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December 06, 2022, 11:05:27 AM

Author Topic: BeePre2 output upgrade  (Read 213 times)

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Offline heavycowboy

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BeePre2 output upgrade
« on: August 11, 2022, 01:18:25 PM »
Hi Bottlehead,

While performing the output upgrade today and reaching the step where the wirewound resistors are soldered in, I discovered that in my initial build I had accidentally swapped the 22 ohm resistor for a 270 ohm resistor. To clarify, I wrapped a 270 ohm resistor with the 2 rectifiers and capacitor and installed it between 33L and 35L instead of the 22 ohm resistor as instructed. The 22 ohm resistor was installed between 33L and 36L.

Since this mistake won't be easy to correct without ordering new parts and considering that my amp has worked flawlessly since its completion last year, how critical is it to correct this error? And have I caused any potential damage to the amp or tubes by operating it in this condition for so long?

Thanks in advance,

Todd

Online Paul Birkeland

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Re: BeePre2 output upgrade
« Reply #1 on: August 12, 2022, 05:27:37 AM »
You will end up with some extra power supply noise and a little extra voltage by having the 22 ohm resistor where it is.  You'll end up with a slightly less safe amp from the 270 ohm resistor where it is.  Ideally this situation should be corrected, but as you say you've been using it for a while now.  For what it's worth, the second upgrade will knock the power supply noise down substantially, so at least that part of the concern is easily addressed.  If you can just add a 22 ohm 5W resistor on top of the mispositioned 270 ohm resistor, that would likely be an adequate way to address the safety issue.

If the mispositioned 22 ohm resistor is connected between two terminals where the banded sides of the power supply caps land, that is close enough to the intended goal of the second upgrade to leave alone.  If the mispositioned 22 ohm resistor is connected between two terminals where the unbanded sides of two power supply caps land, then you will want to leave the 270 ohm resistor alone that's connecting the other sides of those same caps. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline heavycowboy

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Re: BeePre2 output upgrade
« Reply #2 on: August 12, 2022, 06:47:43 AM »
Paul,

As always your prompt response and thorough explanation is much appreciated.

If I understand correctly, since the mispositioned 22 ohm resistor is already installed on the banded side of the power supply caps (33L to 36L) then I can use one of the 22 ohm resistors provided in the upgrade kit to connect on top of the mispositioned 270 ohm resistor between 32L and 35L. And then go ahead install the other 22 ohm and (2) 270 ohm resistors as instructed in the upgrade manual?

Online Paul Birkeland

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Re: BeePre2 output upgrade
« Reply #3 on: August 12, 2022, 01:21:43 PM »
Yes, that will get you where you need to be without having to do major surgery. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man