There are 3 oscillators in total.... did you check all 3?
8.46MHz ceramic oscilator for DSIC2 IC7000
4MHz ceramic oscillator for microprocessor MC68HC05D9P
16.9344MHz cristal oscilator for DAC IC SAA7341
8.46MHz ceramic oscilator for DSIC2 IC7000
4MHz ceramic oscillator for microprocessor MC68HC05D9P
16.9344MHz cristal oscilator for DAC IC SAA7341
Yes I have checked all three oscillators and they are working correctly. All IC's have been replaced with known good and I just spent 2 days checking every circuit board trace from one point to another. next I need to start looking for board layer shorts.
Also...
When first turned on. the turntable motor hums for 1 second then spins backwards. at which time the display says "ERR" then displays "Loaded", pressing play results in the disc immediately spinning backwards and "Err" on the display.
When first turned on. the turntable motor hums for 1 second then spins backwards. at which time the display says "ERR" then displays "Loaded", pressing play results in the disc immediately spinning backwards and "Err" on the display.
You can monitor all of the above with a 2-channel oscilloscope and two cheap multimeters.
The motor control is done by:
- IC7102, pin 27
- IC7700, pin 11
- IC7700, pin 13
- IC7660, pin 3 (via pin 5 & 6)
Do you have a +5V ref at 3140?
In addition, does pin 12 on uPC IC 7700 read the correct voltages:
- 0V opening and +5V closing?
You need to check the waveforms 75, 76, 77 and 90 to confirm the I/O port B (uPC) is not faulty.
Also, did you replace uPC IC 7700 and the OP amp IC 7660??
You may have damaged the PCB tracks and/or caused a short between two adjacent eyelets (pins) on DIL's... when you were removing, and then installing all IC's.
back on this project again.
yes there is +5V on 3140
yes pin 12 on 7700 reads 5v correctly
IC 7700 has been replaced and socketed so I can swap it between a couple of test units i have. The IC works perfectly in another machine.
ALL of the IC's have been replaced. ALL of them. and the old one's swapped into a test machine, even the SMD parts and all work fine in the test machine. Using a microscope i have confirmed no shorts or damaged traces on the faulty unit. I have considerable experience replacing small pitch large package SMD's so I am sure that is ok.
I have swapped transports between units. no change in the faulty unit. all work ok in the test unit.
I need to understand the start up operation better.
without a CD i can confirm that the drawer closes. laser turns on. focus is attempted, BUT the turntable motor spins backwards. it hums for a second and you can see PWM signal, but, then PWM stops and the motor then spins backwards.
SO I need to understand the operation between the SAA7341 and the MCU. I "THINK" the 7341 supply's PWM to spin the disc up, then the MCU is supposed to take over and spin the disc from there at speed locked to the signal being read from the cd.
yes there is +5V on 3140
yes pin 12 on 7700 reads 5v correctly
IC 7700 has been replaced and socketed so I can swap it between a couple of test units i have. The IC works perfectly in another machine.
ALL of the IC's have been replaced. ALL of them. and the old one's swapped into a test machine, even the SMD parts and all work fine in the test machine. Using a microscope i have confirmed no shorts or damaged traces on the faulty unit. I have considerable experience replacing small pitch large package SMD's so I am sure that is ok.
I have swapped transports between units. no change in the faulty unit. all work ok in the test unit.
I need to understand the start up operation better.
without a CD i can confirm that the drawer closes. laser turns on. focus is attempted, BUT the turntable motor spins backwards. it hums for a second and you can see PWM signal, but, then PWM stops and the motor then spins backwards.
SO I need to understand the operation between the SAA7341 and the MCU. I "THINK" the 7341 supply's PWM to spin the disc up, then the MCU is supposed to take over and spin the disc from there at speed locked to the signal being read from the cd.