Sansui SR-838 - An Atypical Speed Issue

[petesui]

I've had significant speed fluctuations and other issues with my otherwise sexy SR-838. Most of the drama has been covered in @JimEGR's Sansui turntable thread, if you're so inclined. I'm happy to say that my tech seems to have resolved the worst of it and it's mostly under control. I've been spinning it a lot this week and it sounds great on the 555A. One little glitch persists, however. The pattern during any given listening session seems to be that towards the end of the first side of the first record, about 20 minutes in, the table will suddenly speed up and stay there (this is in quartz lock mode). I've taken to simply jumping up and quickly cycling the power button/switch, off-on, while the stylus is still down and the record is spinning. Speed returns to normal immediately and seems to stabilize. It may happen one more time during a session of say three or four more records. Again, cycle power and speed is restored.

I've read several of the 838/929 speed issue threads on the forum including @manyberg's SR-838 speed thread which seems the most comprehensive. That thread captures the typical speed issue that several folks have experienced where the speed fluctuates quickly for a brief second at a consistent point in the platter's rotation. The successful fix is some combination of cleaning/adjusting the chopper wheel and the optical sensor reading it that live just under the motor cover beneath the platter. My chopper wheel was clean as a whistle and the sensor does not appear to be out of whack, and a light dusting for good measure did not solve my issue, nor has @bluesky's suggestion to remove and rotate the platter position.

Given my symptoms and the current remedy of cycling the power, I wonder if this intermittent speed fluctuation is actually being caused by dirty switching. Might cleaning the power switch as demonstrated by @MIJ_Pioneer in his SR-838 restoration thread solve the problem? Or, does this sound more like a problem in the circuit or elsewhere that cycling the power somehow resets? Again, this is all happening in quartz lock. I haven't experimented/observed too much with quartz lock off, but it seems that the speed/strobe is wonky there too and the speed pot doesn't really dial it in. So, perhaps a thorough cleaning of all switching - power, speeds, and quartz lock - and the speed pot is in order? I read one reference in another Sansui group where the owner said her tech replaced the "servo" and that fixed her problem. I'm not sure what that means. Appreciate your thoughts. Pic of the 555A/838 combo for attention!

 

[tonysrep]

Haven't had this issue with my 838 but I have with the 929. there were several diodes situated in a row next to each other on the board that were leaking voltage that were the cause.Also had the strobe bulb flashing. Very cheap to buy but a slight pain in the butt to replace I imagine the 838 is the same

 

[JimEGR]

Has your tech gone over the electronics yet? There is $20 "speed control" recap kit on eBay still. I have thr kit sitting on the bench here for mine, for a preemptive makeover.

 

[Vintagear]

I've had significant speed fluctuations and other issues with my otherwise sexy SR-838. Most of the drama has been covered in @JimEGR's Sansui turntable thread, if you're so inclined. I'm happy to say that my tech seems to have resolved the worst of it and it's mostly under control. I've been spinning it a lot this week and it sounds great on the 555A. One little glitch persists, however. The pattern during any given listening session seems to be that towards the end of the first side of the first record, about 20 minutes in, the table will suddenly speed up and stay there (this is in quartz lock mode). I've taken to simply jumping up and quickly cycling the power button/switch, off-on, while the stylus is still down and the record is spinning. Speed returns to normal immediately and seems to stabilize. It may happen one more time during a session of say three or four more records. Again, cycle power and speed is restored.

I've read several of the 838/929 speed issue threads on the forum including @manyberg's SR-838 speed thread which seems the most comprehensive. That thread captures the typical speed issue that several folks have experienced where the speed fluctuates quickly for a brief second at a consistent point in the platter's rotation. The successful fix is some combination of cleaning/adjusting the chopper wheel and the optical sensor reading it that live just under the motor cover beneath the platter. My chopper wheel was clean as a whistle and the sensor does not appear to be out of whack, and a light dusting for good measure did not solve my issue, nor has @bluesky's suggestion to remove and rotate the platter position.

Given my symptoms and the current remedy of cycling the power, I wonder if this intermittent speed fluctuation is actually being caused by dirty switching. Might cleaning the power switch as demonstrated by @MIJ_Pioneer in his SR-838 restoration thread solve the problem? Or, does this sound more like a problem in the circuit or elsewhere that cycling the power somehow resets? Again, this is all happening in quartz lock. I haven't experimented/observed too much with quartz lock off, but it seems that the speed/strobe is wonky there too and the speed pot doesn't really dial it in. So, perhaps a thorough cleaning of all switching - power, speeds, and quartz lock - and the speed pot is in order? I read one reference in another Sansui group where the owner said her tech replaced the "servo" and that fixed her problem. I'm not sure what that means. Appreciate your thoughts. Pic of the 555A/838 combo for attention!

