MPC 60 II issue::ghost in the machine::need help

Definetly the DRAM. I had the issue popping up on my MPC60 MKi lately and so i replaced all DRAM chips on the voice board with DIP-20 sockets and bought a bunch of UPD424256C80 chips.

Since the chips are already rather old, i tested them with the Retro Chip Tester Pro. Most chips turned out passing the tests but still after installing them i had a bunch of faulty ones and things got even worse with samples being completely messed up soundwise, parts of the samples missing on playback and also the amount of DRAM being read as 1536k vs 768k occasionally on startup… thought i messed up the voice board while soldinger but after trying a couple of the NEC chips i had i found a bunch that worked rather well.

Still the issue is happening occasionally and i am guessing there are still some faulty DRAMs on my RAM extension card since if i remove the RAM extension i no longer get the occasional, faint playback of different samples when for instance hitting a kick sample repeatedly.

I ordered some KM44C256C and will report back if this helps with the issue.

What i observed is that after loading sounds/ programs i only get the issue if:
* samples were already played: if i load a rather big program, i cannot trigger the issue instantly. only after all samples where triggered/played, i can achieve the ghost in the machine issue with the faint sample playback
* when it occurs, i can “flush it out” so to say: repeatedly triggering a pad that sometimes results in the additional faint playback of another sample seems to be occuring more often in the beginning and after several times of triggering the pad the issue seems to fade away again
* loading a big (RAM filling) program the sounds that were loaded last are those that will be faintly triggered. early loaded sounds are not being faintly heard (again pointing to faulty RAM on extension card)

I will see if by swapping the extension card DRAM chips the issue gets resolved and will report back.

I swapped all mem chips, on the voice pcb as well on the ram expansion pcb and the issue still persists.

I have checked all DRAM chips with the Retro Chip Tester Pro, which gives a good overview, but it still leaves room for potential error when it comes to their clock speeds and the like.

The good news is: i never hear it when playing a sequence/song, so thats that, only when pads are being triggered manually. It comes and goes.

I tried the stereo outs, individual outs, etc etc, still occasional faint playback of different sounds, even if they are assigned to another individual out then the pad which i am triggering and the individual out of the "ghost sound" pads are muted on the mixer (as well as the stereo out).

So could be the dram, could be crosstalk, who knows. It is an old machine after all, things like that are annoying but to be expected. In my case, i did not encounter this issue when my expansion memory banks are removed.