View Full Version : Thorens TD 150 speed change issue
The TD150 project is progressing very well - new spring kit from Netherlands, Mission 774 courtesy of Geoff (walpurgis) - suspension levelled and bouncing nicely but I can not get the belt to move up onto the 45 rpm part of the pulley. The control fork lifts the belt but it won't run up over the bevel onto the top. The belt is pukka Thorens and new and I've trimmed the motor so the belt runs vertical between pulley and inner platter. All thoroughly cleaned. The belt runs at the correct height on the pulley and inner platter in the 33 rpm position. Maybe the pulley is worn?
It's no big deal as I never listen to 45's.
Any thoughts of anything in I've not covered?
Photos in next post
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Photos of belt in 33 and attempting 45 positionshttps://uploads.tapatalk-cdn.com/20200820/944dc8f6be307a80fed6f15e09d2eca7.jpghttps://uploads.tapatalk-cdn.com/20200820/19006a3d639f094a7e2b1f73cca65621.jpg
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walpurgis
20-08-2020, 19:53
Wash the belt with washing up liquid in fairly hot water and clean the pulley with meths, could be all it needs, otherwise it's new belt time.The belt guide looks about right I think.
Hi Geoff - I'll do that but it's already a new belt. The powder in the photos is talc BTW.
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walpurgis
20-08-2020, 20:31
Could be the talc causing the problem.
Hi, I have a couple of thoughts looking at the photos...
Talc probably won't help as it won't grip the pulley as well.
I also wonder if the 'fork' raises it high enough to get the belt over the chamfer.? Could it be bent or worn somewhere down the mechanism?
Good luck...
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Talc will assist grip with humidity present, as in a weight lifter where his hands are moist, but in this situation it will cause slippage; remember using talc after a puncture repair?
It is quite apparent from the pictures that the fork range is not covering the required positions correctly, and I agree entirely with Geoff. If there is no adjustment for the 'fork' position allowing it to be adjusted to cover the two positions correctly, if it were mine I would carefully bend the fork up a little, the further away from the pulley the better because this reduces the amount of bending required, only a tiny amount with a pair of small toolmakers clamps.
The 33 position will also be improved, at the moment the belt is being guided towards the bottom of the 33 pulley
Many thanks for the suggestions - I'll take a look at the fork adjustment tomorrow.
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Wash the belt with washing up liquid in fairly hot water and clean the pulley with meths, could be all it needs, otherwise it's new belt time.The belt guide looks about right I think.
You the man Geoff :respect:
I did as you suggested and now it works a treat :)
Very glad I didn't take a pair of pliers to the fork :eek:
walpurgis
21-08-2020, 08:50
We aim to please! :lol:
You don't disappoint.
TT is now all fettled and working nicely - level with good bounce.
I'm just about to test the audio aspect by connecting the Supergold - hoping for the best but planning for the worst wrt hum and noise.
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walpurgis
21-08-2020, 10:09
The Decca will almost certainly want fluid damping. It could be a bit bass light and bright otherwise.
Indeed - I'll be pleased if I get to the stage of fine tuning without having to redo the ground connection s inside the plinth
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Unbelievable! No hum or crackles from the Supergold on the setup jig into the MM stage of Quad 33https://uploads.tapatalk-cdn.com/20200821/ac930369d1c64a59e729163a350ab010.jpg
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And now all setup and playing tunes - no Decca hum! Tomorrow it goes onto the TT wall shelf that's just arrivedhttps://uploads.tapatalk-cdn.com/20200821/4236a229750fdfdc18c3a7107d2bdc5f.jpghttps://uploads.tapatalk-cdn.com/20200821/de9fa9f0d1d8fbde2330edc04b46964b.jpg
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Looking good Stephen.
Are you using the M2 setting with a 5.6mV sensitivity?
Looking good Stephen.
Are you using the M2 setting with a 5.6mV sensitivity?
Thank you Barry.
Well yes and no. ;)
The 33 and 303 were fully upgraded by NetAudio several years ago. So all the modular boards were upgraded along with the tape adapter board and PSU. I now use the tape input as my line level input for a Chord Gem DAC either for USB streaming from MacBook or Bluetooth from smartphone.
NetAudi did not do any upgrades for the disc adapter board so I did this myself - essentially stripping out all the existing components and swapping them for high quality ones of the same value so it should be exactly the same sensitivity as the OEM one although I've no way of measuring it. I did notice that the overall gain on all inputs except the radio is reduced following the NetAudio work. The radio gives good volume at 3 o'clock on the volume pot whereas for digital and vinyl replay it needs to be at 6 o'clock. There's no hum or distortion so it's no big deal.
Although I only did a quick test to check for hum I noticed earlier that when I connected the Rothwell Simplex phono stage to the line level/tape input instead of the DAC the gain was essentially the same as going straight to the inbuilt phono stage.
Photo is of my reworked DA board.
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If you have replaced all the components value-for-value, then the sensitivities of the disc adapter board will not have changed. So which side of the square board do you use? - M1, M2 and C1 are marked underneath on the track side.
Deccas have high output for a fixed coil cartridge (7mV at 5cm/s), so you ideally need a disc sensitivity of no more than 5mV, preferably 10mV. One criticism or the Quad 33 was of the limited headroom (or overload capacity) of the disc input. For the M2 (5.6mV), the maximum input level before clipping is 120mV (27dB) which ought to be sufficient.
I have used many Decca cartridges, but none with a Quad 33. I have used them with a Quad 44 having a 10mV disc sensitivity (300mV max input, 29.5dB) without problem. Once you have been smitten by the Decca sound, there is no going back. :)
Yes it's in the M2 position Barry. I note reading the 33 manual that Quad suggest that for high output MM's position 2 is the one to use and that volume at position 6 should be about right sound level wise which is just what I'm finding so all is good. The 774/Supergold are dialled in now - the whole combo works very well to my ears. Very musical. Just listening to Buena Vista Social Club - great dynamic range and control.
Many thanks to Geoff (walpurgis) for the 774 and advice - a true gentleman.https://uploads.tapatalk-cdn.com/20200822/0d1f8b7630bde31d2f19ca4aced77e35.jpghttps://uploads.tapatalk-cdn.com/20200822/673afbf35de77419ca1fdab6553bde8a.jpghttps://uploads.tapatalk-cdn.com/20200822/cf4904f75d193e2791a98073667c6afb.jpg
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walpurgis
22-08-2020, 09:47
I see the armrest came in handy. :)
I see the armrest came in handy. :)
Could have been made by Mission :)
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