[sdiy] 303 problems!

[Daniel Araya]

I recently bougth two really banged up Roland TB303's, one painted blue
and the other red with various stickers and grafitti on...

The resonance pot is broken so I'll buy a new from Chipforbrains.
One of them has the pitch-mode LED lit up all the time, I checked the
transistor Q202 but it seems ok.
The line (number 19 in schematic) is connected to the PC3 port on the
processor but also to the datalines on the uPD444 RAM ics. One of the
SRAMs might be broken, I'll desolder R39 tonight and see what happens. I
hope the processor isn't busted.... 

Digital part:

http://machines.hyperreal.org/manufacturers/Roland/TB-303/schematics/roland.TB-303.schem-4.gif



The other one has even more problems, the pattern group selector has a
broken shaft, the resonance pot is broken and the volume/on-off pot is
almost pushed through the PCB and lots of traces are broken.
I resoldered all the broken traces I could see using wires. The machine
worked intermittantly and when I tried to find the fault it stopped work
alltogether.
There is only about 0,6v on the +6V line so the fault is in th PSU
somewhere. 
The PSU part is pretty crowded with components so i'm thinking of
removing all of the components to get a better wiew of the pcb and
possibly find more broken traces.

Analog part with psu:
http://www.hylander.us/images/schematics/roland/tb303.gif 


any hints?


/daniel