Cassette Pinch Roller Carnage…

[sweetbeats]

So I just thought I’d share a little project I’ve allowed myself to fall into, which is usually how it goes…but I’ve had a couple (for me) minor revelations in the process. This is about pinch rollers, and specifically for cassette-based machines…and I’m talking about the common Philips Compact Cassette format. Anyway, it goes like this…prepare yourself for storytime, or feel free to tap or click your browser “back” button and get out while you can :

Sometime in the last year or two…hm…maybe three…I sold the Tascam 424mkII 4-track Portastudio I’d had forever in favor of a 244…much more robust build, easier to work on, potential for better sonics, and nicer aesthetics AFAIC. I traded a rare remote I had for the 244 and sold the 424mkII outright. Turned out two of the head coils were roached on the 244 if you can believe that…but it was otherwise in “okay” shape. Well, what to do…then I saw a pair of semi-basket-case 244s on eBay…there’s my parts donors I thought, and maybe enough I could get a spare up and running and make some money back. So I bought them. $150 shipped IIRC. I set it all aside, and then in the meantime, maybe a year, 18 months ago…something like that…I see on eBay…I need to stop looking…a minty condition 244 in original box for $200 shipped…transport not working. I figure it needs all new rubber, but it had the box and was in REALLY nice condition. So I got it. So there I was quite fully invested in 244s. I really like them…clearly. The construction ideology and components remind me a little of my prototype Tascam console from the same era…I did a little collaborating with a couple friends and analyzed the signal path, identified areas of potential improvement and got this idea of building the ultimate 244…bought a crap-ton of components to do this. And then as a part of that I knew all the transport rubber needed replaced and at that time I stumbled on the fact Athan was making device-specific replacement pinch rollers for cassette-based machines…so I thought I had to have one of those for the “ultimate 244”. So I got one. Now, anybody that knows me knows this is all likely to sit in the closet, attic, various places and eventually I’ll start tinkering on it. Well from time to time I might find a local deal on something that needs work and I’ll buy it and fix it, sometimes keep it, sometimes flip it…I typically have no idea what I’m actually going to do or when. So after all the 244 acquisitions I picked up another 688 (my second…repaired and sold the first), and a 488mkII (my first, though I had a 1st generation 488 that I repaired and sold), and I picked up another 238 (the “$50 238” that’s the subject of this thread starting on post 15: https://homerecording.com/bbs/threads/what-is-it-that-compells-me….415149/…it’s the 3rd 238 I’ve owned…returned the first I ever owned, repaired and sold the 2nd). I repaired and sold 688 #2 and the 488mkII after being reminded of my distaste for the finicky edge tracks, but 238 #3 is still here…it has the full-function remote, is, like, 9/10 condition, has the new capstan servo board I installed…just not ready to let it go. Rubber seemed okay, like, everything works, though track 1 is finicky. Okay…take a breath. So I ALSO have a Tascam 122 (1st generation) that I got years ago…related thread here: https://homerecording.com/bbs/threads/tascam-122-story.402165/. I got it so I had something to play all my cassettes from back in the day…huge box of them…lots of gigs recorded on cassette…would like to archive them someday. The 122 was a little beat up and transport non-functional, which I figured I could fix, but with these detriments it was cheap…I think $60 shipped. I really like the 122…I know it’s not the preferred generation but I don’t care. It has huge solenoids (like, open-reel machine sized solenoids), huge capstan flywheel, absolutely all discrete signal path…it’s neat. So, yes, when I found a second one I bought it…better cosmetic condition, and it’s