Traynor YCS50 Service Manual page 22

SERVICE BULLETIN
Tube Bias Adjustment
1. Adjust the amplifiers bias when in the 50W mode (YCS50/H) or
90W mode (YCS90). A speaker/load should be connected at all
times when amplifier is powered.
2. Turn the amplifier on; allow it to warm up for 2-3 minutes.
3. Once the amplifier is warmed up, make sure the amplifier is out
of Standby mode. Do not apply any input stimulus (signals etc.).
4. Using a meter set to measure mV DC, attach the negative
(black) probe to the GND. Place the positive (red) probe on TP1
5. Adjust the Bias Trim Pot until you measure 75mv DC between
GND and TP1.
Measure the bias between GND and TP2. It should also mea-
sure as 75mv DC. (For the YCS90 the measurements should
read 75mV on Tp1, Tp2, TP3 and TP4 which signifies that all
tubes are matched).
Power Mode
Switch
GND
TP1
TP2
TP3
TP4
Canada
Voice: (905) 837-8481
Voice: (716) 297-2920
Voice: (905) 837-8481
Fax: (905) 837-8746
Fax: (716) 297-3689
Fax: (905) 837-8746
Yorkville Sound
550 Granite Court
Pickering, Ontario
L1W-3Y8 CANADA
Products Affected
Traynor YCS50,
YCS50H & YCS90
Bias Trim Pot
YCS90 tubes
U.S.A.
Voice: (716) 297-2920
Yorkville Sound Inc.
Yorkville Sound
Fax: (716) 297-3689
4625 Witmer Industrial Estate
550 Granite Court
Niagara Falls, New York
Pickering, Ontario
w w w . y o r k v i l l e . c o m
14305 USA
L1W-3Y8 CANADA
Yorkville Sound Inc.
4625 Witmer Industrial Estate
Niagara Falls, New York
14305 USA
SERVICE-BULLETIN-Bias-Adjust-YCS-00-1v0 • May 3, 2010