Thorens TD-124/II restoration / upgrade

[Ant]

Tony, please excuse my ignorance but how does the lower platter fit? I'm a little confused as on post #1 the photo shows the original platter (upper/alloy?) to fit the recess in the chassis with little room for anything else, the "lower" platter seems to have an extruded face (the yellow bit), does the 'upper' fit on the 'lower' sharing the same O/D?

Also, the lower has the black dots which I presume are for visual RPM tracking, to which that confuses me more as there is no room in the chassis for such.

Thanks,
Ant

 

[Tony L]

Tony, please excuse my ignorance but how does the lower platter fit? I'm a little confused as on post #1 the photo shows the original platter (upper/alloy?) to fit the recess in the chassis with little room for anything else, the "lower" platter seems to have an extruded face (the yellow bit), does the 'upper' fit on the 'lower' sharing the same O/D?

Also, the lower has the black dots which I presume are for visual RPM tracking, to which that confuses me more as there is no room in the chassis for such.

Easiest starting point is perhaps the exploded view on the cover of Joachim's Swiss Precision book, but basically the thin alloy upper platter is little more than a biscuit-tin lid that sits over the very heavy and solid cast lower platter or flywheel. This is to enable a quick start clutch mechanism: the lower platter is left running throughout a listening session and if the user wishes to stop the deck to change a record or whatever the clutch switch at the left hand side of the chassis is engaged which raises the top platter very slightly so it is no longer in contact with the lower platter / flywheel. Thus instant start/stop on a deck with a 5kg rotating mass. This mechanism (which is visible in the picture of my deck with the platters removed upthread) also considerably reduces wear on the idler and motor as most of the stresses they face are at start up, not maintaining the rotating mass. The black dots are rubber and the interface between the two platters.

 

[awl]

PS I've just refitted my original bearing and the new Swissonor platter runs perfectly straight and true, so it looks like I'll be needing a replacement replacement bearing...

You have my sympathy with the process you're going through – you've chosen to do the best you possibly can and these frustrations must seem all the more real having bitten the bullet and spent the money. My hunch is that it will all be worth it in the end and that you'll be very happy with your 'keeper'.

Andrew

 

[Ant]

Perfectly clear now.

I thought the dots were a similar/early version of the 1210 indicators, to which is what made me wonder - thanks for the explanation Tony.

 

[Tony L]

Well, less than 24 hours on from the DL-103 'incident' a replacement has arrived and is currently playing Coltrane's Impressions. Many thanks to Dave Cawley / Sound Hi-Fi for such prompt service.

 

[pickwickpapers]

The 103 is annoying, not so much for the cash but for the sheer level of personal stupidity involved. This is not the first time I've done this, I also trashed a Ortofon MC10 Supreme in the exact same way about a decade ago. To be able to do this with a cart in a detachable headshell, and one with a very good stylus guard takes a special calibre of idiot.

ah, but you describe such an unfortunate occurrence in a manner which warms the heart and lightens the mood in such relentlessly 'interesting' times. Not much consolation for you, I'm sure, but a slight silver-lining for the reader [umm, this is meant to be a compliment btw...]

 

[Newboy]

Is that the Blue Note reissue, Tony? I was playing that only the other day on my recently rebuilt Lenco GL75. (Beautifully rebuilt & plinthed with a Layers of Beauty rosewood plinth by Dom Harper of Northwest Analogue).

I seem to remember paying a small fortune (£90?) for this fantastic disc set. but

Julian

 

[Newboy]

P.S. If anybody wants to see my Lenco, go to Northwest Analogue's site & it is the last one in the gallery; happy bunny, though I slaver over & crave a TD124

Julian

 

[Mr Tibbs]

Nice sounds!

Tony, if you want to hear what you are recording; between the meters is a microphone symbol - click the button beside it and select 'start monitoring'

Mr Tibbs

 

[Fox]

I had to buy the stickers from an ebay seller to stick on the underside of my TD124's brass platter as they were only marked for US which Tony's Schopper platter seems to have already thought of....

I initially had collywobbles WRT self installing the platter but it was measured as fine as the machining tolerances of a modern platter are so much better than the cast platter of the original, I'd expect the Schopper to be the same. I also replace the steel screws with stainless hex bolts and equally torqued them.

 

[Tony L]

Is that the Blue Note reissue, Tony? I was playing that only the other day on my recently rebuilt Lenco GL75.

It's a wonderfully obscure Japanese 12" 45:

I had to buy the stickers from an ebay seller to stick on the underside of my TD124's brass platter as they were only marked for US which Tony's Schopper platter seems to have already thought of....

I initially had collywobbles WRT self installing the platter but it was measured as fine as the machining tolerances of a modern platter are so much better than the cast platter of the original, I'd expect the Schopper to be the same. I also replace the steel screws with stainless hex bolts and equally torqued them.

