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Hoffman Amps Forum image Author Topic: just to make sure...  (Read 3620 times)

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Offline Bieworm

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just to make sure...
« on: September 05, 2022, 08:32:46 am »
Hey guys

Is it all right to put the standby switch on the HT center tap when using a half wave SS rectifier and fixed bias amp (6V6GT)
It's the intention to add a bias vary trem on the 6V6's...

thanks
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Offline kagliostro

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Re: just to make sure...
« Reply #1 on: September 05, 2022, 08:51:23 am »
Standby, is really a controverse matter

However to place it on the CT isn't the best choice, a tech can have problems during manutention

better a mute switch

Here you can read something about

http://www.valvewizard.co.uk/standby.html

Franco
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Offline pdf64

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Re: just to make sure...
« Reply #2 on: September 05, 2022, 10:07:09 am »
...
Is it all right to put the standby switch on the HT center tap ...
Yes, but depending on how a bias supply is derived, the voltage on the bias caps may rise.

Quote
when using a half wave SS rectifier and fixed bias amp (6V6GT)
It's the intention to add a bias vary trem on the 6V6's
It's unusual to use half wave rectification for HT supplies. With a centre tapped HT winding, you can splash out on an extra diode for a push pull (2 phase), full wave rectification
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Offline sluckey

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Re: just to make sure...
« Reply #3 on: September 05, 2022, 10:10:32 am »
You have a half wave SS rectifier with a HT center tap? I've never seen one. Bet you really mean a ss conventional full wave rectifier.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline Bieworm

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Re: just to make sure...
« Reply #4 on: September 05, 2022, 02:03:16 pm »
You have a half wave SS rectifier with a HT center tap? I've never seen one. Bet you really mean a ss conventional full wave rectifier.

Yes I meant the full wave conventional.. sorry😬
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Offline tubeswell

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Re: just to make sure...
« Reply #5 on: September 05, 2022, 04:47:30 pm »
The wide Panel tweeds ('5Dthis' and the '5Dthat') had standby switches on the CT of the High Tension winding and then Fender stopped this practice.

But then 'Fender' put it back on the Eric Tremolux. So ...

I've used it with 5U4 rectifiers and had no problems. YMMV
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Offline Bieworm

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Re: just to make sure...
« Reply #6 on: September 06, 2022, 04:54:53 am »
I finished the schematic. Might be some tweaking involved at the bias, but this should work.. I think.
BTW, I put the standby switch after the rectifier...
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Offline DummyLoad

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Re: just to make sure...
« Reply #7 on: September 06, 2022, 04:58:27 am »
The paraphase seems wrong. The 270K gridleak on the non-inverting path should be grounded? Seems like positive FB at that 4 wire node connected as shown. 


Offline Bieworm

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Re: just to make sure...
« Reply #8 on: September 06, 2022, 05:48:32 am »
The paraphase seems wrong. The 270K gridleak on the non-inverting path should be grounded? Seems like positive FB at that 4 wire node connected as shown. 



I guess it's kind of confusing, but it's a LTP PI. Look at the green marking balloons.. they connect to the power tubes...
I borrowed that part of the schematic from Sluckey's Deluxe Reverb Lite
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Offline pdf64

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Re: just to make sure...
« Reply #9 on: September 06, 2022, 07:39:18 am »
The paraphase seems wrong. The 270K gridleak on the non-inverting path should be grounded? Seems like positive FB at that 4 wire node connected as shown. 

I think it’s a version of floating paraphase, ie that node is a virtual earth http://www.valvewizard.co.uk/paraphase.html
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Offline Bieworm

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Re: just to make sure...
« Reply #10 on: September 06, 2022, 07:58:11 am »
The 6G3 Brown Deluxe Also has this type of PI. I thought this was a LTP PI... well, learning things here...  :smiley:
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Offline pdf64

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Re: just to make sure...
« Reply #11 on: September 06, 2022, 08:20:41 am »
The 6G3 Brown Deluxe Also has this type of PI. I thought this was a LTP PI... well, learning things here...  :smiley:
Yes, you’re using an LTP.
We’re discussing the 5D4 phase splitter, sorry I meant to make that clear  :icon_biggrin:
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him! BBC News feature  https://www.bbc.co.uk/news/articles/cm26llp

Offline 66Strat

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Re: just to make sure...
« Reply #12 on: September 06, 2022, 10:42:17 am »
The paraphase seems wrong. The 270K gridleak on the non-inverting path should be grounded? Seems like positive FB at that 4 wire node connected as shown. 

I think it’s a version of floating paraphase, ie that node is a virtual earth http://www.valvewizard.co.uk/paraphase.html

It is a floating paraphase. It is self balancing. See figure 12.31 in the attached.

Regards,
JT

 


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