Hi,
I have a 1540050 Rev C 1541 that is exhibiting a behaviour that I can't find any information on.
When powered on (connected via serial to a C64) the red light comes on, spindle turns for usual second or so then stops, red light stays on.
I swapped in all the main IC's ( UB4, UB3, UB2, UC4, UC3, UC2, UC1) from another working drive (and tried the ones from non working in that) and there are no issues with them - I even socketed the SRAM to test that.
Board inspection shows no obvious blown caps.
Initially any command issued to the drive would hang, I replaced UC5 and now the hangs have stopped but I get DEVICE NOT PRESENT ERRORS. Neither of the device pads have been cut so it's not a device ID issue.
So far I have replaced:
UA1, with a quality ST part (tested working in an IC tester - the removed component tested OK)
UB1, which was a MOS 7707 (which tested OK when removed)
UC5, this part was bad
There is a bodge wire running from 6502 pin 39 to UC6 pin 2 - the track from UC5 pin 12 to here is cut (not sure why - any ideas?). Reverting this bodge results in no appreciable change.
I've replaced the ROM with a freshly burned EEPROM which works in the other drive.
Next I'll be pulling UC7 & UD2 to test these.
Voltages are good.
Clock looks good just a hair below 1mhz.
Address bus on the 6502 shows activity.
Reset on 6502 is high.
Thoughts?
PS Hello, this is my first post.
I have a 1540050 Rev C 1541 that is exhibiting a behaviour that I can't find any information on.
When powered on (connected via serial to a C64) the red light comes on, spindle turns for usual second or so then stops, red light stays on.
I swapped in all the main IC's ( UB4, UB3, UB2, UC4, UC3, UC2, UC1) from another working drive (and tried the ones from non working in that) and there are no issues with them - I even socketed the SRAM to test that.
Board inspection shows no obvious blown caps.
Initially any command issued to the drive would hang, I replaced UC5 and now the hangs have stopped but I get DEVICE NOT PRESENT ERRORS. Neither of the device pads have been cut so it's not a device ID issue.
So far I have replaced:
UA1, with a quality ST part (tested working in an IC tester - the removed component tested OK)
UB1, which was a MOS 7707 (which tested OK when removed)
UC5, this part was bad
There is a bodge wire running from 6502 pin 39 to UC6 pin 2 - the track from UC5 pin 12 to here is cut (not sure why - any ideas?). Reverting this bodge results in no appreciable change.
I've replaced the ROM with a freshly burned EEPROM which works in the other drive.
Next I'll be pulling UC7 & UD2 to test these.
Voltages are good.
Clock looks good just a hair below 1mhz.
Address bus on the 6502 shows activity.
Reset on 6502 is high.
Thoughts?
PS Hello, this is my first post.