Mark Bass cmd151P schematic?

[nosaj]

Got a Mark Bass CMD151p,, just curious if anyone out there might have a schematic for it.

Preamp fine output barely a whisper.

Looking at disassembling it this weekend to check the outputs.

nosaj

[nosaj]

When turning it on you can see the relay by the outputs clicking.. Output protection maybe. Speaker is good. No AC or DC at speaker jack.

nosaj.

[Enzo]

SO with amp on, verify solid continuity from amp side of output relay to speaker hot lead. And assuming the output is not a bridged circuit, is there continuity between speaker cold lead and system ground?

[nosaj]

Hi Enzo,
With the amp on there is continuity to speaker hot lead, when turning off relay clicks off and continuity is gone. So it's not a speaker protection issue.
I am not getting continuity from spk cold lead to system ground, there is a cap in between.
Now that it's out of the case I can check the outputs which I believe are IRFp240 and IRF9240's
Thanks,
Jason

[nosaj]

I checked the 33ohm 5watts none are open. The mosfets I have never really checked before but from what I have found online they mostly short from Drain to Source. With no power they should have resistance higher than a meg.
Is this valid or should I desolder them and test them out of circuit.
Other things to note. There are a few test points labeled on the board -80, +15 , -15. Voltages are correct. There are also 2 Red LED's on the board that are not lit up, but they do work with a diode test.

Thanks, nosaj

[nosaj]

Ok the issue came out to be the MV connector would loosen with the frequencies so I hot glued it. An the other thing the 1/4 speaker male jack was a cheap making intermittant contact also fell apart on me. So I put a switchcraft plug on and so far its fine.

Jason

[nosaj]

Ok the issue came out to be the MV connector would loosen with the frequencies so I hot glued it. An the other thing the 1/4 speaker male jack was a cheap making intermittant contact also fell apart on me. So I put a switchcraft plug on and so far its fine.

Jason

It's back and here's what the guy says
Quote
It plays fine for a while and then just cuts out. Sometimes soon after turning on-other times much longer. No Pattern to it.
Sometimes gets fuzzy and quit then cuts out. Quote

I opened it and can't see anything that looks funny. And i have yet to make it do it my self.
Anyone have any ideas?

Thanks,
Nosaj

[The Dude]

Maybe effects return jack not switching? It can be hard to duplicate sometimes. Try very slowly inserting a plug and pulling it out slowly to see if you can prove the switching contact not working. It sucks when you can't duplicate symptoms in the shop.

[nosaj]

Maybe effects return jack not switching? It can be hard to duplicate sometimes. Try very slowly inserting a plug and pulling it out slowly to see if you can prove the switching contact not working. It sucks when you can't duplicate symptoms in the shop.

Well using a short cable to loop the effects jack running an mp3 through input you can hear more of the music when the effects loop is jumpered. when it's removed it seems some frequencies are missing. Music sounds much better jumpered. Which I'm thinking supports dirty contacts. just can't clean it till I get back to town.

nosaj