Yamaha YP-D8 direct drive turntable inconsistent RPM [SOLVED]

Mr. Yamaha

Not so much Yamaha lately...
Hi there, I have this amazing Yamaha YP-D8 playing for some time, but since last Sunday the RPM is not stable. It spins stable, then falls back in RPM for 2 seconds, speeds up again, etc. When I remove the platter, the spindle is turning 1 second, then pauses, spins 1 second, pauses, etc.

Problem occurs in both speeds and the pitch knob(s) do not change the problem other then that it's changing the RPM as normal.

So that's odd. If it's the motor, then this table becomes instantly junk and that would be really sad :(

So I hope it's something else. It already has a none working auto-stop / auto-lift function which I was planning to fix. Very sophisticated system with no mechanical connection between the system and the tone arm. It works with a small sub arm which runs with the tone arm and at the end of the record the sub arm blocks the light of a LED which shines into a sensor. When completely blocked for a few seconds, the output voltage of the sensor increases and 'tells' an actuator to lift arm after going through a 'discrimination' section.

Everything works up to the increasing voltage of the sensor according to specs, so it must be the actuator or the discrimination board.

Anyway, I'm not sure what whether the unstable RPM has something to do with the auto-stop / auto-lift function.

Any idea where to start? :dunno:
 
Some direct drive turntables require the platter be in place to spin normally - that's why it's "chugging" when you observe it with the platter off. I'd give the speed trimmer pots a thorough cleaning with DeOxit. There could also be secondary speed adjustment trimmers within the TT that require cleaning as well.
 
I had similar issues with a different DD turntable and recapping solved it, many of them were very low in value and the motor sometimes wouldn't spin.
You may as well give it the gold treatment if it's a daily driver, I've seen your neat work on the B-2 and this would be child's play in comparison.

Check this thread out:
http://www.tapeheads.net/showthread.php?t=55832

Particularly post #3:
http://www.tapeheads.net/showpost.php?p=671181&postcount=3

Wow, that's great, thanks! I hope that those 2SC458's are causing my non-working auto-stop system ;)

I'll replace all caps and the 2SC458's. That was something what needed to be done anyway.
 
I ordered everything for a full recap (a massive amount of 11 caps) and also 6 KSC1845's to replace the 2SC458's. I'll go from there.
 
I replaced the caps and the 2SC458's, but no luck. The problem remains. Auto-up also still not working.

I gave the pitch pots (also trimmers) a de-oxit treatment. Also no luck.

I did notice a slightly grinding noise from the motor, but when I pull out the spindle, it has some sort of oil on the shaft. But when I move the spindle up and down in the holder (it looks like an air gap bearing) it also grinds. No damages visible on the shaft.

I ordered some v/d Hul spindle oil, maybe that will help with the grinding, but whether it solves my problem? Not sure.
 
Sorry to hear, I have no knowledge of this table personally, though I didn't read of any motor failures when I searched so maybe there's hope yet?

I'd post the question in the turntables forum if the oil doesn't help, maybe someone more knowledgeable could offer a suggestion.
 
Relubed the spindle with high grade vd Hul spindle oil. The problem still remains.

In the meantime I did fix the auto-up system by replacing TR208, D210, C201 and C202. Also removed all old sticky red grease and regreased with ceramic grease.

Some ideas for the next steps? I uploaded a short movie of the symptoms. Please see the upper ring of dots on the platter.

 
Check if the platter is rubbing on something underneath. I'd keep blasting the hell out of those trimmer pots with DeOxit. I recently worked on a Rotel receiver which had a noisy volume pot for the first quarter turn. It took over six applications of DeOxit to work out the noise.
 
Check if the platter is rubbing on something underneath. I'd keep blasting the hell out of those trimmer pots with DeOxit. I recently worked on a Rotel receiver which had a noisy volume pot for the first quarter turn. It took over six applications of DeOxit to work out the noise.
Thanks, but I'm pretty sure the pots are not the problem. Each speed has it's own pot and the problem arose all of the sudden at both speeds. Also turning the pods does not influence the problem.

Platter is running freely.

I can't get my head around why the motor has 12 wires and there are around 15 transistors on the motor servo board. There must be a function on that board which controls the speed I guess. But the service manual is not speaking a word about the servo board and motor.
 
Update here. I checked and measured all components of the power supply board and the servo motor board. I desoldered all of them and tested them.

In the meantime I found out that the 24V power supply voltage is dropping sometimes for a second to 15V or 18V (or something in between). I have only 1 set of eyes, so I can't look at the meter and the strobe at the same moment, but I'm pretty confident that the voltage drop is causing the motor to slow down in RPM.

Any idea what component can cause the drop? The rectifier bridge (D101)? Or the regulator (TR101)? Maybe something else I can test?

I already checked for loose wires / contacts.

Capture.JPG
 
I'm certainly no expert - but would it be possible to connect a different 24Vdc supply and see if your motor operation becomes smooth again? The power drawn by these things is quite small (usually rated <10W) so it probably doesn't need to be a very substantial supply.

My (rookie) concern would be that the voltage drop might be caused by whatever's happening at the motor end, and may not necessarily be a fault in the PSU.

I'd pull and test TR101 if it's easy though, make sure gain is in-spec etc.
2SD234 -> TIP31 to my knowledge (A/B/C shouldn't matter, just confirm pinout)
http://mouser.com/ProductDetail/ON-Semiconductor/TIP31AG

(Edit - wait, you already pulled and checked all parts on the board pictured? ignore the above if so)
 
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I'm certainly no expert - but would it be possible to connect a different 24Vdc supply and see if your motor operation becomes smooth again? The power drawn by these things is quite small (usually rated <10W) so it probably doesn't need to be a very substantial supply.

