Repairing Commodore 64 - PLA replacement

Also, worth inspecting C10 and C11 (hopefully your both has both of those - near the SID probably). Both are 470pF caps, just worth inspecting them to make sure they arent broken off or something. We could have been barking up the wrong tree and maybe the caps are causing no sound to be generated on some channels or something. I do know if those caps are the wrong size a SID can sound very strange - almost like lacking a channel or two.

Maybe consider getting a diag cart, but certainly also re-test with both SID chips to see if they behave the same. If they do behave exactly the same, that might suggest that they are probably OK and the fault is with something else still. It is quite mysterious to be honest! I bet it ends up either both SIDs are faulty, or something daft like the 12v level is low (have you measure the 12v line going to the VDD pin on the SID?). Also check the 5v VCC pin on the SID too. Be careful not to short pins btw, in particular when measuring the 12v VDD pin. For reference pin 28 is VDD (12v), pin 25 is VCC (5v) and pin 14 is ground, as per this diagram:- https://ist.uwaterloo.ca/~schepers/MJK/pics/6581.gif

Sorry you're not having much luck with it =/ If you look on this site:- http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/ See the 2 pages for 251469 (pages 1 and 2) - The SID gets its CS from the 139 (which you've swapped, and which seemingly fixed your KB input issue). The only other connection to SID that could be related is on the address and data buses, eg. A0, A1 etc, D0, D1, D2 etc. So unless you've got a bad connection on the SID or the 139, or the PLA (you could follow the diagram and test with continuity on your multimeter just to check that say the 139 has each pin connected according to the schematic there, then if not a bad connection it must be either one of two things - either an intermittant data or address bus fault (perhaps a CIA or something, or the CPU itself, but either case would be quite rare and I would expect other behaviour if those were faults), or perhaps the SID you bought is not as 'working' as it was claimed to be.