Rhodes Chroma Polaris

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)

> 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@...

ok... i didnt clean everything  100% , i didnt think that flux would be conductive or a problem ...but i did swab the pc board  with alcohol  around the  smaller .068 mfd caps .... [after I tried to retouch the soldering for  voices 5 and 6] . It was these .068 ones that i had the problems with. because i started with them and hadnt developed a good touch .  It took 2 1/2 hours to do the  whole replacement surgery, but im sure i would be faster now. [ It was an extra  nusieance to have to detatch  the right side  wooden end cap to get to the last couple screws that held the main pc board in.    that didnt seem very 'thoughtful' for maintenance]

----- Original Message ----
From: Paul D. DeRocco <pderocco@...>
To: chromapolaris@yahoogroups.com
Sent: Tuesday, September 11, 2007 10:27:36 PM
Subject: RE: [chromapolaris] out of tune polaris

> 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@ix. netcom.com