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Author Topic: Revox A77 - Brake drum belleville washer  (Read 9540 times)

Offline oceansmoving

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Revox A77 - Brake drum belleville washer
« on: September 06, 2013, 02:10:08 AM »
So, I've been having problems with grinding noise at FW. It is probably caused by worn felt on drum so I'm gonna replace the brake drum.
Took it apart yesterday to see if previous owners has done any changes and I just need to double check something with you.

The belleville washer highlighted in my attachment, which way it it supposed to be mounted.
Convex side facing screw or vice versa?

Joakim Jensen
Gothenburg, Sweden

Offline Tim

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Re: Revox A77 - Brake drum belleville washer
« Reply #1 on: September 06, 2013, 10:47:17 AM »
Grinding noise during fast wind is likely not a problem with brake drum lining.  In fast-wind mode, the brake bands do not (should not) contact the drums.

-check left tape guide ball-bearing or counter as sources for noise during fast-wind .

-If you have noise only when stopping from fast wind, then you could have defective (sticky) brake drum linings.  That sometimes can be repaired by cleaning the brake bands and baking the drums. Baking can remove the stickiness of the drum lining cloth.

To answer your original question, concave side should face screw.  Both orientations will work, however. It's not critical.
« Last Edit: September 06, 2013, 02:43:46 PM by Tim »
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Offline oceansmoving

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Re: Revox A77 - Brake drum belleville washer
« Reply #2 on: September 06, 2013, 03:18:27 PM »
Thanks, I'll check that out!
By the way, tape is wound really close to the inside of the take up reel and I've been looking into the alternative to remove the height adjustment washer (part 16)
Is that safe to do without inducing more ware to the brake parts or emergency precaution only?
Joakim Jensen
Gothenburg, Sweden

Offline Tim

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Re: Revox A77 - Brake drum belleville washer
« Reply #3 on: September 06, 2013, 03:35:17 PM »
Washer 16 is how you adjust reel table height (by removing or adding).  Changing the height by small amounts does not effect brake wear. Be aware that 7" plastic reels and 10" metal reels have different heights.  If you want to use both size reels, adjust reel table height for 7" plastic reels and then use rubber spacing pads when using 10" reels (or use an NAB adapter with a built-in spacer. Some Teac adapters have that feature)
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Offline docb

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Re: Revox A77 - Brake drum belleville washer
« Reply #4 on: September 06, 2013, 03:57:53 PM »
FWIW that spacer is typically about .025" thick. And so is the cardboard on a cereal box.
Coincidence? I don't think so.
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Offline oceansmoving

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Re: Revox A77 - Brake drum belleville washer
« Reply #5 on: September 09, 2013, 05:51:22 AM »
Thanks a lot!
Joakim Jensen
Gothenburg, Sweden

Offline oceansmoving

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Re: Revox A77 - Brake drum belleville washer
« Reply #6 on: September 09, 2013, 05:54:41 AM »
Grinding noise during fast wind is likely not a problem with brake drum lining.  In fast-wind mode, the brake bands do not (should not) contact the drums.

-check left tape guide ball-bearing or counter as sources for noise during fast-wind .

-If you have noise only when stopping from fast wind, then you could have defective (sticky) brake drum linings.  That sometimes can be repaired by cleaning the brake bands and baking the drums. Baking can remove the stickiness of the drum lining cloth.

To answer your original question, concave side should face screw.  Both orientations will work, however. It's not critical.

I get the same noise as in this video, only from the right side:
http://www.youtube.com/watch?v=8h8421oWOOQ
There the noise disappears as soon as the break band is removed, so to me it looks like a worn felt.
Joakim Jensen
Gothenburg, Sweden

Offline ironbut

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Re: Revox A77 - Brake drum belleville washer
« Reply #7 on: September 09, 2013, 12:19:46 PM »
Nice video! (Even though I don't speak a word of French)
Now, I wonder if that brake lining tape can still be found?
If so, it sure would be a lot cheaper than replacing the drums.
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Offline oceansmoving

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Re: Revox A77 - Brake drum belleville washer
« Reply #8 on: September 10, 2013, 12:12:40 AM »
Nice video! (Even though I don't speak a word of French)
Now, I wonder if that brake lining tape can still be found?
If so, it sure would be a lot cheaper than replacing the drums.

