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Bias setting questions

WhiteSE

WhiteSE

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I have the Pilot SA260, I need to set the Bias...I have the instructions from the Sams folder...

Now, on the side there are 2 bias adjudsting pots, but I need to adjust 4 times (4 tubes). When you adjust the first one, its voltmeter from A1 to chasis, and then the next one is A1 point to A2 point and then adjust...

My question: After I adjusted to 1 volt as it says, that stays put while I adjust the second tube, even if i move the pot again?
 
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Although I'm purely speculating, it sounds as though this amp has one bias voltage level pot per channel (like my LK72A that I modified). Then you use the DC balance control to zero out the reading when measuring between the A1 and A2 test points. (and later, the other channel's test points)

Then repeat the process for the other channel.

Generally, adjusting the bias voltages between the channels will also make small changes to the other channel. e.g. when you turn up one bias pot, the voltage on the other channel will drop slightly.

But, again, that's only educated speculation.

. . Falcon
 
You might have to go back and forth to attain the ultimate setting. Some of the circuit designs I've seen for achieving correct bias are unfortunate at best.

The other thing I've learned is that while one is tempted to bias for cooler operation to save money on repeated renewal of ouchput tubes the best sound comes from when they are biased as hot as they can stand to be.
 
Maby like the Pilot 240?

My Pilot 240 has two bias pots on the top inside, and a set of test points on the back with two small pushbuttons.

The procedure is to push the switch in, measure between the two test points and set the Voltage for zero (balancing that side) and repeat for the other channel.

This assumes your Pilot has cathode bias on the OP tubes,and you are not really biasing them, but adjusting the balance for EQUAL bias between the two output tubes.:scratch2:

Mark T.:music:
 
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never mind..the pots on the side is bias and balance....so no big deal now...tomorrow I buy voltage meter!!!
 
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