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B-15N bias pot V1.2
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B-15N bias pot V1.2
by
bax.
2
layer board of
1.02x1.02
inches
(26.01x26.01
mm).
Shared on
July 10th, 2015 13:47.
Ampeg 1974 B-15N bias pot
Bourns 3250W-1-203 this is a multi-turn, 20K linear taper pot. A 25KL such as a 3296W-1-253 will work as well. The required pin spacing is 0.1".
The total target resistance with the pot and serially connected resistor is 47K ohms. The design allows for either a single or a pair of parallel resistors to be used. You can use one or two 1/2W or two 1/4W resistors. The resistor pad footprints have a 10mm pin spacing. I prefer to use metal film resistors but this is not a requirement.
Different parallel combinations of resistors can be used to attain a resistance that gets you in the desired range. There are many possibilities. For example, two 75K ohm 1/2W resistors can be used such as Vishay-Dale CMF5575K000FHEB. Alternatively a single 33K ohm 1/2W resistor such as Vishay-Dale CMF5533K200FHEK can be used. These are available from Digi-Key. It is easier to find a pair of 75K ¼W resistors with a 10mm or less pad spacing.