TR 909 memory problem

Synth Repair
1

Hi all,
I was wondering if someone could help me with a recent purchase of a 909 that is having some strange issues with patterns…
When I turn on the 909 I’m getting very weird patterns that are added to the machine from 1-16 automatically and it’s a one big noisy mess. It happens every time when I turn power on. Then i have to clear the Patterns, and then I can start programming and it’s fine but if I turn it off and on again those bad patterns reappear again. I have no idea what to do, batteries have been changed to brand new and the unit was factory rebooted multiple times…

would replacing these 2 IC possibly help fix this?

IC TC5514APL-3 SRAM chip
IC TC5517APL static CMOS RAM
thanks,
G

2

The symptoms sound like a ram chip is not retaining the data after the unit is powered off. The data will be in a scrambled state when the unit is turned back on.
Before replacing the chips i would check to see if the battery voltage is present at the ram chip when the unit is powered off. There may be a bad component or bad connection affecting the battery backup circuit. The service manual is available for download.
Pat

3

Thanks a lot Pat,
this is very helpful and I will verify if there is in fact battery connection and if so I’ll order the ram chip to replace.
G