Horizontal problems on a Trinitron KV1712 - Videokarma.org TV - Video

zenith2134 · #1 07-30-2007, 03:54 PM

Hey everyone! Hope everyone is enjoying their afternoon.

Well, I posted a thread a few months ago about this Sony set which I found curbside. Originally, all was great, then the horiz started losing sync and shrinking/breathing.

I replaced about 5 caps, around the horizontal output and HV transformer, which were testing weak. I check the majority of all the other caps, and these were within spec. I patched up the set, and all was great again.

The raster now fluctuates in size and at times the whole raster rapidly changes size from medium to regular, as if the HV is out of control. However, the high voltage is stable and fine. Does anyone know if this was a common fault with these sets? The TV has a truly amazing picture when it works.

Also, this was built in 1977, and the CRT is very strong still. Please, experts, I need some help here. Thanks

andy · #2 07-30-2007, 04:33 PM

Check the B+ voltage. I had one of these where the B+ pot was dirty and causing the voltage to change sometimes.

kx250rider · #3 07-31-2007, 12:09 PM

There's an electrolytic on the power board that causes that, and you likely also have a blown 2SC867 B+ 130-volt regulator. That's on a heat sink mounted on the CRT shield. It's been YEARS, but I used to see that problem a lot. Be careful, because that's putting a big load on the SG-613 Horiz. output SCR. You don't want to blow that at $75 a piece last time I bought one!!!!

Charles

zenith2134 · #4 07-31-2007, 04:10 PM

Andy, Charles, great info there! I am going to break into the set once again this weekend. Maybe sooner, got to see what the work schedule is like. I was very close to dumping the set at first, because the VHF tuner knob is gone and its the skinnier type which I never see anymore. Good set though. Thanks again

Findm-Keepm · #5 08-02-2007, 10:27 PM

I had one of those years ago - was an old Navy Shipboard Studio Monitor. It had been modified for shipboard use by installing some isolation transformers. I fixed it twice - ate the SCS (SG613) one time and I had to troubleshoot the B+. From what I wrote on the Sams folder, I gather it was a 4.7uF 160V cap that opened up.

Second one was a bad solder joint - those early Trinitrons were famous for bad solder joints on the coils near the Horizontal (H?) board - also check the pincushion coils and transformers.

BTW, if you do blow the SG613, Prelco ( no affiliation! ) has them for 28 bucks.

But try to find an SG629........

Cheers

andy · #6 08-03-2007, 12:00 AM

Several years ago I replaced the SG6XX in a 12" Sony with a regular transistor and it worked fine with no modifications. It's worth a try, at least for trouble shooting without risking the expensive original part.

zenith2134 · #7 08-03-2007, 12:10 AM

Great stuff, I'm gonna open up the set near my PC so I can go by these notes! Hopefully I won't have to substitute anything , but I may have to here. I remember how bulletproof the build-quality is from last time I had 'er open - Thats the kind of thing that makes me blow my time and money in an old set. But you guys understand me here, right?