old bass 400 has no clean sound, Help

[strat88]

I got a hold of an old bass 400. It needed new output transitors, that I replaced. My problem is the sound is distorted in both channels. If I turn down the bass control it cleans up a little. Hopeing someone can point me in the right direction to fix this. Ive built soildstate and tube amps, Im just not that good at troubleshooting.

[Enzo]

Make sure to try a different speaker cab, bad output transistors could have damaged your speaker.

Which one you got? Four input jacks or six?

Isolate the problem, preamp, power amp, or power supply? The preamp receives +24vDC from the power amp. Is it there and clean? The preamp sends its signal to the power amp, scope it or connect it to some other amp or signal tracer. is it clean or distorted?

Is there a three wire cable connecting the preamp and power amp? should be ground, +24v and signal. If you unplug that from the power amp, you can clip a test signal to the ground and signal points. That will test the power amp.

[strat88]

It is the six input. One ch has fuzz and distoriton the other clean

[Enzo]

6-inputs means it is the B series version. So we can all be on the correct schematic.

[strat88]

I dont have access to a scope. Checked voltage to preamp and it is only 16.1v

[Enzo]

Set your meter to AC volts and measure that 16vDC. If your meter reads something like 40v, then the meter needs help. More sophisticated meters will read JUST the AC part. I am suspicious you have loss of filtration causing HIGH ripple. That drops the resulting DC but also clouds the music.

Otherwise, the 24v regulated supply on the power amp may have failed.

[strat88]

I looked at the scematic and saw it had a 10K trimmer to adjust the 24volts. I used it to bring the voltage to 24v. The amp sounds fine now there is no hum or 60hrz rumble. Hope that is all it was. should I watch for anything else, and I will still check the voltage with the AC reading
Thanks for the help.