Posted By
Richard42
on 2012-07-14
18:41:32
|  Re: Getting a pair of 1551s
Another update.
Today I got the 1540009-02C (120/240v) transformers, so I took apart both of my German 1551 drives. I found that drive S/N 10754 had the newer-looking (open windings w/ solder lugs) 1540009-06 transformer, which I previously wrote about, while drive S/N 11476 had an older-looking 1540009-03C transformer (paper+glaze covering the windings with, red/blk/white primary wires and no solder lugs). This transformer looked just like the -02C transformers so I thought maybe it was also 120/240v, but I tested and alas it is also 220v/240. I swapped in the -02C transformers in both drives. I had to also swap in the (taller) support brackets for S/N 10754, because the -06 transformer is smaller than the others and has shorter brackets. I put 1A fuses in both drives and used heat-shrink to make it all nice, and, viola both drives power up.
Unfortunately drive S/N 10754 wouldn't work at first; the +4 reported "device not found" and the drive gave a repeating 2-blink code on the red light. I tried to find a service manual for the 1551 but couldn't. I did find an old PET drive service manual claiming that a 2-blink code means DOS ROM error. I pulled the EPROMS out of both drives and found that the working drive had the correct eprom data (as tested via md5 hash with a ROM that I downloaded from the web) while the non-working drive had different eprom data. I took a spare 27C128 eprom and burned it with the correct dos eprom data, and viola, I now have 2 German 1551 drives which work properly here in the US with 120v mains.
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