Hi everyone,

I picked up a Quasar WP3422QW at a thrift store recently. It's a late 70's color TV. When I turn it on, I hear static out of the speaker for about two seconds and then no sound. I don't see anything on the screen, not even a glow with the lights out. I can feel static on the surface of the screen though.

If I turn the TV off and back on again I don't hear static. But if I wait about a minute before I turn it on again, I do.

I assume step one here is to replace all the electrolytic capacitors, but is there anything else I should check out?

Sounds like HVSD ( high voltage shut down) . If you have a variac
try running the set at @95 VAC. IIRC this chassis had a repair kit
for the power supply. Too long ago to remember the details. A recap
not in order, fix the HVSD first then there are a few caps to change.
A wholesale recap usually ends in sorrow:tears:
Anyhows they were good sets & odds are it will come out fine.

73 Zeno:smoke:
LFOD !

Thanks! I don't have a variac, could I use a light bulb in series with the power cable for the same effect?

I looked up the part number on the bottom of the chassis, it's a TS-969 apparently.
https://www.worldradiohistory.com/Archive-Radio-Retailing/80s/ETD-1980-06.pdf

A schematic for the board is on page 58

Thanks! I don't have a variac, could I use a light bulb in series with the power cable for the same effect?

I looked up the part number on the bottom of the chassis, it's a TS-969 apparently.
https://www.worldradiohistory.com/Archive-Radio-Retailing/80s/ETD-1980-06.pdf

A schematic for the board is on page 58
Shure dim bulb it. You should also pull the back & find the horz out transistor.
Then fire it up for a few seconds. Un power & feel the transistor & see if it gets hot. If so dont go further. If cool do again for 10 sec, 30 sec etc. That will get you started.

Zeno

IIRC this chassis had a repair kit
for the power supply.

Sounds like maybe OP should pull and check the components in the PSU. I know in some cases, you're not supposed to directly measure B+, but this set schematic doesn't seem to warrant that, so could start off by checking that is okay?

I went ahead and ordered a variac. At 90VAC the TV appears to work fine. Is the next step to measure the temperature of horiz out transistor?

I went ahead and ordered a variac. At 90VAC the TV appears to work fine. Is the next step to measure the temperature of horiz out transistor?


I'm not sure what Zeno meant, but I would pay attention to the components in the power supply. Check the values of the components in that whole area and make sure there isn't anything obvious like a blown or shorted resistor.

If you really want to get help though, it's best to make it easy for people to see the schematic. For example, someone could quickly look at this and maybe offer a suggestion.

https://i.imgur.com/pMObV32.png

I would first check or replace those two 33mf electrolytics, C809 and C812. Measure the b+ at the F2 fuse and see if the 130 volt adjustment does anything at all. If it doesn't and the electrolytics are good, suspect R811 the 47K resistor connected to the control, or the transistors.

I went ahead and ordered a variac. At 90VAC the TV appears to work fine. Is the next step to measure the temperature of horiz out transistor?
Good tips so far. Next step is check the 130 V line. Put meter on that
and slowly turn up variac. The 130 V must not go over 130 V. If it does
you have a regulator prob. If it shuts down on 130 V its a HVSD problem, not shown on the schematic, probably a bad zener diode.

Zeno:smoke:

Thanks everyone. I'll measure the 130v but first I think I need to give the chassis a serious cleaning.

Thanks everyone. I'll measure the 130v but first I think I need to give the chassis a serious cleaning.

That's pretty filthy. Be careful though. I would just use compressed air, or a soft paintbrush and a vacuum cleaner

you'll probably want to clean all those pots with fader cleaner. Caig Faderlube works good, but I guess there are other kinds

Fader cleaner is a good idea. I have some deoxit that should do the trick.

I also noticed what appears to be a stain on the bottom of the case towards the back. Maybe somebody spilled something in there

Fader cleaner is a good idea. I have some deoxit that should do the trick.

I also noticed what appears to be a stain on the bottom of the case towards the back. Maybe somebody spilled something in there


Be aware that there are different kinds of Deoxit. The red kind is mainly for metal to metal contact and corrosion. The green kind is for carbon traces.

The green deoxit is less harsh with the solvent and designed to not dissolve delicate carbon traces (which can sometimes happen). It also contains a conductive lubricant that clings to the traces and keeps it gooey and smooth over time, lengthening it's useful life.

Before I knew this, I ruined a couple of rare-ish walkman pots that had tiny carbon traces known for being fragile and vulnerable to harsh contact cleaners.

I was not aware of that! I think I have deoxit gold.

I was not aware of that! I think I have deoxit gold.

I've never used the gold stuff before. Not sure about that. It says it's okay on plastics, which is different than the red stuff. Probably fine?

Good tips so far. Next step is check the 130 V line. Put meter on that
and slowly turn up variac. The 130 V must not go over 130 V. If it does
you have a regulator prob. If it shuts down on 130 V its a HVSD problem, not shown on the schematic, probably a bad zener diode.

Zeno:smoke:

With the Variac set at 90VAC I measured the 130V at 124V. I raised the variac to 100VAC and the 130V was 138V. I didn't go any further than that but I guess that confirms it's a problem with 130V regulation?

Should I adjust the 130V pot? It's got some sort of goop on it to keep it from being adjusted

Yes its the regulator. Q801 the most likely suspect. The pot was
part of the old kit. IIRC a zener diode also. Shouldnt need to adj it,
most times its a hard failure of a semi.
BTW on these & its Panasonic cousins the front controls would freeze up. A few
drops of WD 40 lubes & cleans them.

Zeno

Thanks - I'll start with replacing Q801.

I found this "Service Caddy for TS-969" on eBay but none of the part numbers seem to match what I'm looking for https://www.ebay.com/itm/204578889156

I replaced Q801 but I get the same behavior - works with variac set to 90VAC but not at 110VAC. Anything else I should be replacing?

I haven't tried adjusting the 130v pot because it's been covered in some sort of epoxy or potting compound. I might be able to get it out with a dremel, otherwise I'd probably just have to replace the pot itself.

I replaced C809 and C812, made no difference. I'll try replacing the 2k potentiometer and see if turning that changes the voltage or not. I'm measuring an open circuit between the wiper and either leg on that potentiometer so it's either bad or dirty.

I replaced C809 and C812, made no difference. I'll try replacing the 2k potentiometer and see if turning that changes the voltage or not. I'm measuring an open circuit between the wiper and either leg on that potentiometer so it's either bad or dirty.

Before you go throwing more parts at it, you should start by checking some voltages. If you look in the schematic, you can see that voltages are called out at points around the transistors and other substantive junctions.

If you can confirm that voltages are all correct around a transistor, then you probably have a working transistor.

If the voltages aren't right, then pull the transistor and do a diode test on all of the legs to confirm it's still a transistor. If it looks good and the voltages are wrong, then you have more information about where the problem is (depending on which leg(s) of the transistor are wrong.

Then you just keep going this way until you encounter a bad part.

Like, if the out seems to following the output, triggering protection with full input, maybe the Q802 is defective or some part around that.

I used a knife and small saw to chisel the melted plastic off the 130v adjustment potentiometer and gave it a blast of deoxit and that did the trick! Thanks for the help everyone