HP 8590A softkeys do not react

[Bjoern]

I bought this unit second hand and when I switched in on I got the display showing: ADC-2v Fail, LOCK OFF, SMPLR UNLOCK.

None of the soft keys react at all.
I bridged the 10Mhz input and output reference at the back as well as the cal output and input at the front.

Could a faulty battery cause this problem since this unit must have been in storage for a long time.

Where shall I start looking??

[Bjoern]

OK today I opened the Baby up and found that the +15v were missing.
After disconnecting board by board and measuring 15v against ground I could isolate the issue to one board on which TWO tantalum capacitors needed replacement due to short. (no visual sign !).

Now it works !

[jjoonathan]

I saw something similar on my HP 8340 signal generator: they put protection resistors on the power supplies so that instead of "explode, leave skidmarks, and catch fire" the shorted circuit simply got hot. It saved my butt even if it wasn't what I expected