QSXM2 troubleshooting!!

[W1DAN]

Per Anders:

The RIAA stage came up fine for the left channel. On the right channel RIAA section I still have some offset on the output when the preamp has 10mv at TP1. For now I inserted a 10UF capacitor in series with R93, and the main output DC is now fine.

On the preamp DC servo amp IC1, when my test oscillator is set to 20hz, I see a sine wave on the output pin 6, as well as a little at C9. Would this AC audio correction signal "subtract" the from the main signal low frequency audio? Either way I added 10uF across C9 to make the correction voltage pure DC.

I'm listening to the preamp now-sounds clean. I will then look for the cause of the right channel DC offset and eliminate the audio coupling capacitor.

Good progress this weekend! Thank you again for your assistance!!

Cheers,
Dan

[W1DAN]

Hej Per Anders!

I would like to increase the gain about 6dB. Would I increase R51 to do this?

I am using a MM cartridge and the preamp is working pretty well (still have an issue with the right channel DC offset without input termination).

Thank you,
Dan