It's surprising the brass platter only duplicates one strobe as the shape looks the same as the original iron platter, i.e. there is room, unlike on the zinc alloy casting, which only has 33rpm 50/60Hz. The Swissonor one is a nice tight fit on the spindle, so none of the alignment issues of the zinc platter which can take me about 15 minutes or so to gently nudge into correct position so there is no run out.

 

[Tony L]

I have learnt something today: a huge amount of the mechanical noise / rumble I'm experiencing with this deck is down to the eddy current brake / stepped-pulley interface. If I turn the fine speed control to maximum (i.e, all but disable the eddy current brake) the deck stops doing it's washing machine impression to the extent I can't hear it. How to cure this I have no idea. I'm certain neither the eddy-current device nor magnet are physically fouling the stepped pulley, but the resistance they create seems to set off some kind of mechanical resonance, I assume in the stepped-pulley itself. Weird stuff, but at least I've narrowed it down a bit - I know where the problem lies even if I've no clue how to fix it!

 

[Shuggie]

I know what you mean. I am awaiting a PSU for my TD124 from Martin Bastin, which will allow me to adjust the motor speed and dispense with the eddy current brake entirely. Martin told me that the Thorens motor will operate happily down to 130v, but I don't want to risk losing any of the deck's characteristic sense of 'drive' and shall therefore ask him to specify the PSU output at around 200v.

 

[Teme]

This is a fascinating thread.

Anyway, I am under the impression that Swissonor also builds or at least has built a rather nice power supply for the TD 124 - as per the attached picture. I guess it would also be rather expensive.

Br,
Teme

 

[Tony L]

Dropping the power has crossed my mind (and with the Garrard too). I don't really want to spend out on a fancy expensive PSU (even though the Swissonor is one of the coolest looking things I've ever seen in an audio context), but I may see if one of our DIY folk could make me something just to knock the voltage down to 200v or something. I think much of the issue is I need to use so much eddy current brake to slow it down to correct pitch, this deck really wants to run fast - I've already moved the magnet closer so I didn't need the speed knob turned to it's minus end-stop. I guess I may be in a high voltage area or something.

 

[jcbrum]

I have learnt something today: a huge amount of the mechanical noise / rumble I'm experiencing with this deck is down to the eddy current brake - I know where the problem lies even if I've no clue how to fix it!

Tony, I'm not sure this will help, but I've found that on several 124 motors that I have serviced, the motor field coils are not tightly bonded to the field armature. (not the rotating bit).

When the eddy current brake is operating this seems to make the field coils wobble, causing rumble.

It can be fixed by glueing card wedges in to stop the field coils moving. I have seen 124s with such wedges fitted from the factory. It seems to depend on the tolerance of the field coils former's fit on their armature

JC.

 

[jcbrum]

p.s. 124s are harder to fix for rumble, than 301s, because the arm board is mounted direct on the 124 chassis, rather than on the plinth (as per 301), which means the plinth can be used to kill any rumble by material and design selection.

JC

 

[Tony L]

I'm pretty certain (very, in fact) that the motor is not the source of the noise, e.g. if I take off the platter and belt and add resistance by just lightly touching the motor spindle or pulley I get no noise or vibration. It's definitely coming from the step pulley. The motor is actually very quiet indeed. I'd like to find a totally mint / NOS replacement step pulley at some point and see if that helps, I want to find a new idler too... I'll have replaced all the moving parts soon...

 

[Shuggie]

Tony, I'm not sure this will help, but I've found that on several 124 motors that I have serviced, the motor field coils are not tightly bonded to the field armature. (not the rotating bit).

When the eddy current brake is operating this seems to make the field coils wobble, causing rumble.

It can be fixed by glueing card wedges in to stop the field coils moving. I have seen 124s with such wedges fitted from the factory. It seems to depend on the tolerance of the field coils former's fit on their armature

JC.

Martin Bastin serviced my motor and set the coils using a benign type of silicone sealant, for the very reason that you give above. I'm content to take his advice on this matter and the motor is running very nicely (new bearings too, though).

I am not at all technically competent to talk about the TD124 motor, but if I'm correct, Martin told me that it's a shaded pole design and the motor speed is influenced by both input voltage and AC frequency. As I understand it, his PSU allows the frequency to be adjusted using a knob on the front, and he can set the output voltage by selecting different taps on the output transformer. The PSU is, I believe, very similar to the one that he produces for Garrards.

 

[Shuggie]

Out of curiosity, I have removed the magnet from my TD124's eddy current brake, to hear how the deck manages without it. Unsurprisingly, it runs too fast, but that aside there's a lovely sense of musical agility without any braking action. This is enough to confirm my suspicion that regulating the motor speed using an adjustable PSU is a more elegant and effective option than applying braking force.