View attachment 3638452

I would try replacing the three electrolytic capacitors (C75, C77, C78) on the S-0014 PLL Servo board. The boards are easy to get to on the 838 because you don't have to remove the tonearm, only the bottom cover. I had a similar issue on a SR-929 (that would also correct itself by turning it off and back on) and replacing the two small electrolytic caps on the PLL board solved it. One of the small caps was out of spec.

Hope this helps.

 

[markkb]

It seems like replacing the electronics with the 838 kit is a good next step. (seller 'Affinity for Artifacts' on eBay). I have the 636 kit that I'll be using soon to see if that will clear up my 636 speed issue, along with cleaning the pots, checking the chopper wheel/ sensor...in that order, as it's all a science experiment.

 

[petesui]

There were several diodes situated in a row next to each other on the board that were leaking voltage that were the cause.

Has your tech gone over the electronics yet? There is $20 "speed control" recap kit on eBay still.

I would try replacing the three electrolytic capacitors (C75, C77, C78) on the S-0014 PLL Servo board. The boards are easy to get to on the 838 because you don't have to remove the tonearm, only the bottom cover. I had a similar issue on a SR-929 (that would also correct itself by turning it off and back on) and replacing the two small electrolytic caps on the PLL board solved it. One of the small caps was out of spec.

" It seems like replacing the electronics with the 838 kit is a good next step. (seller 'Affinity for Artifacts' on eBay).

Thank you, Gentlemen. I appreciate all the suggestions. A little backstory on this table. When I bought it Seller represented that it had been recapped. It developed (or already had) very erratic speed issues, much worse than the problem is now. I took it to my tech - a very good turntable guy. He confirmed that it had indeed been recapped with a mix and match hodge podge of different branded capacitors, but nonetheless "recapped." He discovered some atrocious solder work on the boards and reflowed them. This resolved the wildest of the speed fluctuations and the table runs substantially better, yet this intermittent glitch persists. I would describe my tech as a "minimalist" in his repair philosophy. A fix only what's broken type. He is hesitant to install the kit as unnecessary given that the table does indeed have new caps in it. Certainly, we've missed something and I'm happy to have him redo the whole thing. The cost is not material. I'm waiting for my turn in the queue to bring it back to him.

This is mostly me being impatient and wanting to get the table back in the rotation. I've never been inside it. I think I'll open it up tomorrow and inspect/test the various parts suggested in your replies and see for myself what Seller's "recap" looks like. I'm happy to purchase the kit from AFA. I appreciate your replies because it sounds like were drilling down on the issue. The consensus here seems to be a circuit fault rather than dirty switching.

Edit to add that I've ordered @EastPoint's kit.

 

[JimEGR]

Edit to add that I've ordered @EastPoint's kit.

Game on!

 

[petesui]

Game on!

I'm recommitted to the 838! I've been spinning it all week on the bench with the 555A through my Dahlquist M-905s. Needless to say, it sounds fantastic.

 

[bluesky]

When I first got my 838 20 years ago, or whenever it was, I had a speed problem, All I did was take the platter off and put it back on. The third time it worked perfectly.
Needless to say - the platter has NEVER been off since. I ain't touching it! That was my solution. Functions perfectly.

 

[tonysrep]

the problem I saw was the terminals turn black ,I imagine there's a high silver content in the components used

 

[petesui]

I would try the three electrolytic capacitors (C75, C77, C78) on the S-0014 PLL Servo board. The boards are easy to get to on the 838 because you don't have to remove the tonearm, only the bottom cover. I had a similar issue on a SR-929 (that would also correct itself by turning it off and back on) and replacing the two small electrolytic caps on the PLL board solved it. One of the small caps was out of spec.

Hope this helps.

This helped! I did not replace these caps as they all appeared new consistent with seller's recap before I bought it last winter. C75/77 are black and gold Nichicon, clearly new. C78 is an all black Nichicon that also appears new. C78 is rated 63v47uF, but it tested at ~135uF, so 35% out of spec if I'm understanding/calculating correctly. I left it though because I don't have anything to replace it with at the moment. C75, however, appeared to have a cold joint with poor solder coverage on one of the leads. I hit that with some fresh solder, et voila! I'm now four and half records into a spinning session on the SR-838 and ***fingers crossed*** I haven't had a single speed glitch. Seems to be running stable and smooth. Thank you @Vintagear! I'm kind of amazed at the simple fix and I would never have known where to look without your tip.

