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SR838 running too fast - advice needed!

Alfanijs

Alfanijs

Always learning
Hi all, in particular you turntable experts. May I bother you with some questions on this beautiful piece of equipment.

I am considering buying an SR838. Ultimately it should replace my Thorens TD320 Mk III, unless this outperforms the Sansui of course... any opinions on which should be the better turntable?

Now my actual question. It comes with a speed problem. The platter is spinning too fast, no possibility to adjust. Regardless whether 33 or 45 rpm, manual adjustment or quartz lock, all have no effect. A previous owner has already replaced a number of passive components (trimmers, capacitors) but to no avail apparently.

Now I am not an expert in electronics, let alone turntable speed control, but looking at the schematics this problem seems to be traceable with a proper troubleshooting procedure. However, there are 2 OKI ICs (MSM5810 & MSM 4069) which could be hard to find. So I would be interested to know if these are prone to failure, and if this could be a likely cause of the symptoms.

There are other issues - a cracked cover and missing hinges - would these be a show stopper?
Thanks in advance for any directions!
 
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The service manual has a series of internal adjustments that set the base speed. That would be the first place to start. To do do these adjustments accurately you need an oscilloscope but I think there is also an alternative using a voltmeter.

- Pete
 
There is a an electronic pick-up that gets readings from a disc than runs through it. IIRC it is fairly easy to access after removing the platter. I would check the clearance and operation of it first off. I got one with speed problems when I bought it, although different than your symptoms.
 
I don't know if that TT is a good idea.
While they are in demand and have sold recently for $266 to $885 usd, that is for working units.
Missing hinges, broken dust cover will be expensive to replace
The speed problem, combined now with "parts being replaced by others" would make me hesitate because you now have a possibility of the original problem as well as possible other issues as a result of the repair attempt and parts replaced. I am a tech with lots of experience, but am always wary of units that have been worked on. Compounding that is the issue with those 2 chips not being available, which if bad, make this turntable an expensive boat anchor.
If you are good tech and think you can fix it, you can take a chance if you can get it for $100usd equivalent.
Understand that if you need to bring it to a competent tech you can easily spend $150 on up to get it working. Replacement or repo dustcovers if available can go for $50 to $125usd equiv. Hinges if you can find them will be $30 to $50 again if you can find them.
It may be better to wait for one that is complete and working that you can get for $266 to lets say $400 usd equiv
 
There's a write up somewhere of someone fixing a speed issue with this turntable. Along the line of grillebilly's answer, the disk is accessed below the platter. It's slotted, and dust/lint etc. muck it up and it needed to be cleaned. That fixed the problem. Search both 636 and 838 speed issue. The tables are essentially the same
Let us know how it goes...
 
Thanks all for your replies! Really helpful.

I have read the other thread about the wobbly speed issues, but tend to agree with LBPete that this appears to be a different problem. Now I do have access to an oscilloscope, DMM and function generator so I am relatively confident that I will be able to pinpoint the problem. Whether I can then also solve it remains to be seen. Later this week I can visit the seller and have a look myself also to assess the state of the electronics after the repair attempt. This is also the big risk with Sansui stuff - if I can see and touch it, my sensibility loses from emotion and I just want to have it! But hey, you know what I am talking about ;):rflmao:

The Thorens is indeed a very good TT; I have no real need for the SR838. But still...
It also appears to me that prices in Europe are quite a bit higher than in the US. Difficult decision albeit a luxury one... I'll keep you posted!
 
Sounds like a great opportunity to buy a classic for cheap and then repair it. How much took fast is it running? I wonder if the previous tech caused this problem.
 
SR-838 tone wheel.jpg
that dirt on the slits causes speed variation. Don't know if it causes fast.

TT needs to be complete in good shape to command money. Only needs to work well to be enjoyable to some.
 
Based on your feedback I have decided not to buy this machine. There are too many unfinished projects lying around already!
Will spend my money on an MC cartridge for the Thorens - probably a nice Denon DL-103 :)
So this thread is dead and we will never know what caused the problem...
Thanks all and have a nice day!
 
We'll the thread will fade away. I don't know of but a few dead threads on ak and most of those deal with cables and folks telling others how to spend their money.

Maybe someone with the same issue will bring this thread back in 2023 or sometime. Could even be the guy that does buy that table in a month or three.

Good decision on a cartridge upgrade.
 
Hi! I've been reading this thread as I've recently acquired an 838 with the notorious speed problem. I checked for crud on the slits and saw that the disc with the slits is not even, it is partially raised - like someone tried to pull the thing off :( Could this be causing the speed problem? How do I flatten this thing back without doing more damage? Thanks in advance for any feedback guys, I'm really at a loss here.
 
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Eprimitiv said:
Hi! I've been reading this thread as I've recently acquired an 838 with the notorious speed problem. I checked for crud on the slits and saw that the disc with the slits is not even, it is partially raised - like someone tried to pull the thing off :( Could this be causing the speed problem? How do I flatten this thing back without doing more damage? Thanks in advance for any feedback guys, I'm really at a loss here.
Click to expand...

You could try and remove it, and flatten it with things like clamps, and blocks of wood. But you know, the sad truth is only a replacement will probably make it work like new. And a replacement would probably have to come from another machine... so this will be hard to find. Sorry to hear about your bad luck!
 
Eprimitiv said:
Hi! I've been reading this thread as I've recently acquired an 838 with the notorious speed problem. I checked for crud on the slits and saw that the disc with the slits is not even, it is partially raised - like someone tried to pull the thing off :( Could this be causing the speed problem? How do I flatten this thing back without doing more damage? Thanks in advance for any feedback guys, I'm really at a loss here.
Click to expand...

Before doing anything drastic, please post a picture of your disc and the pickup that reads it. As long as the part of the disc that runs through the pickup is flat, it should be OK and your problem is elsewhere.

- Pete
 
maxhifi said:
You could try and remove it, and flatten it with things like clamps, and blocks of wood. But you know, the sad truth is only a replacement will probably make it work like new. And a replacement would probably have to come from another machine... so this will be hard to find. Sorry to hear about your bad luck!
Click to expand...
Thanks for the input. I'll try to figure out how to remove it and see what can be done. I was thinking along the same lines and checked ebay. These things don't show up too often "in the wild" as they say, especially where I'm from, so big bummer. It would've looked perfect with my AU 999 :( I've been reading the threads here at AK before I pulled the trigger and figured it was an easy fix with just dirt probably on the disc. The previous owner sold it for a little over $100 and has given up on the thing after replacing caps.
 
LBPete said:
Before doing anything drastic, please post a picture of your disc and the pickup that reads it. As long as the part of the disc that runs through the pickup is flat, it should be OK and your problem is elsewhere.

- Pete
Click to expand...
Thanks for the input! Unfortunately, I have zero skills when it comes to troubleshooting and don't even know what the pick up looks like :( I will post pics in a bit after work. Just crossing my fingers that I can save this beautiful machine!
 
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