Instructions on how to retube/bias JCM 2000 DSL100?

[hand amputation]

New to the forum, so my apologies if this has been asked a million times, or if there is already a thread covering this, but is there any instructional youtube vids or sites dedicated to re-tubing / biasing tubes for a JCM 2000 DSL100?

Any help would be greatly appreciated.

Thank you!

 

[houseofrock]

https://www.youtube.com/watch?v=lxplMWOpIVc

 

[hand amputation]

https://www.youtube.com/watch?v=lxplMWOpIVc

Thank you for the video, but I am not sure exactly why he is doing what he is doing. I have a multimeter.. Could someone explain what I need to do, or point me towards a web link that could explain things a little more clearly...?

 

[Murray]

THIS THREAD post #9 by Toastmaster is a Marshall Service Bulletin 'how-to' on bias. Might help.

Or THIS LINK Same info. Maybe better explanation.

Or...if you want to get into the circuit, take a look at Dr. Tubes JCM2000 DSL100 schematics

Look at something like JCM-60-02 iss7. V5 &6 are one pair of EL34's that have their cathodes (pin 7) connected to a shared resistor R6, which is a 1 ohm/1W. V7 &8 are the other pair of EL34's that share cathode resistor R9.

Chase the lead coming off of pin 7 & it takes you to 7-pin Con1. Pin 3 for V5 & 6, pin 5 for V7 & 8. And that tells you to go to drawing JCM2-64-00, which is the bias board. This shows another 7-pin connector that matches the power board end. Pin 3 leads to bias connector pin 1. Pin 5 leads to bias pin 3 & pin 4 is connected to ground (back at the power board end).

When you read from pin 4 to pin 3 you are reading V5 & 6 cathode voltage, thru the 1 ohm R6 resistor to ground. Doing the math w/ Ohm's Law tells you that 1 volt read across a 1 ohm resistor = 1 amp, what you read in voltage equals amperage for the two associated tubes.

Also, looking at the bias board schematic it shows you where the adjusting pots are in the circuit & following them back to the power board end it shows where they affect the control grid & alter bias.

Sorry if I got long winded on this. Sounded like you wanted an explanation of 'what-happens-when-I-do-this'. Hope some of this helps.

 

[houseofrock]

Marshall DSL-TSL-JVM "How To" Bias Page

 

[paul-e-mann]

Pop in your new tubes and there's three pins and two screws on the back of your amp, that's where you adjust bias.

This guy explains the process:

[ame]http://www.youtube.com/watch?v=_OSoXJ6qTGA[/ame]