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  #1  
Old 09-13-2017, 12:40 PM
chapai's Avatar
chapai chapai is online now
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High Five Revox B77 few questions and motor run cap

Hi,
Get a B77, so went in restoration and research.
Read a lot of threads but do not have a complete understanding.

1) first, do the A77 and B77 capstan motors exchangeable?
so can I buy 7/15ips A77 motor and put in B77?
a77 motors available and cheap, but b77 not.
I know about changing speed in the capstan controller with cap replacement but prefer a deal with the Revox way.

(popular simple recommendation posted by Arian Jansen with reusing caps from other boards - incorrect. at least wrong caps type, with parameters like capacitance drift versus temperature and ppm + precision).

and curious - anybody tries to build quartz controlled? (other than 200EUR Revoxonline.de, which IMHO too much).

2) motor run caps. B77 have three of them 2x3.3uF (on schematic 3.5uF) and 4.3uf. The old and sticky, look like rubber deteriorated and oil(?) spilled. Probably old paper /oil caps. So plan to replace with PP.

I check mouser, etc, and most available 3uf and 4uf.
no 3.3 and 4.3. Is it any big and important difference?
Yes, I know eBay sales, but they offer a cheap Chinese or Taiwan caps for the 100x price.
I prefer good reputable vendor other than noname, even peoples claim "special order" etc.
Any experience with go 3uf and 4uf on real devices?

3) tantalum. should I replace with good electrolytic, like nichicon or still go with tants.
On the controller boards, etc. they are pretty small and not enough space for the el's.
Other than that - any specific thought why they use tants over the regular el caps? Why I am asking: on capstan board, for example, capacitors are chosen according to temperature behaviors to compensate drift, so very fine details accounted for.

5) how the wima polyester survive over the years? it 1977 mark on most parts. but it is not easy to find a proper cap (mks, fkc, fkp)with size to fit.

6) bearing replacement - any recommendations? in terms of noise and precision. Capstan kind of noisy.

7) trimmers/pots. This very interesting moment as I can not find a source.
B77's look old and flaky, so definitely should be replaced.
all trimmers on the board have a 5mm between legs line, modern- 2.54mm.
I check all stores but no flat trims anymore, only plastic sealed and smaller.
Any particular places, recommendations? other than drilling boards.

thanks
  #2  
Old 09-13-2017, 01:00 PM
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dhnash dhnash is offline
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You might want to check out this website from one of our sponsors (Erhard Audio). Some of the parts you are asking about are offered by them.

http://www.revox-r2r.com/
  #3  
Old 09-13-2017, 01:14 PM
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Thanks, I already saw them. Nice faceplate design idea.
But I am more interested in common part stores.
  #4  
Old 09-13-2017, 01:18 PM
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steerpike steerpike is offline
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Quote:
Originally Posted by chapai View Post
1) first, do the A77 and B77 capstan motors exchangeable?
so can I buy 7/15ips A77 motor and put in B77?
No, the are not the same. B77 motor has 'clean' holes, A77 holes are threaded. You MIGHT be able to drill out the holes.

Quote:
2) motor run caps. B77 have three of them 2x3.3uF (on schematic 3.5uF) and 4.3uf. The old and sticky, look like rubber deteriorated and oil(?) spilled.
The caps looking sticky is OK. Only if you can see that fluid has leaked out (drops on other parts) that is a problem.

Quote:
I check mouser, etc, and most available 3uf and 4uf.
no 3.3 and 4.3. Is it any big and important difference?
Any experience with go 3uf and 4uf on real devices?
You CAN use 3.0uF of 4.0uF, since the caps are only accurate to 10% or so, so you are just on the limit of the specification. But you can also parallel a 0.3uF capacitor across the 3.0uF to get the right capacitance. The motor will run cooler and have more torque with the correct capacitor.

Quote:
3) tantalum. should I replace with good electrolytic, like nichicon or still go with tants. On the controller boards, etc. they are pretty small and not enough space for the el's.
Other than that - any specific thought why they use tants over the regular el caps? Why I am asking: on capstan board, for example, capacitors are chosen according to temperature behaviors to compensate drift, so very fine details accounted for.
Aluminium Electrolytics will fit. I have not had any problem finding small enough ones. The type is not important, they are not precision types or temperature critical in the B77.

