Technics SP 10 Speed Problems

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I have enjoyed my Technics SP 10 Mk II for many years. Recently though, it began to...what sounded like...loose sync. It would
wow momentarily, then resume at speed. Slowly, the wows became more frequent, and then, it stopped running at any correct speed alltogether. It spins very fast...faster than 78 rpm.
Any ideas from the most knowlwdgable diy members or gurus?
Thanks!
 
Rollinr,
I don't know the SP10 but if it has the same electronics as the SL1200 I could maybe help you.
If not, ignore this post.

/Hugo :)
 

Attachments

  • mvc-618f.jpg
    mvc-618f.jpg
    80.9 KB · Views: 887
rollinr said:
I have enjoyed my Technics SP 10 Mk II for many years. Recently though, it began to...what sounded like...loose sync. It would
wow momentarily, then resume at speed. Slowly, the wows became more frequent, and then, it stopped running at any correct speed alltogether. It spins very fast...faster than 78 rpm.
Any ideas from the most knowlwdgable diy members or gurus?
Thanks!


Hi rollinr,
The two SP10's I repaired had detoriated powersupply electrolytic caps. Some were even at the point of bursting!
I replaced all electrolytics in the remote powersupply and it worked fine again. I first searched in the speed control circuit but ended in the powersupply. Especially the capacitor that gets slightly warm was very bad.
:cool:
 
rollinr said:
I have enjoyed my Technics SP 10 Mk II for many years. Recently though, it began to...what sounded like...loose sync.


Hi,
I have service manual for SP10 in pdf, but it is huge. (5-6Mb). If your mailbox is large enough, just mail me the address.

Netlist said:
I don't know the SP10 but if it has the same electronics as the SL1200 I could maybe help you.

Those turntables have completely different electronics.

Regards
 
SP 10 help

Thanks netlist, fof the offer, but the SP 10 is really a different animal. There are 4 (at least) circuit boards under the platter that are populated by scores of ICs...then there's the outboard power supply!

Elso, I'll give your idea a try. Replacing 20 year old caps couldn't hurt! Was runaway speed the problem you had encountered?

Netlist, thanks for the offer of the manual!

Warmest Rs

rollinr
 
Re: Re: Technics SP 10 Speed Problems

Elso Kwak said:



Hi rollinr,
The two SP10's I repaired had detoriated powersupply electrolytic caps. Some were even at the point of bursting!
I replaced all electrolytics in the remote powersupply and it worked fine again. I first searched in the speed control circuit but ended in the powersupply. Especially the capacitor that gets slightly warm was very bad.
:cool:

Elso,
Somehow I have ended up with a mint SP 10 Mk II, a mint SP 10 Mk I, and a ragged out ex radio station MkII.
The Mk II locks and never drifts. The Mk I wanders a lot. The ragged one does not have a working strobe, speed selection switch, or other nicities.
I assume you fixed two Mk II's. I have never looked inside the remote box. How many caps are in there?

George
 
Re: Re: Re: Technics SP 10 Speed Problems

Panelhead said:


Elso,
Somehow I have ended up with a mint SP 10 Mk II, a mint SP 10 Mk I, and a ragged out ex radio station MkII.
The Mk II locks and never drifts. The Mk I wanders a lot. The ragged one does not have a working strobe, speed selection switch, or other nicities.
I assume you fixed two Mk II's. I have never looked inside the remote box. How many caps are in there?

George

Hi George,
No I repaired only Mk I's. There are a handful of electrolytics inside. Just have a look. The bad ones have bursted or convex rubbers. Strobe lights also burn out in the long run.
:cool:
 
SP 10 MK II

Trusting that replacing the caps will solve my speed problems, I move on to the burned out strobe in my SP 10. Does anyone know a supplier for these apparently high end neon lamps. Is the voltage the same as a small night light style neon? Any ideas? Thanks!

Rollin
 
Re: SP 10 MK II

rollinr said:
Trusting that replacing the caps will solve my speed problems, I move on to the burned out strobe in my SP 10. Does anyone know a supplier for these apparently high end neon lamps. Is the voltage the same as a small night light style neon? Any ideas? Thanks!

Rollin

Hi Rollin,
I replaced the neon lamp by a smaller standard bulb.
It did not last as long as the original lamp.
With some modification a ultra bright LED would work perhaps.
:idea:
 
Hi rollinr,

i have no idea about the sp10, but I have had a technics turntable that suffered the same symptoms as yours.
Min was caused by a dodgy switch, from memory itr was the speed selector push buttin switch, if you tap it while rotating, does the speed change?
Good luck.

cheers ab
 
Ex-Moderator
Joined 2003
It's a standard fault.

Years ago, I spent hours chasing round the oscillator and servo to be casually told by a colleague to look at the 5V reservoir capacitor in the power supply. When it dies, spikes upset the dividers etc in the pulse generator.

