How to pull apart an SR-929

This unit spins mega fast. Does it whether quartz locked or not, and manual adjustments (both top and underneath) make no difference.

So, figured I'd pull it apart and have a look about. But I've never done one of these before and the service manual doesn't show me.

From the top I removed the three inner circle bolts and the motor fell down a bit. Also removed the 2 countersink screws on the out inside-edge of the top bit. It wouldn't budge and I didn't want to try too hard. So, I put the above bolts back in place and looks okay.

So, tried from underneath and removed three large long brass bolts, the four feet and the tone arm cover plate. The base didn't seem to want to move. Tried it a bit but didn't want to force it.

So, what's the go with pulling this thing apart?

I think the large tone arm nut on the bottom has to come off before the base comes off If I remember correctly. Does the platter spin fast or just the light? Fever

Last night just before I went to bed I had another look at it and realised the brass bolts hold the top in place. I then loosened the counter sunk (2) screws at the top and I got it apart.

I haven't taken off the tone arm as it looks pretty fiddly with some very fine wires. So, the unit is on it's side and I got the centre out and laying face down on some cloth, and I'm having a good look around.

First thing is a broken wire. I don't think this was me as I did a proper check about when lifting out the centre to make sure no wires were being stretched. Anyway, I think I know where it goes. I'm going to meter it out to be sure. Looks like an earth wire that goes to the Control Board, into a PCB hole (ID 10 in the service manual diagram of the Control Circuit Board layout - conductor side). Tracing this wire it goes to the earth plate of the tone arm. I don't think this would be causing my speed issues, but it certainly may affect the sound, so I'll solder it up.

A visual inspection shows no bad caps or components. Everything is very clean with no signs of distress anywhere to be seen. All solder joints look solid and no cracks.

Johnny, the speed of the platter is really fast. It's just not the light.

The SD313 transistor is loose and looks like it can do with more heatsink paste. I'll meter it out also just in case.

I do remember cursing the layout of the tone arm wires. My strobe light flashes real fast sometimes. Seems like when I don't use It for long periods of time It acts up. The platter stays true. Good luck. Fever

Well, I'd like to say it was a fruitful endeavour, but it wasn't.

I pulled down the motor and cleaned the phototransistor. Also the disc was not centred between the diode and phototransistor, but was closer to the trannie. I pulled the motor down and fitted a small shim which brought the disc in the centre.

I repaired the broken wire and put it back together.

Same thing. It spins around 200+ rpm. The only switch or knob or button that makes any difference is the power button. This unit is either 200+ rpm or off.

Bugger! I was hoping I may be fortunate enough that it all it needed was a little clean up. I don't know what to do now... dive in for a deeper fix or put it away for another day. I'll go listen to some music while I give it some thought.

My guess is that you have bad caps. Very common in these. Even if it isn't the issue it probably needs it anyways.

Can you post the schematic??

I got a list together of all caps, so might just do the lot as they're all the same age.

Is there anything else I need to look at or replace on this model in regards to the speed issue?

vigman, the schematics are in the service manual which you can download for free from Hi Fi Engine... http://www.hifiengine.com/

It is free to register.

Never mind… found it…
SO basic stuff.. you have a bi polar 5 volt supply and an 18 volt.. I assume you checked that and it OVER 5 volts 5.1X older CMOS hates to be below 5.
and the +18 is CLEAN ( as well as the 5's
And I further assume all fuses check out and there are 5.
I assume it's at 200 RPM in servo or quartz?
Quartz would be .. internal FIXED clock
Servo would be VSO ( vary speed )

I would start in Quartz 33 1/3... first look@ IC 03 pin 4 ( which is your master clock ) and see if you get 2,430hz ) and a CLEAN 50% duty cycle wave. Move to TR-13 base
90 hz 50% duty cycle.
If that's all cool, it's possible you have a ( short / open ) in one of the motor windings or the drive.. OR a shitpile of ripple on the + 18

Looking at the schematic the voltage quadrupler that could be a WAY bad source of noise to drive the neon ~ 90 volts hanging on the 18 volt rail...

I'll take the unit downstairs to my workshop. It was cold on the weekend and I was being lazy (and hopeful) and wondered if a general clean-up would suffice. It didn't, so it's to the workshop where I can get my test equipment onto it. I just ordered some new caps.

The weekend wasn't a total disaster though as I was able to fix an old JVC L-F41 turntable. So while I was working on the 929 the JVC was happily spinning some vinyl.

Nice~

River,, any news on this… I'm curious …
Mike

No action yet. I got all the parts ready but lack of time has been the issue. Working some long hours at the moment and when I get home it's jsut nice to lsiten to some music with a whisky or three.

I hope to get onto it this weekend and will let you know how I go.

Getting some different caps. I got some 450V caps to replace the 160V caps, but not real happy with that, so ordered some 200V caps. This is more a space issue as the 450V caps are plenty big... may just fit, but I feel happier with the 200V ones. Should get these before the weekend, along with some other goodies (I like buying surplus electronics, even if I have the faintest notion I may use it).

So, this weekend... again.

My fingers are crossed that this cures ya' ills.

Nice table

I have a 929 that has the same problem.
Sadly I don't have the time or knowledge to fix it.
I descibed it's speed problem in this old thread:

http://www.audiokarma.org/forums/showthread.php?t=433561

Really wish you good luck.

Hi,

Well I was able to spend some quality time with this fine old table.

The 5V was moving from 4.2 to 4.6 volts. The 18V had some nasty ripple and would dip below 18V at times.

I repalced all the elctro caps on the three boards (power supply, controller board and the PLL board). There are 2 electro caps on the PLL board. According to the schematic and service manual, these are 4.7uF/25V units, however one of those caps on the actual circuit board was a 47uF/25V part. I didn't have a 47uF spare, so used the 4.7 I purchased as according to the schematic it's there to clean up any noise on the 5V power rail from the digital circuits. I will get a 47uF today and put it in this evening.

Anyway, late yesterday evening, after the re-cap I powered up the unit. Good news and bad news. The platter starts off quite slow now and after a few revolutions she get faster, but nowhere near the speed she used to run at. Looks like it's gone from about 200+ rpm to about 40 or so. So that's good news, but now I got no neon strobe light.

I need to check the neon and the 100V circuit that supplies it. Also will check the relevant power rails again, but last night they were all in spec.

I left the speed pots (on the controller board and can only be accessed from under the unit) in the middle position. I have never seen this table operate perfectly yet, nor do I (or have I) another 929 to compare.... so not sure if tweaking these pots back a bit will bring down the speed, and then the speed pot on the outside of the unit (ie the pot next to the speed/quartz buttons) will do the rest?

I can try it out this evening, but without the neon strobe light it I won't be able to determine if the speed is accurate.

Anyway... mixed outcome, but certainly seem to be heading in the right direction.

In this circuit the 5 needs to be over 5 eg 5.05...
Get the neon working again or life will be more difficult...
I'll look at the schematic again