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#1
02-12-2021, 02:09 AM
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Zenith Color Console (1990)
Hello!
I've written about this TV long ago .... it is a Zenith Advanced System 3 27" solid state console, model SG5745H9. It uses a 9-959 main board, and a 9-754 Sweep board. Both boards have been changed since new; I changed the last one because the sound stopped working and the IC was not available. Luckily I found a good board ... this was maybe 15+ years ago. Maybe 20. It hasn't been used much over the past ten years, but we keep it around. When I moved it a few months ago, when I first plugged it in, it made some odd sound through the speakers, but settled down and worked fine. It's been working on the few times I've tried it (watching old TV shows). Tonight I turned it on and the video was off - a little wavy; when I turned it off, the sound stayed on and the picture went off. I unplugged it and plugged it back in and then the amp came on with a hiss only, no picture. The power switch does nothing any more. The TV makes a click at times when plugging in from one of the relays, though I am not sure which (or if there is more than one ... I kind of remember it being related to a signal source selection) I figure it's not really worth repairing in general, but am willing to try. Do you think it would be worth the time just changing all the capacitors on the sweep board (which I think is the board with the power supply) ... or is that just a colossal waste of time? OR is it perhaps actually worth taking it in to a good shop that still works on CRT sets (any good ones near Torrance, CA?)? All thoughts are appreciated. It's one of those things I hate to throw away since it truly had a great picture ... even though I am sure it's not a desirable set from a collection standpoint. Thanks, Richard 
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#2
02-12-2021, 03:57 PM
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Relay may not be for ON/OFF but degausing. They act different.
Yes its worth nothing but if you like it & it ran good give it a whirl. My memory is bad after the 80's & my duties changed so take this with a grain of salt. 1) there is a small 'litic cap in front of the FBT. Caused video problems. 2) In the primary of power supply there are 2 small 'lytics that kill the set. 3) pull both boards & go over them for cold joints real good. You will find some. Hopefuly one is the problem. The set is in Sams 2921. I will see if I got it. Beyond the above you will need it. DO NOT buy it from Sams. Too much $$ for a crappy PDF or Xerox copy you cant read. 73 Zeno  LFOD !
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#3
02-12-2021, 04:34 PM
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I appreciate it! Thanks very much!
So you think it might be just cold joints rather than the capacitors themselves? That would be great. Cold joints are how I fixed the dash gauge lights in my truck AND the ABS controller in my truck... Quote:
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#4
02-13-2021, 03:04 PM
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Bad news is I dont have the Sams for it. Maybe someone else
has it. While you have the boards out look over the electrolytic caps. Look for swelling, discoloring & puss leaking out the top or bottom. Cold joints & 'lytic caps probably account for 70% of failures on sets from the late 70's on so keep that in mind. Funny thing is they almost always are in the same places & across all brands. The engineers could have easily & cheaply cured most of them. But I dont complain. They paid for my house, kids collage & kept beer in the fridge ! Mostly T-bone steaks & not much pasta....... 73 Zeno LFOD !
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#5
02-14-2021, 12:37 AM
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Thank you again. i'll check it out.
Interestingly, I found a schematic in my literature stack ... but it's so small I can't read it. I wonder if I have it as a download somewhere and tried to print it out from the last repair. Regardless, I will check the caps and let you know. I appreciate the encouragement. (If you or someone else happens to know someone good near the 90275 zip code, I wouldn't mind paying someone to take a look ... still probably not worth it, but I do that often it seems).
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#6
02-17-2021, 10:38 PM
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Finally had a chance to check out the boards. The main board 9-959 seems flawless. Caps look perfect, solder joints look perfect. Nice and clean. This is the board I changed 15+ years ago from Tri-State Module.