My (rookie) concern would be that the voltage drop might be caused by whatever's happening at the motor end, and may not necessarily be a fault in the PSU.

I'd pull and test TR101 if it's easy though, make sure gain is in-spec etc.
2SD234 -> TIP31 to my knowledge (A/B/C shouldn't matter, just confirm pinout)
http://mouser.com/ProductDetail/ON-Semiconductor/TIP31AG

(Edit - wait, you already pulled and checked all parts on the board pictured? ignore the above if so)

I should note: every component except TR101, because it is mounted on a heatsink. So, thanks for the useful tips :biggrin: But I do have some new 2SD234's laying around, so I maybe just replace it to be sure. I do not have a real transistor tester. I can only check / test whether a transistor is working or not.
 
Hello

1) changing all TR 2SC458 is silly and you do confirm that replacing all did not change your trouble . This is your time and your money . I already post the same message regarding 2SC458 but everybody still copy this silly "upgrade"
I already said whitch 2SC458 was involved and cause problems in many units ; I will not repeat again here .

2) This turntable is direct drive and what you see is normal when the platter is not in place (Electone is right)
3) TR 2SD234 is really poor in specs after a certain lap of time and I will suggest you to replace it by a new 2SD526 and not a NOS 2SD234 who will fail in some time ...Remember 2SD234 was used in CR2020 and CR1020 power supply pc board and many members can tell you how much that replacement of 2SD234 was necessary
 
He had the problem with the platter installed initially anyway...
I suspect he also already knows which shape of 2SC458 is problematic.

I should note: every component except TR101, because it is mounted on a heatsink. So, thanks for the useful tips :biggrin: But I do have some new 2SD234's laying around, so I maybe just replace it to be sure. I do not have a real transistor tester. I can only check / test whether a transistor is working or not.
So apparently Yamaha themselves recommended upgrading those 2SD234s in some amps to a higher Ic version (2SD476) - but it's NLA. I think the 2SD526 clinic recommends might be NLA too?

If you have genuine 234s I'd swap one in to see if it fixes your problem, and then maybe look for a better part (4A or 5A) later. Since the original lasted 30+ years it's probably not really needed in this application.

I had a quick look on mouser morning and thought TIP41 might work, but it's Ic=6A (unsure about that, I'm an amateur at best). I'll have a better look tomorrow.
 
@ clinic-audio: Audiokarma is about helping each other, and not about giving lectures.
Please change your angry school teacher tone a little...... or please just say/post nothing at all.
Nobody comes here to be barked at.

If you have posted something about 2SC458, put the link to your thread in (or again: don't post here)

Regarding 2SD526: tell them about the tree, then send them into the forest....
It's well-available as Fairchild's KSC526 (Mouser item 512-KSD526Y)

Measure where the voltage fluctuation starts:

1) before the rectifier (AC swing -> possibly dirty contacts in the mains voltage selector)

2) across the reference voltage (Zener diode D102), which should be quite stable (it might fluctuate a few mV as a function of the current flowing through it, caused by the feedback transistor TR103 opening and closing). If it fluctuates a lot (say > 25mV) ; then either the Zener diode is at the end of its life, or C104 might be reversed installed.

3) Resistors R105/R106 (feedback network with TR103) may heat up for some reason and therefore vary in value.

Now.... was that so difficult ?
 
Blablablablablablablablablabla 2SC458 blablablablabla

:boring:

He had the problem with the platter installed initially anyway...
I suspect he also already knows which shape of 2SC458 is problematic.

So apparently Yamaha themselves recommended upgrading those 2SD234s in some amps to a higher Ic version (2SD476) - but it's NLA. I think the 2SD526 clinic recommends might be NLA too?

If you have genuine 234s I'd swap one in to see if it fixes your problem, and then maybe look for a better part (4A or 5A) later. Since the original lasted 30+ years it's probably not really needed in this application.

I had a quick look on mouser morning and thought TIP41 might work, but it's Ic=6A (unsure about that, I'm an amateur at best). I'll have a better look tomorrow.

Yeah thanks Zaibatsu, he always 'recommends' to use other obsolete substitutes which can't be found. But he has 'm :naughty: And he keeps repeating himself over and over and over again about a few subjects.

@ clinic-audio: Audiokarma is about helping each other, and not about giving lectures.
Please change your angry school teacher tone a little...... or please just say/post nothing at all.
Nobody comes here to be barked at.

If you have posted something about 2SC458, put the link to your thread in (or again: don't post here)

Regarding 2SD526: tell them about the tree, then send them into the forest....
It's well-available as Fairchild's KSC526 (Mouser item 512-KSD526Y)

Measure where the voltage fluctuation starts:

1) before the rectifier (AC swing -> possibly dirty contacts in the mains voltage selector)

2) across the reference voltage (Zener diode D102), which should be quite stable (it might fluctuate a few mV as a function of the current flowing through it, caused by the feedback transistor TR103 opening and closing). If it fluctuates a lot (say > 25mV) ; then either the Zener diode is at the end of its life, or C104 might be reversed installed.

3) Resistors R105/R106 (feedback network with TR103) may heat up for some reason and therefore vary in value.

Now.... was that so difficult ?

Thanks Oilmaster, I think I'll rebuild the complete PSU board to make it future proof. The problem is very intermittent. All caps are installed properly, Voltage across D102 is around 6,17 - 6,22. I will order a new zener to be sure and the two KSD526Y's I need. Shall I replace the rectifier diode bridge also (D101)? Then I need to find a substitute for the 1D4B1.
 
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