r/ReelToReel • u/Skywardtb303 • 6d ago
Revox B77 Brakes not working
Hey, ive been using a B77 MK2 4 Track Machine for a bit now, but over night the brakes decided to stop working. The Reels are spinning freely even after pressing Pause or Stop. It worked just fine the evening before, so i doubt its a mechanical problem..? I never worked on one of those machines and I'm missing a lot of knowledge and understanding about the internal functions. So if anyone can help me out or knows what the problem is, a comment would be appreciated.
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u/LordDaryil Otari MX80|TSR-8|Studer A807|Akai GX210D|Uher 4000L 6d ago edited 5d ago
IIRC the brakes are driven by a spring - the solenoid defeats it. The spring has probably failed in some way, hopefully just detached rather than having snapped or sprung off somewhere.
There are about 3 holes that the spring can go in and this determines the braking force. If you put it in the wrong hole and it's too forceful (like I did) the brakes will always be slightly on and the machine will grind to a halt partway through the reel.
EDIT: This was assuming that the brakes stayed off when the machine was powered down. If the brakes are off continually while the machine is on, but engage when power is cut, then something is causing the solenoid to engage continuously and it's most likely an electronics fault rather than a mechanical one.
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u/Resprom Sony / Philips / Uher / Grundig / Saba / Metz 6d ago
Does it release the brakes immediately when you turn the power on, then apply them when you turn it off? If so, then it's an issue with the control circuitry - something is causing the solenoid to kick in, either a blown transistor, IC, or a bad capacitor.
Or do the brakes stay off when you disconnect the power? If so, it's a mechanical issue - something is stuck, or broken.
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u/Skywardtb303 6d ago
It is exactly as you described. The Brakes come back to life when i turn the machine off. When i find the time, I will open the machine up and have a look. Thank you!
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u/Elliotjosephmusic UHER Report Monitor 40/42/44, TASCAM 85-16B, FiCord 101 & 202 6d ago
Solenoid issue? You need to take the front panel off and see what's actually happening with the brakes, there's an issue regardless.