E-MU SP 12 memory battery issue.

[RickSlater89]

I would be very grateful if anyone can help me out on a rather vexing issue. After months of searching for an E-mu SP-12 Drum Machine, I finally found one. When I got it the battery was dead, but having researched it, it seemed all I had to do was replace the battery and I would be good to go.

I sent it in to a local music repair store. When the tech changed the battery everything seemed fine. But then he started calling and messaging me about an issue; the memory battery in the unit goes dead in a few days after it is installed. Everything else works fine. The battery however draws too much current killing it. He tried removing and replacing everything associated with the battery looking for the issue. Nothing worked. The batteries just kept dying.

His final conclusion is it must be a defective circuit board and cannot be fixed. I am hoping someone has a workaround this or has a second opinion on my techs guys's conclusion.

Thanks!!


This is the link to the E-mu service manual:
www.theemus.com/documentation/sp12/SP12_Service_Manual.pdf

[stj]

Re: E-MU SP 12 memory battery issue.

a music store??
wrong people for the job.

2 diodes, 6 capacitors and a bunch of rams to test.
nothing custom or worth more than a few $

[redwire]

Re: E-MU SP 12 memory battery issue.

Music store tech's are pretty basic (or worse). I wouldn't take vintage gear like this to one unless they have a very good reputation. You have to ask around where local musicians and recording engineers are going for repairs.

Are you sure the new battery is going dead? Then you'd have to isolate which memory IC is bad and consuming too much power. Both main memory and expanded sound memory are powered from the battery.

There are several Engineeing Change Orders (ECO) for the Emu SP-12, a few just for the memory battery backup issues.
So a few circuit board mods required or may already be done, you'd have to check.

ECO #144 add resistor + capacitor
ECO #149 change battery isolation diode D13 from germanium to silicon
ECO #151 improve POWER OK; resistor R38 to 10k
ECO #155 Add ferrite inductor to filter line transients power up/power off causing NV memory "fry" (erase)

I would guess you have a bad SRAM IC causing high current drain, or bad capacitor on power to the SRAM's. But you'll need a better tech

[RickSlater89]

Re: E-MU SP 12 memory battery issue.

Thanks. I will send it to a place that specializes in the repair of these units. www.forat.com. I sent it for repairs locally because I thought it was simply a dead battery and once that was changed, it would start working again.

Unfortunately I have no ability or know how to fix this myself based on your advice. I was going to pass the advice to my tech but I think I need a new tech guy working on this.