> From: spistrich
>
> so i finally replaced all the s+h caps- all 6 sets.... but still its
> out of tune and isolating voices 5 and 6 show that they are raspier
> than the normal scratch sound as heard in 1-4... i had trouble
> soldering 5 and 6 and worked on them longer than the others. and i
> wonder if lets say i over heated those caps .. did i screw
> them up?
> I did damage the trace just a bit on one The little copper ring came
> off the hole, but I cleaned the lacquer off back a bit and
> made sure
> the solder flowed to cover to it and got a good continuity.
> I think i
> had one bad voice before, now i have 2 i guess ....I have
> no 'scope' ..so do i need to order a few more caps and try again? or
> could it be something else.. (It wasnt really hard to do the
> soldering
> after i did the first couple. but i started with 5 and 6 and
> possibly messed it up)

It's impossible to know for certain whether you damaged something--that's
the sort of thing you need a scope for to figure out--but it might be useful
to have a few more caps on hand just in case. Remember, the pitch is only
affected by Cx00, Cx01, Cx04 and Cx05.

Did you clean the board after soldering the caps back in? If not, the most
likely cause of the problem is that the solder flux and other crud is
causing leakage. When working around the sample-and-hold circuits, you
really have to clean all the flux away very carefully with a good flux
remover and a stiff toothbrush, until all you see is shiny metal. Don't be
afraid to pour the stuff on the board, and let it run off the side, to make
sure there's no residue.

It's also possible that the 4051 CMOS switches Zx01 and Zx02 are
leaking--I've seen that happen. It's also remotely possible that the
LF347/TL084 FET-input op-amps are leaking, but I've not seen that happen.
The easiest way to replace a DIP IC is to cut the leads right next to the
chip package, then remove each pin from the top side of the board
individually with needle-nose pliers while applying heat from the soldering
iron, then suck the solder out of the holes from the underside of the board.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...