Burn-In Procedure For New Output Tubes - DYNACO Stereo 80 Owner's Manual

Burn-In Procedure for New Output Tubes

Note: This procedure applies only when you have installed new output tubes which have not yet been
burned-in. (The tubes installed on your new Stereo 80 have already been burned-in at the
factory.) Also see section entitled: Tube Replacement.
1) Turn off any equipment connected to the amplifier inputs.
2) Turn the bias adjust potentiometer for each newly installed tube fully counter-clockwise. This can
take as many as 30 turns. A faint "clicking" sound, which is not harmful, may be heard if you
continue to turn the potentiometer beyond its fully counter-clockwise position. (Use the
adjustment tool provided with the amplifier.)
3) Switch the amplifier on and allow it to warm up 5 to 10 minutes. Ensure that the Bias Display
On/Off switch is set to ON. Note that all bias indicator lamps adjusted in 2) glow green. If any
bias adjustment lamp is not glowing green, ensure that its bias adjustment potentiometer is turned
fully counter-clockwise.
Note: If an output tube indicator lamp cannot be adjusted for both green and red, the associated output
tube is probably faulty.
4) Adjust the bias potentiometer for each newly installed tube as follows:
a) Turn the potentiometer clockwise to a point where its lamp goes off (glows neither red
nor green.)
b) Slowly turn the potentiometer counter-clockwise, again, to the point where its lamp just
begins to glow fully green again. Repeat this step for each lamp as necessary until all
four are glowing green.
5) After 10 minutes check the indicator lamps to see that they are still glowing green. For any lamp
not glowing green, slowly turn its potentiometer counter-clockwise only until it glows green
again.
6) Check every 30-45 minutes to ensure that the indicator lamps are still glowing green and adjust
them if necessary.
7) After three hours, adjust each bias potentiometer to a position where its lamp does not glow
(midway between red and green).
This completes the burn-in procedure for new output tubes. As future bias adjustments become
necessary, use the Output Tube Bias Adjustment Procedure on page 9.
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