the ‘B’ version with balanced I/O. Of course the transport is also non-functional but they’re easy to work on. So the 122-B is the primary machine and the original non-B unit will be the parts donor. Both the pinch rollers actually seem fine, but my plan was to try and hunt down a new one or see if Terry Witt could make one. But I think what’s in them would allow them to run and drive. Okay. I’m getting closer to the point. THEN more recently I satiated an almost 15 year curiosity about the Audio Technica AT-RMX64 multitracker/mixer and bought one…related thread here: https://homerecording.com/bbs/threads/audio-technica-at-rmx64-story….419129/. SO, here I am with a pile of 244 stuff, a 122-B project with parts machine, a fully functional (but finicky track 1) 238, and the AT-RMX64. The AT-RMX64 is, as I figured, and why it’s always been in the back of my mind to own one for so many years, the coolest all-in-one 4-track multitracker/mixer. I figure I’ve gotta have an Athan pinch roller on it, even though here again the original one that’s there seems okay, but I want the best on it and the Athan rollers are amazing. So then I start thinking geez, that Audio Technica roller (actually Sankyo roller as the AT-RMX64 transport was made by Sankyo) looks really similar in size to the 244 roller. I reach out to Athan to ask if they make a roller for the AT-RMX64 and they ask me to just send the original to them so they can make one, but in the meantime I pull out the still sealed in plastic 244 roller I have and disassemble the AT-RMX64 pinch roller assembly…get out the dial calipers and, yep, exact same dims as the 244 roller. So I get ready to install that, but then I think maybe it’s better to still have one for the 244 project. I then notice Athan has a “Nakamichi Sankyo Transport Pinch Roller”, which is the correct roller for the AT-RMX64…the AT-RMX64 Sankyo transport is very similar to a Nakamichi BX-150 transport, also made by Sankyo. So I order the Nak/Sankyo roller. Then one evening while stowing the original disassembled AT-RMX64 pinch roller assembly I notice something…while the rubber is still appropriately soft and “grippy”, it almost looks no longer precisely cylindrical…like, the sides of the cylinder are no longer parallel, but tapered. I got out my dial calipers to test what I was seeing, and sure enough the roller is 0.15mm smaller in diameter from one side to the next. That might not seem like much, but this is a small roller (13.62mm), and think about it…that likely means there is greater pressure when engaging the capstan shaft toward the end with the greater diameter, and also the conical difference in diameter from one side to the other might skew the tape because of the difference in circumference of the roller as you progress from one side of the roller to the other. Yes, the roller as a whole is turning at a constant rate, being driven by the capstan shaft and the roller being in a solid metal or plastic hub…but the rubber itself would be *trying* to rotate at a progressively different rate from one end of the roller to the other, and I have to wonder how that might effect the driving of the tape by the capstan shaft, stretching or skewing the tape, etc. Not to mention the progressive difference in how much the tape is being wrapped on the shaft due to the difference in diameter of the roller and resultant difference in deformation of the roller against the shaft. The tape on this particular roller rides more toward one side of the roller, which coincidentally is the end of roller with the smaller diameter. So my theory is, over the decades, the roller has deformed due to the greater pressure where the tape travels. So this was a revelation to me because I never considered this sort of aging factor with the roller. I always only considered the condition of the rubber, either hardened/glazed or decomposing to an uncured state (turning to goo). Now I’ve got a third reason to consider with an aged pinch roller, particularly on a cassette machine.

