epiphone triggerman 100h weird problem

[pontiacpete]

Hi, This amp came in with lots of burned transistors in the output. So replaced all the bad parts.
I went to fire it up on the light bulb without a load and all seemed fine, no DC on the output.
Plugged in a speaker and the light comes up bright and there's a hum. But no DC on output. Now weird thing is this:
If I plug in a load while on, all is well, or if I turn it off after trying it without load and then plug in load quickly it comes up fine.
But if there's a time lag of being turned off and turn-on with a load , it doesn't work.
I know I'm probably explaining this terribly, but I sure am stumped.
If anyone has an idea what the problem might be, I'd love to hear it
Thanks
pete

[g1]

Sometimes the bulb limiter will cause this problem.
If you have no DC on the output, and can connect a load with no problem while it is running, why not try it without the bulb?

[pontiacpete]

It's all hum.

[pontiacpete]

Actually there is about 17vdc when the bulb is bright , ,, don't know how I missed that.
This seems to be a matter of how much the caps are draining. I put a meter on the filter caps to monitor the voltage and the draining dc.
It takes 2 minutes for the caps to drain. If I put in the load at that point I have big hum, the speaker stays in the out position and there's 17v
If I let the caps drain down to 25vdc , plug in the load it will work and the amp sounds good or as good as it can get.
If I turn on without a load, no problem and no problem putting the load on if done so before the caps fully drain.
Are the filter caps breaking down? or something

[pontiacpete]

This morning I hooked up the output '16 ohm' to a 16R load. Metered across the load and R313, the base of Q314.
Turned the amp on and the load read 17vdc and the Q314 base 16vdc, light bulb limiter shining bright. Don't want flip the limiter off and destroy my new transistors. Then I powered down scratched my head, about half minute goes by, power on, the light limiter does not shine bright, there's no DC on the load.
ANy ideas?

[Jazz P Bass]

You may have to bite the bullet on this one.
The amp is not stabilizing when you have the 17Vdc on the output.
Get rid of the limiter & try it without a load.
When you do get around to attaching a load, use a larger resistor that will not draw huge amounts of current.

[pontiacpete]

Did that, got rid of the limiter amp works normally, sounds good(as good as it can get).

Larger resistor?
Do you mean a larger dummy load? 1K?
I don't have anything with a high enough wattage capability. Or does that matter?

[Jazz P Bass]

Sometimes it may help to use a larger load resistor as it is not stressing the amp.
Wattage does not matter as it is only being used for start up issues.

[pontiacpete]

So I was just being a wimp for not just throwing the switch to turn off limiter. Never seen an react this way.
Well it's working so be it.
I can't help but wonder why it would react that way to the limiter. ?

Thanks for the help, guys

[pontiacpete]

BTW, I did try it with a 330R and light bright, no DC

I guess it's the initial in-rush of DC that hangs the amp up on the limiter.

[Jazz P Bass]

If you slowly raise a solid state amp on a variac, while monitoring the driver bases, you will see a voltage on the bases higher than what you would expect (ie: expecting 1.5 Vdc).
Then, while still raising the variac, as the feedback circuit kicks in the reading gets all jumbly & then (whew) it settles down to a rightfull 1.5 Vdc (or something similar).
So my thoughts are that the limiter was messing with all that & the amp could not compensate.

[pontiacpete]

thanks for the explanation Jazz. I'll try that. This amp has a rather strong turn on pop. It probably is the dc hitting the output.

[Jazz P Bass]

What's with RLY 1?
It looks like a mute.

[pontiacpete]

Do you mean a mute for the pop when power on and off?
This amp makes 2 pops when powering up. One when when going off.
Should I test the relay?
Not sure I know how.