A few other notes. This simple repair was not without drama. I made it more complicated. When I went to test after buttoning the table up, I had no strobe light and the platter wasn't spinning. Well damn. I really screwed something up. Opened her back up. In manipulating the S-0014 PLL Servo board to make the initial repair, I'd broken two wires. One was the red wire attached to Post 17 on the neighboring S-0016 power supply board that runs back to the S-0013 motor control board (platter rotation). The second was the gray wire from the S-0014 PLL servo board to Post 16 on the neighboring S-0016 power supply board (strobe light). After some very careful wire stripping I was able to reattach and solder both wires back to their respective posts successfully. Finishing up another side of a record as I type and still no speed glitches! The SR-838 is running smoothly!

Also, I spritzed the pitch control pot with electronics cleaner and gave it a drop of F5. Doesn't seem to have had any effect. I can't get the strobe dialed in with the quartz lock off using the pitch control. The pitch control doesn't seem to do anything.

 

[Rickypoo]

When I first obtained my sr-838 the platter would start up & get to the correct speed but within a few seconds it would surge forward then back repeatedly, Shipped it off to my tech. He stated the Servo needed replaced, which he did. It keeps exact speed now with absolutely no issues.

 

[Vintagear]

This helped! I did not replace these caps as they all appeared new consistent with seller's recap before I bought it last winter. C75/77 are black and gold Nichicon, clearly new. C78 is an all black Nichicon that also appears new. C78 is rated 63v47uF, but it tested at ~135uF, so 35% out of spec if I'm understanding/calculating correctly. I left it though because I don't have anything to replace it with at the moment. C75, however, appeared to have a cold joint with poor solder coverage on one of the leads. I hit that with some fresh solder, et voila! I'm now four and half records into a spinning session on the SR-838 and ***fingers crossed*** I haven't had a single speed glitch. Seems to be running stable and smooth. Thank you @Vintagear! I'm kind of amazed at the simple fix and I would never have known where to look without your tip.

A few other notes. This simple repair was not without drama. I made it more complicated. When I went to test after buttoning the table up, I had no strobe light and the platter wasn't spinning. Well damn. I really screwed something up. Opened her back up. In manipulating the S-0014 PLL Servo board to make the initial repair, I'd broken two wires. One was the red wire attached to Post 17 on the neighboring S-0016 power supply board that runs back to the S-0013 motor control board (platter rotation). The second was the gray wire from the S-0014 PLL servo board to Post 16 on the neighboring S-0016 power supply board (strobe light). After some very careful wire stripping I was able to reattach and solder both wires back to their respective posts successfully. Finishing up another side of a record as I type and still no speed glitches! The SR-838 is running smoothly!

Also, I spritzed the pitch control pot with electronics cleaner and gave it a drop of F5. Doesn't seem to have had any effect. I can't get the strobe dialed in with the quartz lock off using the pitch control. The pitch control doesn't seem to do anything.

Excellent! Glad it helped. A bad connection (cold solder) on one of those caps on the PLL Servo board I pointed you to can definitely cause the issue you were experiencing, just as a cap that is out of spec would. Hopefully your 838 is still running properly and we got to the source of the problem.

Now as far as your issue with adjusting speed, a few questions:

When you take quartz lock off are 33 & 45 both fast, slow or different?
When you try to adjust the speed is there any change on the strobe speed at all (even minimal)?
When the previous owner recapped it did they change all the trimmers or are the originals still in there?
Have you attempted to go through the adjustment steps outlined in the Service manual?

 

[petesui]

Now as far as your issue with adjusting speed, a few questions:

When you take quartz lock off are 33 & 45 both fast, slow or different?
When you try to adjust the speed is there any change on the strobe speed at all (even minimal)?
When the previous owner recapped it did they change all the trimmers or are the originals still in there?
Have you attempted to go through the adjustment steps outlined in the Service manual?

I'll have to compare 33 & 45. 33 is fast and I really couldn't detect any change in speed using the pitch control. I'll check both this evening and report back.

