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Troubleshooting CD Players

I have a Sony 5 disc player recorder that plays perfectly on side B, but when playing a Cd in side A after a while or near the end the skipping starts?
What should I look for ? Let me add that this was brand new years ago and then it sat for some years and then I discovered the trouble trying to use it again.
 
jcmusic said:
I have a Sony 5 disc player recorder that plays perfectly on side B, but when playing a Cd in side A after a while or near the end the skipping starts?
What should I look for ? Let me add that this was brand new years ago and then it sat for some years and then I discovered the trouble trying to use it again.
Click to expand...
The first thing to determine is if the skipping is something that is caused by the location on the CD or by the time it's been on.
1. Play a CD and when it starts skipping, try to play track 1. If it skips, the laser power is low. If it doesn't skip, it has to do with the region on the CD.
2. Oil the top bearing of the disc motor with a light machine oil.
3. Clean the machined posts that the laser slides on with alcohol and oil with a light machine oil.
If that doesn't fix it the laser is probably bad.
 
Circumpunct said:
Hi dr*audio, thankyou for sharing your knowledge all those years ago and keeping the thread going. Some weeks ago i put aside two days to read the entire thing and take notes. Anyway, i have my friend's Hitachi Opus 1 music system he wants me to fix. I have the service manual, but it's a weird one to me. As soon as i select CD on the right hand main panel the spindle motor starts spinning at full speed, which it shouldn't do of course. Doesn't matter if there's a CD loaded or not. None of the cd control buttons on the left hand side do anything if i press them. No sled movement or focusing routine going on, just this straight-to-spin and all other controls locked up.
The unit other functions all work perfectly. I see an inch crack in the bottom case near the CD mech - makes me wonder what may have happened there.
Any ideas?
Click to expand...
Start with the power supplies for the CD unit. No buttons working sounds like the microprocessor isn't working. All microprocessors need Vcc, ground, clock and reset to be in the "not true" condition. Thus, if the schematic shows a line over reset, it must be high for the unit to operate.
 
dr*audio said:
The first thing to determine is if the skipping is something that is caused by the location on the CD or by the time it's been on.
1. Play a CD and when it starts skipping, try to play track 1. If it skips, the laser power is low. If it doesn't skip, it has to do with the region on the CD.
2. Oil the top bearing of the disc motor with a light machine oil.
3. Clean the machined posts that the laser slides on with alcohol and oil with a light machine oil.
If that doesn't fix it the laser is probably bad.
Click to expand...
Ok usually it doesn't start to skip until after it's been playing for awhile, I don't remember it ever skipping one track one. I have used several different CD's even brand new never played before Cd's.
It just seems odd that side B will play all day flawlessly but, not side A???
 
jcmusic said:
Ok usually it doesn't start to skip until after it's been playing for awhile, I don't remember it ever skipping one track one. I have used several different CD's even brand new never played before Cd's.
It just seems odd that side B will play all day flawlessly but, not side A???
Click to expand...
When you say Side A and Side B do you mean there are 2 drawers?
 
dr*audio said:
No buttons working sounds like the microprocessor isn't working.
Click to expand...
Thanks for setting me on the right road. The way this unit has so much crammed in, it's not easy getting to the micro pins which are on the reverse side of the pcb. Not sure i can power things after more disassembly. The chuck switch for the reset circuit is working fine at least. On the back of the unit they put a hole for testing the main crystal which should be 8.468MHz. My DMM says 2.35MHz...so that could be fallout from the cracked case episode i guess. Never got involved with crystals before, but a quick Google turns up no parts for that frequency. Should i give up hope at this point?
 
Bear in mind that if you probe a crystal at the wrong point, you can kill the oscillation. You need to find a buffered point. An oscillator cct on a chip will usually have two pins: one is the sense input from one side of the xtal, the other is the buffered, inverted drive to the other side of the xtal.
 
cpt_paranoia said:
You need to find a buffered point.
Click to expand...
Trying to follow what you wrote and thanks for chipping in. The micro pins to the crystal are labelled XTAI & XTAO. So does it matter which way round i put my probes?
There's another crystal by the D/A converter chip running at 35MHz btw.
I read that dmm's can load crystals under test, but what do you think in the huge difference in results here? Crystal basically dead?
 
Circumpunct said:
The micro pins to the crystal are labelled XTAI & XTAO.
Click to expand...

Almost certainly 'In' & 'Out'. Safer to probe the 'Out' pin.

