These pertain to the PCB# 1540050 (early version) with ALPS drive mechanism
This reviews most of the main electronic components in the 1541 disk drive having the PCB# 1540050 (early version) with ALPS drive mechanism which has the push down door.
Partial failure: common cause of "FILE NOT FOUND" error or fail to reset when computer is turned on.
Total failure: when drive powered up, red LED stays on and spindle motor runs continuously
Common Fault:
UA1 74LS14 LOGIC
Also check UB4, UC2, UC4, UC5, UC6, UD3, and UD5.
Partial failure: most common causing "SEARCHING FOR" (also check UC3), computer lockup or "DEVICE NOT PRESENT"
Total failure: drive may power up normally but will not reset when the computer is turned on.
Common Fault:
UB1 7406 (M53206P) LOGIC
Also check UC3
When drive powered up, motor runs continuously and red LED flashes slowly (about 1 flash per second).
Common Fault:
UB2 TMM2016AP-10 16K SRAM
Also check TMM2116AP-15 or MB8128-15
When drive powered up, red LED flashes 2 or 3 times repeatedly.
Common Fault:
UB3 325302-01 DOS ROM 1
When drive powered up, red LED stays on and spindle motor runs continuously. DOS ROM is a common failure.
Common Fault:
UB4 901229-03 or -05 DOS ROM 2
Also check UA1, UC2, UC4, UC5, UC6, UD3, and UD5.
When drive powered up, red LED comes on and goes out, but spindle motor does not turn. When LOAD attempted, spindle does not turn, red LED flickers, screen displays "FILE NOT FOUND" and red LED flashes. Can also cause spindle to run when drive not accessed.
Common Fault:
UC1 325572-01 MOTOR CONTROLLER
When drive powered up, red LED stays on and spindle motor runs continuously.
Common Fault:
UC2 6522 VIA (MOTOR CONTROL INTERFACE)
Also check UA1, UB4, UC4, UC5, UC6, UD3, and UD5.
Drive powers up and resets normally. When LOAD attempted, screen may indicate "SEARCHING FOR ...", but no motors run and red LED does not light. Computer will be locked up until reset or turned off.
Common Fault:
UC3 6522 VIA (SERIAL INTERFACE)
When drive powered up, red LED stays on and spindle motor runs continuously.
Common Fault:
UC4 6502 MPU
Also check UA1, UB4, UC2, UC5, UC6, UD3, and UD5.
When drive powered up, red LED stays on and spindle motor runs
continuously.
Common Fault:
UC5 74LS04 (74LS14) LOGIC
Also check UA1, UB4, UC2, UC4, UC6, UD3, and UD5.
When drive powered up, red LED stays on and spindle motor runs continuously.
Common Fault:
UC6 74LS00 LOGIC
Also check UA1, UB4, UC2, UC4, UC5, UD3, and UD5.
When drive powered up, motor runs continuously and red LED flashes
slowly (about 1 flash every 2 seconds). Red LED may stay on and/or
motor may stop.
Common Fault:
UC7 74LS42P LOGIC (DECODER)
When drive powered up or reset, spindle motor runs momentarily, but red LED doesn't come on. When LOAD attempted, screen indicates "SEARCHING FOR ..." but red LED does not light, spindle runs continuously, and screen shows "FILE NOT FOUND" error.
Partial failure: no read, no stepper movement or just buzzes or chatters.
Common Fault:
UD1 7406 (M53206P) LOGIC
When drive powered up or reset, red LED comes on and goes out, but spindle motor does not turn. If LOAD is attempted, red LED comes on, stepper moves slightly, spindle doesn't turn, "FILE NOT FOUND" and red LED flashes. One failure causes motor to run all the time but the drive otherwise works normally. This IC can corrupt formats.
Common Fault:
UD2 7407 or 7417 (M53207P or M53217P) LOGIC (R/W CONTROL BUFFER)
When drive powered up, red LED stays on and spindle motor runs continuously.
Common Fault:
UD3 74LS86 LOGIC
Also check UA1, UB4, UC2, UC4, UC5, UC6, and UD5.
Drive powers up and resets normally, but if LOAD is attempted, spindle motor runs with red LED out. Screen displays "SEARCHING FOR ..." and stepper does not move.
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UD4 9602 (8602) LOGIC (MMV) no sub with later board 74LS123!
Also check UE6
When drive powered up, red LED stays on and spindle motor runs continuously.
Common Fault:
UD5 74LS197 (74177) LOGIC (TIMER)
Also check UA1, UB4, UC2, UC4, UC5, UC6, and UD3.
Powers up normally. When LOAD attempted, spindle turns and red LED comes on, but "FILE NOT FOUND" and red LED flashes.
Common Fault:
UE4 LM311 COMPARITOR (READ LOGIC)
Also check UF3 and UF4.
Drive powers up and resets normally, but if LOAD is attempted, spindle motor runs with red LED out. Screen displays "SEARCHING FOR ..." and stepper does not move.
Common Fault:
UE6 74LS193 LOGIC (BINARY COUNTER)
Also check UD4.
Powers up normally. When LOAD attempted, spindle runs and red LED comes on, but "FILE NOT FOUND" and red LED flashes.
Common Fault:
UF3 NE592N READ PREAMPLIFIER
Also check UE4 and UF4.
Powers up normally. When LOAD attempted, spindle runs and red LED comes on, but "FILE NOT FOUND" and red LED flashes.
Common Fault:
UF4 NE592N READ AMPLIFIER
Also check UE4 and UF3.
Drive powers up "normally", but motors run slowly or not at all. If that happens, drive access will produce a flashing red activity LED and errors "file not found" or "drive not ready" on the error channel.
Common Fault:
VR1 UA7812KC (LM340KC-12) +12 VOLT REGULATOR
Also suspect an overload (shorted C15) on the supply line.
Green (power) LED dim, flickers, or does not come on at all, but spindle may run continuously and red LED may be dark.
Common Fault:
VR2 UA7805KC (LM340KC-5.0) +5 VOLT REGULATOR
Drive appears to power up normally, but motors do not run. Should get warm only if the drive is being accessed (motors running).
Common Fault:
CR1 - 2 AMP 200V BRIDGE RECTIFIER (FOR +12V)
On power up, green and red LEDs are dim or dark and spindle motor runs continuously. May be intermittent and "die" after warmup. Part runs very hot normally and is a common failure in this model.
Common Fault:
CR3 - 2 AMP 200V BRIDGE RECTIFIER (FOR +5V)
-- Ray Carlsen --
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