that's hot!

[studio neal]

Hi all

the heat sinks on my C84 are very hot to the touch and I can smell the heat coming from them.

My voltges at pin 4 and 8 are +14 and -13. I tried to turn them up to +/-18 and I popped cap 34. My diodes are correct and the caps are correct too.

Any suggestions?

Thanks
Kyle

[tpryan]

U1 and U2, pin 4 should be negative, pin 8 positive. Are you measuring those correctly? Have you installed U1 and U2? C34 should be a 50v cap. There's no way to blow it up by adjusting the regulator, even if you crank it the whole way, assuming the cap itself was not defective or installed backwards.

[studio neal]

I think that I am measuring these correctly. 4 is -13 and 8 is postive 14. I have not installed the the opamps I'm just measuring off of the sockets.

I have not added the opamps yet.

I replaced that cap and I am going to try to bring it up to the correct voltage tonight. It may have been a defective cap as it was installed correctly

Should i be concerned that the heat sinks are hot to the touch?

thanks for the help

[tpryan]

The output buffers conduct all the time, so that disippation in the regulators is probably what you're seeing. As the rail voltages increase, the regulators should run cooler, since the voltage across them decreases. I'd install the op-amps and see what happens.

[studio neal]

These voltage regulators are still hot. Hot enough that I cannot touch them and I can smell the burning metal smell. I have another C84 and the regulators don't even warm up. I've compared the two preamps and I can't find a difference. Any suggestions?

Thnaks
Kyle

[tpryan]

Clearly, you have a serious problem somewhere. First, can you measure the voltages at pins 1, 4, 7, and 8 of the op-amps? Second, measure the voltages of the BC550 and BC560 transistors in the output buffer. Let us know what you find.