Zenith 9-181 module

[Zenith26kc20]

I adopted a 13 inch Zenith with the 9-181 module. It had no start. It is the one that does not have the "kick start" sub module. I subbed the 9-181 with a module off the shelf and now I have high voltage, sound, good sweep. But, no video or color. I suspect this module was shelved a long time ago for no video.
The question! Does anyone have a schematic of the 9-181 module?

[zeno]

Be sure none of the little jumpers are in the wrong place.
Also check the IC pins that none bent when you moved them over.
Give the model ## I may have the Sams but try to get a free
one first !

73 Zeno
LFOD !

[kf4rca]

I'd check the voltage adjust pot in the power supply for an open spot. I have replaced it with fixed resistors in the past.

[jstout66]

I think I have the same set as you, and mine just developed an odd problem. After running for about 20 minutes it shuts off. If you wait a minute, and turn the switch off and back on, it will run a bit and do the same thing. Did these have a shut down circuit if the HV crept up too high? I haven't taken the back off mine yet, but assume everything is crammed in there pretty good.

[zeno]

Yes they do have HVSD circuits. The sets not crammed but
since they were built for board level service its not that easy
physically. At its age I would look for cold joints on both the
9-181 & 9-186 boards. Also some had a small start board
on the 9-186 bracket. If the IC's have sockets watch that too.
Later models have them soldered in.

73 Zeno
LFOD !

Originally Posted by jstout66

I think I have the same set as you, and mine just developed an odd problem. After running for about 20 minutes it shuts off. If you wait a minute, and turn the switch off and back on, it will run a bit and do the same thing. Did these have a shut down circuit if the HV crept up too high? I haven't taken the back off mine yet, but assume everything is crammed in there pretty good.

[zeno]

BTW I missed that it was a S3 set. It uses the big 9-160
board. 9-181 sets were called "Custom Series".
The 9-160's had lots of bad PC cons. Pull it & give
it a good goin over.

73 Zeno

[Zenith26kc20]

On a 9-160 I found shut down was usually caused by connections on a large diode front right as viewed from the rear of the set. Also, horizontal driver transformer pins were known for poor solder joints. Except for the 10 mfd/315 volt cap, parts failures were rare. Usually a hard failure (horizontal output transistor and a few other parts) was caused by a flyback arc over. As age did get to these modules the dual power supply electrolytic would open.

[Zenith26kc20]

It lives! After digging out five(!) 9-181 modules all in different stages of having been scavenged over the years, I thought this little guy was hopeless. OOPS! Fleabay! A factory refurb in the box! Well, it was a late refurb that included the IF IC and was as clean as can be! It looks so much better than the picture! It will live atop my T-933 and my TS-4J.

[jstout66]

FANTASTIC!
And of course.... I took mine in to be repaired, and do you think it acted up once???
Glad yours is going. Keep your fingers crossed on mine.

[Zenith26kc20]

I have seen weak (high ESR) capacitors on the 9-186 board cause intermittents. As mentioned earlier, these sets are a bit of a bear to deal with. My big complaint is the service literature. No voltages marked except for power supply. It is a bit of struggling with the harness' being short. I feel lucky that 9-181 popped up!
I remember the one with kick start being a failure prone set. I also remember when all 9-181 modules had regular start added when sent in for "rebuilding".
I just wish we still had analog OTA. This set has a good tuner and I would bet DXing would have been a lot of fun with it!

[radiotvnut]

Several years ago, a church gave me a 25" table set (digital tuner, pull on-volume knob) with a 9-181 module. The problem was a roar from the speaker, very reduced HV, and no raster. All power supply voltages checked low and I was pulling my hair out. I then noticed that one of the B+ lines going to the tuner had a dead short on it. After unplugging that line, the chassis came up with full HV and raster. After looking inside the tuner module, I found a dead shorted large value electrolytic capacitor that was tied between tuner B+ and ground. One new capacitor later and the set worked like new. Coming from a church, it probably did not have a lot of hours on it.

[NowhereMan 1966]

Originally Posted by Zenith26kc20

I have seen weak (high ESR) capacitors on the 9-186 board cause intermittents. As mentioned earlier, these sets are a bit of a bear to deal with. My big complaint is the service literature. No voltages marked except for power supply. It is a bit of struggling with the harness' being short. I feel lucky that 9-181 popped up!
I remember the one with kick start being a failure prone set. I also remember when all 9-181 modules had regular start added when sent in for "rebuilding".
I just wish we still had analog OTA. This set has a good tuner and I would bet DXing would have been a lot of fun with it!

I have been using my 9-181 set from 1982 since it was new and I'm using it now. I might have a small cap issue myself, every once in a great while the screen gets a reddish hue but it flicks out and is good for a long time, it's been like that for over 10 years of constant use. BTW, I remember late at night back in the summer of 1988, I did pick up WRC-TV from Washington DC when our local Pittsburgh channel 4 (WTAE-TV) signed off at 1:30 AM using the standard tuner and 1959 rabbit ears (still hooked to the TV)

[Zenith26kc20]

At the shop we use a 19 inch sentry all day long. I picked it up a few years ago off the street and was going to part it out but it worked when I plugged it in. It appears to have never been serviced!