Some more information.
When the XTAL lock activated (Pitch button pushed in), the platter/makes a noise while rotating and is NOT spinning at 33.3 rpm. When XTAL lock is deactivated (Pitch button pulled out), the noise is gone and the speed can be adjusted to 33.3 rpm by turning the Pitch. Granted, the alignment hasn't been carried out, thought I'm not sure that would explain the noise.
Also, the strobe window is dark, thought that may just be the neon bulb.
When the XTAL lock activated (Pitch button pushed in), the platter/makes a noise while rotating and is NOT spinning at 33.3 rpm. When XTAL lock is deactivated (Pitch button pulled out), the noise is gone and the speed can be adjusted to 33.3 rpm by turning the Pitch. Granted, the alignment hasn't been carried out, thought I'm not sure that would explain the noise.
Also, the strobe window is dark, thought that may just be the neon bulb.
I'll have to think on that tomorrow 
What I would do is scope the oscillator and see what its doing and then we have a reference if things change again. Is it now running all the time?
Also check the sawtooth osc, again for reference.
Something has changed hasn't it... soldering the crystal. Its possible the oscillator is running but now out of spec, perhaps noisy or intermittent low amplitude.
I'm assuming the crystal is a metal can. You can heat these (the can, not the pins) with the soldering iron and get it to say 100C (sizzle temperature) without harming anything.
That's worth a try as well. And keep looking with the scope to see if anything changes on the osc output.
What I would do is scope the oscillator and see what its doing and then we have a reference if things change again. Is it now running all the time?
Also check the sawtooth osc, again for reference.
Something has changed hasn't it... soldering the crystal. Its possible the oscillator is running but now out of spec, perhaps noisy or intermittent low amplitude.
I'm assuming the crystal is a metal can. You can heat these (the can, not the pins) with the soldering iron and get it to say 100C (sizzle temperature) without harming anything.
That's worth a try as well. And keep looking with the scope to see if anything changes on the osc output.
I actually think that you having me touch the pins with a damp finger is what changed things, at least in part. Does that make sense? It's like the crystal was asleep, which doesn't make sense, I know. The solder joints looked absolutely fine, but I had figured "what the heck, I'll do it anyway."
Yes, it's running all the time now.
I'll check/monitor the waveform on the oscillator and try heating the can with my iron.
I'm also going to attempt to carry out the electrical adjustments in the service manual to see what happens
Yes, it's running all the time now.
I'll check/monitor the waveform on the oscillator and try heating the can with my iron.
I'm also going to attempt to carry out the electrical adjustments in the service manual to see what happens
A bit more fodder for discussion.
I heated the crystal with my iron to around 70 degrees Celsius. Now the frequency of the waveform on pin 16 measures approximately 4 MHz and the amplitude is about 310 mV peak to peak.
The waveform on pin 1 is the same as shown earlier, i.e. that odd non-sawtooth. That said, I haven't tried checking with the platter spinning yet.
I heated the crystal with my iron to around 70 degrees Celsius. Now the frequency of the waveform on pin 16 measures approximately 4 MHz and the amplitude is about 310 mV peak to peak.
The waveform on pin 1 is the same as shown earlier, i.e. that odd non-sawtooth. That said, I haven't tried checking with the platter spinning yet.
I think the next step, given all this, is that the crystal has to be changed. Just heating a crystal like this shouldn't alter its behaviour at all. Of course you can get heat spread to other parts nearby that can confuse things... however.
It might be worth removing the crystal and having a good look at the base and pins. Give it all a clean with ISO and do the same for the top of board where it locates. Then refit and retest. Maybe some residue from manufacture is under there. Its one more thing to cross off the list.
It might be worth removing the crystal and having a good look at the base and pins. Give it all a clean with ISO and do the same for the top of board where it locates. Then refit and retest. Maybe some residue from manufacture is under there. Its one more thing to cross off the list.
Ok, I'll order a new crystal, and go from there.
One other observation, fwiw. When I attempted to carry out the Turntable Speed Adjustment on page 16 of the service manual, I encountered the same results that freebee describes in the first post of his thread.
Adjusting Sony PS-X70 with scope
One other observation, fwiw. When I attempted to carry out the Turntable Speed Adjustment on page 16 of the service manual, I encountered the same results that freebee describes in the first post of his thread.
Adjusting Sony PS-X70 with scope
Hard to say with the other thread. In post #3 he says it seems to all work OK and yet he's not seeing the correct waveform. A lot of unknowns, the scope and how its set up to trigger and so on can all give misleading results.
What you mentioned yesterday about the pitch pull knob and the platter noise etc could all be related to the oscillator issue. If the oscillator signal isn't clean and repetitive then that randomness in frequency and duty cycle could (would) still get divided down and the result is the motor might sing and make noises in response to the constant rapid fluctuations.
Before looking to hard for other issues I think we have to be 100% sure on the crystal oscillator and get it running at the correct speed and amplitude. The frequency tolerance is minuscule, tiny tiny fractions of a percentage point and so the 4Mhz you saw, and while close is a million miles off in crystal terms. So sorting this is the priority.
What you mentioned yesterday about the pitch pull knob and the platter noise etc could all be related to the oscillator issue. If the oscillator signal isn't clean and repetitive then that randomness in frequency and duty cycle could (would) still get divided down and the result is the motor might sing and make noises in response to the constant rapid fluctuations.
