Stduiomaster PowerHouse 300 8.2 schem wanted

Archived from groups: rec.audio.pro (More info?)

gwood@audioproducts.co.nz wrote:

> This one is 1996, and service info is not available on the
> info site http://mysite.wanadoo-members.co.uk/studiomaster , and the
> 'new' Studiomaster company don't want to know/tell about anything
> before their 'restructure'.

Who did you speak to ?

I'll ask a certain person if he'll put the schematics up. He's usually
fairly busy so don't expect anything overnight.

In the meantine can I assist with whatever problem you presumably have
with your product ?

Graham

Archived from groups: rec.audio.pro (More info?)

gwood@audioproducts.co.nz wrote:

> 140mV DC offset on one channel. One o/p transistor and driver has been
> changed previously, and the relay, but no components obviously faulty.
>
> geoff (@paf) calling from work this time...
>
> PS Ain't it time you were in bed - it's lunchtime here !?

I'm a night owl - lol.

What's the offset on the other channel ? Is the channel in question
misperforming in some other way ?

First off, I'd considering checking the Vbe match on the input transistors
( 2N5401s IIRC ). They may be on one of those 'plug in' boards.

I'll grab a copy of the amp schematic ( although I *ought* to have one
lying around here somewhere ) to help with the component references.

Btw. A tip. Check the soldering on *all* the TO-220 drivers. Dry joints
can sometimes develop there.

Graham

Archived from groups: rec.audio.pro (More info?)

In article <1116889546.981595.250250@g47g2000cwa.googlegroups.com> gwood@audioproducts.co.nz writes:

> This one is 1996, and service info is not available

See Kevin Aylward of Mic Preamp fame. He's a former Studiomaster designer.
Maybe he designed yours.


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Archived from groups: rec.audio.pro (More info?)

gwood@audioproducts.co.nz wrote:

> Other channel offset a few tens of millivolts.

Sounds about right.

> Original complaint was distortion and wild oscillations, though I have
> not seen this.

No evidence of any other misbehaviour at all ?

> So that leaves the slightly high offest on the one
> channel. Did find one resistor track-pad broken in the + supply.

What effect did that have ? Have you got the component reference ?

> Bit of a pain about those "plug-in" boards...

A lack of space. It also helps to have certain sections of circuitry
'isolated' from high current areas too ( just done something similar for
an smps ). Long story about that board. It was an 'emergency redesign' I
had to do.

I've found out why the schematics aren't online btw. During one of
Studiomaster's troubled periods the CAD files were 'lost'. I grabbed some
photocopies of the archive copies though.

I can scan them and post them at alt.binaries.schematics.electronics if
you want.

Made any progress btw ?


Graham

Archived from groups: rec.audio.pro (More info?)

gwood@audioproducts.co.nz wrote:

> That would be great - thanks (just the power amp rqd).
>
> Things do get a bit noisy from the mixer section when gains wound up
> though - all around. DC looks fine and have cleaned/treat 'ribbon''
> connectors, sockets, grounds,etc, and firmed up the IDC crimps..
>
> After fixing the resistor connection (0R1 ? in series with TO3
> collector ????) I can not hear or see the reported oscillations, etc.
> Offset still there, but not a magnitude that is necessarily a terminal
> problem.
>
> I hope Studiomaster still occasionally send you a cake or something.

I'm still there actually.

Occasionally Kerri ( the MD's PA ) will bring some cake in for us !

Graham