Got a Revox B790, no power when plug in. Power board had a Cap that was shorted and broken power switch. Repaired power switch, Rebuilt power board( caps, thermistors, bridge rectifiers, and regulators), recapped all electrolytics on other boards. TT now turns on, digital LEDs light, motor spins, arm moves, cartridge raises and lowers. Voltage from Power board appear in spec. Great, but here are the problems:
1. When first turn on, motor turns on briefly then stops, even before the tracking arm is moved into position
2. The LED display turns off when arm is moved into tracking position.thus no reading of rpm is possible
3. the motor has a clicking sound ( when motor is manually spun (not turn on) no clicking/ noise noted
1. When first turn on, motor turns on briefly then stops, even before the tracking arm is moved into position
2. The LED display turns off when arm is moved into tracking position.thus no reading of rpm is possible
3. the motor has a clicking sound ( when motor is manually spun (not turn on) no clicking/ noise noted
With point 1&2 I can't help...pull the ICs out and see if the legs are tarnished, especially the ones of the tonearm PCB.
With point 3 I might help. Post a video (with sound) of the platter spinning (capture the display as well) and change speed 33-45 a few times - let them ran for a bit before changing.
Then take a same one without platter.
By platter spinning I mean tonearm-gantry swung in...or out to the right.
With point 3 I might help. Post a video (with sound) of the platter spinning (capture the display as well) and change speed 33-45 a few times - let them ran for a bit before changing.
Then take a same one without platter.
By platter spinning I mean tonearm-gantry swung in...or out to the right.
Once again...regarding clicking/clacking...@Thmartin has a reason to like my post. Not only that; he is way more experienced/knowledgable, than I ever will be.
You don't need another motor, for sure - well, almost...nobody experienced everythin going bad in course of decades.
PS: Thierry, as you know, I'm downloading every free crap about Studer-Revox...auidolalies - your excellent blog - I can't find. Is there any way you can supply me with a mirror, or the likes?
You don't need another motor, for sure - well, almost...nobody experienced everythin going bad in course of decades.
PS: Thierry, as you know, I'm downloading every free crap about Studer-Revox...auidolalies - your excellent blog - I can't find. Is there any way you can supply me with a mirror, or the likes?
I was working off this post: https://audiokarma.org/forums/index.php?threads/revox-b790-underdamped-speed-regulation.910432/
THis guy had a problem with the hall sensor and motor clacking
JIm
THis guy had a problem with the hall sensor and motor clacking
JIm
Hello friend,
Unfortunately my website crashed and went belly up years ago, and - stupid me - I couldn't retrieve any backup. All I can provide is a link to the photo albums I saved on Google images library. For instance :
https://goo.gl/photos/jAx9vhrewXwGKhXo8
https://photos.app.goo.gl/f2AmcG2stQjSRcd13
True.
First thoughts that come to mind :
1. When first turn on, motor turns on briefly then stops, even before the tracking arm is moved into position
Normal behaviour, both B790s I restored did the same.
2. The LED display turns off when arm is moved into tracking position.thus no reading of rpm is possible
If the phase loop driving electronics is unable to "lock" on proper frequency this is normal. Fix the driving board, Service Manual is easily available online and it contains a precise description of how this driving circuit works.
3. the motor has a clicking sound ( when motor is manually spun (not turn on) no clicking/ noise noted
Likely an unwanted mechanical contact somewhere under the platter. Its height has to be perfectly adjusted, Studer used ultra-thin washers to ensure correct level and height.
Way back in the early 90's I ran a 790 for a few years. It's a one of a kind beast. Beware of warped records and I hope your not running a fragile thin cantilever. I lost a fine sapphire one which I'll never forget. I had it rebuilt with ruby but it was never the same afterwards. So had a 791 and I thought the 90 was better.
DD
DD
It really is a one of a kind TT. And quite enjoyable. Your in good shape unless you hear something above baseline with the aid of a stethoscope. Naturally, your shouldn't hear any out of balance electronic triggered nonsense. Unfortunately, I was never able to clean my 790 completely up years ago. The same can be said for any, and especially DD systems. So the stethoscope almost always tells the tale. Make sure to use it if tweeking adjustments.
DD
DD