F5 power amplifier

[studeb]

Originally Posted by jackinnj

Anyone know where my son put my micrometer? I found the DMM and the socket wrenches.

Try under the bed, in a shoe, or my favorite, the toilet.

[Ryssen]

Originally Posted by tinitus

I have no idea, but I dont think you can remove inductance
Will a series cap do anything ?
But probably not
It doesnt in a speaker xover

You say your trafo output have 1Kohm in series and 2.2nf to ground, as I understand it
How does that work/couple with the F5 input, 1Kohm/100Kohm
The paralel 2.2nf might worry me a bit
But I really dont know
DC related or what
What will happen if you remove the 1kohm/2.2nf on trafo output ?
Might it be a low pass filter to prevent passing on high FR problems, and that it really dosnt work well

Because of the exstreme simplicity F5 might be somewhat sensitive to any ground coupling, but I dont know

But maybe be a bit careful until someone with knowledge have evaluated this

I will try to remove the 1k/2,2nf and try a 18pf across R10 instead of 2,2nf.
I thought Nelsson could answer this..but no sign of him..

[enochRoot]

just wanted to get a concensus on where the thermistors should be placed. the way i have my board and mosfets attached to the heatsink give me two options. hopefully my photos can aid in determining what i'm talking about. it's hard to get a clear photo that is large enough!

the options are:

1. thermistor is in contact w/ the mosfet and 2 of its pins. it also touches the strip of aluminum i am using to clamp the mosfets to the heatsink. it seems to be electrically isolated still, but touches several pieces and is kind of wedged in there. no pressure is on it, but it's a snug fit (but still loose enough to slide in there easily). i have the leads covered with insulating sleeves. this is how i currently have things set up.

2. i could also position the thermistors "above" the circuit board and they could sit next to the aluminum clamping strip. my concern with this is that they won't be in direct line of the mosfet package and the aluminum strip might provide some thermal shielding so the thermistor doesn't have a good idea of what's going on.

any ideas?

[steve jones]

Originally Posted by tinitus

Honestly I dont believe theres much advantage due to the added complexity and connections, its probably just a winn and loose game
I believe in proper dimensioning and smooth mounting, concervative and careful attention to complete design, thats all it takes

KISS, I get it.

[ma_coule]

Originally Posted by fishski13

are you suggestion that i have a screw loose?

Ha, ha!
No, no... it was mint as friendly suggestion!
The proof is below photo!
BTW:
my A-class Death of Zen upon Rod Elliott's PCB with L bracket 6x40x45/200 mm.

[ma_coule]

Originally Posted by ma_coule

The proof is below photo!

Maybe now...?

[fishski13]

Originally Posted by ma_coule

Maybe now...?

i got it now. those heatsink aren't going anywhere. i know my heatsinks will need to be reinforced.

[fishski13]

enochRoot,
are those Bergquist K-10 pads isolating the MOSFETs? i realized last night that i don't have any TO-247 pads. i also found some TO-3 rectangular mica from Mouser that could be trimmed down as well.

[enochRoot]

yes they are. i got sample sheets a while ago of both the K-10 and Q-Pad 3. i simply cut some squares out of the K-10 to use. i had hoped to use mica and grease as everyone seems to say they work better, but i could not locate TO-247 pads anywhere easily. since i am getting anxious for sound and i had this lying around, i figured it should be sufficient

let me know if you want a square as i have plenty left and could drop some in the mail for you.

Originally Posted by fishski13

enochRoot,
are those Bergquist K-10 pads isolating the MOSFETs? i realized last night that i don't have any TO-247 pads. i also found some TO-3 rectangular mica from Mouser that could be trimmed down as well.

[steve jones]

Originally Posted by fishski13

enochRoot,
are those Bergquist K-10 pads isolating the MOSFETs? i realized last night that i don't have any TO-247 pads. i also found some TO-3 rectangular mica from Mouser that could be trimmed down as well.

TO-247 Transistor Mica Insulator,Insulation sheet, x 50 - eBay (item 250541364333 end time Jan-01-10 08:46:42 PST)