Servicing 1988 Sony TV

[dtvmcdonald]

I've done lots of tube TVs, and lots of 1960s - 1980s scientific solid state stuff,
but none of those were the super-complicated super squashed together kind
like this tiny Sony Indextron TV. I'd need tips.

I've got the complete service data book and schematics.

Its stone cold dead, presumably blown fuses due to bad electrolytics.
I will of course take it apart and look for bulged caps and replace any
that are (and all others of identical type?? Yes?).

Other than that ... what is the "usual" procedure for finding faults that are
not of obvious location? If I don't see bulges ... what do I do?

What are the precautions I need to do to avoid damage while servicing? Will
using a multimeter across all the caps on the main "in" 12V line possibly
cause damage?

[zeno]

Never worked on one but a few notes.
Sony often uses very low ohm resistors as fuses. On
most of there sets a shorted hoz out will take the
power supply with it.
Typical is either a cold joint in hoz drive or bad FBT shorts
the hoz out & it shorts the 2 converter transistors & opens the
fusable resistor.
Working on it shouldnt be to physically hard. Sonys usually
fold open for service. The trick is to find everything at once
so you dont have further chain reaction failures.

73 Zeno

[dtvmcdonald]

I inspected the set and found no exploded or bad looking capacitors.
However I found unplugged speaker and CRT HV cup. Reconnecting those I found
sound, both on the NOAA weather channel and our remaining Ch. 39
QVC analog station.

However, still no raster.

After a couple of minutes I noticed a smell which may be well be acetonitrile,
CH3CN (yes, its a cyanide but only slightly poisonous, I'm actually a chemistry professor.) This means a bad electrolytic somewhere.

Its not easy getting the thing apart, even with instructions,

Somebody around here must have worked on one of these things. The
model number is KVX-370. Any takers for advice?

[dtvmcdonald]

I got it apart and there were no "bulged top" electrolytics.

However, C1530 has a puddle of goo under and around it. This is the
filter cap for the +18 volt line. Its next door to the HV adjust control.
There is no obvious serious corrosion around it. Its also possible its C1545, 1546, or 1511.
One of the latter three, either 1546 or 1511, is a completely different
cap type, yellow-green in color. These caps are a 50V area.

What should I do? Just replace them and clean off the goo? If so, clean off with what?
Isopropyl alcohol does remove the stuff.

It is of course possible the goo is coming from something other than a cap.

Or perhaps send to someone who has worked on one of these or similar before?

[WISCOJIM]

Originally Posted by dtvmcdonald

Or perhaps send to someone who has worked on one of these or similar before?

I suggest you get hold of Chris Cuff and ask his advice. He's the only one I know of that has lots of experience fixing the 370's.

.

[dtvmcdonald]

I thought it was Andy Cuff, with the three-gun shadowmask closeup avatar.

If so, I'm trying.

[Electronic M]

I've worked on some Sony Beta decks. Bad cans often don't bulge (A cheap Chinese ESR/RLC/transistor tester is a must for smoking out bad caps in SS gear). If it is 80's sony and there are any surface mount lytics; CHANGE them...Do not pass GO or collect $200. I hear when the surface mounts pee themselves it corrodes the traces off the board...Beware of that.

[dtvmcdonald]

There are no surface mount electrolytics, I countd 16 radials with the same
"logo" pattern on top, all fairly large. There are many
smaller ones with no logo on top. I'm told that only some are typically bad.


I washed all the goo off, it took several tries, It apparently did not
do any damage.

[WISCOJIM]

Originally Posted by dtvmcdonald

I thought it was Andy Cuff, with the three-gun shadowmask closeup avatar.

If so, I'm trying.

Yep, you're right. Chris is the AM-Stereo guy.

.

[dtvmcdonald]

I got my caps from Mouser today and git it ALMOST recapped (the 105 degreeC electrolytics only.)

But I hit a snag ... two caps are 0.47 uF 50 volt Non-Polarized ones. I did not
notice that ... they parts sheet does not say so, and I assumed that when examining
them physically the polarity bar was in a hidden position. The only suggestion
that they are non-polarized is an obscure symbol on the schematic instead
of the usual polarized one. If I had ordered two more 1 uF 50v regular caps
I could use two of those back to back, which will barely fit.

I will see tomorrow (they closed 4 minutes before I arrived!) if our stockroom
has something that will fit. All my .47 uF film caps are 630 volt and too large.
Otherwise its another week and $5 for postage from Mouser.

[dtvmcdonald]

I got some suitable monolythic ceramics to replace the bad non-polar electrolytics.

These were replaced and it was reassembled.

I turned it on!

I got a partial raster, full width but not full height, quite bright,
that lasted about 2 seconds and then started to get smaller.
I then unplugged the set.

I've contacted Andy Cuffe, Mr. Indextron, for advice.

I've never done a solid state TV before.

[dtvmcdonald]

I've decided to send it to Andy Cuffe. I think it needs somebody with
experience working on corroded surface mount stuff.

Doug McDonald

[dtvmcdonald]

It returned from Andy today working nicely. He washed it in his ultrasonic, found
a few bad solder joints caused by the goo, found one more 105 degree cap
I missed, and then it had a raster but no picture. He remembered an identical
problem from another such set, and that was it: a shorted cap
in the video amp.

It works like new. The color line grid is very coarse and the purity on
saturated color screens not perfect, but the picture is quite watchable
on my local modulators.

The off the air reception is not great on our local Ch. 39 NTSC (HSN
shopping channel) with its built in antenna indoors, but its great
on the balcony. Moving around with this gizmo sure explains why
its so hard to get any picture on my RCA 3 inch ATSC portable.

Its fun to have a working CRT color TV that is not shadow mask.

[dtvmcdonald]

Its been five years on this thread. I'm watching the World Seris on it. Its "bete noire", bright red screens, isn't used in the World Series. The red T-Mobile sign is afflicted.
The low line pitch is bothersome.