Thorens TD160 Mk1 Suspension Levelling / Arm Board Condundrum

[TellMeWhy]

Hi everyone. I spent some time levelling the suspension on my TD160 MK1 last night, but it seems like either I can get platter level OR the arm board (visually) level. Common sense tells me this shouldn't be the case and the arm board is simply screwed down to the sub platter, right?

Is it enough to level the suspension and make sure there's reasonable bounce? The left spring is floating quite near it's stop limit, the arm and front spring have plenty of bounce. If I level the spring tension then the arm board sits flat but the platter is way off level!

I checked and the plinth and top board are level. Should there ever be a need to level the arm board mounts with spacers or am I missing something really easy?

Advice gratefully accepted!

Thanks, Jon

 

[nkorah]

You're right- it shouldn't be this way.
Is your sub-chassis straight? are you using the TP16 arm, or a replacement one?

what isn't levelled at the tonearm side?

 

[TellMeWhy]

You're right- it shouldn't be this way.
Is your sub-chassis straight? are you using the TP16 arm, or a replacement one?

what isn't levelled at the tonearm side?

Hi, yes it's the tp16. Can the sub chassis be bent? To be honest I've not had it apart, just levelled the platter. When the platter is level the arm board is way off level, and the spring tension very uneven between left and right

 

[TellMeWhy]

IIRC the Mk-I did not have the later 2 plastic alignment pins down the mounting plate, (or the sub-chassis did not have the corresponding alignment notches) so it's easy to misalign and mis-level. It could get visually misleading, so I'd unscrew the 3 tightening screws half way open, align the mounting plate in mid air, then re-tighten while making sure it's leveled against the sub-chassis. No spacers needed but If the plate is mis-leveled, it would appear to have that crazy spacer effect and you don't want that. Your springs setup with the left being most compressed, sounds pretty normal to me.

Hi Tom, Thanks for your reply, very helpful. So with the original plastic arm board (mounted to the sub frame with 3 screws) is there a way of aligning it? I assumed it would always be screwed all the way in? Cheers, Jon

 

[tnsilver]

Yes, it's screwed all the way in, but if not aligned properly, it screws in uneven and ends up tilted. All you need to do is make sure it tightens down evenly. With the 2 alignment pins, that's easy. Without them, not so much. What you basically want is for each mounting hole in the plate to be exactly above the threaded hole in the sub-chasis. In other words, all 3 mounting screws must mount exactly 90° to the sub-chassis.

BTW: If you are not the original owner or not sure of the TT history, you may want to make sure the bottom of the mounting plate is smooth. Sometimes the plastic alignment pins break off and end up between the plate and sub-chassis, effectively consisting an unwanted spacer.

 

[TellMeWhy]

OK that's awesome I'll give it a go- thanks!

 

[TellMeWhy]

Good morning Tom. I checked that but the armboard is perfectly well mounted. The issue is the sub chassis below not lying straight. As the platter and plinth are perfectly level and the distance between the bottom of the platter and the top plate is even all the way round (about 8mm). So I can only assume the sub chassis is bent / warped. I got around the problem by shimming 2 of the 3 arm mounting points with small metal washers and lowering the VTA accordingly. Now the arm board sits 8mm clear of the top board, which I believe is way higher than it should be, but setting the suspension any lower on the right hand side and keeping the platter level means the left spring rests on it's lowest stop (and therefore the system is no longer suspended) which I know is not right. So must be a warped sub platter right?

 

[TellMeWhy]

Good morning. So... we got the mounting plate conundrum out of the way. Good! Yet, I'm not buying into the bent sub-platter or sub-chassis theory. I think it's more likely your spindle came loose of the press fit in the sub-platter which now rests higher than it should. It could mislead you to believe the sub-chassis is much higher than it really is. An 8mm gap between the platter and deck is, IMO, quite too much. If this is the case, you can't lower the suspension and level the platter b/c it's already too low.

You could tap the spindle back in place with a hammer and a block of wood, or a mallet. Be gentle at first. Test my suggestion with a series of small taps. If you feel any play in the spindle shaft position, go for it - but don't knock it out of the press fit if it's not already loose.

