The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
Studer B67 slow rewind.. Other Controllers
Old 6th March 2018
  #1
Here for the gear
 

Thread Starter
Studer B67 slow rewind..

My Studer B67 is having trouble loading tape from the reel on the right to the left in order to playback it back. It plays just fine and loading from the left reel to the right is fine up until the very end of the reel, then it does seem to slow down just a bit but now much. Mainly though it's from the takeup to the playback reel that is really slow. Any suggestions on what to take a look at? Motor going bad?

Thanks,
Eddie
Old 6th March 2018
  #2
Lives for gear
 

Quote:
Originally Posted by leopold View Post
My Studer B67 is having trouble loading tape from the reel on the right to the left in order to playback it back. It plays just fine and loading from the left reel to the right is fine up until the very end of the reel, then it does seem to slow down just a bit but now much. Mainly though it's from the takeup to the playback reel that is really slow. Any suggestions on what to take a look at? Motor going bad?

Thanks,
Eddie
Did you already check the manuals?
ftp://ftp.studer.ch/Public/
Old 6th March 2018
  #3
Here for the gear
 

Thread Starter
Quote:
Originally Posted by Schoeller View Post
Did you already check the manuals?
ftp://ftp.studer.ch/Public/

I have the manual at the studio, not with me at the moment. Is there a troubleshooting section? I spoke with my tech and he doesn't think it's the motor but rather a sensor or a card...
Old 6th March 2018
  #4
Lives for gear
Good Lord! How does a post about a working vintage Studer tape machine get posted in the Low End Theory forum?
Old 6th March 2018
  #5
Lives for gear
 

Tape motion sensor? It's some sort of crude incremental optical encoder with a segmented disk and two reflex light barriers generating A and B pluse trains.

As usual, the Studer service manuals are very detailed, using a DSO it whould be possible to perform some preliminary diagnosis. It's probably not even audio-related so any good maintenance specialist should be able to start helping. What I mean is that while some parts require very specific audio expertise others don't.

The speed control is not very complex but it should be first determined if issues are related to the "encoder" feedback signals (check that the slot wheel is clean as poor reflectance could randomly affect speed feedback pulse generation). Also it should be determined if the problem is related to the set value (Sollwert, valeur consigne) and its generation and/or to the servo-control of the motor or the motor itself.

Hopefully it's not the TDA1000 (p. 262/362 for the Mk II) which could be an OEM IC for Studer made by Telefunken (found that information online). That said, it would still be possible to handle speed control differently, servomotor control is a very common task and which can be performed with a very high precision. It seems parts can still be found but if not maybe it would be worth designing a new speed control system, it's relatively simple, ideally replacing the motor by something like a brushless Maxon (will require some mechanical adaptation).

Audio and tape transport functions seem quite separate so for tape transport I don't see special issues to rebuild controls if required.

Which service manual applies to your model?


Edited:
I didn't check details, especially if there's a tachymetric feedback (direct motor shaft speed acquisition).
Old 6th March 2018
  #6
Here for the gear
 

Thread Starter
Quote:
Originally Posted by Bushman View Post
Good Lord! How does a post about a working vintage Studer tape machine get posted in the Low End Theory forum?
Ha! well, I searched for where other folks posted on issues they had with their B67s and quite a few were in this forum. It is a lower end Studer...but I guess you have a point.
Old 6th March 2018
  #7
Here for the gear
 

Thread Starter
Quote:
Originally Posted by Schoeller View Post
Tape motion sensor? It's some sort of crude incremental optical encoder with a segmented disk and two reflex light barriers generating A and B pluse trains.

As usual, the Studer service manuals are very detailed, using a DSO it whould be possible to perform some preliminary diagnosis. It's probably not even audio-related so any good maintenance specialist should be able to start helping. What I mean is that while some parts require very specific audio expertise others don't.

The speed control is not very complex but it should be first determined if issues are related to the "encoder" feedback signals (check that the slot wheel is clean as poor reflectance could randomly affect speed feedback pulse generation). Also it should be determined if the problem is related to the set value (Sollwert, valeur consigne) and its generation and/or to the servo-control of the motor or the motor itself.

Hopefully it's not the TDA1000 (p. 262/362 for the Mk II) which could be an OEM IC for Studer made by Telefunken (found that information online). That said, it would still be possible to handle speed control differently, servomotor control is a very common task and which can be performed with a very high precision. It seems parts can still be found but if not maybe it would be worth designing a new speed control system, it's relatively simple, ideally replacing the motor by something like a brushless Maxon (will require some mechanical adaptation).

