Busted Sony 1210 Fixed!!

[Eric H]

Well I pulled all the electros on the Oscillator board, all three of them, they look pretty questionable with slightly swollen rubber on the bottoms and one with the plastic pulled down so the top 1/4" of the can is exposed.
I wish I had an ESR meter to confirm their badness but since it's 40 years old I'll just assume they are bad and replace them.

I also made a list of some other fairly large Electros I can see, not sure what circuits they are in without a Schematic but figure they should go too, some of them look questionable as well.

One is a large Non Polarized cap mounted in front of the Oscillator board, it's only .1Mf but it's rated at AC 450 Volts, I guess it's just a normal non polarized cap?

There is also one large can mounted in a recess on the bottom of the chassis, I'm guessing it's the main PS Filter and since it's got HV, sound and no hum I'm going to leave it alone until I get the set working, (if I get the set working).

All the rest are modern Poly Film Caps and most likely good so I'll leave them alone.

[mpatoray]

Make sure you have that brightness down so you don't burn a line into the CRT!

[Eric H]

Hi Chris, well they didn't call today to tell me the part was in so maybe early next week.

If it at least works with the NTE long enough to verify the set is worth fixing then I wouldn't mind buying the OEM part if I have to.

[ChrisW6ATV]

I have had Sony color monitors that went "all white" (and then the protection circuits shut off the set) when electrolytic capacitors were bad.

Since you work on a lot of solid-state "newer" TVs, I highly recommend that you get an ESR meter for testing electrolytics. They are worth their weight in gold. I have a Creative Electronics one; they seem to come up on Ebay fairly often and sell for under $100 there. It is actually not that complex a device, just an oscillator and a circuit to measure the signal that comes through the capacitor being tested, I think. Decades ago, my co-worker duplicated the one we had in our shop in Illinois when they could not find any new ones to buy anymore.

[Eric H]

Tonight the set wouldn't start again, there were voltages missing in some places where I knew they should be, poked and prodded, checked Diodes and so on but nothing.
Finally I just took the soldering iron and soldered a lug on a terminal strip that I had poked previously when the set mysteriously started running, sure enough it started running again. The connection on the lug looked fine but maybe it was a cold solder joint somehow, I'll see tomorrow if it'll still run but it worked all evening while I was trying to figure out the video problem.

If I disconnect any of the RGB wires on the CRT socket board that particular color goes away so I know the CRT is responding, the Picture control grounds the Base of a small transistor and that seems to be working OK too.
I'm not sure how the brightness control works just yet.

I just found and bought a factory service manual for this thing on eBay so perhaps when I get that I may be able to figure this out.

I suspect bad caps too but without knowing which ones are in what circuit it could be difficult to figure out, I don't want to go through the expense of shotgunning them right now either, not until I see a picture on this thing.

[Eric H]

I bought a service manual for this set, now I can actually check some voltages and know what section I'm working on.
I also took the manual to the Electronics Store and bought a bunch of electrolytics, this isn't every cap in the set but it's enough to make a start and to have on hand if I find I need a particular one.

This whole pile of Caps was only $10, because they are very small values and voltages. One is only .47@10v, the tolerance on most is -10% to +150% so that gives a lot of wiggle room on those odd values.

[Eric H]

And this is why I hate working on Solid State gear.

I was rotating the set to get to the Horiz Hold control and the tip of my Soldering Iron came in contact with the metal chassis of the TV, pow, dead set, I wish I had had one or the other on an Isolation Transformer!

I figured I blew the fuse, there are two fuses in this thing and one circuit breaker but none of them blew.
Funny thing is nothing else seems to be shorted or blown either, the set just won't run, the CRT heaters don't light either despite being on a separate transformer which is getting AC voltage as far as I can tell, however the workings of this set are a bit confusing to say the least.

I did check the CRT to see if the heaters are still ok and they are so it's a power problem.

I do get a dial light however, and when the set is plugged in but switched off I can clearly hear the Horizontal Oscillator running, it winds down though when I switch it on.

The set was having a power supply problem to start with, it didn't want to power on cold first try, tonight I had to switch it on and off about three times before it would start so maybe I just finished off a bad Filter in the PS somewhere?

I can upload the PS portion of the schematic if anyone thinks they can assist me here, I would sure appreciate it!

This thing is from another planet, or so it seems.

[AiboPet]

Yup.....Used to say that when I was 20 even, that Sony Trinitron sets were "alien"....and I have NEVER managed to bring one back.