Here is a picture of the roller. It’s probably impossible to see in the picture, but the taper caught my eye in person which is why I measured it:



To be continued…

 

[sweetbeats]

So then I naturally started thinking about my other machines, the 122B and 238. The 244 is taken care of with the new Athan roller on-hand, and I just received the Nak/Sankyo roller for the AT-RMX64. I look on Athan’s website, no 122/122-B specific roller listed, but it uses a standard 2mm axle pin, and is a common 8mm wide. The diameter is about 12.5mm. Athan says to send an OEM roller to them so they can measure and make one for me. I do the same with the 238 roller, which has a smaller 1.5mm axle pin, and is wider than 8mm and bigger in diameter than other rollers listed, but they ask me to send it to them. So those are on the way, but I really, really wonder if all these years my consternation with the cassette 8-track finicky edge track issue has something to do with a worn pinch roller skewing the tape than just plain finicky mechanics. I’m sure we can all appreciate the consistent precision tape handling necessary with such narrow track width, and also how little lifting from a track it takes to severely diminish the ability to record or reproduce, and that’s what tape does when skewed into a fixed guide…it curls slightly and lifts. This is even an issue on a poorly setup 1/2” 8-track…let’s shrink everything by a factor of four and now we *really* have an issue. Out of all seven 8-track cassette multitrackers I’ve owned, I’ve never replaced a pinch roller. Belts and reel table drive tires yes, but, luck of the draw, the pinch rollers have always seemed like they’ve cleaned up nice, are soft and “grippy”, but not too soft or tacky…just right. So I’ve left them alone. BUT…what if the rollers were no longer a precise cylinder? I think a majority of those seven machines had some degree of diminished performance on one edge track or the other. Now, we’re talking about diminished signal reproduction with 1K and 10K tone…maybe 3dB to, in some cases up to 6dB difference from other tracks cumulative between recording and reproduce processes, which you can make up during calibration, but the signal is also not as stable as other tracks. Well…what if this was a worn pinch roller? In most cases the issue isn’t as audible with program source material vs tone, but I remember my first 238 had a pretty significant issue with track 8 that could be heard in the mix. I returned that one. Anyway, all this is to say this is how a spot of my workbench came to look like this:



From left to right that’s a factory 122/122-B roller assembly, then the 238 roller assembly, then the AT-RMX64 roller assembly, and finally the new Athan roller for the 244. Here is a view from the other side:



SO…I’ll follow up once I get the new roller for the 238 and get it installed, because the machine I currently have was, IIRC, about 6dB diminished on track 1 at 10K with some signal integrity issues…not so bad with program source material, better than others I’ve had, but the machine seems to have such low hours and is otherwise very clean and complete so I just accepted the issue as “comes with the territory” and it still lives here. Maybe these machines can perform better with a new precision roller assembly. These issues wouldn’t be as prominent on a 4-track or consumer half-track machine of course, but could still be problematic.

As a closer here’s a familiar sight…the melted roller. This is on my “nice” 244, the last one I got that came with the original box. What a mess.

 

[RFR]

Does look a bit wonky. Appears the left side is narrower? Also noticing the tape seems to be riding on that side more.

 

[sweetbeats]

View attachment 125207Does look a bit wonky. Appears the left side is narrower? Also noticing the tape seems to be riding on that side more.

Yeah the left side of the roller in the picture is the side with the smaller diameter…and yes the tape doesn’t ride in the center which is what I was saying in my post. That doesn’t concern me, it’s just a basis for my theory as to why the roller is a smaller diameter on the left.

 

[AnalogApples]

$200 for an in-the-box Tascam 244? I’m green. Nice find! And very informative post!

 

[60's guy]

I have to admit that this thread caught my interest because of the photos that Sweetbeats posted and the measurements of that rubber covered pinch roller, which is only what? 3/8" or 1 /2" wide. The left and right side diameters measured .015 mm (.006" ) less than the center of the pinch roller, which, in my opinion is hugely excessive.

I can only speak from my own experience as an engineer and designer of web transport machines that the crowning of rollers (larger diameter centrally.....smaller diameter at the ends) was a common design practice to keep the web traveling central. Years later, edge sensors and steering devices negated the necessity of crowned rolls. Prior to steering devices......a roller 100" in length only needed a small amount of crowning.

I apologize for espousing.

There is one more thing, however, I'd like to learn.I

I'm not familiar with the recorder.

Have you studied the mechanism that applies pressure to the pinch roller?

I assume that that both bearing ends of the pinch roller are supported by a yoke.

The question is.......is that yoke a y configuration where pressure is applied centrally or is the pressure off center?

 

[grimtraveller]

prepare yourself for storytime

You'll soon be out-selling Prince Harry and JK Rowling at this rate !

