Bad SC99?

[mikeyg]

Hi,

I'm on the last of 4 J99's and I'm having trouble with the input bias on one of the SC99's. The first 3 J99's checked out and adjusted fine.

The op-amp(#608) on U1 adjusts fine but when adjusting for the op-amp(#609) on U2, I get a reading of 17.48mV when SW1 is minimum gain and 17.46mV on maximum gain.

R47 has no effect on adjusting.

I swapped op-amp(#608) to U2 and it's able to adjust as expected.

Op-amp(#609) in U1 was unable to adjust with R43 and gave similar readings as when installed in U2.

Could the SC99(#609) be bad? Anything else I can check?

Thanks,
Michael

[tpryan]

17.48mV isn't a problem. 17.48V is a big problem. Which is it?

[mikeyg]

Sorry Tim , you are correct. I typed wrong and reported a bad reading.

As of today, SC99(#609) measures 17.31V and not mV in U2.

Measuring at U2 pin 4 and U2 pin6.

R47 and SW1 has no effect on adjusting as reported earlier.

Thanks.

[tpryan]

Probably the op-amp. Please e-mail rma@seventhcircleaudio.com for return instructions.