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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 21st Jan 2017, 10:40 pm   #1
JohnROH
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Default Revox B77 MkI-4 track

Switched on machine - loud bang and smoke coming from top vents! Rubber on pinch wheel partially melted. Any thoughts on possible cause. The machine was purchased in 1977 and serviced five years ago. No previous problems.
HELP!
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Old 22nd Jan 2017, 12:56 am   #2
AC/HL
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Default Re: Revox B77 MkI-4 track

I've no particular knowledge of this machine, but a common cause seems to be the mains filter capacitor self destructing. A Forum search (top of page) on Revox or Rifa will give chapter and verse. The decomposed pinch wheel will have no connection with the fireworks.
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Old 22nd Jan 2017, 1:05 am   #3
Ted Kendall
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Default Re: Revox B77 MkI-4 track

This is two separate faults. Some pinch wheels (particularly green ones) turn to goo - replacement is the cure. Nagravox do a good one if you can't find an original. The fireworks are caused by a 470nF Rifa capacitor across the mains input socket. It fails due to moisture ingress when the encapsulation fails. This and a similar component on the capstan drive board should be replaced. It's alarming when it happens, but doesn't cause other damage.
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Old 30th Mar 2017, 2:06 pm   #4
MikeCross
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Default Re: Revox B77 MkI-4 track

Had lots of these capacitors go. Lots of smoke but little other damage.
Easy to spot as the body usually cracks apart.
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Old 30th Mar 2017, 7:03 pm   #5
Kentode
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Default Re: Revox B77 MkI-4 track

Before they go bang they look like this.
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