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Hoffman Amps Forum image Author Topic: Standby method  (Read 2074 times)

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Offline phsyconoodler

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Standby method
« on: December 13, 2021, 11:01:08 am »
One question. Is Traynors method of simply lifting the secondary center tap a viable standby method for all amplifiers
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Offline sluckey

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Re: Standby method
« Reply #1 on: December 13, 2021, 11:26:30 am »
One question. Is Traynors method of simply lifting the secondary center tap a viable standby method for all amplifiers
One answer. No.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline phsyconoodler

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Re: Standby method
« Reply #2 on: December 13, 2021, 11:27:51 am »
Can you elaborate on that?
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Offline pdf64

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Re: Standby method
« Reply #3 on: December 13, 2021, 11:32:13 am »
Leaving the screen grids energised whilst the anodes aren’t will probably result in them passing excessive current and overdissipating.
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Offline phsyconoodler

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Re: Standby method
« Reply #4 on: December 13, 2021, 11:54:12 am »
I went and looked at Valve wizards page on this and it really helped. I'm using a valve rectifier so I just think it's best that I don't implement the standby switch.
  Just think now of what else I can use the switch for. Hmmm...
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Offline shooter

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Re: Standby method
« Reply #5 on: December 13, 2021, 12:17:32 pm »
FWIW;
my last build I did 2 different NFB schemes, used a switch to choose which one
Went Class C for efficiency

Offline sluckey

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Re: Standby method
« Reply #6 on: December 13, 2021, 12:27:35 pm »
Can you elaborate on that?
OK. I'm using this schematic as a reference. The bias circuit is the same as the Traynor YBA1 except slight component value differences...

     http://sluckeyamps.com/phoenix/phoenix.pdf

The bias voltage at the first filter cap is normally -56V. (I just checked all this stuff a few minutes ago.) Then I disconnected the PT CT from ground (simulating a STBY switch). This killed all the B+ voltages as expected ***BUT*** the bias voltage started climbing and after 30 seconds it had settled at -104V!!! No big deal for the tubes but the bias filter caps are at risk if not rated for higher voltage. My caps are rated for 150V, so no harm. And the YBA1 bias caps are rated for 250V. See schematic...

     https://el34world.com/charts/Schematics/files/Traynor/Traynor_bassmaster_mkii_yba1.pdf

So switching the PT CT will work in my amp or the YBA1 amp. But think of something like a Princeton Reverb that has a bias cap rated for 25µF/50V. Guess what will happen to that cap if you switch the PT CT?   :think1:

     https://el34world.com/charts/Schematics/files/Fender/Fender_princeton_reverb_bf_aa1164.pdf
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

 


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