HP 9825 refurbishing

Hi Rik, Thanks for the info. I would be grateful for your tape conversion description, since I would like to restore the machine fully. At $38/tape, I doubt I'll be using the tape drive much :-( Until I come up with another storage method, a tape will have to do. Looking at the PSU, I have rev. E. It looks like a crowbar could be useful after the 5V switcher, and the 12V linear reg. I would think it couldn't hurt to replace the pass elements of the 5V reg and the 12V reg (Q3 and Q4). Did you find that the 723 regs failed, or the pass elements? The electrolytics are looking aged, so I'll replace them preemptively. I would be very interested in any diagrams and/or photos of your PSU mods. Best regards, Dave, If you want to use the HPDrive util, you need the 9895A ROM and the IO ROM. The 9895A ROM is hard to find the IO-rom isn't with those rom's you can use HPDrive on a PC with a HP-IB card as Mass Storage Unit. Tape drives are easy to refurbish but most of the HP-tapes are bad they losing the magnetic layer. It's possible to convert the drives so they can use QIC40 tapes, I do have a short description and drawing of this mod. You can order new DC100A tapes by Athana at ~ $38,- a piece. It's also advisable to add a crowbar circuit to the psu the 723 regulator IC's and power transistors don't life forever. When they go you will be grateful for adding the crowbar circuitry. -Rik