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Old 7th April 2006, 04:10 PM   #1
JDeV is offline JDeV  South Africa
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Default 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.
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Old 7th April 2006, 06:26 PM   #2
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http://www.schematicheaven.com/fender.htm

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Old 7th April 2006, 06:40 PM   #3
testlab is offline testlab  United States
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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.
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Old 7th April 2006, 07:03 PM   #4
JDeV is offline JDeV  South Africa
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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.

Click the image to open in full size.
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Old 7th April 2006, 08:06 PM   #5
Netlist is offline Netlist  Belgium
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I'm sure you'll find the answer in this link:
http://www.fenderforum.com/forum.htm...15:57&offset=0

/Hugo
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Old 7th April 2006, 08:13 PM   #6
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Ach, sorry. I thought you meant how to install new pots. Well, cheers anyway.
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Old 7th April 2006, 08:17 PM   #7
poobah is offline poobah  United States
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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.
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