Only RECENTLY claimed my ONE and only Sony victory....and it's an old 700U set I had sitting around for like 25 years. I had that 700U since I had JUST come from Hong Kong and wanted a real portable set since I wasn't stable yet. From a garage sale, it ran for maybe a year or two and then VERY suddenly had only a white raster. It's an old B/W set...but to this day the only Sony I have ever revived. My next one looks to be the 8-301W that I have MOSTLY running.

[ChrisW6ATV]

Eric-

I first learned (the hard way!) what a "hot chassis" is when I was installing a little kit "frequency counter calibrator" into my Sony KV-1922, in 1980. I started to hook an oscilloscope probe's ground clip to the chassis when I got the big BANG! and the TV went dead. On mine, one or more of the main diodes after the power switch had blown.

I hope you can find a good deal on an isolation transformer if you do not already have one.

[Eric H]

Originally Posted by ChrisW6ATV

Eric-

I first learned (the hard way!) what a "hot chassis" is when I was installing a little kit "frequency counter calibrator" into my Sony KV-1922, in 1980. I started to hook an oscilloscope probe's ground clip to the chassis when I got the big BANG! and the TV went dead. On mine, one or more of the main diodes after the power switch had blown.

I hope you can find a good deal on an isolation transformer if you do not already have one.

Hi Chris, I do have one, I haven't been using it much lately because of the voltage drop it causes, probably not an issue with the little Sony being as it doesn't have 30 tubes, also I have the Variac now that will compensate.

Too late now, I really wasn't thinking the Sony was a hot chassis, should have guessed by the shock I got while touching the bench and the set but I guess I thought I was touching a terminal and not the chassis.

This set has a lot of Top Hat Diodes, do they usually fail open? It's not blowing any fuses or smoking so I don't think anything is shorted but the B+ seems to be dead.

Now that I have a "nice" (cough) new Meter I can do some more testing. (See the test equipment forum for more on my new meter )

[AiboPet]

Does a variac also serve as an isolation transformer? I have been trusting that I'm isolated by using a variac. My assumption being...that it's a big transformer.

[electroking]

Originally Posted by AiboPet

Does a variac also serve as an isolation transformer? I have been trusting that I'm isolated by using a variac. My assumption being...that it's a big transformer.

It's a big AUTOtransformer, therefore not isolated. Better add an isolation
transformer between the variac and your load.

[AiboPet]

Thanks. Will do.....kept thinking I was killing "two birds with one stone" with a variac. So far I don't work on many actual "chassis" sets at all (since I'm micro and solid state, mostly wall warts), but I do have a couple 9" sets and the older sets that do have AC plugs and real (such as they are) chassis.

[Eric H]

Son of a...gun

Got my $20 worth out of my new meter tonight.

I finally figured out some basics on how the power supply works on this set and I didn't have any AC line voltage going in to it.

To make a long story short the Circuit Breaker is bad, it apparently blew out when I shorted the chassis and didn't reset, even though I pressed it a dozen times it never even made the slightest contact.

I would have figured this out sooner if the breaker wasn't such a PITA to access the lugs on without breaking anything else.
I finally got desperate and figured it HAD to be the breaker so I hooked a jumper across it and viola, it works again, this probably also explains the intermittent no start problem I was having as well.

Now I'm back to just having a white raster but at least I can continue recapping it, but enough for tonight, I can rest easier knowing I didn't ruin anything unobtanium.

[Eric H]

that I had to keep going.

I replaced a couple more caps in the AGC circuit with no results and then I remembered, I have a factory service manual! I can check some voltages.

It didn't take long to realize the 140+ supply to the Video board was missing, like zero volts.

The supply is on the same board I had recapped a few weeks ago and came off of one leg of a 4.7 Cap that I had replaced, it was zero at that end too, and no wonder, when I replaced the cap there is a wire that is also soldered to one of the lugs, it's supposed to be on the + lug, I had attached it to the - side!

I quickly switched it around and...Picture!

Did a little adjusting and here's the result.

Vertical is stretched out but the adjustment is underneath so I'll wait until I have it put back together before I adjust it.
I still need to repair or replace the Circuit breaker, anyone have a 1.25 Sony breaker? I may simply put a fuse across it.

When I get it finished I want to get a picture of it with Ted Baxter on screen, maybe a picture of Ted on WJM's 1210 playing on my 1210, that would be kind of cool.