Posted By
JamesC
on 2003-07-13
|  1551 Service Manual?
Does anyone out there have a 1551 service manual?
My 1551 (imported to US from Germany 15 months ago) has never communicated well with my Plus/4. *When the Plus/4 can find the 1551* I can do one, maybe 2 disk operations before the computer and drive lock up. Reset button does not help, I have to physically turn them both off and back on again to regain control.
I replaced the 6525 tonight from a Magic Voice cartridge. I was able to ONCE TONIGHT get the 1551 to run for about four minutes with multiple operations, and that was showing Fantastic Four to a friend. When she left the room, the drive began acting up again, same symptoms as before. However, one reset gave me a red LED blink four times, then pause, then repeat the four blinks.
If this were a 1541 then the four blinks would indicate a bad ROM. However with this being a 1551, constucted of very few similar chips, the 4 blinks might point to something else.
Also the 12V round thingy on the power circuit (next to the 5V round thingy) is very hot to the touch..... the 5V is cooler but still warm.... chips all feel cool. These 'round thingys' are on their own heat sink on the right side of the circuit board, and are the same as found in a 1541. However my 1541s have heat transfer grease under them and this 1551 does not.
Since the 1551 is common in Europe and very very rare in the States, I ask in this forum for help. Does anyone out there have a 1551 service manual that they could look this up in, and give possible diagnostics?
I have tried this on both a 1541's 110v power transformer as well as 1551's transformer on a 110 to 220v step-up transformer.
Both the 1541 and 1551 have 16khz crystals, otherwise I would suspect 50/60hz differences. Two other people in the States that also have 1551s have simply changed the transformer without changing the crystal, and theirs work fine.
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