Hello - I am trying to repair a broken cassette player (dual-deck, one of the larger cables that connectors to the motor is broken). I measured it to be about 20cm or 8in. I found this website for parts:
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But I'm not sure what to choose exactly. They said to account for stretch (measured the 20cm w/out stretch), but then they have 1) flat belts, 2) square belts, 3) square belt small types. From what I can see on my broken belt, it appears to be square shaped, 1mm in diameter. Any guidance, please?
If you think it's square, it's probably square. If it measures 1mm, it probably is.
I've had to replace one or both belts on my phone machine every 8 years or so. It uses a square belt also, less than 2mm iirc.
I couldn't get the original width, so I got the next size bigger. No problem. It never slippped off the pully, although I'm sure if it was wide enough it would.
I've probably gotten about 10% shorter than the measured length, and like I say it lasts about 8 years. They sell them, or used to, at a store here, but I ended up buying two the last time, I guess because I thought the second belt would fail too.
Maybe if I bought shorter, it would have enough tension to last longer, but I think it might stretch out even sooner.
Now this machine uses microcassettes and there isn't much drag on the wheel it has to turn, even when the cassette is in place. I wonder if you are using full size cassettes, if that would make a difference. It might need more tension to keep the belt from slipping??? See how hard it is to turn when the cassette is in place. Still, I don't think I'd go below 85% of the measured length, probably measured on the stretched out/broken belt.
The belt manual at the store gave a guideline, and it's been 18 years since this started, but it might have said 10 to 15% shorter. Does it say anything on the webpage you're looking at.
Right now I'm using another machine from about the same date, 1984. I got it on ebay 2 years ago. I don't know if the belt has been changed or not, but surely it must have been.
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gives a belt length caluculator, but I don't know for what size belts.
It says "Enter stretch percentage desired (7.5, 10, 12.5%, etc.)"
I see that some are in the range our machines use.
This is not a problem with a telephone answering machine, where speed is not important, but it is with an audio cassette deck. It is especially a problem if it is a dual deck machine, but driven by a single motor. If both belts are not the same dimension across the section, then one deck will run at a different speed to the other. Even a small discrepancy can cause a significant speed error. As far as picking a size goes, many belt manufacturers quote the sizes as a diameter when the belt is made into a nice circle. I have a chart with many concentric circles on it, each marked with a diameter. The size to pick is the next one down from where the belt sits on the chart. Most cassette decks don't mind too much if the belt is slightly tight, and in general, better that than loose, but it doesn't want to be so tight that you have to really stretch it to get it on, as this can rapidly cause bearing wear, and stop idler arms from swinging, where these rely on light belt tension to form their spring return.
Thanks. It does look like it's driven by just one motor. What you said suggests I would have to change both belts at the time time, in order to keep the cassette decks running at the same speed? If I change both belts, and it differs a little bit, would that mean I would have to readjust the speed of the motor? The service manual for the shelf stereo mentions speed adjustment of the tape deck.
Thanks. It does look like it's driven by just one motor. What you said suggests I would have to change both belts at the time time, in order to keep the cassette decks running at the same speed? If I change both belts, and it differs a little bit, would that mean I would have to readjust the speed of the motor? The service manual for the shelf stereo mentions speed adjustment of the tape deck.
- Eli
If you have it down it would be foolish not to replace both belts since they are the same age presumably and to avoid doing the job again when the older one fails.
That seems right to me. If there is no slippage, the speed of the motor and the size of the two pulleys seem like the only things that control the speed of the driven wheel. An even more extreme case is a bicycle chain where there can be plenty of slack on the bottom, but the top is tight.
They appear to use the old PRB measuring system. PRB had a cross refference by brand and model number. Check and see if thay have updated it to include your unit.
I've never dealt with them, but finding belts is getting harder and harder. Most of the old suppliers are out of business.
The size of the belt section *does* matter. If one belt is of smaller section than the other, they will ride at different points on their drive pullies and capstans. This effectively alters the diameters of the pullies with respect to one another, making one deck run at a slightly different speed to the other. It's not a lot, granted, but certainly enough to hear, and most definitely enough to see on a speed-test strobe tape. Sometimes, if not using manufacturer's original belts, there is no option but to use different section-size belts on the two decks in order to get the correct length-sizes. When this is the case, any speed differences can be removed enough to not hear them, by adjusting the motor speed such that one deck is running very slightly slow, and the other very slightly fast. All this of course, refers *only* to dual decks driven by a single motor - for instance the hundreds of Aiwa models with the three and five CD carousel units in the top, that were popular barn items a few years back. Where each deck is driven by its own motor, then the speeds can be set independantly.
Whenever a main drive belt is replaced on any cassette deck, the speed should be checked anyway, purely as a matter of good and professional repair practice ...
Same this side of the pond. I have a row of probably 30 nails in the wall at the back of the bench, each marked for a different size of drive belt, with the smaller sizes going up in one and two mm steps. I used to be able to keep these stocked from several suppliers without any problem at all. Now there are only a couple that keep them, and as they run out of stock of any size, they do not seem to replace them - or maybe they can't obtain them themselves. I would guess that at least a third of my nails are now either empty, or down to one or two belts from the ten minimum that I used to keep ...
I wonder how difficult it would be to produce rubberized belts. Anyone know if they were mold injected or extruded and joined at the ends, or anything about the process. I work in a mold injection plant right now, so even if it's not feasible, it would still be interesting for me, to know the process.
... No probs. A good example just occured to me. Do you remember the "DAF Variomatic" auto transmission ? This was a belt-drive system able to provide continuously variable 'gear' ratios by squeezing the sides of the pullies together or allowing them to part differentially, which altered the point at which the belt 'rode', effectively altering the ratio of one pulley diameter, to the other.
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