The HP8350A and 8350B is getting common on ebay and other used equipment places. Most generators are getting old and there are several known issues. Before starting fault finding an main frame or plug-in, http://www.hparchive.com/Journals/HPJ-1982-02.pdf should be read.
The battery consist of 3 AA NI-CD cells, that after some years start leaking. If caugth before the leaking starts, the batterys can be replaced and excanged for 3 regular NI-CD or NI-MH batterys. If they have started to leak, one option is to remove the batterys, and clean the holder in hot water with some dish detergant and an old toothbrush (use gloves). As an alternative, the battery can be removed, the generator should work without the battery, but would not remember the frequency or markers after power off. If the battery are leaking, make sure you clean all the cards, contacts and surounding surfaces. The battery is placed so that if it leaks, it will leak all over the GPIB and processor board, A7 voltage regulator board and main board.
This error means there are no plug-in in the main frame. If all leds on the power supply board is ligth, check the card contacts and the connectors between the main frame and plug-in.
The most common error is leaking tantal capacitors on the A7 board. Replace all of them, they will go bad after some time. If all supplys are found to be within tolerance, take an look around the op-amp U17 on A7 board.
Several of the plug-ins use the HP33321 attenuator that may have one or several sections stuck. An good cleaning and replacement of the o-rings help. The following are reported to be an good replacement:
O-rings, NBR, 70 Shore.
The latest firmware for the A verson is ? and for the B version it's 7. To find the FW version press SHIFT 49.