Individual Bias Pots

knowledge base for the classic Dynaco ST70

Individual Bias Pots

Postby antiquekid3 » Sun Mar 07, 2010 9:42 am

Hey guys,

I found four identical 10K pots, two of which I will use with my ST-70. I'm keeping the original two in their places. However, if I do end up using these bias pots, need I worry about having a total of 2.5K instead of the normal 5K across all of these pots (after paralleling them)?

Thanks!

Kyle
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Postby mesherm » Sun Mar 07, 2010 5:01 pm

You are reducing the total resistance of the bias circuit from 25K to 22.5k which will drop the maximum voltage available by about 6%. You should be ok but if you find you need more bias voltage then lower the resistor value closest to the diode by 1k or 2k by paralleling a resisitor on it.
Mike's N-1 Rule: When looking for N number of components to finish a job, you have a 95% chance of only finding N-1 of them.
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Postby antiquekid3 » Sun Mar 07, 2010 6:55 pm

Okay, that's good. It took me forever to find these little potentiometers out at my radio club, and I got some knobs at the hamfest yesterday for them, so it seems as though all will be good.

I'm taking lots of pictures of my progress...I can't wait to show it off! :-)

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Postby Thor61 » Mon Mar 08, 2010 8:25 pm

Where did you find the 10K pots and are there anymore available ?
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