Revox A77 tape guides modification?

[john_benham]

Greetings,

I have the Revox A77 R-R tape deck. The tape source and take-up guides are static and eventually I the tape will wear these guides. Also, older tapes will squeal adding that noise to a digital transfer. To remedy this, I added Teflon tape (plumber's tape) around the guides. This works for a while.

Does anyone know of a addition, modification, or conversion to these tape guides to make them roller?

I have a Pioneer RT-707 and Otari MX5050 - both with roller tape guides. Not sure why Revox didn't engineer this fine tape deck with roller guides. I use it to transfer clients old R-R tapes to digital and would like to use it as a safety backup recording of live concerts which I'm periodically hired to do. The other R-R units I have weigh to much for transport.

Currently as a safety backup to a computer digital live recording, I use a stand-alone Tascam digital unit, obvious much lighter and more convenient, but I want to offer my customers an analog alternative.

Any information would be appreciated.

Thanks,
John B.
Spokane

 

[radiokom]

Originally supply guide has ball bearing, take up fixed, but can be converted to roller guide.
Perhaps yours supply roller is simply stuck.

This is what you need:

https://www.ebay.com/itm/222808872609?hash=item33e07196a1:g:684AAOSwZq1gEAi0&amdata=enc:AQAHAAAA4DexpZXnd0CrdGDB4ldjs+8tNXKil/BbUWReezXAfYdqCvss13deW1Xe7TG2ySMMpc6C8u/FDhf8XAjIP06uKmmd+rbIVqIfTf0XL6MkifXu8xiYYXaODWshiLGp6cPJQbTlnn3AU/MHTdG2pthmZyi5eOTe118wnYs/a+I8lrYdendY5Ba7ov4EwGTXpYwvD+yKHAZH4Txf/A2ngZvDh/mNOPKIA8Oij9DImdkCg8/5nGiJpIf073tQ6nBoSlk05jLD+S5je6GW3NhJi9/ulA33FSt0r4mz1whJHfj5jOB1|tkp:BFBMtLDW8r9h

Or similar, 2 SKF bearings + shims.

 

[ConchBoy66]

Originally supply guide has ball bearing, take up fixed, but can be converted to roller guide.
Perhaps yours supply roller is simply stuck.

This is what you need:

https://www.ebay.com/itm/222808872609?hash=item33e07196a1:g:684AAOSwZq1gEAi0&amdata=enc:AQAHAAAA4DexpZXnd0CrdGDB4ldjs+8tNXKil/BbUWReezXAfYdqCvss13deW1Xe7TG2ySMMpc6C8u/FDhf8XAjIP06uKmmd+rbIVqIfTf0XL6MkifXu8xiYYXaODWshiLGp6cPJQbTlnn3AU/MHTdG2pthmZyi5eOTe118wnYs/a+I8lrYdendY5Ba7ov4EwGTXpYwvD+yKHAZH4Txf/A2ngZvDh/mNOPKIA8Oij9DImdkCg8/5nGiJpIf073tQ6nBoSlk05jLD+S5je6GW3NhJi9/ulA33FSt0r4mz1whJHfj5jOB1|tkp:BFBMtLDW8r9h

Or similar, 2 SKF bearings + shims.

Unless its an early mark 1 then they won't work. Peter at Nagravox says he may make some in the future but for now it's a no go

 

[radiokom]

Unless its an early mark 1 then they won't work. Peter at Nagravox says he may make some in the future but for now it's a no go

Oh yes, I see! I am not familiar with early MK1. But I wonder is it possible to replace complete guides or head block? There are lot of parts available including cheap head blocks.

