Stephen, I'm not an engineer, but the little theory I know would answer your question like this:

I think the motors are AC synchronous motors. If they were DC motors, the line frequency would be completely irrelevant in this context.

Having said that, there are two options for the designers (well, maybe three)...

1) Rewire the motor to use a different pole count that would result in the same # of revolutions at the higher AC frequency (remember, the voltage is mostly irrelevant in this situation); and/or

2) Use a smaller motor spindle, so even if the motor turned faster, the end result would be the capstan itself (the flywheel, etc) turning at the same speed; and/or

3) Use a bigger capstan (flywheel) - this would result in a much more accurate "ratio conversion".

It sounds like they may have done all three in this case.

The best way (the least unreliable, if you like) to check the belt size (assuming you don't have to do the three-hand belt replacement just to see) is to do the following:

1) Measure the distance between the centres of both the motor and flywheel spindles. Let's call this distance D.

2) Now measure the DIAMETER of the motor spindle, multiply by Pi (to get the circumference of the actual spindle), and halve it (since the belt only touches half the spindle at any one time. Call this Dm.

3) Do the same thing with the capstan spindle. The half circumference is Dc.

4) now add the two spindle half diameters, and add twice the centre distance: Dtotal := Dm + Dc + 2*D.

That's (to within a reasonable degree of error) your belt's TOTAL circumference. Now divide Dtotal by Pi, and voilá: your belt's true diameter.

I've doublechecked my figures with the old belt I have, and the measurement is about 2.2mm less than the actual physical belt's diameter. Taking into account stretching, that resulted in a darn good main belt replacement number.

I've also heard back from the Aussie belt supplier, they're shipping me a selection of the thicker O-rings for my 50Hz deck this week sometime. So hopefully I'll have some good news to report.

Please note, I can't even spell injuneer, so my "rule of thumb" measurements may be off a little - perhaps someone who passed high-school maths could elucidate a better way...

Good luck with the response from the B&O gurus!

Cheers,

Mathematically-challenged Pete 

well, I did it!

I finally figured out what happened: I never ever did install the slightly shorter belts, and the "right" belts have been sitting in my drawer for all that time.

 As I think I mentioned, I found the old capstan.

As I started on the belt replacement, I realised I had never ever touched the famous "Jesus" clips. For a while tonight I thought I wasn't going to get the job done. But I have a vivid memory from exactly 30 years ago of holding the belt in place whilst I put the new capstan on the main drive shaft. So I expect I got the belts and said "**** it, I'm not doing *that*". Whenever I got them, they seem to have survived. I think the weather being more temperate here - I bet you have hotter summers in Oz - has something to do with it. In addition the thick "clutch" belt (the manual calls this the drive belt) shows no sign of degradation. Perhaps this machine wasn't so heavily used as yours.

I think you are right, the back belt is probably 105 mm or so and definitely thicker than the other ones, I thought it looked like about 2mm, so we can try and figure out which o-ring if you agree with me on the size.

I'd be delighted to order some belts and send 'em on to you, keeping a few for myself. All part of the service, as they say. If you feel guilty you can send me something on Paypal, but really, the money's no object in this case, this is not a large expense.

Meanwhile I have a working machine, and can finally start on recording some tapes to MiniDisc again (my Minidisc died recently too and I had to replace it). Thank you and also to the other Peter.

A couple of small problems with the unit maybe you or the other Peter could help me with.

a. I noticed the same noisy sliders (of course I havent used them since hooking up to external amp so they have probably been this way for ages. They are carbon track, right? So would spraying some graphite powder (like you buy for "oiling" locks) do the trick?

b. The counter lost its belt some time ago. What can you tell me about the belt? I have a vague recollection it's extremely thin. But not even obvious where the driving pulley is (ok I admit it, the manual probably shows it, I am just a bit resistant to analysing those diagrams until I really have to). If it's not a big hassle perhaps you can tell me its size, and I will order a couple of those as well - the pulley suggests again that it is an O-ring.

Now if someone could help me with the microswitch on my Kenwood 5060S Cassette Deck.... the one that controls the door opener. I currently have the lid off and twiddle the wretched thing by hand. And IT'S ONLY 10 YEARS OLD!!!!!!!

I look forward to your requests and comments in due course.  

That's great news, I'm glad you found the belts.

Thanks for the kind offer of the belts, but I'm waiting on mine to arrive locally shortly. Hopefully (Ha) they'll be in the right ballpark...

There are a number of commercial preparations that work for noisy sliders, but it depends on whether the noise is just due to dirt and crap, a combination of the above with grease or oil, or whether the carbon composite (or whatever the track's made of) is worn out. Compressed air will clear away dust, but grease and dirt may need some liquid hydrocarbon cleaner. Perhaps some other B&O owners and/or the technical folks could recommend something practical? (I usually replace the sliders if they're noisy, I have access to some old Alps sliders occasionally and that keeps me happy as a clam).