Audio and tape transport functions seem quite separate so for tape transport I don't see special issues to rebuild controls if required.

Which service manual applies to your model?


Edited:
I didn't check details, especially if there's a tachymetric feedback (direct motor shaft speed acquisition).
I have the MKI. My tech hasn't been by yet to check it out. He'll be in tomorrow and see what we can figure out. From the symptoms I described he suspected the things I mentioned.
Old 6th March 2018
  #8
Lives for gear
Quote:
Originally Posted by leopold View Post
Ha! well, I searched for where other folks posted on issues they had with their B67s and quite a few were in this forum. It is a lower end Studer...but I guess you have a point.
There aren’t any lower end Studers. There aren’t even any lower end Revox.
I haven’t used a Studer since 1989 and your post reminds me of those days. I’d love to have your “low end” problem (and your Studer).
Old 7th March 2018
  #9
Lives for gear
 

A good tech who's used to service Studer reel tape recorders will probably be able to quickly find the fault.

The service manuals are really very detailed.

Overall I'd mostly only be worried about the availability of some semiconductors like custom-made ICs as well, though less critical, a couple of ICs which are COTS but hard to find nowadays. Don't know about the availability of motors and heads, I suppose those are all custom designs as even some faders are OEM designs.

As those recorders are very well built it may be worth developing some alternative control solutions (i.e. unrelated to the audio path as such) if parts become unavailable. The different drive systems are not really exclusive to tape recorders and some rebuilding would be possible but would still represent a lot of work. The easiest solution would be to rely on PLCs with motion control functions.
Old 14th March 2018
  #10
Here for the gear
 

Thread Starter
Update

Well, my tech suspects it's the guide roller bearings. The one on the left you can really tell how bad the bearings are.
Ok, so I went to a bearing spot and they sold me what's a standard bearing "625" (5x16x5) 625ZZ Bearing 5x16x5 Shielded Miniature but that one is slightly thinner than the stock Studer bearing, so the components are not functioning correctly, the caps grab etc. The stock seems to be 5x16x6 or 5x16x7. I can't seem to locate a bearing that size online. Any leads on where I can find it? Is there a Studer parts place out there?

I was thinking maybe I can use the "625" bearing and add a 1mm washer to raise the space...

Eddie
Old 14th March 2018
  #11
Lives for gear
 

625-ZZ (also written 625-2Z)

625 is the standard basic designation of the discussed bearing. All dimensions and tolerances are standardized, they're 1:1 drop-in replacements.
d= 5 mm
D= 16 mm
B= 5 mm (width)

The suffix ZZ, also written 2Z, means simply that there are 2 metallic shields (one each side). Sometimes there are additional important codes like for example C3 (increased clearance), very common for electric motor bearings but it's not the case here.

625ZZ, 625-2Z, 625-ZZ, 625-2Z are all equivalent designations. Though it's better to use the "-", as the number of digits is variable (a 6252-M is something else).

It's a common deep groove ball bearing so you shouldn't have any problem getting one. Personally I prefer SKF and FAG (Schaeffler).

The discussed bearing is cheap, just a few CHF/EUR/USD. As it's not humid you don't require stainless steel (much more expensive and reduced load performance).

I don't know where you're located but such bearings should be very easy to find. Just call the national office of SKF or Schaeffler and ask who stores such bearings. Usually there are lots of resellers stocking such common bearings.

Of course there are also other good manufacturers. Avoid no-name bearings, they can be several times less expensive but they're not worh the hassle.


Edited:
I reply about shimming in a few minutes.
I must check something in the 1382 pages PDF SKF catalog, you can download it if interested (I had to go to the media center to find it).


Edited:
Bearings for STUDER

Do you know the manual page or Studer part #?

I'd be surprised if Studer used a non-standard bearing and the discussed bearings are probably standardized since the 50's or so or maybe even before. I remember machine tools from the late 40's and IIRC the bearings were already standardized thanks to the German engineers who are over-formal and very rational. Good that many EN standards are based on DIN/VDE standards.


Edited:
According to the link, Studer part 41.99.0106 would be a 5/16/6 mm but 6 mm width doesn't seem to be a standard (or at least common) width but I haven't checked it in detail yet.

(Referring to the left tape tension roller, the one wirh the "pole wheel" acting as crude incremental encoder disk.)

Normally you can use a washer or ring to compensate the missing 1 mm tickness but you must very carefully check the mechanical design. It's probably not a problem. Check which surfaces are in contact and how forces "flow" through the assembly.

