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Post subject: 5E3/Tremolux hybrid power supply question
Posted: Thu Feb 10, 2011 5:12 pm
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I am looking to build a higher powered 5G9 type of amp without the tremolo. I see from the schematics that the 5E3 and 5G9 pre-amp's are the same, until the PI of course. I am using a Weber 5E3 chassis and after discussions with Patrick at Mercury I think the best choice for an OT would be the 5E8 version. I can fit the pre-amp and long tail pair PI on the standard size 5E3 board along with a SS rectifier and adjustable bias components.

The Mercury PT I have chosen puts out 380-0-380 unloaded B+ and would like some comments or advice on what values to use for the bias supply. I am also considering adding another stage of filtering for V1, perhaps 16 to 32 uf's. I don't care that much about sag as what I am going for is a Tweed Bassman type of sound without sag. I plan to use a FRED, (Mouser pt.# 747-DSEI12-12A) that are recommended by Don-Tone Man-Butler.

On a related note could someone explain why on the 5E8 why Fender tied the OT center tap to the screen supply instead of putting it after the first filter cap and choke. After I get a schematic and layout diagram drawn up I will post them here for comments.

Thanks to all,
Bigampdaddy


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Post subject: Re: 5E3/Tremolux hybrid power supply question
Posted: Thu Feb 10, 2011 9:20 pm
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My WAG on your "screen grid connection question" is this is a cheap & simple way to insure that the anode plates & the screen grids are activated and de-activated at the same rate. Esp when you hit the standby or turn the amp off... there is less chance of the screens staying "on" for a short period of time... after voltage is removed from the plates. Like during flyback, when OPT magnetic fields collapse.

Grids can't handle much current. If the anode plates are turned off, but the screen grids remains charged, even for a short period of time... it could lead to damage.

Told you it was a WAG. :mrgreen:

http://www.kbapps.com/audio/schematics/ ... n5e8a.html


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Post subject: Re: 5E3/Tremolux hybrid power supply question
Posted: Fri Feb 11, 2011 4:08 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
About 6V6 screen grid : you have to put a resistor on each 6V6's grid, a 470 ohms to 1000 ohms, 1 watt minimum.
A must to protect your grid. Like most Fender amp have it.


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