Found a Monkey Wards (Zenith) PLF2589H12 Won't power up. - Videokarma.org TV - Video

MRX37 · #1 08-20-2008, 06:42 PM

After fixing the last Zenith I found only to discover its CRT is shot, I want to know if I should try fixing this one. It was manufactured in November of 1989, so I HOPE it's before the era of bad Zenith CRT's.

This TV won't power up. No click, no sound, nothing. It acts as though its not plugged in, even though the cord is fine and the outlet has power. I know the cord is fine, as this TV didn't have a cord and I used the one from the last Zenith I had. (perfect fit).

So, should I try fixing this one? It has AV inputs, so that's some motivation.

radiotvnut · #2 08-20-2008, 07:11 PM

Does it have a switching power supply board bolted to the right hand side (looking from the back) of the cabinet? If so, look for bad caps. I think I remember a 47 uf electrolytic going bad and causing a dead set.

Also, if that set uses one of those "membrane" keypads, that could very well be the problem. Try turning it on with a universal remote.

'89 was before the CRT's got really bad. I have, however, seen plenty of weak ones from the late '80's. I would say that you'll have a better chance with this one than with the newer ones.

MRX37 · #3 08-20-2008, 07:33 PM

No switching PS bolted to the side of the TV that I can see.

The TV has hard plastic buttons. I assume that means no membrane keypad.

Carmine · #4 08-20-2008, 07:37 PM

My 27" 1990-built Zenith has been in near-daily use for 18 years, and the picture is still excellent. However, an identical appearing 27" set purchased for my grandparents in '93 was junk within three years.

radiotvnut · #5 08-20-2008, 08:09 PM

OK, is it the "flat on bottom" chassis with the power supply/deflection board on the right and the main module on the left? I think there's a 100 uf cap close to the main filter cap that will fail on the "dual module monster" that will cause it to be dead.

It might be better if you could give the module numbers. They are usually more familiar to me than the set model number.

MRX37 · #6 08-20-2008, 08:14 PM

Main module is 9-871

Sweep/Power supply module is 9-874

MRX37 · #7 08-20-2008, 11:57 PM

So, where should I start looking on this one? I'm going to try and save it. If it was even 2 years newer I wouldn't bother, but maybe, just maybe the CRT is good.

radiotvnut · #8 08-21-2008, 12:22 AM

The problem will probably be on the 9-874. See if there's a 100uf, 50V cap close to the large electrolytic filter. They usually measure very low on a capacitor tester. I think I may have a good power supply module for one of those sets. I'll see if I can find it tomorrow and check the number.

MRX37 · #9 08-21-2008, 01:12 AM

Okay, found and changed a light blue 100uf at 160 volt cap. The TV now turns on, but there is no picture. I hear a faint crackling from the speakers. No on screen menus either.

MRX37 · #10 08-21-2008, 06:06 PM

Another update: I connected an antenna and turned the Tv on, and got a picture! The static looked pretty bright. I tuned it to a channel and was rewarded with what appeared to be a decent picrure. i didn't scrutinize it too closely, as I turned the Tv off to reconnect the speakers. TV turned off, now it won't come back on.

I'm going to resolder any suspect connections in the power supply, and maybe replace any relays I find.

radiotvnut · #11 08-21-2008, 11:07 PM

I've seen bad connections on those power supply boards. Also, make sure all the plugs are firmly seated.

I have not uncovered that power supply board yet. I've still got some more digging to do.

MRX37 · #12 08-21-2008, 11:25 PM

I *think* I've fixed the power supply board. The TV is up and limping now, and I'm presented with a new issue:

This is Channel 62, the strongest station in my area. I have a pair of rabbit ears connected to this TV. This picture should be crystal clear, but it's not.

Someone before me was inside this TV and messed around with some of the coils. After some diddling around with them, I got a picture like what you see in the above photo. I can't get the picture any better then this. Luckily however, the image is stable and smacking the TV doesn't affect it, so I think I can rule out a bad connection. Other then that, I am at a loss on what to do now.

PS: The CRT seems to be in good shape for being almost 20 years old.

radiotvnut · #13 08-21-2008, 11:50 PM

If someone has been screwing around with the coils; you may never get it back right without an alignment generator. How does it look through the video inputs?

That CRT does look very good to be a 20 year old Zenith tube!

MRX37 · #14 08-21-2008, 11:52 PM

Quote:

Originally Posted by radiotvnut

How does it look through the video inputs?

Good question. Can't find a button to switch it to video. Can't find an option for it in the menu either :-/

I'll diddle with it somemore tomorrow.

andy · #15 08-22-2008, 12:27 AM

On those Zeniths there should be an input menu. If it's not there, someone might have gotten into the service menu and told it there is no video input.

This is from an old newsgroup post (I'm not sure if it's correct, but it's close):

To access the service menue from the front panel
press and hold the"menue"key until the menue disappears.Then without
delay press simultaneously the "adjust Right"and "Channel up">Use
"select Up/Down"key to toggle through the menue to go where you want to
go to.Press "Enter"to exit the service menue.(You may have to
press"Enter"twice on some models).