[sdiy] Future SYNTH-DIY/breadboard

[Roy J. Tellason]

On Wednesday 25 May 2005 06:03 pm, Rainer Buchty wrote:
> >I'm fixing up a '70s analog synth and an '80s digital synth at the
> >moment. If they were SMT I probably wouldn't go near them, true.
>
> But that's not a problem of SMT per se, but rather that there is nothing
> fixable in any newer machine.
>
> The 70s and early 80s machines were basically made from off-the-shelf
> parts with some dedicated stuff like CEMs/SSMs. Later, the first
> fully-custom sound chips appeared, and soon after the machines were more
> or less based on company-specific parts with a little bit of glue logic.
> ROM and CPU were "fusioned" into microcontrollers, and -- of course --
> the ROM couldn't be read out anymore, or doing so would at least require
> some major effort.
>
> *That* is the reason why one wouldn't want to repair anything past
> ~85, because it's basically impossible without access to original
> parts and/or detailed descriptions of those parts which might enable
> cloning.
>
> Rainer

I opened my last repair business in 1985,  which seems to be typical of when i 
get into stuff -- all too often at the wrong times!  What you say is true,  
and there are a lot of custom parts out there I'll never get enough info on.  
The least they could do is tell you how the parts are going to act,  what the 
"expect" to see on various input pins,  what technology is used to make the 
chip (NMOS, CMOS, etc.) and so forth.  That would at least give some 
possibility of troubleshooting things in some reasonable amount of time and 
effort invested.

(Please do NOT use "reply to all",  I'm posting this to the list and will get 
replies to it,  don't need two copies of everything coming in here to be 
downloaded at dialup speeds!  :-)