YP-D6 speed issue redux

[Carlp]

I've read up on the relevant posts here and elsewhere, but after a bunch of work, my deck still has the speed issue. Speed varies. The platter strobe advances then stops, advances then stops. I have replaced all electrolytic caps, cleaned/"deoxited" all potentiometers and the two switches (the speed and the shut-down switches), re-lubed the motor and still it varies. Could be "seeking" behavior of the motor drive circuit (which suggests maybe something other than the caps are at play) or perhaps the platter has a problem. One post here talks about replacing the diodes and possibly the transistors.

Here's a quick clip via that video site. I couldn't upload it here, unfortunately. If you look closely you can see the platter bottom edge move up and down along with the strobe marks.

I got this around 2012, discovered the issue and did some cleaning of the pots. Ulitmately put it away unfixed. I now have 16+ turntables and need to start sending them out into the world.

Today I noticed that the platter may have some wobble in it. Meaning the bottom edge relative to the plinth may go up and down a small bit. Motor bearing isn't loose, so it's not that. If there is an issue there (e.g. the spindle shaft might have been bent when it was shipped to me long ago), I could imagine that might cause the strobe marks to appear to advance and hold, advance and hold. Is that possible? That doesn't necessarily mean the motor has speed variations. But I suppose even if the motor is working perfectly, does that matter? Would I still hear wow and flutter in playback? If the spindle speed is constant but it is bent, that might cause the problem I'm seeing, but would it be heard? I haven't put it into the system yet, but I am very sensitive to wow and flutter. Perhaps another user might be OK with it even if it isn't perfect.

I'm wondering if anyone has any strong ideas about where to look next. The diodes in the speed control circuit aren't as simple to replace as one might think, but if it's a likely fix I'll do it. Soldering skills are up to the task. But I'd also like to know if my suspicion about the wobble caused by a bent spindle is a possible cause.

Thank you all!

 

[Johnny_Law]

For me it was diodes...

Thread 'Yamaha YP-D6 Pulsing Speed - Rebuilt - Parts List - SOLVED YAAAAYYY'

Feb 24, 2018

EDIT NOT QUITE SOLVED: Issue with all three pots & pot adjustments but came back aaaagggghhhh

EDIT2: Was the diodes!!!

This wasn't holding speed so I cleaned the pots and put in all new electrolytic caps & transistors, and it still won't hold speed. But now, it pulses fairly aggressively as if I put in the wrong transistor somewhere. Yeah, the new parts seem to have made it run worse.

So I bet I messed something up somewhere. I double and triple checked my transistor pin orientations and they all appear correct three times over. So I'd love it if someone could...

• Johnny_Law
• parts list rebuild recap transistor yamaha yp-d6
• Replies: 68
• Forum: Turntables

 

[dr*audio]

This turntable has pretty simple speed control, so it looks like the problem may be with the drive.
1. Turn it by hand with the power off and listen for any rubbing sounds. Make sure it takes a long time to stop without appearing to have much friction.
2. Put a piece of tape on the platter for reference and run it. See if it always hesitates at the same spot.
3. Lightly put your finger on the platter and see if there is a position where it stalls or has less drive.

 

[dksp]

I don't know how the strobe is powered on this exact turntable, but it might reflect fluctuations in your mains voltage. Dual turntables are known for this.
If the platter really runs that bad, you should be able to hear or measure it. Best would be to use a test record to confirm the wow, or a record with piano music on it.
The up and down motion of the platter doesn't seem that bad.

On my YP-D71, speed issues where caused by a faulty transistor on the motor control board.

 

[Carlp]

Thanks all. Johnny, I had read your thread which is what led me to the notion that the diodes could be involved. I don't recall but did you end up coating them with anything (the originals are covered in a caulk-like substance)? If so, what did you use? Dr. and dksp, the platter doesn't have any spots I can feel, and it spins maybe 15-30 seconds after being turned off. Not as long as I'd like, but reasonably long. The motor doesn't run fast enough without the platter for me to see any wobble in the spindle but I'll dig deeper. I may put it into the system and try out a test record soon. I wondered if the PS might be involved (including mains fluctuations) but it has two 470uF caps for smoothing so even that should be mitigated some. I may be able to scope the PS to see what, if anything, is going on there.

Alright, I'll try to get on this and report back. I appreciate the input.

 

[dr*audio]

1. With no platter, does the motor keep turning? Does it hesitate at all?
2. If it keeps turning, load it by gently putting your finger on it and see if it stops and if so, if it's always in the same place.

 

[Carlp]

With no platter it cogs - turns one rotation of the motor shaft, then stops, the another rotation then stops. I'm going to work on a parts list tomorrow for the diodes and the board pots (10, 27 and 28). I'll replace them all. I was going to test them in circuit to the best of my ability but I have to de-solder them to be able to measure, so I expect to just replace them. We'll see.

 

[Johnny_Law]

Thanks all. Johnny, I had read your thread which is what led me to the notion that the diodes could be involved. I don't recall but did you end up coating them with anything (the originals are covered in a caulk-like substance)? If so, what did you use? Dr. and dksp, the platter doesn't have any spots I can feel, and it spins maybe 15-30 seconds after being turned off. Not as long as I'd like, but reasonably long. The motor doesn't run fast enough without the platter for me to see any wobble in the spindle but I'll dig deeper. I may put it into the system and try out a test record soon. I wondered if the PS might be involved (including mains fluctuations) but it has two 470uF caps for smoothing so even that should be mitigated some. I may be able to scope the PS to see what, if anything, is going on there.

Alright, I'll try to get on this and report back. I appreciate the input.

No, I don't think I did coat the new diodes in anything. I'll have to see if I took any pics. I may have just touched them together with some thermal grease but memory is foggy!