RCA CTC 187 squealing noise - Videokarma.org TV - Video

MRX37 · #1 03-21-2009, 12:59 AM

I pulled a 32 inch RCA CTC 187 out of the dumpster, thinking that this would become my new TV. I took it home and removed the back. Sure enough the degaussing thermistor was gone. Easy fix, but I decided to plug it in and see if the rest of it worked first.

Good thing I did because the second I plugged it in, I heard a squealing noise. I unplugged it right away.

The flyback's shot, isn't it?

radiotvnut · #2 03-21-2009, 10:50 AM

Maybe not. Those CTC187 flybacks hold up much better than the newer RCA's; but, I'll bet the HOT or the diode in the 140 volt supply is shorted. Usually, when the diode shorts, it takes out that STK regulator IC; but, this could be an exception. If the HOT is bad, check those blue caps around the HOT. Even if the flyback is bad, you should be able to get one reasonable.

MRX37 · #3 03-21-2009, 12:13 PM

A bad HOT I can replace. A bad flyback I won't bother with.

See, I'm not all too thrilled with this TV, as the screen is scratched. So, I don't want to put a lot of work into it since it's unsellable, and if I kept it I'd have to live with the scratches.

I'll check the HOT and diode later tonight.

MRX37 · #4 03-21-2009, 01:31 PM

Okay I had some time, so I took out the HOT.

measuring from center prong to right prong, I get about 2 to 4 ohm's resistance.

Measuring from center prong to left prong I get about 37-38 ohms.

Measuring from left to right prong I get about 35 ohms.

Is this HOT shorted?

PS: the HOT appears to be a BUH517.

radiotvnut · #5 03-21-2009, 05:02 PM

It's bad.

MRX37 · #6 03-21-2009, 05:39 PM

Quote:

Originally Posted by radiotvnut

It's bad.

Yep. I replaced a bad 47uf@25 volt cap, and put in a temporary HOT, plugged it in and the squealing noise did not return.

Now here's my issue. I have lots of TV chassis boards, including one from a 36 inch Zenith that have good HOT's. However, trying to find one where all the ratings meet or exceed the BUH517...

Well, according to a datasheet I found, the BUH517 has a maximum collector to base voltage of 1700 volts. Every HOT I've looked up that I have only has a 1500 volt Collector to base voltage, and I can't find a datasheet for the HOT on the Zenith chassis. The numbers for the Zenith HOT are 1167-01.

I have a few 27 inch TV chassis with D2645 and D2634 HOt's, but they also only have a 1500 volt collector to base voltage.

radiotvnut · #7 03-21-2009, 06:15 PM

I'd strongly recommend using the type that came out of there; but, one of those other HOT's will probably hold up long enough for a test.

MRX37 · #8 03-21-2009, 06:17 PM

Quote:

Originally Posted by radiotvnut

I'd strongly recommend using the type that came out of there; but, one of those other HOT's will probably hold up long enough for a test.

That'd require money to order one. I'm flat broke.

If I can't find a suitable HOT, then when I can I'll order one. But yes, the closest HOT I have will be used to test it.

radiotvnut · #9 03-21-2009, 06:26 PM

You may not have to buy one. I'm sure I can find one on a junk chassis somewhere that you can have.

MRX37 · #10 03-21-2009, 06:35 PM

Quote:

Originally Posted by radiotvnut

You may not have to buy one. I'm sure I can find one on a junk chassis somewhere that you can have.

That would be great if you could... I'd be quite grateful.

I'm going to go solder in a HOT that will hopefully hold up long enough to test it.

MRX37 · #11 03-21-2009, 06:50 PM

Don't bother sending me a HOT. With the test HOT, the TV turned on, then I started hearing a loud "POP POP POP", something was arcing.

So, I'm just going to junk this TV.

radiotvnut · #12 03-21-2009, 07:43 PM

Probably the flyback. I had a CTC177 do that and I found a good flyback from a junk board and fixed it right up. If your screen is scratched, you're probably doing the right thing by letting it go. My flea market friend found a late '90's 25" Magnavox at the dump with a couple scratches on the screen. All that was wrong was a small blue disc cap going from the HOT collector to ground. I've seen the problem many times. The set makes a nice picture; but, anyone who has ever been interested runs the other way when they see those scratches.

MRX37 · #13 03-21-2009, 08:06 PM

Yeah. if the scratches weren't enough, the popping noise was. Since there's a working 36 inch CTC 187 here, I'll save the chassis from this broken one..... too bad the only things I'd really want off of it are shot.