of them but I'm positive somebody on here does. If there is a model number on the back cover that should let us figure out which version you have, if not otherwise marked. It's possible I have a factory service manual for this but that would take some digging.
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  #21  
Old 02-10-2013, 12:02 PM
StratLou StratLou is offline
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Quote:
Originally Posted by hi_volt View Post
The guy who looked at your set obviously didn't want to work on it. It would have been nice if he would have just been honest with you and said that, instead of putting on the show he did. I've never learned the fine art of diagnosing electrical problems (other than intermittents) by tapping the circuit with the back end of a screwdriver

You are so right, as others have been earlier in the thread, in that he did not want to fix the tv. Looking back it's so easy for me to see that his intent was to come by, give me some mumbo jumbo while waving his "magic" screwdriver wand, and then tell me it needed a flyback tranny, output transister, and the tripler is a part of all this, collect his check for $39.95 for coming out and bidding us a fond thanks for the check, see ya later, bye. He first said he wanted to come out 'cause it's an old Zenith and he wanted to see it. To see if it was possibly something simple but turned out not to be. I should've had my first clue when he arrived and was just opening his repair kit while saying "I must be out of my mind for doing this", therefore setting himself up for the "it'll cost to much to fix" exit.
And so here I am in the forum looking to move forward to, hopefully, a happy ending. Thanks again for the assistance and encouragement as next I will attempt to find the chassis model for the proper schematic.
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  #22  
Old 02-10-2013, 12:19 PM
StratLou StratLou is offline
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Quote:
Originally Posted by DavGoodlin View Post
Forget that negative "TV guy" assessment...this IS the best TV made.

Does this set have the black slate on top?

If you have a shorted HO Transistor, its easy to tell. Just set your multimeter on "diode test", put black probe on chassis and red on the (121-831) HOT case (the collector), it should read open but if you get the beep, its probably shorted. reversing the leads will read the damper diode, usually OK.

Never saw a fly go on these, but the "22-5001? white critical cap fails - HOT shorts" always the issues I saw. just my 2c

We'll help you fix and keep it.
Minor, inexpensive repairs will keep yours alive indefinetly!
Like Bryan said, we has parts. just find which one is bad.
Yes, it does have the black slate top! What a great piece of furniture if nothing else.

I attempting to study and understand your and others directions for testing as I learn more about the language, numbers, circuit, etc. Still a bit over my head at this point but I'm trying.
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  #23  
Old 02-10-2013, 07:38 PM
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radiotvnut radiotvnut is offline
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I think there's one guy left in the area who claims to make house calls; but, he pretty much does what this guy did. He comes to your house, he plays with the TV for 5-10 minutes, then he tells the customer that the repair will be too extensive to perform in the home and the set must be taken back to the shop for repair. Then, he adds on an additional $50 for the house call.
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  #24  
Old 02-10-2013, 08:07 PM
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sampson159 sampson159 is offline
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if this guy was really a repair man with many years experience,he would have told you that this is a fine set.another of the "it isnt worth my valuable services"guys.arrogant and snobbish types.we have a few here in central ohio.have no clue about an older set but will work like mad on a plasma or lcd.all crts are"round tube",never heard of a "hybrid"set,etc.they all say the same thing when you inquire about a roundie or tube set:"why are you wasting your time with that s--t?"because its fun and that was when america built something great.
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  #25  
Old 02-10-2013, 08:42 PM
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Carmine Carmine is offline
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I have the exact same set. Mine was used just a few years back for 12 hours a day, over several weeks as part of a vintage Christmas display/prop.

(I'd be glad to trade out of it, perhaps for some repair work on other sets)

Either way, they are good sets and your so-called repairman sounds like a tool.
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  #26  
Old 02-11-2013, 11:46 AM
StratLou StratLou is offline
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You live and learn. Won't do that again. I have looked around the chassis in various places and cannot seem to find the chassis number stamped anywhere. Was that ever done and, if not, how can I find out which of the 2 chassis I'm dealing with? The only number I did find stamped onthe back of the chassis was 6003419 but I'm guessing it doesn't mean anything. And then, if it's the 56 chassis how will I tell if it's early or late production as bgadow alluded to. Thanks guys.
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  #27  
Old 02-12-2013, 10:35 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by StratLou View Post
You live and learn. Won't do that again. I have looked around the chassis in various places and cannot seem to find the chassis number stamped anywhere. Was that ever done and, if not, how can I find out which of the 2 chassis I'm dealing with? The only number I did find stamped onthe back of the chassis was 6003419 but I'm guessing it doesn't mean anything. And then, if it's the 56 chassis how will I tell if it's early or late production as bgadow alluded to. Thanks guys.
I'm 99% sure that your set is a 27dc56. Your chassis picture shows no shaded components. It does use the voltage regulating power transformer.
The "D" models are 1973 model year. That's possibly a later probuction set.
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  #28  
Old 02-12-2013, 11:44 AM
StratLou StratLou is offline
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Quote:
Originally Posted by dieseljeep View Post
I'm 99% sure that your set is a 27dc56. Your chassis picture shows no shaded components. It does use the voltage regulating power transformer.
The "D" models are 1973 model year. That's possibly a later probuction set.
Is it safe to assume that none of the shaded components could be on the underside of the board (I haven't looked yet but plan to remove the bottom cover to see what's there)? Which one of these schematics, then, should I be looking for:
"early production chassis 25DC56 is in folder 1312-3, late production 25DC56 is 1375-3" if these would be the only possibilities. Thank you.
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  #29  
Old 02-12-2013, 04:12 PM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by StratLou View Post
Is it safe to assume that none of the shaded components could be on the underside of the board (I haven't looked yet but plan to remove the bottom cover to see what's there)? Which one of these schematics, then, should I be looking for:
"early production chassis 25DC56 is in folder 1312-3, late production 25DC56 is 1375-3" if these would be the only possibilities. Thank you.
All the shaded components should be on top of the chassis. The parts that are mounted under the chassis are marked as such. The late production Sams would include all the latest engineering changes.
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  #30  
Old 02-12-2013, 11:09 PM
StratLou StratLou is offline
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Well I tried the Sam's Photofact Index site which had me downloading a huge file, then a zip file which unzipped to a Microsoft Access file, but then Sam's says don't open the file using Access, etc....Needless to say, I got nowhere trying to obtain the schematic. So can anyone tell me how or where to find the schematic for the 25DC56 chassis so I can get started. I didn't think the frustration would start so early. Many thanks again.
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