In case others would like to know.
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I put tesla tubes in my DSL401. They are not as clean as the Ei's but sure do sound better in my opinion. As for biasing, any tech could do it. Note you only need to bias if you are replacing the output tubes. I actually biased my amp by myself. It is super easy, but you have to be extremely careful so you don't accidentally kill yourself by touching any high voltage connections. DON'T DO THIS IF YOU DO NOT KNOW HOW TO WORK SAFELY WITH HIGH VOLTAGE ELECTRONICS. Dana123 and SGstrat gave the sequence a while back and it goes something like this.
Instructions:
1) unplug the amp and remove the head unit from the cabinet.
2) locate the 3 pin molex connector labelled (CON 5).
3) securely attach the red probe of the voltmeter to one of the outer pins (use aligator clips).
4) securely attach the black probe of the voltmeter to the center pin (again use aligator clips).
5) plug the amp in (make sure the head is connected to the speaker) and let it warm up for a couple of minutes.
6) then turn on the standby and let the circuit stabilize for a few minutes.
7) adjust the mini pot (PR1) until the voltmeter reads
DSL201 0.675 V
DSL401 1.375 V
DSL50 45 mV
DSL100 90 mV
TSL60 80 mV
TSL100/122 90 mv
I bought some nonconducting pot screwdrivers
from Radio Shack for this.
turn off the amp, unplug the amp, and place the head unit back.
(optional)
9) plug in your guitar.
10) turn the amp on channel 3 making sure all knobs and the master volume are cranked.
11) play til you wake the dead.
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service bulletin given by Dana123
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If the tubes you replaced are exactly the same as your previous set then the bias may be close enough. That being said it is always best to check. I don't like to encourage people to bias their own amps unless they are confident in what they are doing. Below you will find the exact technical bulletin for your amp. Again please be careful. Also they recomend using a multi meter to read from the pin out biasing section of your amp. Good luck.
Dana.
MARSHALL SERVICE BULLETIN
SUBJECT: Bias Info/Procedure for JCM2000 series Marshall amplifiers
THEORY OF OPERATION: We are setting the bias using the current method instead of cross over distortion method. The Bias PCB assembly is as follows:
PR1: Bias mini-pot adjustment for pin1 which is one side of the push pull amp (two output tubes in a 100watt amp and one output tube in a
50watt amp). Pin1: Connected to the cathode of the output tube(s) which then goes through a 1 ohm resistor then to ground. Pin2: ground reference.
Pin3: Same as pin1 but for the other side of the push/pull amp. PR2: Bias mini-pot adjustment for pin3, the other side of the push/pull amp.
PROCEDURE:
1. Make sure amplifier is connected to a load with the proper impedance
selected. 2. Power up amplifier on STANDBY and let the circuit stabilize for a couple of minutes.
3. Locate the male three pin molex connector (CON2) with the two mini-pots (PR1 and PR2) on both ends found on the bottom of the tube bay. 4. Connect DMM (set to read mV) with alligator leads, reference common lead to center pin (pin2) on molex connector CON2 and positive lead to pin1 on CON2.
5. Take amplifier off of STANDBY with no signal, adjust mini-pot (PR1) closest to pin that the positive lead from your DMM is connected to and set it to the mV voltage that is listed in the chart below. 6. Repeat steps 4 & 5 for pin3 and until both pin1 and pin3 mV are the same.
BIAS CHART mV SETTINGS
(pin1 and pin3)
DSL50 45mV TSL60/1/2 80mV
DSL100 90mV DSL401 1.375V
TSL100/122 90mV DSL201 .675V
