What is this clicking in the color tv?

Sounds like you have a shorted semiconductor somewhere causing the power supply to shut down. Check the horizontal output transistor first. Diodes in the power supply are another suspect.

Wow. I didn't know they could click!

That has obviously been replaced once already, so I thought the odds were higher that it was good. Maybe I should have thought the odds were lower that it was good??

So I tested it, a D1398, and all three points on the output transistor had the same voltage, 128.

With an ohmmeter, it was almost zero between the base and emitter, so I removed the transistor. With it out, it was 46 ohms in both driections between the base. It turns out there is a transformer across the base and emitter, so that's why it was 0.3 ohm, but 46 ohms is too low also, right. I need a new one.

It is 220 ohms in both directions between the base and collector, and 175 ohms in both directions between the emitter and collector.

I plugged it in again with the output transistor out, and it still clicks!

The powersupply diodes are all in one box, and the chopstick on the box doesn't make the clicking any louder.

I used a digital multimeter to measure the B+. Is it worth digging out an analog meter...would I see pulsing in the voltage because of clicking in the diodes?

BTW this thing even has MTS sound, but only one RCA output jack for it. I probably don't have a device to separate the left from right, do I? Or to extract SAP, which I never listen to on the tv's I have that have it.

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That does not always mean it's shorted, i assume you're talking about the HOT (Horizontal output Transistor), many of those have an internal resistor from the base to emitter.

THat sounds like it's bad. bare in mind that many of those transistors also have the Damper Diode in the case between the collector and emitter. so you should get the common diode reading on one direction.

Most likely because the flyback isn't starting up in the required time and the power supply is reseting for another attempt.

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Is there any chance that replacing the bad horizontal output transistor will get me the voltages I need, and cure the clicking, even though it clicks with the H.O.T removed?

I don't like just replacing parts without being sure I have found the root problem, but I'm lucky with your help to have found this, let alone other problems. I don't know how to trouble shootwhen the set is not running at all, or without replacing bad parts when I have found them.

If so, it's going to be days or weeks before I have time to get the part and put it in.

I realize I'm just not very good at this, for this sort of reason. It's confusing. I did learn that at least in tube tvs the horizontal output circuit provided the high voltage that was used all over the tv. I never learned if transistor sets are the same.

Even though I found a few google hits for a D1398, including a spec sheet and a company that sold them, I also found an article in google groups from this very newsgroup back in 1996 where JohnSon replied to Michael Portmann, and Michaal asked about a 2SD1398, which was also a horiz. output transistor, and JohnSon referred to it two ways, as a

2SD1398 and as aD1398. So I guess they are the same? He also suggested as a substitute an ECG2302. That should be easy to get. Well, Mouser has an NTE2302. The local electonics store in Baltimore, Baynesville Electronics, is usually pretty expensive, and there is no rush.

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On Sat, 17 Feb 2007 20:37:30 -0500, Jamie wrote: ...

Yes, the HOT. And yes, I found the specs for an NTE2302, which Mouser also says is a substitute for the D1398, and it does have a damper diode in it. (I never heard of that before, but makes sense.)

So this might get it working again. I'll try it. It's been replaced once already, but maybe it lasted for years after that. Since I didn't find out outside an electronics shop, I guess it worked long enough to return it to the owners... Unless some guy like me replaced it, it burned out immediately, he threw it away and I found it. ;)

It's a little strange. He cut the leads to the transistor and soldered the new one to the stubs. I tried that but for me, it was much easier just to unsolder at the pcb. Is his way a common techniqe?

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If it clicks with the HOT removed, you probably have another fault. Can you isolate outputs of the power supply to see which bus has a short? Sometimes you can lift one side of a component or wire from the power supply section to the rest of the set.

It's not uncommon, particularly in sets where it's difficult to get to the bottom of the PCB without disassembling a lot of stuff. I don't like to do it that way though, just doesn't seem tidy.

if the HOT that bad off and it's been replaced before, i think you should also look at replacing the Flyback, it most likely was the cause of the HOT short out. I use to always replace the Flyback if the HOT was damaged that way other wise, it normally came back later with the same problem again. finding a HOT opened or just maybe the Base Emitter shorted, i would then just replace the HOT>

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Real Programmers Do things like this.
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Maybe. I'll try.

Aha. OK.

Thanks to you and eveyrone for your help.

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Aha.

Hmmm. OK.

If non-high-def tvs weren't going to be almost obsolete in 2009, I might replace the flyback, but I guess it would be too much money now. At least I won't get too confident that the HOT only will work. I wish they weren't going to make all these tvs depend on set top boxes and satellites. It's such a pretty tv, although it has no remote capability.

Thanks.

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I've actually found flyback failures to be quite rare, aside from certain specific sets that had a tendency to fail in that way. HOT failures I find are often caused by cold solder joints or bad electrolytic capacitors.

mm ha escrito:

first things first. remove the suspect transistor and solder a 100 w bulb acros c-e terminals on the board. switch on and measure the b+ across them. if the bulb doesnt light chances are you have a short elsewhere, the b+ cap is bad, or the power supply is faulty. post results and we can take this a step further.

B-.

So I should look at the nearby cold solder joints and bad electrolytics. I'll do it when this other one is done, maybe tomorrow.

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