Found a couple Sony's troubleshooting one

[Eric H]

OK, found these really cheap so I picked them up to mess around with.

One is a KV1981R, I'm guessing early 80's, Stereo with audio video inputs on the back.
This set is nearly mint, the right speaker grille is bent a little but should pound out OK. It seems to work fine, the CRT is very strong with good gray scale within a few seconds of powering it up, it seems to be low mileage because there's not much dust or crud inside but the outside is yellowish with tobacco stains, it'll clean up but I'll have to strip it bare and wash it.

The second set is a KV1545R, it's one with the "Ball Bearing" control panel, bonus points since I already had the remote for it at home.
It's quite clean with a minor scruff on the top corner.

This one was sitting outside in the junk area for the last three weeks or more, I'm pretty sure it got rained on at least once early on but there doesn't seem to be any rust or ill effects.
I tried it last week when I was at the thrift and it didn't work so I left it, It was dry at that time.
I decided to pick it up this week, it was only $3.98 so little to lose.

It powers on for about a second, the HV hits and the green display comes on briefly, then it shuts down, not entirely though, the relay stays energized until you hit the power button a second time then it clicks off.

It won't power up again (the relay will click but no HV or display) until you unplug it and wait a few seconds, plug it back in and it'll repeat the sequence, seems to be going into auto shutdown?

OK Sony experts, what's wrong with it?

Here are some really lousy pictures.

[radiorich]

Hello Eric,
I may even have the factory service for thst set.
one biggest things I find working on Sony is Bad Electrolytics.

Far as the picture tube goes those older sony pictures were good

[radiorich]

I would check for bad contections also I'm thing this set has a scr regulator.

I was trying to remember it's been ten years since I've worked on a sony tv.

Got like 6 of them here at home

They wre one the best sets far as picture but alot people dreaded working on them

[Eric H]

Hi Rich, would the bad Electros be in the power supply?

[jpdylon]

Our family's neighbor had one of those KV1981R sets. They had damn good pictures and I would always play nintendo on it with their kids. About the only thing I noticed about it was a little excess pincushion correction. Far as I know they still have it and its never been serviced.

[andy]

...

[radiorich]

Hello Eric,
that is where I would check first in the powersupply area.
like I said sony's had a lot of bad caps

If I can find my notes on that set I bet I may have the fix.
My shop sold that set new and also did the warrenty for sony.

I even had beren trained on sony products in school Sony sent my class train manuals .

[radiotvnut]

Years ago, someone gave me a KV1981R that they found at the dump. The speakers had been removed and the flyback transformer was arcing to the heatsink. Not knowing what kind of shape the tube was in, I junked the set.

I've also had the 19" version of that 15" set and I seem to remember having that shutdown problem. It's been a long time; but, I think the B+ regulator was shorted. The shorted regulator caused too much B+ voltage to be fed to the horizontal output stage; which, triggered the shutdown circuit. You can probably run the set through a variac and make it stay on for troubleshooting purposes.

[Eric H]

I'll pull it apart when I get a moment or two.

I don't have a Variac but maybe my Dim-Bulb tester will do the job.

[Eric H]

I took a DVD player out to the garage and hooked it to the 19" set, it works like new, a very bright CRT, Bright set to about 1/3 Picture about 1/2, Color is great and really good detail.

I was using my Isolation Transformer (also a Sony) since i needed two outlets and couldn't find a multi outlet extension cord.

The 19" set and the DVD player ran fine off the transformer, it's small and it drops the voltage slightly but they ran fine off it.

I decided to see if the 15" set would run using the drop from the transformer, sure enough it does, CRT is very strong on this one too, everything seemed to work but I got no sound from the speaker except possibly a slight hum.
It actually was the Isolation Transformer that was humming and it got loud, resonating off the bed of my truck, struggling with the load the set was putting on it.

The set seemed to be working fine still but it was clearly drawing too much current.

So what do you guys think, bad caps loading it down or bad regulator?
I guess I need to take the back off and see if anything gets hot, I don't want to blow the HOT though.

Here's some screen shots of the 19" set playing "The Mothers In Law" DVD, I might just clean this one up and make it my bedroom set!

[sampson159]

i had one of those sonys last year.best picture i ever saw!crt was excellent.it was my garage watcher for awhile.i sold it and am kicking myself!when those sonys were good,they were great

[kx250rider]

Nice find! I like that 15" set... PM me if that one needs a home! It sounds like the HVR block might be leaky, and is putting it in shutdown.

Charles

[Findm-Keepm]

Originally Posted by Eric H

I decided to see if the 15" set would run using the drop from the transformer, sure enough it does, CRT is very strong on this one too, everything seemed to work but I got no sound from the speaker except possibly a slight hum.
It actually was the Isolation Transformer that was humming and it got loud, resonating off the bed of my truck, struggling with the load the set was putting on it.

The set seemed to be working fine still but it was clearly drawing too much current.

So what do you guys think, bad caps loading it down or bad regulator?
I guess I need to take the back off and see if anything gets hot, I don't want to blow the HOT though.

The regulator transistors in those Sonys were a common problem - they'd short E-C, or go leaky B-C, giving you excess B+. Part number is MN8303 (preferred) or use a 2SC2581, and an NTE36 will do as well. Don't over torque the mounting screw when replacing them - the heat makes them expand somewhat and you'll be right back to square one if you torque too much. The driver transistor that feeds the regulator should be replaced as well when you replace the regulator - it'll check just fine, but go open on you, necessitating a call back. Other than that, most other problems were either audio related or bad remote functions - the IR Amplifier chip would short, pulling down the 12V line. OH - Get rid of any yellow glue in the regulator area too - it degrades with heat, turns brown, and becomes quite conductive. They are really good sets - I had a 17" one (KV-1746R) in my den for a few years.

Cheers,

[Eric H]

I found some MN8303 online for cheap, like $7.00, worth taking a chance on.
I'll wait until I can take the back off and do a little checking though, probably wouldn't hurt to replace some of the small caps too.

[kx250rider]

On that 19", watch out for arcing flyback (internal). I had a number of those sets with blown power supplies, and it was caused by the FBT arcing internally once in awhile, and not quite enough to blow the HOT, but enough to blow the regulators. Also be sure to resolder the connections under the horiz drive transformer, and the nearby resistors. There is also a green dipped ceramic disc cap from the collector to base (IIRC) on the horizontal output transistor... That often shorts as well, mimicking a shorted output.

I replaced enough of those FBTs to still memorize the number: 1-439-351-12 Hopefully your set does not have that number, and if so, hopefully it was replaced in the '90s...

Charles