The counter belt. Ah. Yes. The counter belt. Mine went the way of all good counter belts a long time ago, and I've never had the inclination to fix it (like you, I know the "nether" end has to be there somewhere, but where....?) Since I tend only to replay other people's poor recordings, the counter belt is on my "to do" list...somewhere...

I don't dare comment on the Kenwood. Haven't a clue, I'm afraid. But if the microswitch is buggered, it should be replaceable from Mouser or DigiKey (that's where I get most of my replacement bits from nowadays, nobody in Australia has near the variety and quality that the common-or-garden US stores do. Best of luck!

I admit, I don't really care about the counter belt. But if I could recall what it looked like.....

So it's safe to spray contact cleaner in the sliders? This machine is lightly used and I am sure it's just oxidation or build up rather than being worn by overactivity. I was going to do almost the opposite, and squirt some graphite powder in - shows how much I know (not much).

I am going to get a buddy to come look at the Kenwood, I think.

I'm so sure I never took the J-clips off, that these ought to be the right belts. But a first listen late last night makes me think there might be some unexpected wow. Is this to be expected with a belt that is too loose (Lautrec?) or one that is too tight?

The other annoyance seems to be the reel (which is the original), it's hitting the tape on every revolution. I recall I paid a nice Dane to repack the tape spool bearings to remove play. I'm wondering if he simply over did it....... I guess maybe the engineering solution is to put a paper washer on the spool platter .

I just went down and looked more carefully in the cupboard. I found an envelope with the name of a local company and someone's name on it, and my faded handwriting (I am guessing 1982) saying "drive belts for tape recorder"  - and in it some more Orings. A pair with 100mm diameter - way too short (but who knows?) that would fit the main flywheel at least in cross section (although the cross section looks bigger than the busted ones but not by a lot). And 1 belt of  what I reckon to be 185mm diameter and a bigger cross section (but not as big as the "back" belt). Could this be the counter belt? I think not. The other oddity is that the manual shows the counter belt as if the other end is driven by something much larger, ie the white pulley below the 4-digit counter is moving more quickly than that which drives it. Could this mean that the counter belt actually goes round the takeup spool? Maybe the two are related, its sitting low because the belt's not there? My reference to the superiorseals.com chart indicates this is almost certainly a #168, CS=2.62mm diameter 183.82mm.

Perhaps I made some blind guesses back then. And I am willing to get on my bike (well, actually in my chariot) and down there if you need me to, to look at what the local company has.  Oh yes, their old business card has a guy's name on the back of it, but more importantly a slip of paper that says BUNA #154. That doesn't look like anything I have but maybe we decided they are BUNA , or that's all there was.

PCPete:

There are a number of commercial preparations that work for noisy sliders, but it depends on whether the noise is just due to dirt and crap, a combination of the above with grease or oil, or whether the carbon composite (or whatever the track's made of) is worn out. Compressed air will clear away dust, but grease and dirt may need some liquid hydrocarbon cleaner.

Well, i just returned from the electronics store. One squirt of the "right" contact cleaner (yeah I probably made a hole in the Ozone layer) in each slider, and all noise is gone. Amazing.

They also have microswitches so I may be tapping you privately for advice about the Kenwood.

Thanks again!
 

For anyone who's interested, the 0240 BUNA N (Nitrile) O-ring appears to be a perfect fit for the clutch belt (the rear belt at the back of the deck, under the little plastic bearing hat). I'd actually probably go with an 0239, as I get the impression that with considerable water under the bridge, the 0240 may end up being a tad loose.

Can anyone from Beo help with tension or other measurements that might help us decide what's the best fitting belt? I measure about 120 grams force to depress the center of the drive belt (i.e. halfway between the spindles) by 10mm. I suspect it should be higher (tighter), but I'm just not sure. It would also be great if any owners or repairers have any details on any of these belts, as I wasn't even aware of the need for different 50Hz/60Hz model belts.

For anyone who's interested, the Australian distributor of these seals is Norseal (good Scandinavian name there!), in Townsville, Queensland. Their website is at http://www.norseal.com.au. Their direct telephone number is (07) 4775 6144, the chap to speak to there is Steve. Ask for a BS240 (94.84 x 3.5mm). (I strongly suspect I'm alone in this antipodean archipelage, me and my -sob- Beocord...)

As I suspected, the 24X series belts are way too thick for the capstan. I'm going to order some 04X series belts (1.7mm) as Stephen originally suggested, and an 159 and 160 (2.5mm) just in case. More later, as I'm currently recovering a customer tape (yay!)...

I'm beginning to think the belts I had came from the 80's and not from B&O at all, and that I simply stretched the belts to get em on the 60Hz pulley.

Also, I think the crossed out belt numbers I wrote in the manual were just a pair instead of a single one. I think that originally the design was for one main (capstan) belt only, and they redid all the parts to make a more stable 2-belt design. But B&O officially told me they have no information because about 4 years ago all sorts of stuff got junked in a reorganization.