1982 Zenith System 3 Problems

[NowhereMan 1966]

Originally Posted by zeno

OK Sams 2146-2 is the same style & year.
It uses 9-181-02 & 9-186-01
Cap I mentioned is C3496 & seems to be on the 9-181

NOTES
Early 9-181 used IC sockets, they were eliminated. You had to move the
IC's & 3 color outs to the new board. PIA

There were 2 types of start circuit. One used a transformer on the 9-181
the other a multivibrator on a PCB mounted on the hoz out heat sink.

9-186 comes mounted PCB only. You dont get the heat sink, small
parts etc. ( watch for overheated hoz yoke plug ! ).

BTW I have 2146. If you cant find a free one PM me for price MUCH
less than sams & a real quality printing, not a crappy PDF or Xerox.

73 Zeno
LFOD !

Come to think of it, I do remember the 9-181-02 was replaced years ago where the IC's were socketed. I watched the tech do it. I took a look and I'm right, they are in sockets. Even though it could be on the 181, I think the 186 might need replaced too since I did see some white retrace lines and before that, red ones on occasion. Are the 3 color outs IC's too, it has been a long time. I'm also interested in the SAM photofaact too you have, if you're going to work on something, it helps to have the literature to do it since this is my first time getting this deep so I want to be extra careful.

[zeno]

Yup the outputs plug in. Near them is a printed resistor package. Its
black & white, long & thin. Whenever you see one resolder it.
The 10mfd cap I mentioned causes retrace & a bunch of other often
subtle & intermitent symptoms. Just change it, they are a common
fail on ALL brands.
Last go over the 9-186 real good for cold joints.

73 Zeno
LFOD !

[NowhereMan 1966]

Originally Posted by zeno

Yup the outputs plug in. Near them is a printed resistor package. Its
black & white, long & thin. Whenever you see one resolder it.
The 10mfd cap I mentioned causes retrace & a bunch of other often
subtle & intermitent symptoms. Just change it, they are a common
fail on ALL brands.
Last go over the 9-186 real good for cold joints.

73 Zeno
LFOD !

So really it could be the cap on the 9-181 instead of th 9-186? If so I'm glad because I would had to resort to changing the high voltage board if I don't have to. IIRC, we had that problem in 1995 or so and the TV tech did solder in some caps on there.

[NowhereMan 1966]

Well, I did get a new 9-181 board and put in the IC's and transistors correctly from the old one along with the connections like on the old board and I get nothing. I turn on the power and get the channel number, that's it. Any ideas? I'm bummed....... This year sucks, Coronyvirus, riots and now I am having trouble trying to resurrect my baby. I've also got another set of IC's for it. I'm looking for a little guidance. I was trying to get this to work all day but I think i'll give it a few days rest and see what replies I get here. I did blow the 4 amp fuse but I replaced it.

[JohnCT]

Originally Posted by NowhereMan 1966

Well, I did get a new 9-181 board and put in the IC's and transistors correctly from the old one along with the connections like on the old board and I get nothing. I turn on the power and get the channel number, that's it. Any ideas? I'm bummed....... This year sucks, Coronyvirus, riots and now I am having trouble trying to resurrect my baby. I've also got another set of IC's for it. I'm looking for a little guidance. I was trying to get this to work all day but I think i'll give it a few days rest and see what replies I get here. I did blow the 4 amp fuse but I replaced it.

Okay, here's the thing: Zenith servicers hated that toilet. There, I said it... I remember getting two bad 186 modules in a row from Zenith. If you can find a new (yellow label), grab it. Any red label version was "rebuilt" using questionable techniques.

Take a look a the board/metal plate assy the 186 sweep board is mounted to. There are three TO-92 start-up transistors on the small board near the top edge. See if they are blown. If they are, replace all the electros on the 186 board as well as the transistors (and IIRC, a resistor or two will be scorched). There is a lot of voltage on those transistors so choose your subs wisely.

