Playback Amplifier - Revox G36 Service Manual

Adjustment of four track heads
This is a highly delicate operation as with a track separation of only 3/16", slight
inaccuracies in head alignment cause a track overlap and lead to the very annoying
"dead channel" cross-talk.
Where a four track recorder is under examination, it is advisable to obtain the
REVOX four track alignment tape.
Relevant instructions are included with the tape.

3.1.4 Playback amplifier

Before any tests are made on the playback section of the recorder, it is essential to
ensure that the sound heads are scrupulously clean; minute particles may cause false
readings by partially lifting the tape off the heads.
Connect a VTVM to the cathode follower output of each channel in turn. A reference
signal recorded at 32 millimaxwell per 1 mm of tape width should give an output of
approximately 3 db below that specified in the technical data (refer to 5.). The
frequency response section of the calibration tape is normally recorded 20 db below
this level for measuring the performance characteristics of the playback channels.
A response of + 2/-3 db referred to the level at 1 kc/s is acceptable. Where
unsatisfactory figures are obtained it is advisable to replace the playback head as
outlined in 3.1.3. and take new readings. Should this not bring about the desired
improvement, the playback pre-amplifier should be examined. Remove the earth
connection of the playback head and insert a 10Ω resistor in series (fig.10.)