Echoplex Bias Adjust and Alignment

Echoplex Bias Adjust and Head Alignment

EQUIPMENT REQUIRED
OSCILLOSCOPE, Audio Signal Generator and VU meter or AC Voltmeter.

CONTROL SETTING
Set ECHO VOLUME to MAXIMUM, ECHO SUSTAIN to MINIMUM and ECHO DELAY to MAXIMUM.

BRIDGE ALIGNMENT
Loosen screws holding bridge, and tighten them while spacing bridge approximately 1/8 inch from cover studs located near each end of bridge.

HEAD ALIGNMENT
A) Using your eyesight as your judge, adjust the sliding record/erase head until it is level, and the tape passes the head evenly and smoothly.

B) Make sure tape is flat against the head. Move slider across bridge and observe that tape height on playback head does not change. If tape height does change, place a thin washer under the low side of the bridge.

PLAYBACK HEAD
(Left Head, Looking At Front Of Machine)

A) Set signal generator to 1000hz sine wave and connect to INPUT jack. Set ECHO DELAY to MAXIMUM.

B) Using needle nose pliers, gently bend playback head mounting bracket up and down until the maximum sine wave is obtained. Use caution not to break metal bracket loose from bridge. Move slider across and observe level change plus or minus 3db. If out of specification, repeat step B with ECHO DELAY at MINIMUM.

C) Using trimmer potentiometer adjusting tool, turn trimmer potentiometer on the oscillator board until maximum sine wave is obtained with ECHO DELAY at MAXIMUM.

D) Set signal generator to 6000hz.

E) Using pliers, turn head horizontally (clockwise or counter clockwise) until maximum wave is obtained.

F) Slide record head along bridge, stopping at each numbered delay position observing oscilloscope that the 6000hz wave holds maximum heights as much as possible. Make any readjustments needed if wave drops considerably. Slide head next to playback head and check wave. This is necessary for echoing effect.

G) Return signal generator to 100hz. Turn ECHO SUSTAIN control to position "1". Turn ECHO VOLUME control to position "9". Using small screwdriver, adjust record level by matching sine waves on ECHO VOLUME control in positions "1 and "9".

H) Remove input plug enough to stop incoming signal.

I) Turn ECHO VOLUME to position "6", "7", or "8". Turn ECHO SUSTAIN control to approximately "6 or "7".

J) Quickly push and pull in put in far enough to record a signal and pull plug out, and listen or watch for the echoing effect. If unit is set and aligned properly, there should not be any problems. If echo begins, but fades away, turn ECHO SUSTAIN to a higher position, "7 or "8".

SOUND ON SOUND HEAD ALIGNMENT
A) Record approximately one minute of 100hz, no echoing, and proximately one minute of 6000hz, no echoing. Connect VU meter to unused connection terminal on record board, next to orange voltage wire. Set VU meter to 100%.

B) Place footswitch in PLAYBACK jack, and shut off when record time is complete.

C) Adjust sound on sound head same as playback, and flip ECHO SOUND ON SOUND switch until both heads produce approximately the same wave amplitude on both frequencies.

D) Turn foot switch on. During 1000hz playback, with switch in SOUND ON SOUND position, adjust trimmer potentiometer on playback board until VU meter reads 95%

E) Each time the 1000% passes, the VU should drop approximately 1db. If VU meter does not drop 1db, turn the trimmer potentiometer a litter more until the desired results are obtained.

F) Glue heads in this position to maintain setup.