IME, crystals work, or they don't. I did wonder if it was an overtone oscillation mode (an odd harmonic), but the frequencies you quotes don't work for that.
 
cpt_paranoia said:
Almost certainly 'In' & 'Out'. Safer to probe the 'Out' pin.
Click to expand...
Last night i got the scope out and attached the ground to the outer phono ring. This time i got 3.1MHz. Did the same with the dmm and got a similar number. So def loading effects before. I have no experience with the Xtals,but i've just read in a very good book that a well executed thwack can bring them back to life...
 
Circumpunct said:
Last night i got the scope out and attached the ground to the outer phono ring. This time i got 3.1MHz. Did the same with the dmm and got a similar number. So def loading effects before. I have no experience with the Xtals,but i've just read in a very good book that a well executed thwack can bring them back to life...
Click to expand...
I don't know what the bandwidth of your scope is, or the capacitance of your probe so you could be loading the crystal down, It's oscillating so the processor could be running. Check the power supplies and reset. Also we don't know if the testpoint is for the processor crystal.
 
dr*audio said:
I don't know what the bandwidth of your scope is, or the capacitance of your probe so you could be loading the crystal down, It's oscillating so the processor could be running. Check the power supplies and reset. Also we don't know if the testpoint is for the processor crystal.
Click to expand...
It's a 100MHz analogue scope, measured the probe capacitance at 66pF. Such an awkward position and tiny legs on the micro chip, i was guaranteed to short something, so i traced back to the nearest component - Vcc, Gnd & Reset all good. The testpoint i chose was the right one btw.
 
Circumpunct said:
It's a 100MHz analogue scope, measured the probe capacitance at 66pF. Such an awkward position and tiny legs on the micro chip, i was guaranteed to short something, so i traced back to the nearest component - Vcc, Gnd & Reset all good. The testpoint i chose was the right one btw.
Click to expand...
You can and should measure the oscillator at the crystal. Much easier. 66pF is way too high. I think my Tektronix probes are around 13pF. I think this is the same model I have. https://alltest.net/categories/products/P6108-Tektronix
I'll see if I can find a free service manual. Something is keeping the processor from running.
 
There are 2 supply voltages to the CD section, see below:
PL902 pin 6 looks like it should have 12V.
PL902 pin 5 looks like it should have around 5V.
upload_2023-5-10_19-44-4.png
 
Circumpunct said:
It's a 100MHz analogue scope, measured the probe capacitance at 66pF. Such an awkward position and tiny legs on the micro chip, i was guaranteed to short something, so i traced back to the nearest component - Vcc, Gnd & Reset all good. The testpoint i chose was the right one btw.
Click to expand...
Lets make sure you are looking at the correct microprocessor IC. Unless there is another one on the display board, this is the one you need to look at. Looking at the crystal oscillator is not what you want, because the clock on the micro comes from the DSP chip, on the OSC 1 pin (45). You have to check that. If you are worried about shorting something out, solder a 30AWG magnet wire to the pin. Also, Reset must be LOW in order for the processor to run.
upload_2023-5-10_19-57-12.png
 
dr*audio said:
Lets make sure you are looking at the correct microprocessor IC.
View attachment 2883127
Click to expand...
Thanks for all your help. Yeah i noticed IC905 didn't have a crystal connected to it so i figured the one by ic906 was the one to test. I would never have guessed OSC1 was the pin to test though. I would have gone for CLK in my ignorance.
Things have taken a more fundamental turn...i tested all the rail voltages as they enter the CD board. Going from pin 1 to pin 6 (on the cd pcb schematic - on the main pcb schematic it helpfully has the numbers on the exit connector in reverse!) should be 10,5,gnd,-5,-10,-24. I got 10,5,gnd, 0.6, 0.7, -24. Think i've found the problem.
The -10v line goes to the collector of one of the push-pull transistors that controls the disc motor, so that might explain why it's continually on? So i've put the cd board back in for now and taken out all the other boards except the main large pcb which has become a major headache to remove. You can see on the photos where three of the regulators have turned the area below black and horrible. The other regs that didn't do that have this clear glue-like stuff below them. I'll test the board from above best i can for all those negative voltages they spec on the schematic.
Btw, i was measuring my probe capacitance wrong it seems by clipping both on to the BNC. If i clipped the ground to there, but the positive to the TIP then i got 16pF. That's more like it.IMG_20230511_135520_9.jpg IMG_20230511_135501_1.jpg
 
I have a GE CD player from 1990 (model 11-8000A). The CD will start to spin, display reads "00" and then the CD will stop and the display clears. If I take the top off, I can see that the laser is trying to focus, but it will not move along the rails at all (except manually, by turning the gears). Is it reasonable to assume the DC motor for the slide mechanism is dead? It's a MABUCHI RF-310T-11400.

I have also tried lubricating the rails and cleaning the laser, which didn't solve the issue.
 
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