Marshall AS100D Acoustic Amp reading -vdc on the speaker output(s)

[goldtop5]

I've got a Marshall AS100D acoustic amp that passing negative DC voltage to the speaker output(s). I've replaced the whole output/ps board hoping that will save me some time. Regardless, I'm still getting DC voltage on the speaker output(s). Could it be a bad power transformer causing it?

[Jazz P Bass]

Can you post a schematic?
One thing that you can test is the power supply rails.
You should have a +xx Vdc & a - xx Vdc
You may be missing the +.
And the low voltage supply for the opamps should be something like +15 & -15 Vdc.

[The Dude]

If it helps, schematics are posted on THIS THREAD.

[goldtop5]

Can you post a schematic?
One thing that you can test is the power supply rails.
You should have a +xx Vdc & a - xx Vdc
You may be missing the +.
And the low voltage supply for the opamps should be something like +15 & -15 Vdc.

Here is a schemtic of the power supply and output section

[Enzo]

No, it is not the transformer.

Are the 3886s on the board you swapped?

I note the power amps - and there are two, so are BOTH putting out DC? - are all referenced to ground 2, EXCEPT the input, which is referenced to ground1. That appears to be off board somewhere, preamp maybe. SO, is ground 1 and ground 2 showing continuity? Are we operating with any cables disconnected?

[goldtop5]

[QUOTE=Enzo;311240]No, it is not the transformer.

Are the 3886s on the board you swapped?

I note the power amps - and there are two, so are BOTH putting out DC? - are all referenced to ground 2, EXCEPT the input, which is referenced to ground1. That appears to be off board somewhere, preamp maybe. SO, is ground 1 and ground 2 showing continuity? Are we operating with any cables disconnected?[/QUOTE

I didn't replace the 3886s. I replaced the whole amp board.
Yes they are both putting out dc on both speaker outs.
All the cables the cables seem to be intact. But I can check again

[Jazz P Bass]

Without a photo we are winging here GT.
The 3886 ic's are the source of your Vdc on the output.
Are the 3886 ic's part of the replacement board?
As in 'are they brand new?'
What was the initial amp problem that led you to purchase a board?
Have you checked the power supply yet?
Pin 1 & 5 are V+ & pin 4 is V-.

[Enzo]

But the 3886s ARE on the board you replaced? In other words they are not on separate little modules like the TDA7293 based amps?

And have we yet verified ALL power supplies are getting where they are supposed to?

[goldtop5]

Just want to let you know that I got it taken care of. I did what you said about checking the connectors. Everything from the transformer was fine. One of the ribbon connectors going from the output board to the preamp board was reversed causing -14vdc to leak to both the speaker outputs and the input jacks. In fact, it was shorting the -14vdc to every pin on the connector. There are 2 of the same connector(s) next to each other on the preamp board and were accidentally swapped. I swapped them back and the problem went away.

[Enzo]

Great!!