Revox A77 Service Manual

— Loosen brake manually ( push in solenoid core ).
— Check if both brakes clear simultaneously; if not uns-
crew the 3 chassis fasteners partly, slide chassis around
till both bands are clear.
— If necessary, bend one brake adjustment lever.
The solenoid has to be energized for adjustment.
— Cover light at the optical end- of- tape switch.
— Depress " Reel Motors off " ( 42 ), depress button <<
( fast rewind ).
— Loosen fastening of solenoid and reset so that the bands
clear rollers by from . 1 -. 2 mm ( . 040 " to. 080" )
— Secure solenoid during this adjustment. Braking torque
can be varied by hooking springs at different places on
the brake adjustment lever.
4.4. Pressure Roller
The pressure lever is actuated electromechanically. Pressure
is set by the variable spring force ( fig. 4.4 — 25 ).
4.4.1. Pressure Measurement
— Load tape with 1 kHz record.
— Switch on PLAY.
— Tie nylon thread to pressure roller axis I or to a pin
affixed thereto )
and pull with a spring scale ( or contactor ) in sense A
sound volume drops noticeably.
The spring scale must show 1.5 kg ( 3.3 lb. av ).
— Screw C sets pressure force.
Fig. 4.4-25
A
1,5 kg
3.31b.av I
0,3 mm
(D12")
4.4.2. Pressure Solenoid Readjustment
— Switch instrument to PLAY. If no tape is loaded, cover
light at optical end- of- tape switch.
— Slide pressure solenoid to the right gap B ( fig. 4.4-25)
is . 3 mm ( . 012 " )
— Block pressure solenoid.
— Check if.solenoid core is in end position. The core shall
not move if the lever is pulled slightly from the capstan
axis.
— Secure fasteners of solenoid with a drop of lacquer.
— Check pressure, reset screw C if necessary.
4.4.3. Exchange of Pressure Roller
— Hold pressure roller axis at groove from above ( fig.
4.4 — 25 ) and remove bolt fastening E to the side.
— Pull pressure roller axis up and roller to the side. Reas-
sembly is explained in the replacement parts list.
Make sure that no cleaning fluid gets to the sintered bearing
while cleaning the roller.
4.4.4. Pressure Lever Readjustment
After exchanging the pressure lever, it is necessary to read-
till just it with respect to lever F ( fig. 4.4 — 25 ). When the
lever is stopped I solenoid core fully out 1, the distance
between capstan shall be 10 mm
( . 4" ).
axis and
pressure roller
o
o
o
14

Revox A77 Specifications

General

Wow and Flutter	0.08% (7 1⁄2 ips)
Frequency Response	30Hz to 20kHz (7 1⁄2 ips)
Signal to Noise Ratio	60dB
Type	Reel-to-Reel Tape Deck
Track System	4-track, 2-channel stereo/monaural
Reel Size	Up to 10.5 inch reel
Motor	2 x reel, 1 x capstan
Inputs	Mic, Line
Outputs	Line
Tape Speed	3 3⁄4 and 7 1⁄2 ips