F4 power amplifier

[carpenter]

Match the NNN and the PPP. Don't worry so much about the N and P having the same values.

Purchase a bunch and match your own. This gives you experience and spares.

 

[Andrzej Sochon]

another
.

I see a black heatsink with diodes. Are the diodes hot?
a.

 

[carpenter]

diodes are cold as a well digger's butt

 

[Vix]

Here's a Wakefield 392-300AG heatsink given to me from a fellow carpenter. He had no idea what it was, but thought I might be able to put it to good use.

I purchased a mate for it at a cost of $160.00. This will be my first F4. For the rest of the F4s, I'm going to play with water cooling.

Caps in PS are 47,000uF each.

Ugly!

(Choky will wait until you post a pic of a finished amp and present it in its full ugliness )

p.s. In the dark,it doesn't matter if its ugly or not, as long as it sounds good!

 

[carpenter]

p.s. In the dark,it doesn't matter if its ugly or not, as long as it sounds good!

So true; I've been told that the same can be said of the person in our bed, sleeping next to us...

 

[Zen Mod]

woodie
please use metal screws for output fets ; these plastic ones are just begging for bubble gum effect ....... then pufff!

 

[Magura]

woodie
please use metal screws for output fets ; these plastic ones are just begging for bubble gum effect ....... then pufff!

Wouldn't that actually be at least pufff, pufff, puff ?


Magura

 

[Zen Mod]

Wouldn't that actually be at least pufff, pufff, puff ?


Magura

next we'll see woodie's BFR91 amp ..............

 

[carpenter]

You guys are funny...

Metal screws carry the fet tab through the mica and into the heatsink, thereby causing a direct short!

 

[Magura]

You guys are funny...

Metal screw carry the fet tab through the mica and into the heatsink, thereby causing a direct short!

Which is why you use an insulator for the bolt

Really, the nylon bolts are going to give up the ghost sooner than you expect.


Magura

 

[carpenter]

Which is why you use an insulator for the bolt

Really, the nylon bolts are going to give up the ghost sooner than you expect.


Magura

Well, now that you mention it, where do I get a screw kit that isolates that tab. I've been looking everywhere.

 

[carpenter]

I'm thinking about using a bar, like I did on the rectifier diodes.

 

[Magura]

Well, now that you mention it, where do I get a screw kit that isolates that tab. I've been looking everywhere.

No idea, I just machined some of a piece of FR4 board, last time I needed those.


Magura

 

[Babowana]

Re: Re: N to P matching

I'm using P channels that are 0.18 volts apart from the N channel...

Thanks for info. I got similar result.
I measured Vgs with 20pcs each of IRFP240 and IRFP9240.
Luckily, I found that deviation of Vgs among each pieces was
not bad at all. And, the average absolute Vgs of IRFP9240 group
was about 0.17V higher than the average Vs of IRFP240 group.

By the way, did you use the original R of 22.1K between
the reference and cathode of TL431?
What is the Vdc measured between the gate of N-Mosfet
and the gate of P-Mosfet on the bias condition?

 

[carpenter]

Other than the FETs, I'm staying as close as possible to the values in R0 6/4/07

 

[mpmarino]

I'm thinking about using a bar,.......

Might as well, it's the best way anyway

Well, now that you mention it, where do I get a screw kit that isolates that tab. I've been looking everywhere.

Did you check under the sofa

 

[Zen Mod]

Well, now that you mention it, where do I get a screw kit that isolates that tab. I've been looking everywhere.

how do I know that when I'm living in Serbia?

look at CookBook - you'll see them on cover pics........

that's dreky nipple, nothing else

No idea, I just machined some of a piece of FR4 board, last time I needed those.


Magura

why I'm not surprised ?

 

[carpenter]

I'll go with the bar.



babowana: -4.26 volts on the P gate and 4.10 volts on the N gate.


Interesting that there's almost the same mismatch as the Vgs readings.

 

[Babowana]

Thanks!

 

[carpenter]

Did you check under the sofa

Now there's a scary thought!