Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: mresistor on May 31, 2016, 03:43:20 pm
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I have a later 70's Princeton Reverb on the bench. Nothing really wrong with it. Bias set a little low, like 28v instead of 34 volts. I will check Pdis first before altering. But the vibrato intensity is real weak having to turn it up to 6 or 7 to get any vibrato effect audibly. I looked and sure enough someone installed a 250K audio taper pot for intensity and it calls for a linear taper pot. I'm thinking this is why I have to turn the pot up so high to get the effect. Am I correct? I am also aware that increasing the bias helps the vibrato strength, but my 79 and my HPR vibrato intensities don't respond like this.
The amp has had some mods done, one is the addition of a trim pot for adjusting bias, which I really like.
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I have a later 70's Princeton Reverb ... Bias set a little low, like 28v instead of 34 volts. I will check Pdis first before altering. But the vibrato intensity is real weak having to turn it up to 6 or 7 to get any vibrato effect audibly. ..
...The amp has had some mods done, a trim pot for adjusting bias, which I really like.
You should turn that pot to get bias correct and it will be strong, not weak.
If I were you, I'd search this forum and read to understand, all you can find on that circuit. IMO
Raybob
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Bias set at 34v and still have to turn the pot up too high to get audible effect. Ordered Linear pot.
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never mind answered it myself.
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Yep - the depth pot should be linear taper