Autotek Issues

[vincegironda]

Hi the amp is an Autotek 7300 BTS

Issue is the sound is distorted and bitty at low volume, when the vol is increased the sound is clear.

I have cleaned the gain, bass and treble pots and crossover switch with contact cleaner and no change.

The power supply capacitors were leaking so I replaced them - no change

I also replaced all the capcitors in the audio section, sill no change.

All the output transistors checked out fine too.

The amp doesn't overheat, or cut out, at high volume it sounds good, just distorting at low to mid volume?

what could be the issue?

thanks in advance

 

[Perry Babin]

Have you set or checked the bias for the outputs?

 

[vincegironda]

Hi Perry no I haven't.

How would I go about it on this amp?

it has two bias pots, both are currently set fully counter clockwise.

Turning them up makes no difference to the sound?

 

[Perry Babin]

This is how I set them:
http://www.bcae1.com/temp/ausettingbias.swf

Increasing the bias should make the idle current increase. If it does not, there may be other problems.

 

[vincegironda]

Thanks Perry where do the meter probes go to measure the DC amps?

 

[Perry Babin]

I use the amp meter on my DC power supply.

 

[vincegironda]

My power supply doesn't have an amp meter, is there another way?

 

[vincegironda]

I just turned the bias pots up to half way and it made no difference to the sound, Also tried with both pots fully clockwise, again no change so I'm wondering if the pots are working at all?

 

[Perry Babin]

Did the current draw from the 12v power supply change with the pots fully clockwise?

 

[vincegironda]

with both pots counter clockwise shows 0.69 with the meter set at 10A

when I turn both pots fully clockwise the reading is 0.71