[Edi Zubovic]

On Wed, 20 Mar 2013 08:23:19 +0100, "Preben Friis"
wrote:

message ...

I have a Studer Revox PR99 player only that I cant keep in play,
rewind,fast forward mode unless I keep ho;ding that button
down. As soon as I let the button go it stops.
Any ideas where to look?

There is a photo-cell on the left below the heads that detects if there is
tape. If it does not "see" the tape it will disenage the transport.

/Preben Friis

--Right. At Revox B77 / PR99, that arrangement works well but does
have some quirks. Running the machine without head cover at strong
light or sunlight shining directly on the sensor ie. phototransistor
disengages the transport. Also running a thin, partially transparent,
tape, does the same. I placed a tiny drop of black lacquer at the top
of the IR LED, thus making it a kind of floodlight source; this solved
the thin tape problem. Even taking a close-up photography with a flash
of the tape-end sensor while the machine is on can reportedly blow the
phototransistor and possibly the first transistor thereafter. Please
check the service manual for PR99, Section 7/7.

Place your finger over the sensor opening and run the machine. If it
disengages while the opening is covered, then there is a fault.

All the best,

Edi Zubovic, Crikvenica, Croatia