Edit: All the strobe tells you is that the servo has locked the platter to the pulse generator. It doesn't necessarily confirm correct speed.
 
If the crystal oscillator is working correctly, the strobe will indicate
whether or not speed is correct. The whole point of the crystal
oscillator is to have a stable frequency source. I, too, have an
SP-10 (Mk IIa) -- purchased off Ebay relatively cheap because
"speed not stable". Haven't dug into it yet, but much of the
electronics are small-scale logic ICs and custom Technics digital
chips. If they fail, it's not likely to work at all. That leaves power
supply, as others have mentioned, some op-amps in the PLL
circuitry and drivers, or --- scary thought -- dead motor windings.
If motor windings, one is really hosed; you then have a parts
unit for the next one you buy to replace this one...

I'm hoping my problem is power supply caps. $20 to Digi-key and
I'm up and running. They should probably be replaced anyway
on a unit this old. Of course, it'll sound best with Panasonic
caps in it. ;-)
 
SP 10 still running wild

Thanks for all the posts re my SP 10 Mk II. I put all new caps in the power supply and had high hopes. They were dashed. No
change. Let me add now that the power switch has no effect. When you plug the power supply (into the mains, for my Brit friends) and switch it on, the platter starts rotating at a high rate...faster than 78 rpm, and the power switch will not stop it. The speed buttons also have no effect. Still seeking a solution or solace.

Thanks,

rollinr
 
I too have a Technics SP10 Mk II which I have had for a few years, and it just went dead also with speed problems. The turntable turns very fast, the speed controls do not work.

I happen do thave the serfice manual and am trying to se if this can be fixed here. The problem is not with the power supply, it is on one of the 3 boards (the 4th board just conects the 3 together).

My symptoms are: turns on and off from the start button, but spins very fast, the speed change buttons have no effect on the speed. A technician friedn has found some voltage anomolies, but has yet to trace the source of the problem.

If anyone can help on this, I would apreciate hearing from you, and if I can get this fixed here, I will post the solution here once it is done.
 
Ex-Moderator
Joined 2003
Servo loop?

Hmmm, tricky. Still, there are a few things that you can discount. From memory, the three-phase motor is driven by three power amplifiers and some timing logic. All of that must be working correctly, otherwise the platter would sit there and quiver. I suspect that the servo control loop has been broken and that feedback pulses are not getting back from the platter tacho, causing the control electronics to drive the motor harder.
 
Thanks for the suggestion, I'll check this. What you say seems logical, I just hope the exact problem is easy to isolate.

While I have you, perhaps you can give me some suggestions on my SP25's fault. In this, when the control is set to neutral, the turntable quivers, but when the pitch control is engaged, either plus or minus, the turntable works fine. What could be causing this?

I never realized turntables had such complicated electronics. Whatever happened to the simple motor, pulley and belt?

Rgds
 
Ex-Moderator
Joined 2003
Direct drive turntables are complex, and best thought of as a complicated bit of electronics with a motor hanging on the end!

Regarding your SP25, the drive amplifiers are definitely fine, but there's a problem with the feed to them. In variable pitch mode, the turntable may use a completely different servo system to fixed speed mode. In fixed speed, it almost certainly compares the frequency of pulses from an internal quartz refernce with tachometer pulses from the platter. In variable pitch mode, it might not be able to do this. The clue will be in the way that the variable pitch control works. If it adjusts speed in steps, then it is changing the division ratio of the digital system. I would be prepared to bet, however, that in your turntable, the variable pitch control is continuously variable, indicating an analogue control system.

I would check that the dividers from the quartz oscillator are operating correctly and producing a low frequency square wave that can be compared with the corresponding square wave generated by tacho pulses from the platter. Good luck.
 
sp10mII

i have just repaired this turntable with speed control loss. i found the square wave breaking down at ic5, ic6 on the speed control board. im not looking at the scematic and may have these chip numbers wrong. i will look tomorrow at work and make any corrections. i also found these chips to be getting near hot. (pretty warm ). these chips are not available from panasonic but are as generics. i will try to get back to you with the correct chip id numbers.

lectec.
 
Hi. Thanks for the suggestions. I will have someone look at this and hopefully I can get this resolved.

Were your symptoms the same? My turntable runs only in 1 speed, and that is FAST. There is no speed control via the speed selector switches, but the turntable starts and stops as per normal, and the brakes work fine also.

I have a service manual, but fat good that is doing me, with the local technicians hardly able to understand the operation and logic. Most have never worked on a turntable before, so its greek to them.

Any suggestions you can provide would be most useful. Otherwise it will be trying to change one component at a time to arrive at the one which is defective, and that could take a long long time to resolve.

Thanks/ Rgds
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.