I did notice a few trimmers and I believe they were all original. I didn't notice any new ones. Knowing what I know now about the seller, I doubt very much that he would've gone to that length. No, I've not attempted those adjustment steps. I'll review.

Thank you very much for continuing to troubleshoot this table with me. It's a beauty, but it's been a mess. I'm pleased as punch to have the quartz lock stable and apparently under control. Just for fun here are a couple of pictures of the solder work my tech found in July before he reflowed it and resolved the majority of the wild speed wobble issues it was having. You can see that it is indeed S-0014, the PLL Servo board.

 

[Vintagear]

I'll have to compare 33 & 45. 33 is fast and I really couldn't detect any change in speed using the pitch control. I'll check both this evening and report back.

I did notice a few trimmers and I believe they were all original. I didn't notice any new ones. Knowing what I know now about the seller, I doubt very much that he would've gone to that length. No, I've not attempted those adjustment steps. I'll review.

Thank you very much for continuing to troubleshoot this table with me. It's a beauty, but it's been a mess. I'm pleased as punch to have the quartz lock stable and apparently under control. Just for fun here are a couple of pictures of the solder work my tech found in July before he reflowed it and resolved the majority of the wild speed wobble issues it was having. You can see that it is indeed S-0014, the PLL Servo board.

View attachment 3641084
View attachment 3641085

If you attempt the speed adjustment steps in the service manual be sure to first have the speed control knob on the plinth set to as close to approximate center as you can (I realize there are no markings). This will give you room for +/- adjustments later if you are successful. The idea is to have that knob centered and then hopefully the trimmers on the circuit board will allow you to also center the strobe speed. Then if all is well, you should be able to increase and decrease the speed using the knob on the plinth.

Use a plastic Phillips to adjust the trimmers. If you use a regular metal screwdriver, be very careful not to slip and touch anything on the circuit boards because you may short something. Also, take your time and turn the trimmers slowly until you hopefully see the increase or decrease in speed you are looking for.

Good luck

 

[petesui]

If you attempt the speed adjustment steps in the service manual be sure to first have the speed control knob on the plinth set to as close to approximate center as you can (I realize there are no markings). This will give you room for +/- adjustments later if you are successful. The idea is to have that knob centered and then hopefully the trimmers on the circuit board will allow you to also center the strobe speed. Then if all is well, you should be able to increase and decrease the speed using the knob on the plinth.

Use a plastic Phillips to adjust the trimmers. If you use a regular metal screwdriver, be very careful not to slip and touch anything on the circuit boards because you may short something. Also, take your time and turn the trimmers slowly until you hopefully see the increase or decrease in speed you are looking for.

Good luck

Okay well the adjustment procedures as described in the SM are straightforward except for the physical gymnastics required to actually perform them. How does one spin the platter and observe the strobe pattern while turning the trimmers underneath? Do you stand the table up vertically on its side? Seems treacherous.

 

[Vintagear]

Okay well the adjustment procedures as described in the SM are straightforward except for the physical gymnastics required to actually perform them. How does one spin the platter and observe the strobe pattern while turning the trimmers underneath? Do you stand the table up vertically on its side? Seems treacherous.

The turntable must be level. Rest the the edges of the plinth with two blocks. Then you can look under the TT to put your access the correct trimmers, hold tool steady and then look up over at the top of the TT while it spins. Below is a picture of TT worked on showing what I mean.

 

[petesui]

The turntable must be level. Rest the the edges of the plinth with two blocks. Then you can look under the TT to put your access the correct trimmers, hold tool steady and then look up over at the top of the TT while it spins. Below is a picture of TT worked on showing what I mean.

Looks like fun! I'll save the beer for after this adjustment. Thank you. I couldn't visualize this solution when I was looking at this late last night.

 

[petesui]

Thank you, @Vintagear. You and this table have taught me a lot. Fully adjusted and spinning perfectly, whether Quartz-Servo or Pitch-Control, for the first time since it arrived eight months ago, and sounding really good.

 

[Vintagear]

Thank you, @Vintagear. You and this table have taught me a lot. Fully adjusted and spinning perfectly, whether Quartz-Servo or Pitch-Control, for the first time since it arrived eight months ago, and sounding really good.
View attachment 3642350View attachment 3642351

That's fantastic!! Wow eight months, I'm glad I saw your post and was able to help you finally resolve the issues. Good thing you didn't give up on the 838, it's an excellent deck. I've benefited a lot from the collective technical knowledge base here on AK and am happy to give back.

Enjoy your 838.