The Sweep board, which seems to also be the power supply 9-754, had one cap that had some brown under it. Not goopy just like thin paint ... I actually wondered if it was from an old repair that wasn't cleaned correctly (this board was exchanged years ago either under warranty or a paid repair). It cleaned right off and the brown didn't actually "touch" the capacitor, but it was there. Taking the board fully out to get a closer look, I found a totally different area that looked awful. Like a really bad repair from a previous time (probably the board was a repaired exchange). Slightly bulging caps, corrosion on the board traces, odd solder joints. Looks kind of like it overheated a little (though not discolored and not melted, just "wrong")... I can send a photo if anyone cares. Other than the bad caps, this area is a connection that connects to the main board, so I assume it is the low-voltage power supply. The corrosion may or may not have shorted the circuit between traces; I didn't test before cleaning a bit. Now my decision ... repair, or replace? I am not sure if they have them in stock truly, but an online place says they have new old stock boards and this one would cost $130 plus shipping. So do I challenge myself and repair it for basically peanuts, or do I go all out and spend $150 or so on a TV that probably isn't worth repairing but might be fun to have around a little longer? Assuming that this is the bad board (I guess I could replace both ...) Either way (repair or replace) I need to ask a really stupid question ... the anode wire - does it just pull off once the suction releases it, or does it have an internal solid connection? I ask because I pulled it off and didn't realize I may be damaging something. Inside I didn't see anything but (I assume) glass. I also didn't realize I am supposed to ground it first but it apparently had no energy inside because I'm still alive and there was no spark or shock... Richard Quote:
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#8
02-20-2021, 10:32 PM
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Can I ask what may be a stupid question (for even considering this) ... while looking into this repair I had sent a message to a company that had listed the two boards this TV uses. They have both, and are "factory rebuilt, new old dealer stock" and sold with no warranty... $50 each. Is it worth buying them "in case" or should I just plan -- ultimately -- to not repair it if it becomes unrepairable with the current boards?
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#9
02-21-2021, 01:44 PM
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I wouldnt. Its risky buying NOS modules. If its unsealed it may be
a returned dud. A lot of the stuff on Ebay is someone selling off an old shop & knowing nothing about anything. If it was DEFINATELY a former parts suppler selling his NOS you could probably trust them. Watch the Craigs list for free TV's. Investigate any model starting SG57 or SG27. They were common sets. You may find a free one. Quote:
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#10
02-21-2021, 02:18 PM
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Quote:
Back then, we didn't have the option to buy one or the other: when the TVs were new and in current production, warranty parts came in the yellow label boxes. As the TVs were in production for a while, the next order for the same board might come in a red label rebuilt box. John
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#12
02-22-2021, 12:28 AM
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I've been following this thread from the beginning, as I like Zenith equipment (audio gear as well as TVs, and I've had many Zenith TVs and stereo units over the years; I still have a Zenith 19" color set from 1995 that works as well as when it was new, though it doesn't get much use anymore since I replaced it with an HDTV, first a 19" and, later, a 32", the latter being the set I have and use now, some years ago), and am glad to see your 1990 Zenith is working as normal again. Sometimes all it takes is a few new parts to get the set back to normal.
Here's hoping your '90 Zenith keeps working as well as it does for quite a while. I don't know if your set has the infamous Zenith CRT that can and often does short after a few years (!), but from what I've read in your posts you haven't, thankfully, had any problems along those lines. BTW, speaking of Zenith and HDTV, I think it was a darn shame Zenith went out of business when the company did. I can't help thinking they would have had great success with high-definition flat screens (LCD) today if they had stayed around. They did have a few plasma TVs just before they went out of business; however, I'm sure they would have done very well, as I said, with LCD flat panels. It makes me wonder why Zenith went out of business, as they seemed to be doing well right until the end. As much of a following as Zenith had (the company had been making radios and TVs, after all, since 1918), I thought they could keep going indefinitely. When I read of their demise I was amazed, to say the least.
__________________
Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten.
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#13
02-22-2021, 03:50 AM
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I believe my CRT is a few years before the bad ones.
My understanding is that Zenith was one of the companies that developed HDTV ... so weird that they didn't survive. I guess it was the CRTs that did them in. I guess I'll keep this around a while. Quote:
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#14
02-22-2021, 05:33 PM
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Quote:
Now, whether Zenith's engineering helped LG Korea at all I have no idea. John
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#15
02-22-2021, 08:53 AM
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Zenith started hemorrhaging money in the early 80's due to competition from Japan. The Japanese were selling TVs here for less than it cost to manufacture them and could so because it was being subsidized by the Japanese government. Zenith survived by selling off different business units - PCs, cable boxes, etc.
By 1991, they were really hurting and Goldstar bailed them out and then became a majority shareholder in 1995 when Zenith couldn't repay their debt. Zenith bet and invested heavily on HDTV and held a number of patents that turned out to be worthless. Even though they developed 8VSB, they were never able to enforce the patents. Zenith also did a lot of investment around internet cable modems. They also invested a lot into modernizing their CRT production in the 90's and never were able to get the machinery operating correctly.
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