Sony TC-161SD Speed Control

[ButchJames]

I see in an old thread that the TC-161SD has been brought up.

I recently bought one for very little money under a 'not working' title, and have got the machine working to good capacity. It's a beautifully built machine, and quite honestly I don't mind putting the time in to fix these decks. I've seen some folk hand out £250 .. £500 for an old 'hi-end' deck, and taking all the real risks along with it.

Speed control of the TC-161SD is slightly troubling, with its (2-pole?) induction motor having only 3 possible discrete settings - all of which are 'way off'. I guess the best is about 5% too fast, maybe more - I'll measure it later.

Of course there's the option of shopping around on ebay for a pulley system that'll fit, or 'shaving' approximately 5% off the effective diameter of the current one.

Question: I wonder if anyone has had a similar problem with this, and other similar (TC-160SD) machines? Did you find a good workable solution?

So far my work done on this deck is here ... https://cassettedeckman.blogspot.com...-tc-161sd.html

[Welsh Anorak]

I vaguely remember having a Sony motor running too fast because of a faulty 'motor run' capacitor. However that was on a reel-to-reel so of course might not be applicable to your machine.

[TIMTAPE]

Originally Posted by ButchJames

Speed control of the TC-161SD is slightly troubling, with its (2-pole?) induction motor having only 3 possible discrete settings - all of which are 'way off'. I guess the best is about 5% too fast, maybe more - I'll measure it later.

I'm not sure the AC motor is capable of running faster than normal unless it's set for 50 Hz and is running on 60 Hz mains. Are you sure it's running fast? In your blog you wrote of it running slow.

There should be two possible pulley diameter settings, for 50 Hz and 60 Hz mains. They're not meant to be options for fine speed adjustment.

[Radio Wrangler]

Build-up of sludge from old belts on pulleys? On the whole belts and drive wheels are used to reduce speed, so equal build up on both pulleys/wheels will make things run faster.

David

[ButchJames]

Thanks for your input one and all.

@Tim .. there are three settings, two (probs) for the speed and the other to drive the RW/FF operation. Of course I can set the main belt to any of the 3 pulley diameters.
Take your point on 50Hz/60Hz main operation.

Yes, users of such decks are stuck with dicrete speed settings - I am begining to wonder if someone has changed this pulley over the years, or was it imported from the US?

I'll figure something out in time.

@Radio Wrangler - thanks, I did check this and have cleaned pretty much to the bone of both pulley and flywheels. Indeed, it would only take a slight change in diameter and the difference would be heard.

@Welsh Anorak - just fitted a new motor run cap, should be fine. The cap's value is within 5% tolerance, but all possibilities are being considered.

[ButchJames]

Silly me has just realised what the problem is!

I'd put a temporary sq section belt in, yes it's the probable correct diameter (110mm), BUT only 1.2mm x 1.2mm cross section!

So why then would this matter? Well, the narrower sq sec (temporary) belt was sitting deeper into the v-section (smaller effective diameter) of the pulley, whereas the default (~1.5mmx1.5mm or 2mmx2mm?) would be 'riding' at a slightly higher diameter.

Bingo! - I've now put in a 2mmx2mm belt in (although too short) and the speed is back up to normal!

This wider temp belt is 90mm (diam) x 2mmx2mm - it's too tight and was creating some 'wow' effect, so I'll have to search out a wider diameter belt of about 110mm x 2mm x 2mm.

Cheers, and sorry about the daft question!

[TIMTAPE]

Just to clarify, if Sony had machined the three lathed pulley slots at slightly different diameters for the purpose of finer adjustment of the capstan speed wouldnt that be described as such in the Sony TC-161 Service Manual? I've never come across this in any tape machine, only two different pulley diameters for 50Hz and 60 Hz operation.

[ms660]

There's two belts fitted to the motor pulley.

Lawrence.

[ButchJames]

Originally Posted by TIMTAPE

Just to clarify, if Sony had machined the three lathed pulley slots at slightly different diameters for the purpose of finer adjustment of the capstan speed wouldn't that be described as such in the Sony TC-161 Service Manual? I've never come across this in any tape machine, only two different pulley diameters for 50Hz and 60 Hz operation.

I'll look again at the SM (I have a copy), but there appears to be no mention of pulley diameters?

Now that I've finally and partially resolved the speed issue, I can only assume that - yes, a 50Hz/60Hz option is available off the pulley, and the other third pulley is to operate (via a belt) both RW/FF operations. The 'best' transmission lines taken by the belts can be adjusted for the flywheels (2 height settings) and the motor pulley - variable via the motor shaft, but for FF/RW - it's a little restricted.

BTW, I also have two Sony TC-134SDs, from memory and in that SM, they seem to mention options to change the motor pulley to trim the speed. Maybe only for the flat belt version, I don't know. ( I have two 134SDs - one flat belted, and the other sq section)

So far things are looking good for the 161SD.