Quote:
5) how the wima polyester survive over the years? it 1977 mark on most parts. but it is not easy to find a proper cap (mks, fkc, fkp)with size to fit.
They survive well. no need to replace.

Quote:
7) trimmers/pots. This very interesting moment as I can not find a source.
B77's look old and flaky, so definitely should be replaced.
all trimmers on the board have a 5mm between legs line, modern- 2.54mm.
I check all stores but no flat trims anymore, only plastic sealed and smaller.
Any particular places, recommendations? other than drilling boards.
Use a better component supplier. Replacement types are available from companies like Piher. The style does not matter, as long as the pin spacing is the same - Piher DO make all these types. Sealed plastic types are fine.
  #5  
Old 09-13-2017, 01:44 PM
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chapai chapai is online now
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Quote:
Originally Posted by steerpike View Post
No, the are not the same. B77 motor has 'clean' holes, A77 holes are threaded. You MIGHT be able to drill out the holes.
can you explain, please?

Quote:
The caps looking sticky is OK. Only if you can see that fluid has leaked out (drops on other parts) that is a problem.
Hmm. Not sure that they designed that way. Also, rubber sealant in the cups devulcanized. IMO better to replace.

Quote:
You CAN use 3.0uF of 4.0uF, since the caps are only accurate to 10% or so, so you are just on the limit of the specification. But you can also parallel a 0.3uF capacitor across the 3.0uF to get the right capacitance. The motor will run cooler and have more torque with the correct capacitor.
it is no place to put extra caps. for the paralleling I should add another motor run cap with a screw. Do not want drill extra holes in the frame, and it is not easy to do.

Quote:
Aluminium Electrolytics will fit. I have not had any problem finding small enough ones. The type is not important, they are not precision types or temperature critical in the B77.
good point. it is about 3-4mm space, plus legs should be 5mm wide.

Quote:
Use a better component supplier. Replacement types are available from companies like Piher. The style does not matter, as long as the pin spacing is the same - Piher DO make all these types. Sealed plastic types are fine.
Thanks.excellent. Never heard about this company but look like they do what I need. May be you can recommend any other European manufacturers? and where I can buy that (piher, etc) as it not available in the US.
  #6  
Old 09-13-2017, 01:49 PM
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dhnash dhnash is offline
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Quote:
Thanks, I already saw them. Nice faceplate design idea.
But I am more interested in common part stores.
If you scroll to the bottom of the page I sent the link for to you will find additional links to other pages on the website including this one which I think will be of more interest to you:

http://www.revox-r2r.com/upgrade-kits.html

Quote:
Quote:
Use a better component supplier. Replacement types are available from companies like Piher. The style does not matter, as long as the pin spacing is the same - Piher DO make all these types. Sealed plastic types are fine.
Thanks.excellent. Never heard about this company but look like they do what I need. May be you can recommend any other European manufacturers? and where I can buy that (piher, etc) as it not available in the US.
Regarding your interest in trimmers, the home page of the website shows the following:

Quote:
We only use name brand capacitors, such as Nichicon, Panasonic, Vishay, Philips etc, and where ever possible, audio grade capacitors are used, which make up about 95% of each kit.
For the trimmers, we use the Piher brand.
For the transistors, we mainly use Fairchild, to ensure quality and reliability.

Last edited by dhnash; 09-13-2017 at 01:55 PM.
  #7  
Old 09-13-2017, 02:05 PM
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chapai chapai is online now
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Thanks. so confirmed that Piher works.
Will go to do some research in datasheets, to understand the difference.
  #8  
Old 09-14-2017, 04:56 AM
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steerpike steerpike is offline
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Quote:
Originally Posted by chapai View Post
can you explain, please?
The A77 motor has holes in the mounting plate that are cut with a thread, for the bolts to screw into. The B77 motor has clean holes, the thread for the bolt is part of the tape deck chassis.

Quote:
Hmm. Not sure that they designed that way. Also, rubber sealant in the cups devulcanized. IMO better to replace.
A small amount of leakage is OK, since the cap will still work, but it is ageing. I mean that only if drops of liquid ar dripping out, then it is essential to replace - the cap is finished.

