Possible Mark Levinson 431 Problem

[ceulrich]

Hello All,
I have a 19-year-old Mark Levinson model 431 power amplifier. After sitting unused for about 2-years, I wanted to compare it to my current amplifier. I powered it up for a few days to let it warm up. While checking the input and output to adjust gains for the two amplifiers, I noted a -140mV DC at the input, the output was 0VDC. Both channels measured the same.

My question is, can that be considered normal? The manual says the input is a balanced topology, but I use it in single-ended mode. I noted that if I add a load (if that is the proper term here) of about 1K, the DC goes to zero.

Thanks for any help
Cheers,
ceulrich

 

[Hans Polak]

When both inputs measure the same, it’s perfectly o.k.
The input transistors are drawing their base currents from 49k9 resistors, so -140mV means ca. 3uA.

Hans

 

[ceulrich]

Hans, thanks for taking the time to respond!
I was hoping that would be the response.

Cheers,
ceulrich