[ButchJames]

Slightly off topic, but here is a crop from the TC-134SD SM regarding speed trimming. I must admit, I was surprised when I first saw it.

[TIMTAPE]

Thanks for the 134 SM excerpt. As I mentioned I've never seen or noticed this.

It would be interesting to know how often it was necessary for service shops to order the slower or faster pulley. I would have thought the selective use would have been normally confined to setup in the factory but there it is in the Sony SM.

[ms660]

Some of the Sony machines had different pulley sizes to select for the correct speed, both for 50Hz and 60Hz operation I remember changing them on some machines back when I used to work for Sony, the TC-366 for instance had 18 different pulleys available.

Lawrence.

[TIMTAPE]

Amazing detail by Sony especially since the 366/377 etc had mechanical servo back tension which would have tended to moderate the slowing speed from start to end of a tape side.

[ButchJames]

@Lawrence, Tim

I can see why Sony and others eventually (and with motor control tech) abandoned mains frequency regulation. For one good reason (at least) - a smaller sq section belt tucks deeper into some motor pulleys and then effectively engages in a lower gear driving the capstans? Albeit by 2%, 3%, 5%, 10% or whatever. On the upside to the induction motors, there is very little in the way of wear?

Thanks for the fb.

[ms660]

The range of pulleys that Sony did would also cover a change in speed that might result when changing the capstan flywheel.

Lawrence.

[ButchJames]

Originally Posted by ms660

The range of pulleys that Sony did would also cover a change in speed that might result when changing the capstan flywheel.

Lawrence.

Got to try a few 'new' belts this morning - all of this is proving to be a little costly.

However, on the subject of the two belt groves on this dual flywheel - they are slightly different diameters as the frequency counter is indicating.

So far from a 3150Hz ABEX reference tape, the best figure with a 1.4mm^2 cross section belt is 3050Hz and 3090Hz, depending on the flywheel grove I use. Other 1.9mm, and 2.0mm cross section belts work fine too - but the speed is excessively higher than 3150Hz.

The problem when ordering belts, is that we cannot be certain of the actual diameter they specify - one such belt was claimed to be '1.5mm x 104mm', but one measuring it, proved to be between 1.9mm/2.0mm x 113mm!

I think for my Sony TC-161SD, an actual cross section of 1.5mm .. 1.7mm is going to hit the nail almost squarely on the head!

[TIMTAPE]

Yes there was more than one reason for the transition to other motor types. I have a tc-161 and kept it because of the dual capstan and solid build. Unfortunately the ac motor induced a noticeable hum into the playback head. It is the main reason I don't use it. From memory it had substantial shielding around the motor but I felt it would have needed even more shielding for acceptably low hum.

[ButchJames]

Originally Posted by TIMTAPE

Yes there was more than one reason for the transition to other motor types. I have a tc-161 and kept it because of the dual capstan and solid build. Unfortunately the ac motor induced a noticeable hum into the playback head. It is the main reason I don't use it. From memory it had substantial shielding around the motor but I felt it would have needed even more shielding for acceptably low hum.

I must admit Tim, I haven't noticed this with my 161, but will examine this later.

In contradiction to my point earlier, after playing-about with the two grove (settings) on the flywheel pulleys, now I'm not too sure if they make a difference to speed after all?

With a drive belt of physically 1.44mm^2 cross section, the 161 is about 1.25% slower. I'm gonna just have to accept it, and if I see a belt that is definitely 1.5/1.6/1.7mm etc, then I'll go for it. The original belt (I assume?) is about 1.7mm x 1.7mm - it's a pity it's now redundant.

Currently I have one major R2R machine, and 18 cassette decks. I recently eyed-up a 'faulty' 177SD on ebay here in the UK, and the common sense part of my mind said .... 'no,no,no ... you've got too many!'. I don't want to bury myself in this repair game, it is a bit addictive tho'.

[ButchJames]

Just an update on the TC-161SD: A new 1.7mm x 1.7mm x 101mm belt has been fitted.

The deck now plays back my ABEX 3150Hz reference tape to around 3155Hz! As predicted, variable sq section does alter the effective gearing.

However, there is a down side - the belt is too short in my opinion. It is not overly tight, but W&F has risen and I can hear it after recording test tones, even at 400Hz.

Both capstans have been carefully lubricated internally, and exposed capstans are clean of oil. Without the belts, the capstans spins freely.

I have a narrower 1.4mm x 1.4mm x 102mm/105mm ? belt and there's very little audiable W&F, but it is irritatingly slow.

Beggars can't be choosers. ;o)

[TIMTAPE]

How would running it at the correct speed create speed variations? If the belt is overtight, I'd just buy the correct diameter 1.7x1.7 belt.