If it doesn't work out, we'll need to look into the rubber mounts at the ends of the springs and make sure they are in place, not rotten or falling apart, and that the nuts and washers are aligned. We will also need to make sure all struts are tight in place. Pictures of the guts of the TT suspension would then help a lot.

BTW: Are you the original owner? Is there a possibility someone swapped struts locations?

Hi Tom. Thanks for another helpful reply! I'm not the original owner, have had the deck since the 90's though, just never set it up properly until now. The platter is definitely too high as the belt is running right on the edge of the inner platter surface (maybe that's normal?). Also it looks like the motor shaft is very worn and not perpendicular to the sub chassis. The result of this is that the belt is always gently running against one side or other of the guide / speed change mechanism.

However, the sub chassis does appear to be level (measured from the visible part from above), which makes it seem odd that the arm when mounted without spacers is off level. And I can't drop the suspension (sub chassis) any lower without grounding the left hand spring on it's felt covered wooden stop bar.

With what you are suggesting with the spindle, from which direction should I tap? From the top, into the bearing well? If the bearing well was not perpendicular to the sub platter this still wouldn't explain why the sub platter appears level but the armboard not...

Inside, the springs, washers etc all seemed fine... What do you mean by the struts?

Unfortunately, much as I would love to get it all sorted and just right, I'm running out of time for now as my partner is due to have a baby, and there's a million and one other things I should be doing... But any quick fixes or things to look at next time gratefully appreciated! Thanks, Jon

 

[TellMeWhy]

PS I fixed the problem of the rubbing belt on the motor guide with the motor azimuth adjustment. That worked well!

 

[tnsilver]

It's a typo - I meant studs. Great about the azimuth!!! I was just about to tell you about the adjustment screw.
You'd have to knock the spindle shaft on the bearing (long end) to lower the sub-platter and on the spindle (short end) to raise the sub-platter.
The belt should ride low - but not on the edge of the sub-platter. If it's on the edge - the sub-platter is too high (but we know that already).
Do you still have the transport screws wooden stoppers? I knock mine completely off all the time. These just get in the way... No wonder you're having a tough time.

I am losing you with that armboard off level thing. It's a mounting plate - not an armboard - and it's located inside a square opening in the deck (main chassis) and is attached to the sub-chassis by 3 screws.
Is it too high in relation with the deck? Is it too low compared to the deck? Or... is it tilted/crooked/off side? There's not too many options. If it's too high - the suspension is too high. If it's too low, the suspension is too low.
If you need spacers to raise your mounting plate above the deck - I'm assuming it's too low, so you wouldn't want to lower the suspension any more. I'm confused now. Please explain.

(BTW: congrats on the baby)

 

[TellMeWhy]

Thanks Tom I love the community in this place.... Anyway, to clear, what I mean about the mounting plate is that when the 3 screws are fully done up, the mounting plate doesn't sit level, even though the sub platter seems to be level as far as I can tell. I haven't had the sub platter completely apart to check it's true, but everything else seems to be in order. To get the arm mounting plate level I had to put 1mm washers under the left and front screws, resulting the the plate sitting about 8mm higher than the deck. So I lowered VTA to compensate. It's weird, I don't understand it either...

 

[TellMeWhy]

This is how it's looking now. VTA seems about right, platter level, suspension with enough bounce, arm mounting plate level (with 1mm spacers under left and rear mounting points). Everything sitting too high, but doesn't seem so bad... But I don't understand it...

 

[tnsilver]

Got it - thanks. OK, according to all of your accounts - it's all good, except the whole sub-chassis is a little bit too high. However, it's leveled, bouncy and the TA seems parallel with the platter. If you can live with it - there's nothing wrong with it. If you want to go the extra mile and get it 'perfect' - knock the wood blocks that house the transport screws off the inside of the plinth with a hammer - and lower the suspension 2mm - 4mm more. If you really want to get down to the bottom of this - you'll need to unmount the tonearm and have a serious look-see at the edges of the mounting plate and the area in the sub-chassis it contacts. You may find some unwanted debris in there and solve the mystery - or it can remain an uncertainty. It sounds like it's a fine tuned TD-160 anyway you'll have it.

 

[TellMeWhy]

Great stuff. Thanks for all your help, Tom. You've been a star!