Edited:
There are two "Schnorr-style" load washers ("spacesr sleeves" in the manual) mounted in opposition supporting so I don't expect issues.
According to the drawing I can't tell exactly the type of elastic washer but that detail doesn't matter. Must not necessarily be a common Schnorr one.
Old 14th March 2018
  #12
Here for the gear
 

Thread Starter
Quote:
Originally Posted by Schoeller View Post
625-ZZ (also written 625-2Z)

625 is the standard basic designation of the discussed bearing. All dimensions and tolerances are standardized, they're 1:1 drop-in replacements.
d= 5 mm
D= 16 mm
B= 5 mm (width)

The suffix ZZ, also written 2Z, means simply that there are 2 metallic shields (one each side). Sometimes there are additional important codes like for example C3 (increased clearance), very common for electric motor bearings but it's not the case here.

625ZZ, 625-2Z, 625-ZZ, 625-2Z are all equivalent designations. Though it's better to use the "-", as the number of digits is variable (a 6252-M is something else).

It's a common deep groove ball bearing so you shouldn't have any problem getting one. Personally I prefer SKF and FAG (Schaeffler).

The discussed bearing is cheap, just a few CHF/EUR/USD. As it's not humid you don't require stainless steel (much more expensive and reduced load performance).

I don't know where you're located but such bearings should be very easy to find. Just call the national office of SKF or Schaeffler and ask who stores such bearings. Usually there are lots of resellers stocking such common bearings.

Of course there are also other good manufacturers. Avoid no-name bearings, they can be several times less expensive but they're not worh the hassle.


Edited:
I reply about shimming in a few minutes.
I must check something in the 1382 pages PDF SKF catalog, you can download it if interested (I had to go to the media center to find it).


Edited:
Bearings for STUDER

Do you know the manual page or Studer part #?

I'd be surprised if Studer used a non-standard bearing and the discussed bearings are probably standardized since the 50's or so or maybe even before. I remember machine tools from the late 40's and IIRC the bearings were already standardized thanks to the German engineers who are over-formal and very rational. Good that many EN standards are based on DIN/VDE standards.


Edited:
According to the link, Studer part 41.99.0106 would be a 5/16/6 mm but 6 mm width doesn't seem to be a standard (or at least common) width but I haven't checked it in detail yet.

(Referring to the left tape tension roller, the one wirh the "pole wheel" acting as crude incremental encoder disk.)

Normally you can use a washer or ring to compensate the missing 1 mm tickness but you must very carefully check the mechanical design. It's probably not a problem. Check which surfaces are in contact and how forces "flow" through the assembly.

Edited:
There are two "Schnorr-style" load washers ("spacesr sleeves" in the manual) mounted in opposition supporting so I don't expect issues.
According to the drawing I can't tell exactly the type of elastic washer but that detail doesn't matter. Must not necessarily be a common Schnorr one.
Thank you. Well, like I mentioned I tried that size bearing and I'll attach a link of the two bearing so you can see how there is a difference in size. I followed the diagram as to how to place the washers according to the manual.

Here is a link to the pic: Dropbox - IMG_7734.JPG


"According to the link, Studer part 41.99.0106 would be a 5/16/6 mm but 6 mm width doesn't seem to be a standard (or at least common) width but I haven't checked it in detail yet."

Yes, that's the catch, the only solution I can think of is a shim/washer of some type.

Eddie
Old 15th March 2018
  #13
Lives for gear
 

I checked some older (paper) printed catalogs of FAG, SKF, etc. and couldn't find any 6 mm wide version with 5 mm bore. Hopefully the shaft tolerance is standard.

Really very strange as I don't see any valid reason for that design choice, common metric bearing dimensions are standardized since a very long time so why did Studer use something special?

According to the explosion drawings I don't see any problem using some washer, you must just check carefully where the reference surfaces are located but in this case it isn't even critical as we don't talk about very high precision.

If you've problems sliding the bearing on the shaft you can heat the bearing if there's nothing heat sensitive (I mean with the shaft assembly removed).
Common procedure to mount bearings is to heat them, usually inductive heaters are used but you can use a hot air gun, just be careful to now overheat as it will first ruin the lubrication before damaging plastic parts (cages, seals) if present. ZZ bearings are filled with grease in the factory. You can transform as 2Z in Z or no-Z but it's irreversible as the covers are damaged when removing them.
Don't use 2RS bearings in this case due to the increased friction.

