So after replacing my battery in my Ensoniq SQ80 with a new one, the screen is no longer garbled, and I can actually use the synth again! However, the only remaining issue is that the load screen still says “warning low battery/voltage”. It is a brand new 3V battery built exactly to replace BR2/3A batteries. Also, when trying to save custom patches, they disappear after turning the synth off and back on again. Seems like it is certainly RAM issues, but I was hoping someone might be able to give me an in-depth overview of what might be wrong.
You need to figure whether the voltage is actually reaching the RAM. Need a multimeter for that. With the power off measure the voltage at the RAM chips at least one should have about 3v on the power pin which is pin 28, so if you measure between pin 14 and 28 you should see 3v or so. If you’re not then you have had trace or diode in that part.
Definitely check these caps, they are across the battery voltage and ground. If one is shorted or leaky it will hold the battery voltage low. There might be some others but I’d start there.
I expect the SQ80 monitors the battery voltage using a similar circuit to the ESQ-1, if you take a look at my recent repair article there is some information on the demultiplexer chip used to read it. If the battery level measures properly and the voltage is reaching the RAM chips, then maybe you should check for a dead de-mux chip? It would present that way if the CPU can’t read the battery voltage.
