Acoustic Control 260

[pontiacpete]

I don't have the schematic for this. If anyone has it please post.
I have a quick question. This amp when powered without a load starts out with 33vdc on the output. So I figured it would be a good idea to hook up a speaker. But with the light bulb limiter it is not showing a short. And as I watch on meter the voltage on the output slowly goes down. In about 5 minutes it is at 7vdc.
Any ideas why this is?
Should I just go for and hook up the speaker?

[The Dude]

I couldn't find a schematic for that particular model, but looking at a few Acoustic Control schematics, I see that some of them have capacitor coupled outputs. If yours is cap coupled, what you are describing would be normal. If you have it opened up, can you follow the speaker leads and see if they end up at 1 or 2 big electrolytics?

[Enzo]

Without looking it up, I too will assume it has a single power supply, and so a speaker cap. Without the load, the cap cannot charge quickly. So the voltage remains. Hook it up to a speaker and find out.

[gbono]

Service manual is here Guitar Amplifier Schematics and more

ditto what was said above - all the ACC PA designs 150,270, 370, 470, 330 are single ended supply.

[pontiacpete]

Thanks guys, I was being a big chicken, afraid of possibly blowing a speaker, which I shamefully admit has happened before.
Anyway the amp does power up. I had found a large wire wound resistor 1250 ohms that had a bad solder connection. Not sure where it is in the circuit,
perhaps a dropping resistor in the power supply. It has 70vdc on one side and 26v on the other. Repaired solder joint and it works.
Thanks again.

Next time I've got to remember to go to 'bmamps' for schematics.

[g1]

Thanks guys, I was being a big chicken, afraid of possibly blowing a speaker, which I shamefully admit has happened before.

Then I think this next bit must have been a typo:

This amp when powered without a load starts out with 33vdc on the output. So I figured it would be a good idea to hook up a speaker.

[pontiacpete]

jeez, I can't believe some of the typos I make.

Maybe there's room for editing, so future people will get the idea.

[onedamnote]

ACC-260-261.pdf

Any old post, for anyone who might come across this looking for a Acoustic 261 Service Manual or Schematic.