Studiomaster Power House 122

[sunray]

Hi Guys

I have a Power House 122 which started with distorted left output then failure.

I have already identified several failed components but think I am now wasting my time without schematics. I have downloaded several 'other' mixers which are sort of similar but not near enough.

Can any one offer anything or any advice.

Thanks in advance

Ray

[Jazz P Bass]

What failed?
The ouput section?

[sunray]

Hi

Starting at the mains:
Fuse blown, thermister open circuit, transformer [230 - 240V section of primary winding open circuit], 0ne diode of bridge rectifier [open circuit].
Amp board:
Both 63V [+ve & -ve] fuses blown, one PNP o/p transister [short circuit], its and its partners 0R1 emitter resisters open circuit, 10R Zobel resister open circuit and charred & a diode [not yet identified where in circuit]. All on the same channel of the amplifier.
-15V regulator for mixer open circuit.
Diode across fan charred and open circuit.

Basically it looks to me that an o/p transister went s/cct which took lots of psu bits with it.
Maybe the distortion was caused by the -15V reg dying which overloaded the o/p transister and associated parts.

The thing I could do with now is a proper cct diagram to fault with rather than the 'similar' schematics I have.

[Steve L]

Studiomaster Schematics

Hopefully these might help.

Studiomaster Powerhouse Focus, 700D Schematics.pdf

Studiomaster Powerhouse Vision, Horizon Schematics.pdf

Steve

[sunray]

Hopefully these might help.

[ATTACH]13079[/ATTACH]

[ATTACH]13078[/ATTACH]

Steve

Thanks Steve
The circuit of the power amp is similar to the 700 [& 800 & 900 etc] and this is what I am trying to work to at the moment, the big bug is the component No's bear no resemblance at all and values are sufficiently different to make silly assumptions.
If becomes really necessary I will sit down and reverse engineer the board onto the available drawing, fortunately one channel seems to be unaffected so I have a good one to compare it with.
Thanks for trying.