Fender Adjustments

JDeV · 7th April 2006, 04:10 PM

Bussy repairing a Studio Bass for a friend. There are 2 POT's at the rear: HUM adjust and TUBE balance adjust.
What is the correct procedure for setting this up?

Thanx for any assistance.

blacklight · 7th April 2006, 06:26 PM

http://www.schematicheaven.com/fender.htm

Bottom of the page.

testlab · 7th April 2006, 06:40 PM

You may want to convert the bias adjustment from a balance type. This adjustment merely divides the bias evenly between the tubes instead of accurately setting the idle current.

JDeV · 7th April 2006, 07:03 PM

Quote:

Originally posted by blacklight
http://www.schematicheaven.com/fender.htm

Bottom of the page.

Thanx for the link. I also fond this one, very good quality, still need to know how to adjust these POT's for best results.

Netlist · 7th April 2006, 08:06 PM

I'm sure you'll find the answer in this link:
http://www.fenderforum.com/forum.htm...15:57&offset=0

/Hugo

blacklight · 7th April 2006, 08:13 PM

Ach, sorry. I thought you meant how to install new pots. Well, cheers anyway.

poobah · 7th April 2006, 08:17 PM

With a shorting on the input... or no input at all; connect a voltmeter from plate to plate (pin 3) on the output tubes. With the amp warmed up well, adjust the matching pot for zero volts. This matches the idle current (basically) through the tubes.

If the tubes are new, you may want to do this again after tubes have some hours on them.

With that done... simply adjust the hum balance for minimum audible hum at the speaker.

7th April 2006, 04:10 PM	#1
JDeV diyAudio Member Join Date: Oct 2002 Location: Cape Town	Fender Adjustments Bussy repairing a Studio Bass for a friend. There are 2 POT's at the rear: HUM adjust and TUBE balance adjust. What is the correct procedure for setting this up? Thanx for any assistance. __________________ "Be carefull who's advice you buy, but be patient with those who supply it." From Baz Luhrmann's - Everybody’s Free (To Wear Sunscreen)

7th April 2006, 06:40 PM	#3
testlab diyAudio Member Join Date: Dec 2005 Location: Grand Rapids MI	You may want to convert the bias adjustment from a balance type. This adjustment merely divides the bias evenly between the tubes instead of accurately setting the idle current. __________________ It's not whether you win or lose, it's how you lay the blame.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Acoustic 160 adjustments	llwhtt	Solid State	0	28th April 2009 11:55 PM
X-5 bias adjustments	ROLIKOV	Pass Labs	3	11th December 2008 09:49 PM
D1 Volume adjustments	hifimaker	Pass Labs	11	19th October 2007 10:18 PM
Plate amp EQ adjustments?	mike.e	Subwoofers	7	7th June 2005 06:50 PM
trim pot adjustments	walters9515	Instruments and Amps	0	26th April 2005 09:28 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

7th April 2006, 06:26 PM	#2
blacklight diyAudio Member Join Date: Feb 2006 Location: you tell me	http://www.schematicheaven.com/fender.htm Bottom of the page.

7th April 2006, 08:06 PM	#5
Netlist diyAudio Moderator Join Date: Jan 2003	I'm sure you'll find the answer in this link: http://www.fenderforum.com/forum.htm...15:57&offset=0 /Hugo

7th April 2006, 08:13 PM	#6
blacklight diyAudio Member Join Date: Feb 2006 Location: you tell me	Ach, sorry. I thought you meant how to install new pots. Well, cheers anyway.

7th April 2006, 08:17 PM	#7
poobah diyAudio Member Join Date: Nov 2005	With a shorting on the input... or no input at all; connect a voltmeter from plate to plate (pin 3) on the output tubes. With the amp warmed up well, adjust the matching pot for zero volts. This matches the idle current (basically) through the tubes. If the tubes are new, you may want to do this again after tubes have some hours on them. With that done... simply adjust the hum balance for minimum audible hum at the speaker.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)