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Hitachi ht-463 speed control issue

T

tony.goodwin

New Member
Hi. I have had this tt from new. It’s been in its box for a few years and was sporadically used during the cd era. I want to use it again as I still have a lot of vinyl, some emotional.
It works, almost. Sound ok (but, below…), mechanism fine.
It’s direct drive, uni-torque.

Problem: uneven speed and strobe not stable. Seems to wow once or twice a revolution.

Reading other posts I have cleaned up the bearing and oiled with 3-in-1. I am sure that it’s running freely enough, but welcome thoughts. The ball bearing has a little wear in the shape of the contact circle to the cup, but I have positioned it to avoid that being in contact on reassembly. Red herring I think, BECAUSE
After a while (a side or two of an lp) (and after some additional rebuilds as well as cleaning the platter and the reflective segments that had tarnished) it would eventually synch and then was 100% stable (no wow, strobe solid)
But, after switching off and leaving it a bit 30 mins or longer) it went back to wowing.
I left it running all night on repeat (volume down!) to “run it in” which got it stable and then played it all day today, fine.
I stopped again for an hour and after picking another disc the trouble was back. This time it stabilised in the first side. But I want it to work from the start!
What to do? Could the fault be electrical? I read about cleaning pots, but why would that work? 33/45 switch works fine.
Or capacitors? I could do that I guess but do they “warm up and start working” like I am observing?
It’s making a lovely sound now. But will it still love me tomorrow?
Help please?
 
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I recently had the same problem with a Sansui Sr-737 I bought that had been in storage. It turned out the wheel and sensor the motor uses to sense speed was dirty. I had already given it a quick once over, but it needed a very thorough cleaning. After that it locked on speed. Not sure if yours has the same system, but it's something worth looking into
 
Thanks for the reply. I think this is different, the sensor is the strobe and then the back of the pcb in the motor. It’s been running all night so I will see what the situation is today
 
How does the turntable see the strobe? Is there an optical sensor? Just trying to figure out the system they are using. I am unfamiliar with this model, and there isn't much on the web. On the quartz turntables I've seen, motor speed is determined by a hall effect or similar sensor or magnetic strip on the platter or motor. The other type I haven't personally seen is one that uses an optical sensor to determine motor speed. The strobe is usually there on most turntables for just a visual confirmation to the user that it is holding speed. Unfortunately I was unable to find a service manual that doesn't require buying it. The regular wow definitely sounds like a sensor that isn't reading correctly, causing the motor to speed up to try to maintain speed, then when it picks up the sensor again, it realizes the speed is wrong ,and adjusts to resume normal speed again. Like a bad cam sensor on a car causing rough idle
 
As Dan says, the strobe is not a sensor. It's in fact pretty much unnecessary on a quartz lock turntable without an external speed adjustment but handy when you have that. Think Technics 1200 for example.

Can you open it up to get pictures of the circuit board(s)? There's not much online about this model's internals.
 
Dan13105 said:
How does the turntable see the strobe? Is there an optical sensor? Just trying to figure out the system they are using. I am unfamiliar with this model, and there isn't much on the web. On the quartz turntables I've seen, motor speed is determined by a hall effect or similar sensor or magnetic strip on the platter or motor. The other type I haven't personally seen is one that uses an optical sensor to determine motor speed. The strobe is usually there on most turntables for just a visual confirmation to the user that it is holding speed. Unfortunately I was unable to find a service manual that doesn't require buying it. The regular wow definitely sounds like a sensor that isn't reading correctly, causing the motor to speed up to try to maintain speed, then when it picks up the sensor again, it realizes the speed is wrong ,and adjusts to resume normal speed again. Like a bad cam sensor on a car causing rough idle
Click to expand...
Thanks Dan that sounds right.
Dan13105 said:
How does the turntable see the strobe? Is there an optical sensor? Just trying to figure out the system they are using. I am unfamiliar with this model, and there isn't much on the web. On the quartz turntables I've seen, motor speed is determined by a hall effect or similar sensor or magnetic strip on the platter or motor. The other type I haven't personally seen is one that uses an optical sensor to determine motor speed. The strobe is usually there on most turntables for just a visual confirmation to the user that it is holding speed. Unfortunately I was unable to find a service manual that doesn't require buying it. The regular wow definitely sounds like a sensor that isn't reading correctly, causing the motor to speed up to try to maintain speed, then when it picks up the sensor again, it realizes the speed is wrong ,and adjusts to resume normal speed again. Like a bad cam sensor on a car causing rough idle
Click to expand...
I think all this is right. The strobe ‘shows’ the speed but speed is actually controlled by the motor (see attached, this motor looks exactly like mine). Somewhere I read that the Hall effect sensors are inside the motor mounted on the same board where the coils are.
So, if we are blaming a sensor, can these sensors “warm up” in the sense that when initially started one is faulty but after some minutes of bad readings it then atarts to read properly at chich time the motor stabilises?
After this warm up period the speed is 100% solid for hours, until it is switched off and waits/“cools down” after which when starting again we are back to a period of wow
Getting the motor apart is going to be tricky: 4 screws around the outside come out easily but the brass bush which holds the the steel backplate to the pcb won’t budge, so the sensors and coil can’t be accessed. Does the attached help?
 

Attachments

Montycat said:
As Dan says, the strobe is not a sensor. It's in fact pretty much unnecessary on a quartz lock turntable without an external speed adjustment but handy when you have that. Think Technics 1200 for example.

Can you open it up to get pictures of the circuit board(s)? There's not much online about this model's internals.
Click to expand...
Next time I open it I will take pics but there is only one pan apart from the one on the motor. The repeat, start and cut and cueing are all mechanical
 
Don't discount a good cleaning/DeOxit bath. I have a Hitachi HT-353 - very similar turntable. I got it for free because the previous owner said the motor was going bad. I cleaned and de-oxited the speed selector switch, took off the bottom cover and de-oxited the innards, and it came back and has worked perfectly ever since.
 
Hi everyone. Another update, hopefully final.
DONT GIVE UP!
It’s working now pretty constantly.
What else did I do? Well, no switch cleaning though I did buy the necessary; looks like I won’t need it
All I can put the fix down to is keeping in using it, firstly, and also when it started up slow I held the needle up and with my finger sped up the table a bit and let it drop back to speed, whereupon the speed controller took over and held it (at the first or second try)
All this after cleaning out the bearing fully and regreasing lightly.
So that’s it, signing off, hope this helps someone some day
 
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