Capacitor replacement

Typing 472M into google gives you 26,700 replies or thereabouts.

http://www.csgnetwork.com/capcodeinfo.html

Your out by a long way ...

Why are you thinking that is the problem.?

I'd be looking more at the component behind it, as it looks like either a scorch mark, or heat from a resistor.

Mark

Ok, thank you very much! I though that was the problem because it is the only component that has any marks of damage, but it was right in front of a resistor so as you said it could probably be the heat from the resistor that made that mark. Do you suggest replacing both the resistor and the capacitor at this point?

The only schematics I could find are for sale

Keep searching and don't be afraid if some are in the former USSR as they seem to have lots of circuits/schematics.

Try the forums for the TV as often they link to circuits.

You had the supply repaired ... is the shop that did that able to help.?

Just post back here.

mark

Well the shop is probably capable of repairing the tv...the problem is that when I got the supply fixed I was very unhappy with the price. I know that many times people expect lower prices because they don't know how much time and effort it takes to repair this kind of stuff, but when I brought the TV I had already opened it and I told them where the problem was because it was very easy to spot. The only reason I brought the TV to them was because I didn't feel experienced enough to repair an old TV without risking to damage it. The point is, when I went back to get the TV, they charged me 80 bucks just to replace a capacitor. I don't find that to be fair since I know that it didn't take them much work...sorry for bothering you with this long story ahah

Ok, so, after some tinkering and testing I think I might have found the problem...but still, as I am used to, I have a doubt. Here is what I found.

There is a transistor (pretty big one) that does not seem to have any visual damage on it but when I tested it I got the following results:

pin 1 (positive lead multimeter) to pin 2 (negative lead multimeter) gave me the same resistance (almost, slightly higher) as pin 3 (positive lead multimeter) to pin 2 (negative lead multimeter) so I am thinking this is a PNP transistor,

and since pin 1 to pin 3 gave me no resistance I am thinking the transistor is damaged.

The "only" problem is that if I search for the code on the transistor (C3892A) on google I can only find datasheets for NPN transistors that go by that name.

I am seriously confused right now. If you could give me some advice on this I would greatly appreciate it

Here is the complete list of values from the multimeter:

pin 1 (positive) to pin 2 (negative) reads 406;

pin 1 (positive) to pin 3 (negative) reads 40 and beeps;

pin 2 (positive) to pin 1 (negative) reads 1;

pin 2 (positive) to pin 3 (negative) reads 1;

pin 3 (positive) to pin 1 (negative) reads 40 and beeps;

pin 3 (positive) to pin 2 (negative) reads 431;

Franceso.

Really quick reply from the airport.

Try searching for a 2SC3892A.

They usually drop the 2S to save room.

Most transistors don;t show well unless you can bias the base with a finger or resistance to force it to conduct.

Robert Peter Oakes

Peter can you help in my absence.....

cheers

Mark

Hi Francesco,

Your transistor number does cross to an NPN deflection / flyback transistor. How are you determining the polarity of your test leads on your Ohm meter? Several of my meters have the positive voltage on the black lead of the Ohm meter. Confusing but for whatever reason this is the way they were designed. Typically these transistors fail in a shorted condition. If you do not have a short between any of the leads it may not be the transistor.

John

Ok, thank you very much...by adding the "2S" in front I was able to find a lot of information on the transistor!

The multimeter should be "regular" with red as positive and black as negative because all other readings suggest so and I was also able to power up an LED with the diode testing mode and that further suggested what the polarities are. Now, assuming it is a NPN transistor as the datasheets say, I built a tiny circuit giving +5volts to the Collector, ground to the emitter and when I put something around +3 volts on the Base the current went through (I powered an LED). I also am pretty sure of which is base, which collector and which emitter because they are printed on the board. The transistor seems to work fine with low voltages and currents, I don't know if it may behave differently when those currents are increased...this to me suggests that the problem is elsewhere.

Ok, I just did another test...this time I assumed it was a PNP transistor. I connected +5v to the emitter, ground to the base and current went out the collector to power an LED. At this point I figured something was wrong so I disconnected ground from the base and it still powered the LED...I am afraid either I do not understand transistors that much (very very possible) or the transistor is working in weird ways

Francesco

Can you confirm what pins are 1, 2 and 3 in your testing.

http://www.svntc.com/TPDF/2428.pdf

Also can you confirm what the 1, 431 and 40 reading is (Ohms, diode test or ??)

One of the faults that can show is a collector to base short, and the reading of 40 between 1 and 3 doesn't tie in with the other readings.

I would expect a +ve on the base will conduct to the emitter.

I also expect a +ve on the emitter will conduct to the collector (using the protection diode)

Mark

Hi Mark,

pin 1 is base, pin 2 is collector and pin 3 is emitter, just as in the pdf you linked.

The readings are from the diode test.

Francesco

Thanks for the confirmation.

I assume when you use your meter on diode test with nothing connected it will read 1.

if so ...

this is the representing the forward bias voltage of the diode under test, which is usually around 0.4v on these testers.

Using this it appears the transistor is working fine.

1 and 3 = 0.040 which is the resistor

-ve on 2 and +ve on 3 = .431 which is the reverse bias diode

+ve on 1 and -ve on 2 = .406 which is the reistor and diode in series plus the base junction conducting and possibly the C-E also conducting slightly.

One thing an older guy at work taught me for testing switchmode supplies. 

Make up a lead with a lamp in series in the phase wire.

If you use a 100w lamp and the switchmode has a short, it will light the lamp instead of making a big bang.

If the 100w lamp is not enough use two or a 150w lamp.

Mark

Francesco

Thanks for the confirmation.

I assume when you use your meter on diode test with nothing connected it will read 1.

if so ...

this is the representing the forward bias voltage of the diode under test, which is usually around 0.4v on these testers.

Using this it appears the transistor is working fine.

1 and 3 = 0.040 which is the resistor

-ve on 2 and +ve on 3 = .431 which is the reverse bias diode

+ve on 1 and -ve on 2 = .406 which is the reistor and diode in series plus the base junction conducting and possibly the C-E also conducting slightly.

One thing an older guy at work taught me for testing switchmode supplies. 

Make up a lead with a lamp in series in the phase wire.

If you use a 100w lamp and the switchmode has a short, it will light the lamp instead of making a big bang.

If the 100w lamp is not enough use two or a 150w lamp.

Mark