Quantcast Self-made a new VCR pinch roller! - digitalFAQ Forum
  #1  
11-01-2021, 06:39 PM
enois enois is offline
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If not interested to the brief story, jump the first part.
This all started a few months ago, when a friend asked me to take a look at his Grundig video recorder (a Philips Turbodrive deck re-branded VCR) with a cassette stuck inside. As I supposed, the problem was the usual worm gear being broken, yet after fixing it, I noticed the pinch roller also was gone: the surface became polished with no rubber grip left, hardened, and with a few cracks started. So I went to my usual supplier site, where I can still find some spare parts, but to my bad surprise I discovered the pinch roller was not available, and would never be supplied again!
After a few moments of panic, since I own some Turbodrive VCR myself (including the S-VHS "The Clock" VR969), I started to think about possible solutions.
Leaving out some fanciful or impractical ideas (I also found a company here in Italy that re-vulcanizes metal rollers), the solution was simpler than one might think: find a person good at using the lathe! In my case a friend of a friend.

IMPORTANT NOTE: I only made the new rubber cylinder for the pinch roller, so it is essential to reuse the original arm and metal roller with ball bearing!

I started buying a piece of O-RING cord, from a local sealing supply seller, with a diameter at least 1 millimeter larger than the original pinch roller. Then cut a piece of length equal to the height of the roller, perforated in the center of the circular side, run through a metal shaft (with a diameter slightly larger than the hole), and finally plug the shaft, with the rubber cylinder, into the lathe and remove the excess of rubber, bringing it to correct diameter size.
The difficulty here is setting the right turning speed of the lathe: when too slow the cutting tool does not work well (inclined to tear the rubber), when too fast simply the rubber will melt down.
A trick is to make the hole in the rubber slightly smaller than the actual diameter of the metal roller: in this way it is possible to mount the rubber cylinder by "interference" (while pushing very hard), without the need of any glue.
We have tried different types of rubber and almost all of them seemed suitable for the task; EBR, EPDM, generic neoprene pipe for gasoline pump, and even the rubber roller taken from a common inkjet printer (from the paper feed tray). Although not all of the rollers came out good enough in shape and dimension, the pair needed between the pinch roller and the capstan is tolerant enough, the tape run steady and aligned, pressed squarely against the capstan without drifts up or downwards.

After the replacement is done, same as with an original part, probably a re-alignment of the tracking/audio head is needed, both tilt and azimuth.

Last notes: I only tested with Philips Turbodrive and Panasonic G-deck, but I think this solution could work even for different VCRs models and brands.
Not wear/endurance testing of the rubber but even if stand less than original pinch roller, nowadays, with the actual use of VCR, this may be not a big problem.

In anticipation of less and less replacement parts being supplied in the future, I hope this can be of help for our VCRs maintenance.

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File Type: mp4 Philips Turbodrive.mp4 (7.84 MB, 11 downloads)
File Type: mp4 Panasonic G-deck.mp4 (5.90 MB, 6 downloads)
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The following users thank enois for this useful post: drzapp (11-02-2021), hodgey (11-01-2021)
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  #2  
12-07-2021, 05:09 AM
Quasipal Quasipal is offline
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just to say excellent work - congratulations!

The hardening of the pinch roller in Philips VCR's is caused by the capstan lubricant breaking down and migrating to the roller as the tape plays which hardens the rubber and damages tapes.
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  #3  
12-07-2021, 10:53 AM
latreche34 latreche34 is offline
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Those half inch pinch rollers are very common and can be had very cheaply, You may not notice it for video but for linear audio you will have severe wow and flutter if measured with W&F meter, Factory machined are made to manufacturer specification.

https://www.youtube.com/user/latoak34/videos
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  #4  
12-07-2021, 11:28 AM
RobustReviews RobustReviews is online now
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Quote:
Originally Posted by latreche34 View Post
Those half inch pinch rollers are very common and can be had very cheaply, You may not notice it for video but for linear audio you will have severe wow and flutter if measured with W&F meter, Factory machined are made to manufacturer specification.
Why would the pinch roller affect wow and flutter?

The overall linear velocity of the tape remains unaffected unless it's slipping against the pinch-roller.

It's a cool project, well done.
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  #5  
12-08-2021, 06:40 AM
enois enois is offline
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Quote:
Originally Posted by RobustReviews View Post
The overall linear velocity of the tape remains unaffected unless it's slipping against the pinch-roller.
I agree, the tape speed should stay constant.
A possible issue could be the drifts up or downwards, but in my career as a repairman, I found various non original pinch roller that they had worst drift than the ones made as described above.
Drift problem could be also inherent to bearing issue or deformed pinch-roller arms.

Obviously, if you want DIY roller, it is important to turn the rubber as precisely as possible.
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  #6  
12-08-2021, 12:14 PM
latreche34 latreche34 is offline
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Molded rubber will have better uniformity and smoothness of the contact area, Machined rubber tend to feather overtime and slips, If you look at the two under magnification you'll see what I'm talking about.

https://www.youtube.com/user/latoak34/videos
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  #7  
12-08-2021, 12:53 PM
RobustReviews RobustReviews is online now
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Quote:
Originally Posted by latreche34 View Post
Molded rubber will have better uniformity and smoothness of the contact area, Machined rubber tend to feather overtime and slips, If you look at the two under magnification you'll see what I'm talking about.
Ah, cool story.

