Axaholics.com - The Guitar Forum for the Guitar Enthusiast.

Bluesville Junction Band
Axaholics on Facebook
Home
Forum
Mission
Rules
Members Guitars
Links
Guitar Store
Bluesville Junction
Axaholics on Facebook

Axaholics.com - The Guitar Forum for the Guitar Enthusiast. Guitar Forum, Amplifier Forum, Gibson Guitar Forum, Fender Guitar Forum, PRS Guitars, Taylor Guitars, Electric Guitar Forum, Acoustic Guitar Forum, Fender Amplifer Forum, Marshall Amplifer Forum, Peavey Amplifier Forum
Bluesville Junction Band
Axaholics.com - The Guitar Forum for the Guitar Enthusiast. Guitar Forum, Amplifier Forum, Gibson Guitar Forum, Fender Guitar Forum, PRS Guitars, Taylor Guitars, Electric Guitar Forum, Acoustic Guitar Forum, Fender Amplifer Forum, Marshall Amplifer Forum, Peavey Amplifier Forum
 

Search
Members
Calendar
Help
User CP
New Posts
My Assistant



  Reply to this topicStart new topicStart Poll

HRC
Posted: October 14, 2010 - 05:02 PM
Quote Post


Axaholic
*******

Group: Admin
Posts: 189
Member No.: 1
Joined: Feb. 13, 2009
Illinois


How to bias the Fender Super Champ XD




What are you doing by setting the bias on an amp? You are setting the idle current going thru the final amplifier tubes. I tend to think of it as being like setting the idle speed on a gasolene engine. Different types of tube have different idle current requirements. In the SCXD the point where we measure reads the current thru BOTH tubes, thus is twice what you would expect with a single 6V6. R20 is a precision 1 ohm resistor so the voltage drop across it is equal to the current flowing thru it. Its sole purpose in the circuit is to make it easy to set the bias.

To set the bias you must first remove the chassis from the cabinet which means, unplug everything, remove the panel off the back, unplug the speaker if you forgot to unplug it, remove the 4 screws from the top of the amp and slide the chassis out the back.

The amp must be preped by plugging in the speaker, DO NOT plug anything into the guitar input. The settings of none of the front panel controls matter. Turn the amp on and allow it to warm up for a few minutes.

BE CAREFUL THERE ARE LETHAL VOLTAGES IN EXCESS OF +350 DC INSIDE THIS AMP!

The chassis is ground, so connect your black meter lead there. Worst case use a clothespin or other clip to hold it firmly, dont use your hand! Or have a helper hold it! What I'm trying to be sure of here is that you don't touch the chassis and anything else in the amp at the same time as that is a good way to get hurt or killed.

In the picture below you will notice a red arrow on the left side pointing to one end of the resistor R20, connect the red lead from the meter there.

You will adjust the blue pot on the right side of the picture for 40 millivolts (NOT 39, NOT 41) that is 40/1000 of a volt. In case you missed the blue pot, there is a red arrow pointing to it.

You will notice several wires above the pot in the picture. Those are carrying in excess of +350 VDC. Do be careful!

(IMG:http://img836.imageshack.us/img836/9465/fendersuperchampxd.jpg)
PMEmail Poster
Top
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

Topic Options Reply to this topicStart new topicStart Poll

 

LoFi Version
Axaholics.com - The Guitar Forum for the Guitar Enthusiast. Guitar Forum, Amplifier Forum, Gibson Guitar Forum, Fender Guitar Forum, PRS Guitars, Taylor Guitars, Electric Guitar Forum, Acoustic Guitar Forum, Fender Amplifer Forum, Marshall Amplifer Forum, Peavey Amplifier Forum
Bluesville Junction Band
Axaholics.com - The Guitar Forum for the Guitar Enthusiast. Guitar Forum, Amplifier Forum, Gibson Guitar Forum, Fender Guitar Forum, PRS Guitars, Taylor Guitars, Electric Guitar Forum, Acoustic Guitar Forum, Fender Amplifer Forum, Marshall Amplifer Forum, Peavey Amplifier Forum
 

Axaholics.com - The Guitar Forum for the Guitar Enthusiast
Axaholics
2005-2015 HotRodCarts LLC
All Rights Reserved
No part of this web site may be reproduced in any way
or by any means, without the prior written permission of HotRodCarts LLC