Quote:
it is no place to put extra caps. for the paralleling I should add another motor run cap with a screw. Do not want drill extra holes in the frame, and it is not easy to do.
A 0.3uF 200V capacitor is small. It can be soldered onto the tags of the chassis-mounted can capacitor.

Quote:
May be you can recommend any other European manufacturers? and where I can buy that (piher, etc) as it not available in the US.
Have a look at RS Components. They have a very good range.
  #9  
Old 09-14-2017, 06:11 PM
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chapai chapai is online now
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Quote:
Originally Posted by steerpike View Post
The A77 motor has holes in the mounting plate that are cut with a thread, for the bolts to screw into. The B77 motor has clean holes, the thread for the bolt is part of the tape deck chassis.
ok, this means that taper tool can do the job. thats fine. Thanks.
But do the motors the same? I am looking to try 7/15 motor to speed up.

Quote:
A small amount of leakage is OK, since the cap will still work, but it is ageing. I mean that only if drops of liquid ar dripping out, then it is essential to replace - the cap is finished.
I did some research - this is probably a paper-oil cap by ITT. Phase shifting and foil, not a metalized film. As soon as it dries it can loose a capacity, and affect a motor start or short cut inside. The paper cups do not have a self-healing feature.
Replacement about $5-$7 per cap. Only it was concern about capacity. Now you can't find true 3.3uF and 4.3uF.
The best scenario 3.5 and 5.
Most of the Revox part sites offer a 4uF and 5uF. Look like it should be ok.

Quote:
A 0.3uF 200V capacitor is small. It can be soldered onto the tags of the chassis-mounted can capacitor.
Not sure. This is some reasons to have a run cap, different from the regular. Even it is not s dryer, it still has high current spikes and high voltage load.
Run cap designed for that and use a foil inside, not a film or any thin layers. The regular cap will work for some time, but not the same, in terms of current throughput, spikes etc and will burn accidentally.
As Germans design this device carefully, the patch is not a proper engineering way to do so. :-)

Quote:
Have a look at RS Components. They have a very good range.
Thanks. I check it. Unfortunately, they don't have a Piher or ACE. Look like those only two companies to supply wide legs trimmers(5mm).
All other 2.54mm, standards.

I did my research yesterday. As a result, European companies won't ship to the US, and they have a very limited line of the Piher trimmers. Mouser has but 2.54 version.
eBay sellers have them but sell only in a bunches of the same and at least $2 per item, with original price about $0.30 (what I don't like personally, to overpay).
Just need 17 trimmers for my B77, 6 different resistances.
Will keep looking at the options.

Last edited by chapai; 09-14-2017 at 10:13 PM.
  #10  
Old 09-14-2017, 06:19 PM
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evoroadster evoroadster is offline
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From my research I became aware that A77 capstan motors from serial numbers D15500 to G16150 run on a 20 volt higher supply than the later motors. So choose wisely!
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  #11  
Old 09-14-2017, 10:12 PM
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chapai chapai is online now
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thanks, good point.
  #12  
Old 09-15-2017, 12:32 AM
vinro vinro is offline
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trimmers etc

For Piher trimmers Search e-bay for seller saunabaubraunbraungmbh
then search in his shop for Trimmersatz
unit cost about .67 euro..
I think Mousers were about .40

However factor in your time and in my opinion just get a full set from Holger..
great quality..modest profit..he has Piher trimmers in there
I'm in UK at present and had a set shipped over..better quality components than any other kit out there..

I couldn't justify all the time it was taking to nail down the best components at best price..
Mouser/Digi-Key/RS/Farnell..
No-one had everything..factor in shipping costs..
Best option was a decent kit..
and I have no connection with him or anyone else..

all best
v
  #13  
Old 09-15-2017, 04:43 AM
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chapai chapai is online now
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Thanks for the recommendation of that long-nickname-guy. He has a lot of very interesting things and reasonable prices.
But time does not matter in terms of a hobby. few month, year, what a problem?

I read the datasheet for every detail I order, and then often do a research of the parameters meaning and some deep details. As it an engineering hobby.
Noise difference carbon via cermet? Done! (c) Skyfall
Why do Revox use a different type of caps in capstan controller or what exactly different in a motor run caps vs regular cheap Wima PP? Done! (c )Skyfall
:-)

It is not a waste of the time. This is a learning process.

Last edited by chapai; 09-15-2017 at 05:13 AM.
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