[sdiy] synthi reverb

[Magnus Danielson]

From: Steve Thomas <S.Thomas at qmul.ac.uk>
Subject: [sdiy] synthi reverb
Date: Sun, 12 Nov 2006 16:28:58 +0000 (GMT)
Message-ID: <Pine.LNX.4.44.0611121625090.8013-100000 at monopole.ph.qmul.ac.uk>

Hi Steve,

> Hi Magnus..well actually the one thing I havent yet repaired on my VCS3 is 
> the reverb. I thought it was a dodgy reverb tank (it had been disconnected 
> when I purchased the unit) but maybe the mfc6070 has blown. I hope not 
> they are next to impossible to find?Anyway I will change the caps as you 
> suggest..and some detective work should show if the mfc6070 is working or 
> not.

Caps and PSU is _always_ first out. I can tell you from my own experience that
several other things may seem broken because of blown PSU and broken caps. I've
seen a PSU blown such that it delivers full current of the voltage it gets in.
The result was that most of the rest synth was behaving very strangely indeed.
Just locating the error (the drive-transistor for the PSU was shorted) was a
bit of a challenge, but once that worked the rest of the functionality came
along. I still have a few caps to replace though. Oh, the caps into the ring-
mod should be replaced before anything else is done to the ring-mod. The
leakage through them when they are old is enought to make the ring-mod behave
as if it was beyond hope. Replacing the unobtainable TAB-101 will not help.

If you look at the MFC6070 datasheet you see that you could fairly easy build
yourself a drop-in replacement. But don't cross that bridge until you have
found out you really need to. Doing a full recapping (electrolytics) of board A
and the PSU doesn't take that long, doesn't cost much money and should save you
alot of trouble later down the line. Recapping board B and C should come as a
natural followup.

So, recapping and checking up the PSU is extra vital on these machines,
especially if you are into a Mark I.

Cheers,
Magnus

> cheers
> steve
> 
> On Sun, 12 Nov 2006, Magnus Danielson wrote:
> 
> > From: Steve Thomas <S.Thomas at qmul.ac.uk>
> > Subject: Re: [sdiy] Re: [AH] EMS Synthi AKS capacitor count
> > Date: Sun, 12 Nov 2006 15:37:07 +0000 (GMT)
> > Message-ID: <Pine.LNX.4.44.0611121526540.8013-100000 at monopole.ph.qmul.ac.uk>
> > 
> > Hi Steve,
> > 
> > > Hi all..I thought it is that weird 6-legged IC MFC6070 ? ..at least 
> > > looking at my board A schematics and the board A on my VCS3 mkII ..it's 
> > > the same position as in the pic. I seem to recall its part of the reverb 
> > > driver circuit. Actually on my VCS3 board A there is no heatsink on this 
> > > chip..maybe there should be?
> > 
> > If you read on you would see that I just recalled slightly incorrectly, it is
> > that weird MFC6070. Yes, you should invest in heatsinking it. Do not over-
> > invest thought, since additional physical load will make mechanical stress to
> > the joints. Also invest in fresh caps around it so it doesn't blow as a
> > consequence of those. You know all this, I'm just reminding you. :o)
> > 
> > Cheers,
> > Magnus
> > 
>