Original MK 1 is this:

https://www.ebay.de/itm/385337061939?hash=item59b7e0f233:g:g-gAAOSwo4ZjuGx9&amdata=enc:AQAHAAAAoFixcTyuLphOwkzD3qUXQDahQO42oAHJh5AuZQI9zS4pAHx8XbLxaocN7Rtncmx06QBKXkC4PbduVz5KYqhSyuxBDBCnSc1pfts2CVrVImxy3BjLLjUPA3bxyW/auXNMobUTXsbY3C3sjVvmWxgDo55wLMRrNDilzLkyApKzvLdN8Zh+zVbHvQDIizClVLKFOT+edyZtf54gMk2+IUe7OmE=|tkp:Bk9SR7LRjqnAYQ

MK II-IV this:

https://www.ebay.de/itm/385343183008?hash=item59b83e58a0:g:OVUAAOSwsThjvFzX&amdata=enc:AQAHAAAAoGc3xN8UZDwc3U6YXTfsjhPMLjvaUJgiS2l5OkHvAOSxE/VCQTau7EyQkkde4DyP/N1/NDC4xrmzMrZyKldu9E0cUbtdk0T9yT16wCidHLc0FwXTNBvGLXCfBOHYUbKTJlW6LoZkzHnskBJ1urlBgT9JhCx5UKRRm/6c2nc8vYVdxFZXlOzAaWgKQlwMkn4lqMbsDRC8ceGLEsMiWjC3ESs=|tkp:Bk9SR7LRjqnAYQ

Looks similar, except guides.

So I believe this set is what OP needs (with new bearings and shims):



P.S. Or there is different mounting? No thread for guides?

 

[radiokom]

Really, mounting holes in MK1 head block has no threads. And head block has no "loop catcher" tensioner. So I believe it would be good idea to replace MK1 guides together with head block basis and lever.

 

[john_benham]

Thanks for all of the suggestions. The guides are fixed with a small screw from the rear of the head/roller assembly keeping the three piece guide in place. It does not rotate or have any bearings. Taking one side apart, the small screw holding it all together fell into the machine hence total take apart! But I got the photos. As stated previously to get rid of any tape squeal, I warp it with a couple of finds of Teflon tape. If there is a roller bearing replacement short of replacing my entire head unit, please share.
The small screw fell inside the unit hence need for total disassembly. It's a Rubik cube!
One photo shows my mastering station where I transfer old recordings for clients. Some of the R-R tape is as old as the 1950's. I have to clean my heads often!

Thanks, John B.

 

[radiokom]

In my opinion there is only one solution if you do not want to machine custom guides (what would be very expensive so no reason) - you should replace head block base together with guides and tensioner (instead fixed guide in your block). All heads can be replaced without any changes in high however it would be better to relap them because some minor differences in guide high can be. And you need to replace black panel too to fit new tensioner, or machine hole for it.

https://www.ebay.com/itm/1156656445...AsR/63LZWwMZ7dI0c0crSgC0E=|tkp:Bk9SR4qF1cXAYQ

 

[ConchBoy66]

In my opinion there is only one solution if you do not want to machine custom guides (what would be very expensive so no reason) - you should replace head block base together with guides and tensioner (instead fixed guide in your block). All heads can be replaced without any changes in high however it would be better to relap them because some minor differences in guide high can be. And you need to replace black panel too to fit new tensioner, or machine hole for it.

https://www.ebay.com/itm/115665644537?hash=item1aee35abf9:g:4KcAAOSwbThiOLy6&amdata=enc:AQAHAAAAoNtpDvlkoNjTgTxZ4qJYkyP3YDJijmXawufzIekiZiy9uZy/Qdiqdiyo7SaVrycBnc0Ps2Ww7TWnT6i73sx/1O2R/n9+YiWVbYX4jWVagLvjlwWGOdfcnKjOgt9sSlIV1pxs/NYg8K01pRvUNuWtdKw6wByBG28bYO444e1y0P7+hexp/c5Z6/xGNpqx21AsR/63LZWwMZ7dI0c0crSgC0E=|tkp:Bk9SR4qF1cXAYQ

I have purchased from that ebay seller, my product was in great condition.

 

[radiokom]

Thanks for all of the suggestions. The guides are fixed with a small screw from the rear of the head/roller assembly keeping the three piece guide in place. It does not rotate or have any bearings. Taking one side apart, the small screw holding it all together fell into the machine hence total take apart! But I got the photos. As stated previously to get rid of any tape squeal, I warp it with a couple of finds of Teflon tape. If there is a roller bearing replacement short of replacing my entire head unit, please share.
The small screw fell inside the unit hence need for total disassembly. It's a Rubik cube!
One photo shows my mastering station where I transfer old recordings for clients. Some of the R-R tape is as old as the 1950's. I have to clean my heads often!
View attachment 2783737 View attachment 2783739 View attachment 2783740 View attachment 2783741
Thanks, John B.

