Thermionic Soundmirror

[ms660]

As said looking at the photo, the pinch roller needs cleaning, check the rest of the tape path as well, the pinch roller should be parallel to the capstan, and their axis should also be parallel, if not your inviting the tape to ride, it might also be worth checking that the capstan is perpendicular to the deck, usually a very slight amount out shouldn't make much difference but if it's a ways out say due to a worn capstan bearing or the bearing housing is out of alignment for whatever reason then that can also cause tape riding issues.

Lawrence.

[TIMTAPE]

Originally Posted by kalee20

...The pressure on the pinch wheel is set, top and bottom, by a piano-wire spring. Hopefully the two arms of this are parallel (it is easy to take out, to check)...

Ah so is it like a Tandberg with a piano wire spring at the top of the pinch roller and another at the bottom? That is what I was trying to clarify and why I showed the Tandberg pinch roller photo!

[Volatile]

Ok all, Here are my most recent findings.

I cleaned the pinch roller, Replaced the tape with newer stuff and now there is no shed, both legs of that spring are equal, the pinch roller bracket isnt bent (i was hoping it was one of those things)

The capstan has a tiny bit of side to side wobble in it, less than a MM id say though, and im supprised the bearings arent worn out as the rest of this mechanism pretty much is .

It seems like the only thing that makes a difference is that tape head pressure pad, ive spent hours yesterday on the reel tables, tape path etc and problem still happening.

Even when pinch roller turned upside down tape still rides to the bottom.

[ms660]

What's the back tension like?

Lawrence.

[Volatile]

Just enough so the tape isnt slacking , but can still be pulled though easily

[Volatile]

i wouldnt mind getting hold of a new pinch roller for the machine , if anyone knows where there is or has one ?

[ms660]

The play in the capstan sounds suspicious, also the capstan along the tape contact section must not be worn.

At Sony we had shims to shim the bearing housing on some machines to allow for any alignment errors but only good for small discrepancies.

Lawrence.

[Volatile]

Theres not a lot of play, I've seen worse on some well used bsr decks and they have worked just fine, the only other project that had me more beaten than this was an audio line cb radio, I've worked on obscure dictation machines , wire recorders , record players and various reel to reel machines , but this one has me beaten finally, I give up

[Volatile]

Unless I can get a replacement pinch roller to to test in it, or a top plate just to make it nice to look at it's going

[TIMTAPE]

To be honest the old Soundmirror is not a machine I would hang onto for practical use. I'd see it as of historical, curiosity or sentimental value. Its only distinction as a player is being able to play old Soundmirror recordings with the unusual centre track, but there are far better and safer machines on which to play these rare and fragile tapes these days.

I'd be more interested in the old tapes you seem to have acquired with the machine. In the early days of tape recording, many programmes were broadcast live over radio but they weren't necessarily recorded by those concerned. People with the means to buy tape recorders sometimes recorded these programmes, and sometimes they have survived and been reissued on CD.

It's always a long shot but, who knows, you may have some recordings of historical importance there which people might like to hear or even be prepared to buy copies of them.

[Volatile]

I do have some unusual recordings that came with this machine , I really shouldn't let it get the better of me to be honest.

I'd like someone else to have a look at the deck at some point and see if anything else can be done, I'd like to have the machine working, il keep it either way, it is antique, it is a historic machine after all.

The seeming lack of spares is disheartening though, I'd like to send the pinch roller off for refurb but dont know who to contact as I've been able to get spares, even for more obscure machines than this before

[TIMTAPE]

Careful experienced inspection of the pinch roller should be enough to determine whether it needs refurbishment. I wouldn't send off a roller unless I was sure it was the cause of the problem here.

I've repaired a lot of tape machines including ones with pressure pads. Pressure pads are notorious for deterioration. I always replace the felt with new felt and make sure it's a good accurate replica of what the new part would have been like, properly adjusted against the head face.

At the same time, I would always relap the head, especially since a head with a pressure pad usually gets prematurely and nastily worn out from the pressure pad's harsh action. Relapping is a delicate business but with patience and care it can be done with great success.

Apart from the audio performance improvements, a new pressure pad against a relapped head will probably provide more back tension, which your machine seems to need.

[Volatile]

OK, I THINK I HAVE A DIAGNOSIS
After all this, it does indeed turn out to be the pinch roller that is causing this problem, i examined it under a friends microscope, it has the words faintest concave shape too it, And after saying "sod it" and deciding to put it againt a belt sander, the problem has improved and the pressure pad aganst the had can be loosened, preventing head wear ,

Question is, where do i go from here? I ether need to have this one rebuilt or replaced

[TIMTAPE]

Yes a concave pinch roller will not help. New they are either flat or convex. Well spotted.

[Volatile]

Ive done some experiments with small rubber O rings around it and some junk tape, depending where i put the O ring i can make the tape travel further up the capstan, or low enough to slip off, and in the middle causing the same problem, so its the pinch roller, time to hold out for a replacement

[Volatile]

Do these just not like plastic tape ? I wound another paper tape on and it works fine with original pinch roller ? What ?

[Techman]

Back from my road trip with the classic caravan - we all had to get towed off the field with classic tractors today, but it was all good fun!

I've just been talking to the OP and I was telling him that I think that pinch roller looks the same sort of size as the ones in the Collaro Tape Transcriptor, so one from a scrap one of those would be a possibility. He tells me that it's running well now with the original paper tape, which of course is thicker than the more modern tape. He's also replaced the pressure pad. You could possibly fit a long thin nut and bolt through the roller and mount it in a drill and VERY carefully run a flat abrasive pad against it for a moment or two. You'd need to be quite precise with it, but it's a thought.

[TIMTAPE]

Originally Posted by Volatile

Do these just not like plastic tape ? I wound another paper tape on and it works fine with original pinch roller ? What ?

Trying to eliminate possible causes.

With much tape travel, the tape can wear the capstan shaft to a smaller diameter, with ridges at each side. This was more a problem if the shaft itself wasn't made of hard enough material. Have you inspected the capstan shaft carefully, with magnification if needed?

[Volatile]

I have inspected the capstan with magnification, The capstan (wich was dirty and since cleaned) looks in pefect condition

[Techman]

It's great to see all the helpful suggestions that everyone has been giving and it looks like the machine is getting there. The OP was telling me last night on the phone that he'd made a recording on the original tape and was very surprised at the quality of the sound. From what he says, the tape travel isn't perfect by any means, but at least it isn't riding it off and chewing it up. I told him I suspected the pinch roller when he first told me about it the other day, but he said at the time that it looked fine - but they often do!

Depending on the pinch roller bearing arrangement it might be tricky mounting it with a nut and bolt in a drill chuck and may possibly need a couple of metal washers with possibly rubber washers made to grip the actual bearing to stop it spinning separately, but I don't know the actual arrangement without actually seeing it and seeing whether the bearing is definitely part of the roller.