Yamaha CR-620 | POP! And no sound...

[Ritalin]

Picked this amp up for free off craigslist and they said they heard a pop and now the whole control was dead. I did some tracing and came to this part and then the trail ended there, so I think this is the problem maker. The part is so old that I can't find much about it. HELP!

[redwire]

Re: Yamaha CR-620 | POP! And no sound...

That's a transistor 2SD234, probably used as a voltage regulator in the amp. 60V 3A B=40-240. Many substitutes like TIP41A, MJE3055T, TIP31A is lower gain.

But you still have to find out what went pop. How are the capacitors and other transistors looking? Unless the pop was heard in the speakers.

[Ritalin]

Re: Yamaha CR-620 | POP! And no sound...

Caps and transistors look alright, when I disconnect a portion of it I get all the right voltages coming out, but as soon as I reconnect, I lose about half the voltages.

[Ritalin]

Re: Yamaha CR-620 | POP! And no sound...

And I might have a TIP31A, is that alright to put in, or should I order a better part?

[Ritalin]

Re: Yamaha CR-620 | POP! And no sound...

NVM... all I have is TIP31... which I'm sure won't work....

[budm]

Re: Yamaha CR-620 | POP! And no sound...

It sounds to me you have bad circuit some where that draw too much current and cause the voltage drop, this transistor is set up as a linear regulator which is in series with the load.

[redwire]

Re: Yamaha CR-620 | POP! And no sound...

Budm, thanks for digging for the schematic
Ritalin I think you are off track. TR802 is the +30V regulator for the preamp stuff (phono preamp, tone controls) and it also gives bias to the power amp diff amp. But nothing I could see would load it down' it does not drive anything without big resistors. If the vreg is overloaded, it would get real hot and burn up.
You can try a tip31 i think it would work. make sure the Zener is ok giving 29v to the base.
If you have some voltage measurements that helps