I have MK2 head block base somewhere in storage boxes. Guides from that block are in picture above (needs new bearing and shims). If you are interested send me PM and I can try to find it next week.

 

[john_benham]

I have MK2 head block base somewhere in storage boxes. Guides from that block are in picture above (needs new bearing and shims). If you are interested send me PM and I can try to find it next week.

Yes, I would be interested. I could find an internal spacer and try to install the suggested bearings, but it is a 50 yo+ tape deck. My Pioneer RT-707 only accepts 7" reels. Most of my older live recordings I used the larger 10.5" reels. The Otari I have was given to me from our public radio station and it's own its last legs! Dropping that small screw into the inner workings of the A77 was a pain. I had to take everything apart to find it. But I've taken it apart many times before, cleaning circuit board contacts, etc. I know the machine intimently. I have the service manual if you need any information from it. Not sure what you mean by PM. On good quality tape (Scotch 207, TDK, Maxell, BSR) its perfect. The issues I run into when clients want me to transfer a recording from the 50's or 60's to digital and they used cheap tape. It will squeal since its so brittle and the coatings will come off which means super cleaning of heads and guide path afterwards. Really appreciate the advice. John B. Spokane (your pic did not come through)

 

[radiokom]

Yes, I would be interested. I could find an internal spacer and try to install the suggested bearings, but it is a 50 yo+ tape deck. My Pioneer RT-707 only accepts 7" reels. Most of my older live recordings I used the larger 10.5" reels. The Otari I have was given to me from our public radio station and it's own its last legs! Dropping that small screw into the inner workings of the A77 was a pain. I had to take everything apart to find it. But I've taken it apart many times before, cleaning circuit board contacts, etc. I know the machine intimently. I have the service manual if you need any information from it. Not sure what you mean by PM. On good quality tape (Scotch 207, TDK, Maxell, BSR) its perfect. The issues I run into when clients want me to transfer a recording from the 50's or 60's to digital and they used cheap tape. It will squeal since its so brittle and the coatings will come off which means super cleaning of heads and guide path afterwards. Really appreciate the advice. John B. Spokane (your pic did not come through)

With PM I mean "personal message" or private conversation here. OK I will take a look next week in my storage boxes, because I know I have this base somewhere. Guides from that base are in picture in post #4. What is wrong with Otari? It is really built like a tank and except well known problems (capstan motor magnets glue in some models for example) if it is complete it is fully repairable and parts are available.

 

[titanstats]

Greetings,

I have the Revox A77 R-R tape deck. The tape source and take-up guides are static and eventually I the tape will wear these guides. Also, older tapes will squeal adding that noise to a digital transfer. To remedy this, I added Teflon tape (plumber's tape) around the guides. This works for a while.

Does anyone know of a addition, modification, or conversion to these tape guides to make them roller?

I have a Pioneer RT-707 and Otari MX5050 - both with roller tape guides. Not sure why Revox didn't engineer this fine tape deck with roller guides. I use it to transfer clients old R-R tapes to digital and would like to use it as a safety backup recording of live concerts which I'm periodically hired to do. The other R-R units I have weigh to much for transport.

Currently as a safety backup to a computer digital live recording, I use a stand-alone Tascam digital unit, obvious much lighter and more convenient, but I want to offer my customers an analog alternative.

Any information would be appreciated.

Thanks,
John B.
Spokane

Revox made tens of thousands of these machines in dozens of configurations over four different series for more than a decade. They improved the machines with every iteration. Then they used the same transport in the B77.

The one thing they never did is what you’re suggesting. The fixed right hand guide isn’t cost cutting, it was the design. It’s doubtful that anyone has actually improved a Revox transport by improving it.

 

[twiiii]

The later machines have a bearing on the feed side with the appropriate space washers to get the final and correct spacing. I always removed the rigid spacer on the take up side and added an identical bearing with spacer on the take up side. I have forgotten which grade of bearing I used. I think I went from a class 3 to a class 5 for smoother results. Just take your factory bearing or spacer with you to a nut bolt screw and bearing shop and they will get the correct bearing for you.