I think it is, especially in the US but I managed to find a drum in a refurbished state for a reasonable cost so went with it.
Joakim Jensen
Gothenburg, Sweden

Offline Tim

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Re: Revox A77 - Brake drum belleville washer
« Reply #9 on: September 10, 2013, 03:42:18 PM »
The noise on the video sounds exactly like the counter squealing (as I already suggested).  It's a very common problem that I have observed many times in A77 decks. During fast wind, the brake bands do not touch the brake hubs (or they should not). If the band is rubbing the hub during fast wind, you should fix that.

The brake hub material does not "wear out".  As I stated before, the original glue for the hub cloth migrates to the surface and can make the hubs sticky. That would cause other defects, however. 

Also, when you removed the brake band, did you also remove the counter belt?

 

« Last Edit: September 10, 2013, 03:50:11 PM by Tim »
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Offline oceansmoving

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Re: Revox A77 - Brake drum belleville washer
« Reply #10 on: September 10, 2013, 11:22:39 PM »
You are absolutely right Tim, it was the counter.
Counter belt isn't touching the hub or the brake band, sounds like it's coming from the actual counter (gears) rather that friction from the belt.
I removed the belt for now, any tips on how to fix that?

By the way, removing the height washer solved the winding issue, someone previous to me had even put two washers on the left side.
« Last Edit: September 10, 2013, 11:26:17 PM by oceansmoving »
Joakim Jensen
Gothenburg, Sweden

Offline Tim

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Re: Revox A77 - Brake drum belleville washer
« Reply #11 on: September 11, 2013, 01:20:19 AM »
Who said the noise was the belt rubbing the band or hub ("friction from the belt")?  I didn't. I told you it was from the counter. 

It's not from the "counter gears" as you stated. It's counter pulley bearing chatter (due to dried up lubricant). Pull the counter pulley off it's shaft, remove the shaft.  Then cln/lube the shaft & bearing.

Any particular reason you ignored my advice (and had to be told twice what the defect was)? I carefully explained why it was not the reel hub and that it was likely the counter and yet you kept going on about your "defective brake hub". 
Tim Leinbaugh
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Offline oceansmoving

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Re: Revox A77 - Brake drum belleville washer
« Reply #12 on: September 11, 2013, 02:04:10 AM »
Tim, English is not my native tounge so "sorry" for the misunderstandnings.
Technical terms in combination with translation is gonna cause that.
I had already ordered a new drum when this thread was created so I didn't "ignore" your advice, even thoug that video seemed to suggest noise disappeared with counter still engaged, but must have seen wrong.

I'm not 100% sure which part you mean with "pulley bearing".

Btw, mine is missing the small toothed band. Are there versions without it or has is simply been "lost"?
« Last Edit: September 11, 2013, 02:06:49 AM by oceansmoving »
Joakim Jensen
Gothenburg, Sweden

Offline Tim

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Re: Revox A77 - Brake drum belleville washer
« Reply #13 on: September 11, 2013, 11:45:10 AM »
Buy the toothed counter belt from eBay.  Search "Revox belt" and you will see many purchase options.

Pulley is the white round disk that the belt threads onto.  Pulley shaft is a metal rod the pulley is attached to.  "Bearing" refers to the hole in which the metal shaft resides.

 
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Offline oceansmoving

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Re: Revox A77 - Brake drum belleville washer
« Reply #14 on: September 12, 2013, 12:56:19 AM »
Thank you
Joakim Jensen
Gothenburg, Sweden