Out of all eight 8-track cassette multitrackers I’ve owned, I’ve never replaced a pinch roller. Belts and reel table drive tires yes, but, luck of the draw, the pinch rollers have always seemed like they’ve cleaned up nice, are soft and “grippy”, but not too soft or tacky…just right

I had my Tascam 488 MK1 from the end of 1992 until the end of 2018. It was in regular use {thousands of sessions} from '92 through to 2012, then partial use until 2018. In that time, I think the pinch roller was replaced twice. It was sheer wear both times. I was always impressed with how durable the rollers were.
The only time I had an issue with track 1 or track 8 was in early '93 when I'd had the 488 for about 3 months. When recording on track 1, it would show a healthy signal but on playback, you could barely hear anything. I took it in to be repaired and it was fixed and I never had that issue again. I always considered it to be a head issue.
But I'm not technical and my knowledge of the mechanics doesn't even rate the description of 'knowledge' {'no-ledge' would be more accurate !} so I never would have noticed if the roller had become a bit tapered although I can see it in the picture you provided.

 

[sweetbeats]

@60’s guy

…the measurements of that rubber covered pinch roller, which is only what? 3/8" or 1 /2" wide…

The complete roller assembly including the hub is 8mm wide, so just over 5/16.

The left and right side diameters measured .015 mm (.006" ) less than the center of the pinch roller, which, in my opinion is hugely excessive.

Correction, no, only one side or end of the roller was 0.015mm less, and that was less than the other side or end of the roller; think tapered cylinder.

I can only speak from my own experience as an engineer and designer of web transport machines that the crowning of rollers (larger diameter centrally.....smaller diameter at the ends) was a common design practice to keep the web traveling central.

Right. The material will move to or follow the area of great pressure or tension. That concept is used on pretty much all of belt-driven capstan assemblies I’ve worked in from cassette-based to open-reel. The motor pulley is crowned to keep the belt centered. But that’s not a convention that’s used with pinch rollers. The profile of the rollers should be flat, true, parallel, etc. and of course the roller should be precisely round.

Have you studied the mechanism that applies pressure to the pinch roller?

I assume that that both bearing ends of the pinch roller are supported by a yoke.

The question is.......is that yoke a y configuration where pressure is applied centrally or is the pressure off center?

The roller carrier is typical of any cassette deck I’ve worked on…it’s pictured in the first picture of the second post of this thread. The ‘U’-shaped carrier supports both ends of a 2mm precision roller axle pin at one end, and pivots on a rigid-mount post at the other. Here’s a picture of the carrier with roller installed on the transport assembly:



I don’t believe the mounting system is at fault for the old roller presenting with uneven measurements. I think it is related to normal wear/breakdown of the rubber.

 

[sweetbeats]

@grimtraveller

You'll soon be out-selling Prince Harry and JK Rowling at this rate !

Hah!

I had my Tascam 488 MK1 from the end of 1992 until the end of 2018. It was in regular use {thousands of sessions} from '92 through to 2012, then partial use until 2018. In that time, I think the pinch roller was replaced twice. It was sheer wear both times. I was always impressed with how durable the rollers were.
The only time I had an issue with track 1 or track 8 was in early '93 when I'd had the 488 for about 3 months. When recording on track 1, it would show a healthy signal but on playback, you could barely hear anything. I took it in to be repaired and it was fixed and I never had that issue again. I always considered it to be a head issue.
But I'm not technical and my knowledge of the mechanics doesn't even rate the description of 'knowledge' {'no-ledge' would be more accurate !} so I never would have noticed if the roller had become a bit tapered although I can see it in the picture you provided.

Thanks for the real-world account! That’s a good long run there with your 488. Your points shed light on how long a pinch roller can last, but in the end mileage and age require replacement.

That issue you had early on with playback on track 1 was more likely something electronic with the sync/playback electronics. Since the 488 is a two head machine, playback is always via the same head you used to record, so if it records the head core itself is capable of playback. Therefore if it records but doesn’t play, it’s typically something with switching logic OR a physical issue (bad connection) or a failed component. Glad they were able to fix it.

