Revox A77 restoration

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  • SeleniumFalcon
    SeleniumFalcon Posts: 3,539
    edited January 2022
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    There's been some recent progress on reducing the "grumbling" sound of the capstan motor on the deck I've been refurbishing. This effort became a tale of two motors. One motor was from my parts collection which I sent to an eBay seller who claimed to be able to restore, using proprietary techniques, Revox capstan motors. This process became a bit of, "the dog ate my homework" and as a result I began losing faith. So, on to "plan B". I bought a Mark IV capstan motor from a source located in Belgium that I have received. The reason for the IV version of the motor is that they use two sintered bronze bearings instead of the earlier motors which use a combination of ball bearing and sleeve bearings. It is felt these later motors tend to be quieter. However they require a different lubricant than the earlier versions. So, I have ordered from Nagravox in Australia a bearing overhaul kit and a new tachometer sensor which should arrive soon.
    Before that I needed to build a motor mounting jig to hold the motor while removing the rotor. I used some scrap wood and built this.

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  • SeleniumFalcon
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    Here is the motor in place in the jig.

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  • SeleniumFalcon
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    I have heard from the eBay seller that he finished the motor (after a little prodding from eBay) and has shipped it yesterday. So, good news, hopefully.
    I have received a set of upper and lower front panels from Sweden and have polished the upper panel so I can replace the one I now have with a less battered version.
    The overhaul kit from Nagravox seems to be waiting in Sydney for an available air cargo flight. No worries, mate!
  • pitdogg2
    pitdogg2 Posts: 24,676
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    At the beginning of covid i had to wait for more than 3 months for a set of rectifier tubes. It was a two week quarantine before it could be loaded on the ship and once at our port another 2 weeks of quarantine plus time in transit on the boat and transit to my house. Times have gotten much better now.
  • SeleniumFalcon
    SeleniumFalcon Posts: 3,539
    edited February 2022
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    The eBay seller has sent me some photos of the motor.

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  • SeleniumFalcon
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    This is a photo of a stock Revox B77 (the successor to the A77):

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    This is a photo showing the work of a company who has made replacement faceplates and cabinet:

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  • ts8051
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    The wooden cabinet was in good shape, a few scuffs. The first step was to Flitz polish all of the plastic areas, clean with a plastic cleaner and use a car wax to give some protection. I treated the wooden part of the cabinet with a General Finish brand furniture cleaner a few times and then used Watco Danish Oil.

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    Hello, I also have a Revox A77 which needs service and please let me know how can i repair the wooden case which is broken on the upper side of the case. What material is it? Is there a shop which sales this material in order to repair the case?
  • SeleniumFalcon
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    Hello,
    I believe the wood cabinet is made from birch plywood with a thin veneer of another wood. I think Revox used a couple of different veneer woods, teak being the most prevalent (a very popular wood in Scandinavian countries). Usually a deck gets dropped or banged against something and the cabinets are damaged. As far as repairing them you might want to remove the deck from the cabinet and bring it to a furniture repair shop. A friend of mine showed me how to remove the chipped veneer and replace it with a veneer patch a while ago. Another answer is to keep an eye on eBay and there are replacement cabinets for sale. I've done that a few times.
    Good luck!
  • mateusfig
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    Thank for all this information! Did you finish the last steps? I'm looking forward.
  • SeleniumFalcon
    SeleniumFalcon Posts: 3,539
    edited February 26
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    Hello,
    Welcome! Yes, after some procrastination I exchanged the grumbling capstan motor for a MK IV motor which uses two ball bearings instead of a single ball bearing combined with a sintered bushing. Then I had to recalibrate the speed adjustment. The result is a completely quiet deck that sounds great. Here is a photo of it connected to a Dolby 422 unit playing some tapes I made 40 some years ago. A great way to hear how my system sounded then.

    9b4jkdo7t0dv.jpg
  • mateusfig
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    WOW! This is so cool! Your machine is awesome!
  • SeleniumFalcon
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    Thank you, it turned out quite nice. Now I am working on refurbishing another one, not a complete frame up restoration. Just a basic overhaul covering the important things that need to be done to any A77. Motor bearings, replace all the aging capacitors, trim potentiometers and general cleaning.
  • mateusfig
    mateusfig Posts: 3
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    Here's another photo of the board from a different angle.

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    Is it possible to describe what new relay did you use as replacement? Seems like Omron brand, 12vdc, but I'm not certain.
  • SeleniumFalcon
    SeleniumFalcon Posts: 3,539
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    They are Omron MY4-DC12 (S) relays from Mouser.
  • ohnojkd
    ohnojkd Posts: 1
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    After getting some metric sheet metal screws, from McMaster Car, to attach the cabinet to the chassis I can see how things look. In general terms everything looks good, the upper face plate is a bit blotchy depending upon what angle I look at it. The real problem is the capstan motor is making a low level rumbling sound amplified by being inside the enclosure. I can't live with that, I'll have to figure out what's the cause, I replaced the bearing. The shaft may be bent.

    q2lrjc66rs5g.jpg

    Incredible! Can you share what dimensions you chose for the sheet metal screws from McMaster? I am installing a cabinet but it didn't come with the hardware, nor does the service manual appear to specify the length. Maybe you can share a link? Thanks!
  • SeleniumFalcon
    SeleniumFalcon Posts: 3,539
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    Hello,
    They are M4 screws, with a pitch of 1.5 and a length of 25mm with a McMaster Carr part number of 92470A371 stainless steel. The original Revox uses a washer on each screw.