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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 19th Oct 2021, 12:52 am   #1
ben
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Default Worn tape guides.

A problem I often encounter on reel to reel decks is wear on the static tape guides, this is particularly irritating if the heads are still serviceable. One can usually see that plated /chromed guides wear down to the brass. An example picture can be found in this thread by PhilG4SPZ

The main problems such wear seems to cause are:

- Poor fast wind due to increased friction. Presumably this is because the guide surface is no longer rounded but flattened off, increasing the contact area and hence drag.
- Tape damage. If a 'channel' is cut into the guide post then I presume the sharp edges cut into the tape edges slightly, and the flat area (see above) increases friction and tape wear.

Some machines have guides which can be simply loosened and rotated to expose new surface. However, the type in the photo is more of a headache. Sony and Philips seem to use them quite a lot.

Since spares are NLA and in any case can be difficult to fit on some models, I wonder if any members have come up with 'fixes'? I was thinking of using guide roller parts from scrap VHS cassettes, adapting /cutting/crimping them then slipping them over the worn r2r guides so that there is once more a rounded area for the tape to touch. Perhaps there is something better though... Let's hear your thoughts!
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Old 19th Oct 2021, 5:30 am   #2
TIMTAPE
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Default Re: worn tape guides

Yes a common problem with the old tape machines. I like your idea of using the steel guides in VHS cassettes as sleeves over the top of lifter pins.

With a tape lifter pin as in the the photo, if I cant rotate it to present a new surface I've sometimes just removed the top and bottom ridges with a file a little wider than 1/4" and then filed the flattened surface into somewhat of a curve, not unlike relapping a tape head. I did this on the tape lifter pin of a Revox A77 recently.

On some machines like Teac/Tascam where the tape lifter is riveted to its mount I've often used Vice Grip locking pliers to forceably rotate the lifter pin to present a new surface.
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Old 19th Oct 2021, 9:39 am   #3
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Default Re: worn tape guides

If you know someone with a lathe I imagine replacement guides would not be difficult to make.
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Old 19th Oct 2021, 10:05 am   #4
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Default Re: worn tape guides

Quote:
Originally Posted by rontech View Post
If you know someone with a lathe I imagine replacement guides would not be difficult to make.
Indeed - I've successfully used non-magnetic stainless steel, rather than mess around with plated brass. Also wondered if a 'slippery' plastic like PTFE would do as well.
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Old 19th Oct 2021, 10:43 am   #5
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Default Re: Worn tape guides.

Your Thread posting Ben is maybe well timed for me. Even though I know that guide post etc wear can cause problems I tend not to automatically consider it when problems occur.

This morning have been progressing my Grundig TK 23 (#4 for my reference/records) this one -

https://www.vintage-radio.net/forum/...d.php?t=181533

Even though previously working OK, Play and Rewind mechanically are now seriously struggling. The left and right brass tape guides are worn as well as the EOT sensor post and tape lifter.

So will have a look at these before checking anything else. The tape posts will be easy to rotate, the EOT sensor post will be easy, but need to do a bit of stripping to get to its tiny securing nut underneath the heads mounting plate. The tape lifter will need a bit more stripping but think it maybe is riveted in so not easy to rotate.

I should say that in my expereince this TK series (TK's 14, 17, 18, 19, 23 & 27) can suffer with poor rewind performance due to insufficient contact/friction between the metal motor pulley and the black rubber outer surround of the Supply spool carrier/reel table.

David
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Old 19th Oct 2021, 11:00 am   #6
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Default Re: Worn tape guides.

I had a number of Philips machines that had flattened exit and entry guides, I got into the habit of fast forwarding and rewinding tapes with the tape away from the guides, this rapidly sped up the time needed for such modes.
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Old 20th Oct 2021, 11:45 am   #7
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Default Re: Worn tape guides.

Today I tried out a few things.
First I placed a VHS guide 'sleeve' over the fixed lifter pin, initial tests gave good results but of course the thing flopped about.

