I have three DEC RA8x drives that have failed (all
of them fault with
"spin error") because of bad photo-interrupter tachometer sensors. After
talking to a few friends, it sounds like this is a pretty common fault.
Photo sensors like this are fairly common, even today, but the specific
parts DEC used are weird and unobtainable.
I designed a little PC board that uses an ITR9606 photo interrupter, a
2N3904 and a resistor as a replacement. Works great - gives a beautiful 5V
P-P clean waveform and with the PCB it's a mechanical drop in replacement.
Just screws right onto the original mounting holes and plugs into the
I put the PCB design up on OSH Park
If anybody needs one you're welcome to order some PCBs and build your own.
The ITR9606 is as common as dirt, and you can buy bags of ten on Amazon for
a few bucks.
I've also put a few pictures on the Facebook DEC Computer Users group. I'd
post the pictures here, but I don't think cctalk accepts attachments. It's
not really worth making a web page for it.