THe most common problem with OB-8s is the 5V bridge rectifier. It was an under-spec'd part originally and fails when it can't handle the current. Get a beefier version. Install it and measure all your power supply voltages. If you need any parts for the OB-8 I have them.

Doug
synthparts.com

--- In oberheim@yahoogroups.com , "Tommy" <ultanium@...> wrote:
>
> Hello, new member here! I am trying to revive an OB-8 that was has been sitting in a basement for 20 years. It is a factory MIDI version, in surprisingly good condition. When you power it up, it only gives random lights, no switches work, no sound. I opened her up and saw the battery was leaking, new one on order. I cleaned and resocketed all the IC's, one socket is empty, U17. None of the caps look swollen, although I may start replacing them all anyway. Voltage on both rails is 15 & 5, didn't scope it yet. Did scope the Z80, see a nice wave on pin 6 (clk), and a random dirty square wave on pin 21 (rd) that matches the random lights. Sometimes there are 3 square patterns on power up, and all the bank lights are lit. Sometimes there are numerous square patterns on power up, and many lights are lit. There are 4 or 5 different patterns of this, but never any functionality. Dead Z80 maybe Have heard of Switched On in Austin Texas, they supposedly know these synths, but hoping its something I can do before spending the money on a real tech. Appreciate any help, I'm dying to hear this thing!
>
> Tommy Johnson
> Houston, Texas
>