Before looking to hard for other issues I think we have to be 100% sure on the crystal oscillator and get it running at the correct speed and amplitude. The frequency tolerance is minuscule, tiny tiny fractions of a percentage point and so the 4Mhz you saw, and while close is a million miles off in crystal terms. So sorting this is the priority.
Just another follow-up to the crystal behavior. It had been 24 hours or so since I had first heated it with the soldering iron when I checked the frequency again with my counter. This time it showed about 2.6MHz. So I heated the crystal a second time, checked the frequency, and sure enough the value rose to nearly the correct 3.9321MHz. Also, when I press Start while touching the crystal, I can feel (and faintly hear) it vibrating.
I've ordered a replacement, and will circle back after it arrives and I have it installed.
I've ordered a replacement, and will circle back after it arrives and I have it installed.
I installed the new crystal this morning. According to my counter, the frequency at pin 16 is right on the nose. In terms of voltage, I measure 550mV peak-to-peak on the scope. When I press Start, there is no longer any vibration emanating from the crystal.
So since all of that was promising, I put on the platter. With the XTAL engaged, the platter spins with no noise and holds steady at both 33.3 and 45 rpm when checked with my KAB SpeedStrobe. With XTAL disengaged, the pitch control allows adjustment of the speed as you'd expect.
Hesitant as I am to say it, the issue appears to be resolved!
So since all of that was promising, I put on the platter. With the XTAL engaged, the platter spins with no noise and holds steady at both 33.3 and 45 rpm when checked with my KAB SpeedStrobe. With XTAL disengaged, the pitch control allows adjustment of the speed as you'd expect.
Hesitant as I am to say it, the issue appears to be resolved!
Great! So it's working properly now? I just saw your request in your other thread. Can I still help you out with your question below?
[Can you do me a favor? I'd like to see the waveforms you get at pin 1 of IC1 with power on only, then with the Start button pressed, and lastly with a record playing. This would be helpful to me in my attempt to diagnose the motor issue I'm trying to diagnose.]
[Can you do me a favor? I'd like to see the waveforms you get at pin 1 of IC1 with power on only, then with the Start button pressed, and lastly with a record playing. This would be helpful to me in my attempt to diagnose the motor issue I'm trying to diagnose.]
Much of the credit goes to you Mooly. Thanks for sticking with this/me!
I was debating about the alignment procedures, i.e. not wanting to jinx where we're at. I had actually recorded the original positions for the trimmers and made sure to return them to those spots. That said, it certainly shouldn't hurt to run through the steps.
The other outstanding issue is a likely dead neon bulb for the strobe. I'd already replaced the relevant capacitors for that part of the board and checked the resistors there. I suppose I should confirm that I have the correct waveform and voltage at the white wire pin. But assuming I do, I'll need to figure out the best option for a new bulb: the original 150V @ 10mA is no longer available.
I was debating about the alignment procedures, i.e. not wanting to jinx where we're at. I had actually recorded the original positions for the trimmers and made sure to return them to those spots. That said, it certainly shouldn't hurt to run through the steps.
The other outstanding issue is a likely dead neon bulb for the strobe. I'd already replaced the relevant capacitors for that part of the board and checked the resistors there. I suppose I should confirm that I have the correct waveform and voltage at the white wire pin. But assuming I do, I'll need to figure out the best option for a new bulb: the original 150V @ 10mA is no longer available.
Thanks for the kind words
Its good to get a positive result on something like this. Something I've noticed with alignment is that when a unit (no matter what it is) is basically OK then the adjustments generally speaking have a quite a wide tolerance.
When things start getting super critical alignment wise, that can be a sign of problems.
I'll have to look later at the circuit for the neon... could we fit an orange LED I wonder ?
Its good to get a positive result on something like this. Something I've noticed with alignment is that when a unit (no matter what it is) is basically OK then the adjustments generally speaking have a quite a wide tolerance.
When things start getting super critical alignment wise, that can be a sign of problems.
I'll have to look later at the circuit for the neon... could we fit an orange LED I wonder ?
So far, so good on making the electrical adjustments. Both 33.3 and 45 rpm were only slightly off. The mistake I made before was expecting the proper alternating positive negative waveform to appear with just power on and the platter not spinning. Apparently the same thing applies to the next alignment for the speed-detecting head: The service manual just says "Power On" but there's no voltage reading on the test pins until the platter is spinning. In my case, I'm showing about 80mV instead of 20-50mV. So I'll tweak the position of the head.
I've read in some other forums where people have subbed in an LED for the strobe, but I can't recall the particulars. The person I regularly buy bulbs from recommended this one with an additional 100k resistor.
I've read in some other forums where people have subbed in an LED for the strobe, but I can't recall the particulars. The person I regularly buy bulbs from recommended this one with an additional 100k resistor.
So...
Bearing in mind trial and error you could replace the neon with an LED, then remove D402 and C408 and then connect a link from the unregulated 34 volt rail to where the plus end of C408 was.
That would feed the LED from the 34 volt rail. The 12k resistor would be OK as a starting point and would limit the current to just around 3ma. If that was to bright (modern high efficiency LED's are really bright) then you could increase the value to suit.
Its trial and error as to the visual impact and how it looks in practice.
Bearing in mind trial and error you could replace the neon with an LED, then remove D402 and C408 and then connect a link from the unregulated 34 volt rail to where the plus end of C408 was.
That would feed the LED from the 34 volt rail. The 12k resistor would be OK as a starting point and would limit the current to just around 3ma. If that was to bright (modern high efficiency LED's are really bright) then you could increase the value to suit.
Its trial and error as to the visual impact and how it looks in practice.
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