 

[radiokom]

Revox made tens of thousands of these machines in dozens of configurations over four different series for more than a decade. They improved the machines with every iteration. Then they used the same transport in the B77.

The one thing they never did is what you’re suggesting. The fixed right hand guide isn’t cost cutting, it was the design. It’s doubtful that anyone has actually improved a Revox transport by improving it.

This is common modification to replace right fixed guide with the same bearing as supply side. There is no reason for fixed guide in the right. It can improve nothing. This was common modification from beginning. But, of course, it is not possible for OP head block. He needs to replace head block base.

 

[titanstats]

This is common modification to replace right fixed guide with the same bearing as supply side. There is no reason for fixed guide in the right. It can improve nothing. This was common modification from beginning. But, of course, it is not possible for OP head block. He needs to replace head block base.

Yes, it was commonly modded, which doesn't mean anything. For myself, I would imagine Revox would have somehow stumbled upon this improvement at some point during the 30 year production run of these machines if it actually improved anything. Really, why would they not?
I've heard it affects W&F negatively, but have never measured it myself.

 

[radiokom]

Yes, it was commonly modded, which doesn't mean anything. For myself, I would imagine Revox would have somehow stumbled upon this improvement at some point during the 30 year production run of these machines if it actually improved anything. Really, why would they not?
I've heard it affects W&F negatively, but have never measured it myself.

It can not affect w&f negatively because it is after capstan. It is fixed guide what can rise scrape flutter, not quality bearing anyway. So nothing else only cost reduction in my opinion. PR99 has both rotating guides all models.

 

[jlb2]

Yes, it was commonly modded, which doesn't mean anything. For myself, I would imagine Revox would have somehow stumbled upon this improvement at some point during the 30 year production run of these machines if it actually improved anything. Really, why would they not?
I've heard it affects W&F negatively, but have never measured it myself.

I did measure the W&F and scrape flutter with and without the mod, and I didn't find any difference - which is what I expected since it is on the wrong side of the capstan for that. However it does bring an improvement, by removing a stationary surface where aging tapes leave loose oxide and sticky residue. It's an inexpensive mod, so I did it and definitely noticed the difference when digitizing archives.

@radiokom: it is the PR99 Mk II and Mk III that have a rotary sensor for the real-time counter. It also serves as a tape guide but only as an incidental function, and I strongly doubt that the reason to add it was to improve the transport. The Mk I, which does not have a real-time counter, does not need it and has the stationary guide of the B77.

 

[radiokom]

The Mk I, which does not have a real-time counter, does not need it and has the stationary guide of the B77.

Yes, I see in SM there is fixed right guide in PR99 MK1-2. It means a few PR99 I have seen has been modified before. Because you really do not want your tape to touch fixed guide. And modification is very simple, you need only bearing an 2 0,2mm washers.

 

[jlb2]

you need only bearing an 2 0,2mm washers.

0.15 mm in fact (or one 0.2 and one 0.1 mm) so that the total width is 6.3 mm, barely more than the tape which is 6.25 mm wide. You want to keep the gap as narrow as possible, otherwise the phase fluctuations become measurably higher. One of the big weaknesses of the Revox transports IMO. Of course, do not overdo it with two 0.1 mm shims, otherwise you will pinch the tape which will damage it.

 

[radiokom]

0.15 mm in fact (or one 0.2 and one 0.1 mm) so that the total width is 6.3 mm, barely more than the tape which is 6.25 mm wide. You want to keep the gap as narrow as possible, otherwise the phase fluctuations become measurably higher. One of the big weaknesses of the Revox transports IMO. Of course, do not overdo it with two 0.1 mm shims, otherwise you will pinch the tape which will damage it.

With 0,3mm total thickness tape may stuck between side plates (proved). This design is not so precise. Flanges are large, fixed and if tape is not perfect you have a problem. 0,4mm is OK. It is important anyway only for left guide. Right should be 0,4 with left you can experiment, but not less than 0,35mm.

P.S. I just measured original Revox supply guide shims with micrometer. They are 0,36mm together.