Article - Sony VFETs part 1

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#822
With Permender not here anymore, all the more reason to pull out the schematics from Nelson Pass's article. Permender followed that, with only the addition of the additional big caps on his board. I can say I don't know why he added them, but other have said that they help.

I got a pair of Hammond 2VA 12V transformers, and some bolt down bridge rectifiers for my build, as I don't plan to have additional circuit boards for the bias DC supply.

Question to those that do know. Will I be able to just take the AC from the transformer, through the rectifier, straight to the +/- inputs on Permenders board? There is no cap bank in the schematic.
 
#824
I see C6 and C7 in the schematic which are already on Permaneder's boards. Just like the rest of the bias circuit. So it should work.
Though I don't like the idea of wires from the bold down bridges, with ripple on it going through your amp to the boards. I would put another 1000uF close to the bridges and feed that to the board.
 
#825
WalterW said:
I see C6 and C7 in the schematic which are already on Permaneder's boards. Just like the rest of the bias circuit. So it should work.
Though I don't like the idea of wires from the bold down bridges, with ripple on it going through your amp to the boards. I would put another 1000uF close to the bridges and feed that to the board.
Click to expand...

Here's my DigiKey BOM for the bias supply

2 x Transformer MT2114-ND
4 x Bridge Rec. DF04M-E3/45GI-ND
6 x Connector 277-1248-ND
1 x Proto Board V1042-ND

I actually have lot's of prototyping board around for making small P-to-P circuits. That with some nylon standoffs makes life pretty good. I'm also fond of the connectors listed above for hooking stuff up.

Regards,
Dan
 
#826
WalterW said:
I see C6 and C7 in the schematic which are already on Permaneder's boards. Just like the rest of the bias circuit. So it should work.
Though I don't like the idea of wires from the bold down bridges, with ripple on it going through your amp to the boards. I would put another 1000uF close to the bridges and feed that to the board.
Click to expand...

The power supply is separate from the regulator that is on the board. He will need to build the supply with the CRC off board.

The Permaneder boards work fine. I didn't need to modify anything other than to make a few of the holes bigger because I picked parts with thicker leads.
 
#827
Questions regarding transformers for power supply ….

I know that Nelson calls for a 2 x 24V transformers

I have 2 x30 V transformers in my collection

Will the regulation circuit take approx 42V input?

Can I use a 5ohm 20W resistor instead of the .1 ohm specified to get a voltage drop of 1.5A x 5ohm = 7.5V getting close to the 34V required?

or should I just bite the bullet and buy 2 x24V transformers.

Thank You

Bob
 
#838
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