Apricot PC Disk Drive Problems

[DrNick]

I have been attempting to restore an original Apricot PC from 1983 with the two OA-D32 Sony drives. On starting the machine, the drive heads move back and forth, but the disks do not spin at all, although the disk activity LED remains on. Not sure where to start, but I note that the power supplies to the drives measure at 4.6v and 14v. The monitor reports 'System OK' and has the flashing arrow disk symbol as expected.

 

[Zare]

Hi DrNick, welcome to the forums.
Here is a service manual https://archive.org/details/bitsavers_sonySonyOAceNov83_3409602 , is it applicable to your model?

 

[modem7]

Here is a service manual https://archive.org/details/bitsavers_sonySonyOAceNov83_3409602 , is it applicable to your model?

If so, the DC voltages to the drive are out of spec.

 

[Zare]

Indeed, if so, I'd say 12V rail is faulty. Mainboard probably doesn't need one to start the computer up. And both disks exhibit the same failure.

It's an easy check - just connect the drive power to another AT/ATX supply.

 

[modem7]

Indeed, if so, I'd say 12V rail is faulty.

+4.6V is -8%

( The +4.6V 'hit me in the face'. On one of my IBM 51xx motherboards, +4.6V, at the RAM chips, was the reason for intermittent RAM related errors. )

 

[Zare]

Could be, but "System OK" probably means entire POST has succeeded. In any case I'd just try another PSU.

 

[NeXT]

Before we go chasing this too far on the power supply (my Xi totally needed a recap at this point) has the OP tried powering the drive with something different? I recall that with those early Sony drives they are now due for a a recap (I've had weird issues with drives not wanting to work until they were "warmed up" or just recapped entirely) but also the spindle motor should be spinning as long as a disk is in the drive, regardless on if its attached to a computer. Powering it from a different PSU and feeding it a disk, if the disk doesn't spin you got problems with the drive (cold solder on the motor driver? Bad disk presence switch? I've seen both) and the funky voltages from the Apricot are not the main source of the problem.

 

[DrNick]

Many thanks for all your replies. I have recapped the PSU, but the voltages are still 4.6 and 14 from that, so there maybe further problems with the supply itself. I'll try powering the drives from another power supply altogether..