The machine I was using (Philips N4420) has a complication in that the lifter pins are angled at the top (to assist threading by not catching the tape). I tried to reduce the VHS sleeve's inside diameter by gentle crimping, but of course it would not then fit over the bend in the Philips lifter.

I could have dismantled the assembly and fitted it properly, but before embarking on that, I tried gently twisting the lifter pins about 45ยบ so that the worn part was pretty much off the tape. That seemed to significantly improve wind speed so I will leave it that way for now. The tape can still be easily threaded as the angle of bent part has not changed position significantly enough, pointing as it does towards the heads. Picture attached.
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Old 20th Oct 2021, 12:14 pm   #8
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Default Re: Worn tape guides.

I would really like to have a small lathe for making these kind of parts. Hopefully one day...
I like the idea of a PTFE guide provided it does not generate any troublesome static with the tape running against it. Maybe a PTFE sleeve could be stretched over a straight sided guide.
Rotating an existing guide where possible to expose an unworn portion is usually the best and most expedient method provided the guide is not on a thread (height adjustment issue).
The flats worn on such guides generally only become a problem if the wear is uneven leaving the post somewhat conical, or the surface becomes rough. Often this can be solved by refinishing and polishing. Grooves worn in the lower or upper flanges of the guide obviously compromise tape alignment and would need to be filled somehow.

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Old 20th Oct 2021, 1:06 pm   #9
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Default Re: Worn tape guides.

The idea of PTFE guides has been raised at least 50 years ago, in the Wireless World, if I remember correctly. The consensus seemed to be that they were O.K. in play but the heat generated by the tape in high speed spool softened the material and greatly increased the friction.
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Old 20th Oct 2021, 9:46 pm   #10
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Default Re: Worn tape guides.

My suspicions entirely, Barry! I think there is a possibility that as both faces are so smooth, you could get an airtight seal, generating heat and drag.

My feeling is that brass plated with nickel would provide an ideal surface. The question is, whether a couple of microns of nickel will have a magnetic effect?

What are guides plated with traditionally? Nickel is renowned for having low surface friction.
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Old 21st Oct 2021, 9:40 am   #11
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Default Re: Worn tape guides.

Here's a tape guide from a late 70's Nagra. I'm guessing the body is an alloy, the curved tape wearing surface is some sort of hardened alloy, and the red coloured edge guide inserts seem to be Ruby. A lot of tape has run through this machine, wearing the heads, but the Ruby inserts dont seem to have any visible wear from the tapes' sharp edges.
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Old 21st Oct 2021, 9:46 am   #12
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Default Re: Worn tape guides.

Quote:
Originally Posted by knobtwiddler View Post
My suspicions entirely, Barry! I think there is a possibility that as both faces are so smooth, you could get an airtight seal, generating heat and drag.

My feeling is that brass plated with nickel would provide an ideal surface. The question is, whether a couple of microns of nickel will have a magnetic effect?

What are guides plated with traditionally? Nickel is renowned for having low surface friction.
EMI used Chromed Brass on the TR50 variants.

Leevers Rich used Ceramic for all fixed guides, it didn`t wear but probably wasn`t super low friction.

Telefunken also used Ceramic guides on the headblock of at least one machine but they were also tapered so that the tape always ran to the bottom. It gave a very steady output level on test tones.
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Old 21st Oct 2021, 6:26 pm   #13
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Default Re: Worn tape guides.

Depending on size & how they are to be fixed, you might try nickel-plated brass threaded pillars. These are made in various sizes, M3, M4 etc.
Easily obtainable from places such as CPC.

David.
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Old 25th Oct 2021, 11:17 pm   #14
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Default Re: Worn tape guides.

I had this problem on a TEAC A-3440 and I was fearful of the sharp edges damaging tapes.

They do not clear the tape much during play/record so sleeving not possible and you can't rotate them.

I took them out and carefully dressed them with a Gesswein 320 grade stone to remove the shoulders and the shiny area where the tape was in contact, trying not to dish them, not a perfect repair but much better than leaving them as they were.

Google 'Gesswein stones', they are still available, mine is donkeys years old.
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