Don't use any hammer or impact tool to mount a bearing, it will damage bearing races which reduces lifetime. If using a wise or a press, only push the inner ring, the axial force is not allowed to "pass" through the balls.
Many bearings are damaged due to handling errors.

Removing a bearing is less critical (though not always easy), it's mostly about not damaging other parts, the bearing itself can be destroyed if required. There are lots of tools and methods to remove bearings. There's especially a convenient somewhat less common tool to grip a bearing between the rings but I don't know how it's called.
With such small bearings be careful to not accidentally bend the shaft.
Old 15th March 2018
  #14
Here for the gear
 

Thread Starter
Quote:
Originally Posted by Schoeller View Post
I checked some older (paper) printed catalogs of FAG, SKF, etc. and couldn't find any 6 mm wide version with 5 mm bore. Hopefully the shaft tolerance is standard.

Really very strange as I don't see any valid reason for that design choice, common metric bearing dimensions are standardized since a very long time so why did Studer use something special?

According to the explosion drawings I don't see any problem using some washer, you must just check carefully where the reference surfaces are located but in this case it isn't even critical as we don't talk about very high precision.

If you've problems sliding the bearing on the shaft you can heat the bearing if there's nothing heat sensitive (I mean with the shaft assembly removed).
Common procedure to mount bearings is to heat them, usually inductive heaters are used but you can use a hot air gun, just be careful to now overheat as it will first ruin the lubrication before damaging plastic parts (cages, seals) if present. ZZ bearings are filled with grease in the factory. You can transform as 2Z in Z or no-Z but it's irreversible as the covers are damaged when removing them.
Don't use 2RS bearings in this case due to the increased friction.

Don't use any hammer or impact tool to mount a bearing, it will damage bearing races which reduces lifetime. If using a wise or a press, only push the inner ring, the axial force is not allowed to "pass" through the balls.
Many bearings are damaged due to handling errors.

Removing a bearing is less critical (though not always easy), it's mostly about not damaging other parts, the bearing itself can be destroyed if required. There are lots of tools and methods to remove bearings. There's especially a convenient somewhat less common tool to grip a bearing between the rings but I don't know how it's called.
With such small bearings be careful to not accidentally bend the shaft.
Thank you for all of your input. I greatly appreciate it.
Old 15th March 2018
  #15
Lives for gear
 

Can you see the marking on the existing bearing? Still wondering about that odd size. I really do not see any single reason for not using a common bearing size, especially as all connecting parts are designed by Studer. Also OEM size bearings are uselessly expensive (again I highly doubt it's an OEM version for Studer, SRO could have done it but at which price?).

Usually the manufacturer as well as the basic type is mentioned, extensions are not necessarily mentioned as some sealing parts are added or not during the manufacturing process, so if grooves for seals or shields are present the rings can be same for versions with or without seals. C3 is usually marked where applicable.

No idea if the discussed bearing is commonly used elsewhere but AFAIK it's not a common industry size.
Old 16th March 2018
  #16
Here for the gear
 

Thread Starter
Quote:
Originally Posted by Schoeller View Post
Can you see the marking on the existing bearing? Still wondering about that odd size. I really do not see any single reason for not using a common bearing size, especially as all connecting parts are designed by Studer. Also OEM size bearings are uselessly expensive (again I highly doubt it's an OEM version for Studer, SRO could have done it but at which price?).

Usually the manufacturer as well as the basic type is mentioned, extensions are not necessarily mentioned as some sealing parts are added or not during the manufacturing process, so if grooves for seals or shields are present the rings can be same for versions with or without seals. C3 is usually marked where applicable.

No idea if the discussed bearing is commonly used elsewhere but AFAIK it's not a common industry size.
There are no markings on the bearing.
Old 18th March 2018
  #17
Lives for gear
 

That's sort of surprising as usually all good manufacturers mark their bearings and mostly low-end cheap crap bearings come without markings. That said, I don't know for very old bearings, maybe I'm wrong. It's just that all FAG and SKF (and formerly also SRO Schmid-Roost) bearings I remember were marked.
Old 27th March 2018
  #18
Here for the gear
 

Thread Starter
Here's what I found : Bearings for STUDER
They offer a 605 bearing with a 1mm shim/washer.

Since I already have that size bearings. I located the washers here: McMaster-Carr Part number: 91100A140

There were some identical bearings for sale online but the prices were very high and not enough in quantity.

Hope this helps anyone in the future.

Best
Mentioned Products
Topic:
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump