Does anyone know what these 4 pins control on the Sony WM-GX655?

Swapping the rollers for new ones might seem like a logical step to do on any restoration.
However, finding a good roller that's not eccentric can be a challange nowadays.
Not few were the situations where installing a new pinch roller introduced a problem that wasn't there to begin with.
And I'm talking about rollers from reputable sellers, not cheap ones bought by the batch.

Hence why keeping the original roller might actually be a good idea, despite it seems counterintuitive.
If the roller is glazed, has an indentation mark or rubber is hard like a stone, of course it should be replaced.

@TP86 Definetely doesn't seem like a roller problem, but more likely there is too little pressure.
Fact it halts depending on orientation also suggests that spring doesn't do its job. That 30-40% difference, even though is done by feel, seems excessive.
No, wouldn't re-oil the capstan bushings, don't see any point in doing that.
One other thing to double check is if capstan is actually rotating and belt isn't slipping on the flywheel.

 

Well he describing a problem i encountered dozen of times, you clean the roller and all is well and after ten minutes W&F increases or deck stops playing...you could try to revive the old roller but on some the rbber has turned into plastic there is no saving to do...
But with eccentric you mean that the axle hole isn't true, so little of center or is the rubber itself not perfectly round?

 

It could be the roller that is the cause. It doesnt look too bad but one certainly is shinier visually

I tested the walkman again after work. With my new calibration test tape the w&f is about 0.24%rms on both fwd and rev and about 30hz distance between then which im happy with.
What I tend to notice is the fault seems to be comming in when I test some of my old tapes that physically require more torque to rotate the spindals. Im just testing by feel with a pen.
It seems to struggle to pull the tape on fwd and rev if the tension is too great. I mean it could be the pinch rollers but also the tension from the spring. Im 100% sure capstan flywheel is rotating when tape fails to be pulled.
Any suggestions in what I could try next? It looks like you can buy new pinch roller rubber portion on ebay but like you said when I install it theres a good chance it will make things worse

 

@Black Fingers About eccentricity, it's the rubber itself that's the problem.
For example, rollers where you buy just the rubber (WM-700 series, WM-100 series) are almost always eccentric. That's why it's best to only use complete assemblies.
But unfortunately the problem doesn't end there: many complete assemblies are also eccentric. Even from known good sources: if you buy 5pcs, 2 may be eccentric.

Given this, when I restore a walkman or deck, won't jump at those rollers as I do for belts or idlers.
Rather, if the rollers look ok after a good cleaning (most do, but not all), prefer to leave the original ones.

@TP86 It's unclear to me if there is a correlation between that shinier roller and the problem (doesn't seem to be ?).
Cause now you say both sides have a problem with some harder to spin cassettes.
At this point I would indeed change the pinch rollers, just to see if that fixes the problem. For reference dimensions are 6 x 5 x 1.5mm (outer diameter x total height x pin diameter).
Definetely buy complete assembies, not just the rubber as that is almost guaranteed to create eccentric assemblies.
Even if the new rollers are to be eccentric, you should at least have an idea if the stalling problem is fixed or not even if W&F may be higher.

 

Sorry for the lack of clarity it has been difficult for me to understand what is going on. I believe the confusion is because throughout the thread I havent been testing with a consistent set of tapes that have a varying resistence to rotation. I'll make sure from now on I include tape spindle turning difficulty level in analysis.
- I know for a fact both fwd and rev playback capstans are spinning but failing to pull through the tape or a difficult to turn spindle tape. But, I tested this same difficult tape on my WM-EX655 and the playback speed is very slow as its struggling to turn it. It seems to at least be able to pull it without stopping. It may have stopped once or twice but nothing like this GX655 in this thread.
- I also used same battery and battery pack in both tests by the way so that can be rulled out.
- I agree that the pinch rollers seem like the next logical step. I dont see how those springs on the pinch rollers could be deformed or not doing their job. Thanks for providing the dimensions it looks like fya sell them https://fixyouraudio.com/product/pinch-roller-6-x-5-x-1-5-mm-for-cassette-players/

- Sub-question for the EX655 (the other walkman i fixed in other thread): this hard to spin tape is playing with very slow playback even know i have calibrated the walkman properly using a good easy to spin test tape. Is this to be inspected? It seems the spindle is too hard to spin to reach the minimum rotation speed required for correct playback

 

Don't know how hard that tape is to spin, but these walkmans should be able to play even a tape with more drag without problems.
I usually use a not so good pre-recorded tape to first test restored walkmans. This tape has warped hubs and worn slip sheets.
If tape is not spooled evently, it becomes pretty hard to turn.

However found this to work fine in such walkmans in play, problems appear only in FF/REW.
In such scenario, a deck with high torque reel motor would be able to rewind it nicely, while many walkmans will stop.

The EX655 is to be inspected in my opinion. It's possible that one needs new pinch rollers also. Update us how it goes.

 

Thanks mate. I ordered new rollers for both walkmans. I'll let you know if it helps. I'll know in the future to also conduct playback tests on a harder to spin tape en ensure playback speed remains good
By the way I confirmed what you said is correct regarding the walkman should be able to keep up to correct speed even with hard to spin tape. I done this by putting the difficult to spin tape in my best walkman EX621 and it plays flawlessly

 

Hi Valentin. I ordered some 6mm x 5mm x 1.5mm from China and I recieved the incorrect size: 6.22mm x 5.38mm x (not sure inner diameter but looks ok)
The problem is because the full height is 5.38mm (0.38mm above spec) it doesnt physically fit. I am pretty annoyed. It seems to be not only the rubber protruding past 5mm but also that plastic inner piece so there no way to slice anything off.
I have a feeling I wont be able to get my money back on these too as its hard to prove they are the wrong size. Any one who reads this, be weary of ordering pinch rollers from China as the dimensions are far from accurate

I took the existing one out by the way and outer diameter 5.55mm and full height 4.92mm. Im not sure if that 5.55mm tells us they have worn down 0.45mm or not. Anyway not much I can do until I order some more reliable seller

 

Only potential solution is to sand the plastic hub, 0.2mm on each side, assuming the hub is significantly taller than the rubber.

In regard to dimensions, height has to be a bit smaller than the actual specification, since there needs to be some play in the bracket.
The 5mm is supposed to be the height of the bracket, while 0.08mm is the allowed play.
Same thing goes for the pin, hole has to be a little larger than the 1.5mm pin to allow a tiny bit of play.

As for OD, that usually won't match exactly, but would expect it to be closer to 6mm (like 5.8-5.9mm for example).
That 0.45mm less may be the reason why tape doesn't have traction at the roller, since these rollers don't have a lot of tension to begin with.

 

Both the rubber and the plastic hub are fairly flush. i feel like I will make a mess of it if I try to shave off 0.2mm. I asked seller if i could sell back as it didnt fit and like fortunenly were ok with that.
It seems like to manufacture with 0.1mm percision or less is quite difficult and requires advanced technology which this company did not have.

Moving forward with this I'll get from fya or locally if I can find. Thanks mate