Bias-Easy™ Bias Probe Instructions

Warning - HIGH VOLTAGE appears on the test leads during the testing process! If you are not knowledgeable about working safely with high voltage, we recommend you have a qualified amplifier technician bias your amplifier. Follow the instructions below in the precise order listed to ensure your safety. The most important things to remember are these: Always connect the test leads to the meter before plugging the socket into the amplifier. Always remove the socket from the amplifier before removing the test leads from the meter.

1. Turn off your amp. 2. Insert the BLACK banana plug into the COM jack of your multimeter. 3. Insert the RED banana plug into the mA jack of your multimeter. 4. Set your multimeter switch to the mA range (most common is the 200mA range). If your meter is auto-ranging, set the switch to the mA setting. Important - do not move this selector switch once you plug the Bias-Easy™ probe into the tube socket of the amp. 5. Remove one of the power tubes (6L6, EL34, 5881, 6550, 6V6, KT66, KT77, etc) 6. Insert the Bias-Easy™ probe into the power tube socket, making sure to line up the key on the probe post with the key in the center hole of the socket. 7. Insert the tube you removed into the socket of the Bias-Easy™. Make sure the key on the tube base is properly lined up with the key on the center hold of the socket. The other power tube(s) must be in place in their sockets during testing. 8. Make certain that a speaker is connected to the amp. If this is an amp head, connect a cable between the speaker jack and the speaker cabinet. 9. Turn on the amp, allow to warm up, and turn the standby switch to "operate". 10. The meter should read the plate current in milliamps (mA). If the current exceeds 100mA, be prepared to immediately turn the amp back to standby. You have a problem in the amp, or a defective tube. 11 Adjust the bias pot for the proper bias reading. A rule-of-thumb generic setting is about 35mA for 6L6 and EL34, 18mA for 6V6. A much more accurate setting is determined by knowing the plate voltage of the amplifier, and using that information along with the type of tubes (6L6, EL34, etc) on our online Tube Bias Calculator at www.amprepairparts.com/bias.htm. 12 Do not change the meter control switch while connected to the amplifier - meter damage may result. 13. Turn off the amp, allow the tubes to cool, remove the tube from the Bias-Easy™ socket, remove the socket from the amp. It is now safe to remove the test leads from the meter.

Warning - Never remove the test leads from the meter while the Bias-Easy™ socket is plugged into one of the power tube sockets of the amplifier - even if the amp is turned off and unplugged! Filter capacitors store high voltage, and you can still be shocked by touching the banana plugs. Always turn off the amp and remove the Bias-Easy™ socket from the amplifier first, then you may unplug the banana plugs from your meter.