My very first direct experience with a Tascam 8-track Portastudio was sometime in 1991, IIRC, with a 488mkII. A band I was in at the time was doing a home-grown full-length cassette release, and like any good starving band couldn’t afford to buy anything, so we rented the 488mkII from a local music store. But we had to exchange it because the first one had a distinct low-frequency flutter issue, which would typically be related to the pinch roller or capstan shaft. It was disturbing to encounter in the middle of tracking, and to be honest left me feeling a bit like the format wasn’t reliable. I think that’s an unfair bias, but at that time knowing relatively little about multitracking process and available equipment it made an impression on me. I sometimes wonder if that first experience has somewhat tainted my regard for the format all these years, though my experience with the eight other cassette 8-track machines and the significant number of them with edge track issues is real. But I’m hoping a new quality pinch roller might help.

 

[grimtraveller]

Glad they were able to fix it

So was I !
I think it was probably only the 3rd or 4th song I had recorded on it at the time. I was working with kids and a couple of them used to take part in a music workshop I was running. They were 9 and 10 and were learning the clarinet and flute and I showed one of them a few chords on an electric piano. Anyway, I thought it would be an interesting exercise to record a piece I'd written so we spent ages learning it. We were actually learning it before I thought of recording it, before I even had the 488. But anyway, when we got round to adding their parts {my mate on drums and I had laid down bass and drums}, the girl playing flute did a lovely improvisation on a section and that was the bit that showed up really quietly, even though I could see the level was healthy.
Needless to say, when the 488 was repaired and she re-did that part, it wasn't anywhere near as good ! Or maybe I just thought that because in reality, I only ever heard the improvisation once, properly, and that was as she did it.

My very first direct experience with a Tascam 8-track Portastudio was sometime in 1991, IIRC, with a 488mkII

Story of my recording life, that. By the time I got the 488 MK1, it was already ancient and outmoded !
At the time, in the shop it was a choice between that and another 8-track {I can't remember which one}. I never regretted the choice.

I sometimes wonder if that first experience has somewhat tainted my regard for the format all these years, though my experience with the eight other cassette 8-track machines and the significant number of them with edge track issues is real

For about a month or so, I'd been using a Fostex X-15 and had recorded about 3 or 4 songs on it, but I soon realized that my ideas couldn't be contained on a 4-track. The way bouncing more than once killed the clarity of the original sounds {I was a complete beginner when it came to multitracking} on a song I considered a triumph convinced me I needed to ditch 4-track.
All those stories of Sergeant Pepper being recorded on a 4-track.....
So...I went looking and as this was 1992, I didn't come across anything in the digital realm and even if I had, I wouldn't have gone down that route at the time because computers didn't interest me and digitalia was just....well, not in my sphere. And I loved cassettes, they were something I was familiar with. In my research, this being pre~internet, I went to various shops and asked around and I'll always remember this hippie guy that worked in an instrument exchange close to where I lived advising me in the strongest terms not to go near 8-track cassette. He didn't have a good word to say about them.
I'm glad I didn't listen. A couple of years later, someone explained to me about the limited sound because of limited bandwidth and that made sense. But most of what I know, I learned on that 488. Even though I eventually went over to the dark side, I'd never knock portastudios.

 

[sweetbeats]

Thanks to yours truly, Athan now has pinch rollers for the 1st generation Tascam 122/122-B (which is also the same as for the 133 and Teac C-3X), and 238 cassette decks:

https://www.athan.com/store/p549/Cassette_Pinch_Roller_With_Bearings_Tascam_122/122-B_1st_Generation_(NOT_MKII_or_MKIII).html

https://www.athan.com/store/p551/Cassette_Pinch_Roller_With_Bearings_Tascam_238.html

I also confirmed with George Athan the roller he has listed for the “Nakamichi Sankyo” is the correct part for the Audio Technica AT-RMX64, so he now has it listed separately:

https://www.athan.com/store/p552/Audio_Technica_AT-RMX64_Cassette_Pinch_Roller_with_Bearings.html

You’re welcome.