Vintage Synth Repair

hello,
many thanks for your help!
i'll let you know if the SEM repair will not happen
soon.
best regards,
bakis.





--- mantridcat <mantridcat@...> wrote:

> Hi Bakis!
> 
> I am a synth engineer/performer who bought an
> Oberheim 2-Voice, also from 
> Richard @ RL Music & (thankfully) have had no
> problems with it so far.
> I concur with Michael's diagnosis on the SEM being
> A23 (an LM3080 Transc. 
> op amp) being the potential culprit. Another likely
> cause is A24 -This is an
> LM741 common or garden op-amp and I have had this
> cause no or full 
> modulation when it goes belly-up.You should be able
> to get both from George 
> Tait electronic suppliers in Glasgow for about \ufffd1.00
> or less- I get a lot of chips 
> there that are not readily or cheaply available
> elsewhere that I need for fixing 
> & restoring synths at Singing Cat Services (plug!). 
> http://www.tait-components.com.
> I also have a full set of SEM 1a diagrams in jpg
> format which I can post you if 
> you need it giving the schematic, jumper & Etc.
> locations layout and the wiring 
> for all the modifications. If all else fails,
> contact me at Singing Cat (see Links 
> page) and we'll try & work something out!
> 
> Best Regards,
> 
> Mantridcat
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, Bakis
> Sirros <
> synth_freak_2000@y...> wrote:
> > hello list,
> > i had given my standalone SEM module(bought in
> great
> > condition from RLMUSIC - UK, last year) to my tech
> ot
> > transform it and perform all the mods so it will
> > become totaly patchable.
> > he made all the mods but obviously he made a
> mistake(
> > a short sircuit occured somewhere during the
> > modification works probably) and one(or more?) of
> the
> > chips of the SEM board has been broken. the
> result?
> > now, with no patchings at all in the SEM's newly
> added
> > patchboard, the lfo constantly modulates the pitch
> of
> > both vco's.(without the frontpanel switches to be
> set
> > that way of course). normally, the lfo only
> modulates
> > something if it is choosen via the frontpanel
> switches
> > to do so, or if it is patched via the newly added
> > patchpanel. but now the lfo pitch modulation of
> both
> > vco's is constant and noticable all the time.
> > my tech said that, in order for him to find the
> > malfunctioning chip(s), he will have to replace
> many
> > chips and that will take very long time.
> >  
> > is there any chance that you have any idea which
> of
> > the chip(s) could be broken(from the shortsircuit)
> so
> > they create that constant vco pitch modulation
> from
> > the lfo?
> >  
> > the power supply unit is checked and working fine!
> > 
> > my tech's email, in case any of you want to give
> him
> > some technical details/help, is available of
> course.
> > just contact me off-list.
> > many thanks for your help in advance!
> > bakis.
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > Bakis Siros
> > Parallel Worlds / Polariton
> > Athens-Greece
> > [Doepfer_a100] group owner
> > http://www.shimarecords.co.uk
> > http://www.ward12.com
> > 
> > __________________________________________________
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> 
> 
> 


Bakis Siros
Parallel Worlds / Polariton
Athens-Greece
[Doepfer_a100] group owner
http://www.shimarecords.co.uk
http://www.ward12.com


		
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