"Hello friends. I have an old 1990s Sony CFS-W470S boombox. Recently, I wanted to listen to compact cassettes again. But of course, the rubber belts are no longer functional. I removed the cover and saw a confusing situation. I removed three belts and will look for replacements. One belt is completely broken. But one belt from the capstan is in good condition. It hasn't turned into gel — it's firm, elastic, and when I try to stretch it, it resists. As I understand, it was looped with one end onto the motor pulley. I have an important question as a beginner: how can I put it back in place without disassembling the entire tape transport mechanism? I'm trying to think logically: if I removed it from the motor pulley, nothing should have prevented me from doing that. But the capstan shaft is there, and there's no free space for it to have slipped off and ended up in my hands — yet it happened. Now, I still don't see any free space to loop it back onto the two-tier pulley. Or do I have to unscrew many screws, remove two bridges, and thus reach it? I'm asking for help with this puzzle."
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Welcome to AK. Sorry, I'm not familiar with that deck but here are diagrams from the service manual. It looks like there might be 4 belts total.
Manual: CFSW470 SM SONY EN : Free Download, Borrow, and Streaming : Internet Archive
It looks like the pulley is only connected to the motor shaft so you could loop the belt over the top of the pulley.
Manual: CFSW470 SM SONY EN : Free Download, Borrow, and Streaming : Internet Archive
It looks like the pulley is only connected to the motor shaft so you could loop the belt over the top of the pulley.
dhnash
Super Member
I think you already found that there are only 3 belts (258, 259 and 281).
Thank you so much for your reply. I was in despair. For two months or more, I've been stuck with no information. There is some information, for example, I already downloaded the service manual. But practical application is much more difficult. So, thanks to the quote I highlighted, you think I don't need to disassemble a huge number of screws, just apply force to get the pulley to space? But I'm afraid I'll break it.
Belt 258, there are two of them, so they're the same. Could someone tell me the half-length of all three? The belt that's still intact, and I'm puzzled how it could have slipped off the pulley, is 155 mm long.
Don't apply any force to bend the metal parts, you will damage something. If the original belt just came off then there is a way to get the new belt on.
- From the diagram, it looks like there might is only one screw (289 or next to it) that holds the motor bracket (280) to the plate (279). I can't see from the photo.
- If you loosen that screw, it might allow you to tilt the motor bracket a bit to allow you to slip the new belt into place on the pully.
- One more thing to check. Does that pulley have a set screw to allow you to loosen and adjust the pulley on the motor shaft?
- You may be able to loosen it, push it down on the shaft enough to slip the belt on, then retighten the screw.
I had included the belt on Deck A-2, part #186 in the previous drawing.
It has a different part no. than the other three. (3 previously identified + this one = 4 belts total)
Let me, if you will, summarize the belts: Deck B, belt 258 — defragmented; belt 259 is in its place but not functional, it's stretched.
Deck A. Belt 186 — same thing. Belt 281 is shown separately in the photo in the first post. It has retained its elasticity; its half-length is 155 mm. It also passed through the pulley of the small wheel in the photo. I cannot clearly identify it — I'll call it wheel X. It is located between the two large flywheels. However, belt 281 should also have been hooked onto the motor pulley. If it came off easily and remained intact, I don’t understand why that happened, since there isn’t the slightest gap or crevice for it to slip off the motor shaft pulley while remaining unbroken. Tomorrow I will continue to investigate whether it’s possible to loosen the board mounting. It seems to me that screw 289 — I’ve already tried unscrewing it with no result. On the pic belts deck A
Deck A. Belt 186 — same thing. Belt 281 is shown separately in the photo in the first post. It has retained its elasticity; its half-length is 155 mm. It also passed through the pulley of the small wheel in the photo. I cannot clearly identify it — I'll call it wheel X. It is located between the two large flywheels. However, belt 281 should also have been hooked onto the motor pulley. If it came off easily and remained intact, I don’t understand why that happened, since there isn’t the slightest gap or crevice for it to slip off the motor shaft pulley while remaining unbroken. Tomorrow I will continue to investigate whether it’s possible to loosen the board mounting. It seems to me that screw 289 — I’ve already tried unscrewing it with no result. On the pic belts deck A
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everything will be now ;-)
This morning, after unfolding the boom box block parallel to the lighting, I spotted a bingo: there is a gap of about one and a 1.5 millimeters wide between the end of the pulley and the plate. There's no need to disassemble the entire tape transport mechanism — I wouldn't have been able to do that anyway. So the belt 281 is back on the motor pulley again, but I don't know what to do next — its length seems excessive to me, although I repeat, it's not stretched and has retained its elasticity. Besides the two large flywheels of deck A, it also goes through three small wheels — in the picture: wheel one, wheel two, and the previously discovered wheel X. Please tell me how this belt should route through all these three wheels — it seems to me there might be some deviation from the direct path; could it be that this belt was doubled over somehow, like a loop? As for screw 289 and another small screw next to it — unscrewing them did nothing. At the bottom and at the top, we can see the rear parts of other small screws that firmly fasten both boards together.
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Since the Well-Wishers' advice had dried up, I had to turn to Al's intellect. He immediately determined the lengths of the 281 and 258 belts as 122 and 109 mm. I was overjoyed. However, I immediately remembered that the 281 belt was unstretched and 155 mm long, and I had it in stock and intact. Then I was offered a dozen different schemes for stretching it on deck A. There were also options that, according to Al, this belt should also fit on deck B. I didn't have to continue, but I almost wasted another two hours and even tried to follow his recommendations. I can say I've never encountered such inflamed nonsense promoted with such confidence. Al He himself later admitted to me that he was trying to guess and adapt to my questions.
Rey1
Super Member
Just because a belt has some elasticity left does not mean that it has not stretched out. I've seen plenty of belts on CD trays that still had good elasticity but were stretched out so that they no longer worked to open the tray. You may have to resort to getting a batch of different length belts and seeing what fits. There is a Boombox forum called boomboxery.com, some of these guys repair boomboxes all of the time. Maybe they can help you out
It's possible that the 281 belt has also increased in size due to stretching. In any case, I'll need to buy different belts. The main problem is finding out their required length. For the 281 belt, you need to go around three plastic wheels and two large flywheels. So, 5 Al shouldn't be listened to; his advice is contradictory. The belt length can vary depending on the number of turns and the wheel contact patterns. I only know that the belt length is between 122 mm and 155 mm
Restorer87
New Member
try webspareparts, they have loads of belt kits.
You can do this with a piece of thread or light string.
To do it, I first make as small loop in the end of a length of heavy thread. Then it gets threaded around all of the pullies following the path of the original belt using dental picks, thin needle nose pliers etc. The slotted end of that thin aluminum tool with a red plastic cover which comes with Weller soldering iron kits also works well here to guide the string over any pulley sheaves. Once the thread is thru the path, the loose end of the thread is threaded thru the loop on the other end and pulled tight. It is then marked with a fine Sharpie or whatever and pulled out of the transport system and placed on a ruler or tape measure.
The measurement shown will be the total length or circumference of the missing belt. Dividing this number by two will give you the flat, or half length. Deducting 5% or so from this length will give you the actual belt size needed. The 5% deduction is to allow for the tension and friction needed to drive the new belt.
I'm extremely surprised that the service manuals don't specify the belt length; that would be the easiest solution. The belt path is also missing.
It turns out that no one on the English-language internet knows how a 281 belt should be routed. One person showed me where this information is available: Yandex and the Russian version of YouTube. Hahaha, you should check it out if it's not banned in your area.
Магнитола Sony CFS-W470S. Взгляд изнутри.