On the main 181 board there is a dual section PC mount electro. Good probability one side is bad if it's never been changed. If one side is bad, it causes all sorts of collateral damage when it opens including tormenting that start circuit and blowing those transistors.

If all those are good, turn the main board over and resolder every heavy resistor on the board. They usually are mounted in small metal grommets before soldered. What causes many guys to miss this is that the connections look fine, even under a loop, but they go bad. Put some liquid flux on them and reflow them with a decent wattage iron.

If you had the boards out, don't overlook the possibility of getting a connector crossed. The boards are printed so carefully check the legend on the board to the connector number. Fortunately, Zenith was good about clearly labeling those connectors.

John

[NowhereMan 1966]

Originally Posted by JohnCT

Okay, here's the thing: Zenith servicers hated that toilet. There, I said it... I remember getting two bad 186 modules in a row from Zenith. If you can find a new (yellow label), grab it. Any red label version was "rebuilt" using questionable techniques.

Take a look a the board/metal plate assy the 186 sweep board is mounted to. There are three TO-92 start-up transistors on the small board near the top edge. See if they are blown. If they are, replace all the electros on the 186 board as well as the transistors (and IIRC, a resistor or two will be scorched). There is a lot of voltage on those transistors so choose your subs wisely.

On the main 181 board there is a dual section PC mount electro. Good probability one side is bad if it's never been changed. If one side is bad, it causes all sorts of collateral damage when it opens including tormenting that start circuit and blowing those transistors.

If all those are good, turn the main board over and resolder every heavy resistor on the board. They usually are mounted in small metal grommets before soldered. What causes many guys to miss this is that the connections look fine, even under a loop, but they go bad. Put some liquid flux on them and reflow them with a decent wattage iron.

If you had the boards out, don't overlook the possibility of getting a connector crossed. The boards are printed so carefully check the legend on the board to the connector number. Fortunately, Zenith was good about clearly labeling those connectors.

John

It did have a yellow label on it. I know with the old board, the TV might come on for a few minutes and shut off and if you try to turn in on, it would "motorboat" indicating a bad capacitor from my discussion here. It just seems perplexed that nothing happens, I guess I'll have to go over it again. I'll have to check around with my VOM with my SAMs folder in hand and see what's up.

[zeno]

You need to find if this is a start problem or something else.
If the set does not start properly there is a resistor on the
small PCB (2 K IIRC) that will burn. Start process is....

The little board turns on & supplies a pulse to the hoz drive
This is the separate wire with plug.

The HV comes up.

A secondary B+ voltage is developed off the FBT & runs the horz osc IC.

The little board gets turned off & set runs.

If it does not start the set tries to run off the little board. It then burns
the resistor & sometimes transistors.

73 Zeno

[JohnCT]

Originally Posted by NowhereMan 1966

It did have a yellow label on it. I know with the old board, the TV might come on for a few minutes and shut off and if you try to turn in on, it would "motorboat" indicating a bad capacitor from my discussion here. It just seems perplexed that nothing happens, I guess I'll have to go over it again. I'll have to check around with my VOM with my SAMs folder in hand and see what's up.

If it's a yellow label and was sealed, it's likely good, even sitting in the box all these years.

First thing I would do is reinstall the original module and see if you can get back to where it was. If it acts dead like the new board, then something else happened coincidentally. If the original board runs with the shutdown and motorboating, pull that dual section PC mount electro and check it, or better yet just replace it. That cap causes all sorts of mischief including damaging the start transistors on that sub board I mentioned earlier.

On Zenith modules, the suffix is critical. I used to have all those boards memorized, but whereas a 9-181-01 might sub the 9-181, the 9-181-02 might not, but the -03 might!

Our local Zenith distributor (Plymouth Electric NH CT) used to mail us cheat sheets that had all the modules listed with the suffixes that would interchange. Saved a lot of time and trouble. All that stuff I tossed out twenty or more years ago.

John