How's this affecting speed, and audio wow and flutter again?
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  #8  
12-08-2021, 03:48 PM
enois enois is offline
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Quote:
Originally Posted by latreche34 View Post
tend to feather overtime and slips, If you look at the two under magnification
I apologize but my English is not so good: what you mean with "tend to feather overtime"?
And with "If you look at the two" did you refer to the pictures?
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  #9  
12-08-2021, 05:21 PM
timtape timtape is online now
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I think Enois has gone to impressive effort to repair the Philips pinch roller. But as latreche said, for the time being this roller (VPR 124 or VPR 125) and many other VCR pinch rollers are still available as high quality off the shelf spare parts at very reasonable prices.

For some of my decks I ordered a spare pinch roller for when the current one fails. To slow deterioration I keep them in the factory sealed plastic bag.


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  #10  
12-08-2021, 08:35 PM
latreche34 latreche34 is offline
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Quote:
Originally Posted by RobustReviews View Post
Ah, cool story.

How's this affecting speed, and audio wow and flutter again?
The same way cheap belts with shitty rubber do, I'm not going to argue over ancient technical stuff, move on.
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  #11  
12-08-2021, 10:00 PM
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lordsmurf lordsmurf is online now
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Legacy, still in use -- not ancient.

examples:
- VCRs (good models) = legacy
- CD walkmans = ancient, not needed whatsoever to extract content.

Yes, I realize his VCR here is something craptastic. But it's very apparent his method has application to the important good models. Someday, such a thing may be required.

- Did my advice help you? Then become a Premium Member and support this site.
- For sale in the marketplace: TBCs, workflows, capture cards, VCRs
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  #12  
12-09-2021, 06:41 AM
enois enois is offline
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Quote:
Originally Posted by timtape View Post
I think Enois has gone to impressive effort to repair the Philips pinch roller. But as latreche said, for the time being this roller (VPR 124 or VPR 125) and many other VCR pinch rollers are still available as high quality off the shelf spare parts at very reasonable prices.

For some of my decks I ordered a spare pinch roller for when the current one fails. To slow deterioration I keep them in the factory sealed plastic bag.
I still have some original new "unopened" pinch rollers, but for Philips Turbodrive, here in Europe, I have a lot of difficulty to find news one at reasonable price, on e-bay you can found at 30€ or more, few years ago the price was between 10 to 15 euros.
Instead, for example, I still can found new original Pansonic pinch roller from electronics repair suppliers at the same price as some years ago.

I am aware that the solution suggested is not perfect but, as written in the firs post, this is a sort of experiment "in anticipation of less and less replacement parts being supplied in the future", and the first result is more encouraging than I expected. That's all.

Effectively wow&flutter could be an issue, but tape speed is mainly given by capstan motor; if the grip between pinch roller&capstan shaft and the grip between pinch roller&tape is good, the roller rotation will follow the capstan rotating speed. The not perfect cylindricity of the roller should not be a big limitation.
More experimentation & testing is needed, unfortunately I not have a Wow&Flutter meter.
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  #13  
12-09-2021, 06:52 PM
timtape timtape is online now
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Because I found forming the rubber to tight enough tolerances is difficult I try to use a manufacturer's pinch roller but making small modifications or substitutions where the original is unavailable or too expensive.

Speaking of the Philips/Blaupunkt/Teac VPR 124 pinch roller, I had problems sourcing a pinch roller for a fairly common Sony Betamax pinch roller. I measured the Betamax roller and found the VPR 124 had exactly the same dimensions except that the bearing inner diameter was 2.5mm instead of the Betamax's 2.0mm. I carefully drilled the Sony metal bracket's 2.0mm holes out to 2.5mm. Now I can use a common VHS pinch roller on these Betamax machines.

Once we have the dimensions we can look for a roller with the same or similar dimensions. The Wagner catalogue I have, helpfully lists the key dimensions of outer diameter, height and shaft diameter of each roller it sells. Sometimes the height is not critical. So a roller with 15mm outer diameter might be fine with 14mm or 16 mm. We just have to test it on the particular machine, checking that the larger roller will not foul its own bracket or the capstan shaft bracket and bearings and will still drive the tape without issues.
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  #14  
12-09-2021, 09:12 PM
hodgey hodgey is online now
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Quote:
Originally Posted by Quasipal View Post
The hardening of the pinch roller in Philips VCR's is caused by the capstan lubricant breaking down and migrating to the roller as the tape plays which hardens the rubber and damages tapes.
Is it the case on all turbo drive decks or did they fix that issue on later revisions? There are turbo drive decks made up to at least year 2001 for what I've seen (after that it the philips decks seem to be all Funai, LG or in a few cases JVCs), though they did some changes to the mech over time.

Last edited by hodgey; 12-09-2021 at 09:24 PM.
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