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Sansui G2000 smoking transistor

R

Raffi

New Member
The D313 transistor connected to the heatspreader towards the back smokes and sizzles whenever I power the receiver on. I looked at it closely, and the 3 pins are mostly blackened. Aside from the smoke, the lights turn on and it does tune for a split second before I quickly power it off. All lights are nice and bright.

I checked all of the caps, and they're not leaking nor bulging, and the transformer doesn't make any adverse sounds. I also checked the fuses, and they don't have any black to them, so I don't think they're blown. If I solder a replacement D313 transistor on, will that solve the problem, or could it be another part, like a resistor or something?
 
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It's usually a shorted transistor that causes something else downstream from it to smoke. A smoking transistor could be a bad transistor in and of itself but it could have also been taken out by another shorted transistor.

I shudder when I see people try to guess without using a simple volt/ohm meter to check things out because when this happens, the headache just gets much worse and other things end up fried because someone thought that just because a single part was smoking, that THAT was the part to replace. WRONG! :crazy:
 
century tek, you're absolutely right. That is why I came here, instead of trying to fix it myself. I could easily replace all of the transistors, since they're all large and the part numbers are fully legible. If I do that, though, could something else be causing the short? Furthermore, if I try to use a meter, wouldn't the receiver have to be powered on? If so, I'd rather that the whole thing doesn't blow while trying to find out where the short is. Forgive me, by the way. I haven't done this before. I got the unit for free, so if it dies, it isn't a huge loss.

deltalight, assuming those are part numbers for the transistors I need, thank you very much! Found a bunch for cheap pretty much everywhere.
 
Raffi said:
Furthermore, if I try to use a meter, wouldn't the receiver have to be powered on?
Click to expand...

That's where a DBT (Dim Bulb Tester) comes in handy - you can make one very cheaply, and it makes things a lot easier if you know how to use it, (and build it correctly of course ;) ).

We can help with all of that....
 
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When a meter is used for testing purposes, you need to have the unit powered up to take voltage measurements. You don't need to have the unit powered up to take resistance and ohms measurements.

You can remove a transistor and test it with the ohms setting to see if it is shorted.

If you are a novice, read up! Plenty here and plenty folks will help steer you in the right direction.
 
Ok, here's an update: Now I know why it was free... while I was cleaning the exterior, a penny fell out. Clearly, the exhaust vents at the top are large enough for coins to be inserted, most likely by a toddler or careless adult. I don't know where exactly it was while it was stuck in the receiver, but... could the alloy in a penny cause a short? If so, with the penny out, could the receiver work if there isn't too much damage to the transistor, at least for quick testing purposes?

I will be purchasing a meter as soon as possible, either way.
 
If you can post some pics, I or someone else here could show you how to replace the transistor(s), and it is quite possible that only one channel was affected and the other is fine but you will have to learn to troubleshoot it if you want to do it yourself.
 
century tek said:
If you can post some pics, I or someone else here could show you how to replace the transistor(s), and it is quite possible that only one channel was affected and the other is fine but you will have to learn to troubleshoot it if you want to do it yourself.
Click to expand...

I'll post some pictures tomorrow. It seems to have 4 transistors, 2 per channel, and both of the black ones have scorches on the 3 pins connecting them to the board and the blue ones do not. Only one smoked, though, so perhaps the other got totally fried before I got the unit. Could one or more of the resistors on the wire path leading to the transistors be causing the problem?
 
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