F4 power amplifier

[carpenter]

I can re-try this again, ill set P1 to max, then P2 in the middle. Kinda hard to measure now that they are soldered to the board and the board is mounted.

Jase

Count the total turns of your pot and divide by two?

BTW, you'll chuckle if you reread the original posts........

 

[jleaman]

Count the total turns of your pot and divide by two?

BTW, you'll chuckle if you reread the original posts........

Yup i have done this still problems, one side of the fets warm up and the other doesn't. i ca hear it pulling current too, because my variac is humming and the thermistor is getting HOT.

 

[carpenter]

Can you get gate voltage to both banks of power fets?

 

[jleaman]

Can you get gate voltage to both banks of power fets?

I can try, however i'm not powering this amp up to full. Im scared to i don't want to burn it out

 

[Zen Mod]

Have you looked up the datasheets of the two diodes in question?


Magura

 

[carpenter]

I can try, however i'm not powering this amp up to full. Im scared to i don't want to burn it out

Using your variac, turn on the amp a little (assuming P2 is centered) and measure voltage at power fet gates. I would imagine it should match.

 

[jleaman]

Using your variac, turn on the amp a little (assuming P2 is centered) and measure voltage at power fet gates. I would imagine it should match.

Measured from the psu and then measured from the gate, its the same on all.

I looked it up and the IRFP240 go like this, left to right GDS

 

[carpenter]

So the voltage on both sides of Q11 are the same?

Later, it's my bedtime.

bye

 

[Magura]

Yeah, I know....Magura the moron...


Magura

 

[Zen Mod]

Yeah, I know....Magura the moron...


Magura

nope , you moron!

ZM is moron!

 

[jleaman]

any more thoughts for this ?

 

[carpenter]

any more thoughts for this ?

Hi,

What have you experimented with in the last 24 hours?

 

[jleaman]

Hi,

What have you experimented with in the last 24 hours?

Nothing i worked all day hanging 60" plazma tv's i double checked the psu but thats about it so far.

Should i add picture of some sort ?

 

[carpenter]

Close-up pics are good to have. There are plenty of sharp eyes out there to help.

BTW, it never hurts to send a pic. You don't need to ask.

 

[jleaman]

Here we go, i just powered it up a little and im getting 1V across the 3watt resistors.

and still only one bank of fets is getting hot, one side. Weird.


Sorry just changed the picture didn't notice that the one i just posted was blurry.

 

[jleaman]

Picture of how it is setup, for testing.

 

[jleaman]

I think i have figure this out, GRRR,

On peter's boards See attached picture, you will see C5 & C6, they tie grount together into the circuit, when i was asking LONG ago what i should put in here people were saying it just something extra however i can leave them out, so i did, looking at the board as i was just assembling the other board i saw that gnd at that end of the board was not even tied to the circuit so i wonder if i should use the ground near the input then ? or should i put something into C5 & C6 ?

 

[lykkedk]

jleaman, what kind of isolation do you use on pwrmosfet's ?

Jesper.

 

[jleaman]

jleaman, what kind of isolation do you use on pwrmosfet's ?

Jesper.

Im using my trusty ceramic Isolation pads.

 

[Peter Daniel]

On peter's boards See attached picture, you will see C5 & C6, they tie grount together into the circuit, when i was asking LONG ago what i should put in here people were saying it just something extra however i can leave them out, so i did, looking at the board as i was just assembling the other board i saw that gnd at that end of the board was not even tied to the circuit so i wonder if i should use the ground near the input then ? or should i put something into C5 & C6 ?

That ground connection is only when C5/C6 are installed, otherwise it's not being used. I explained it here: http://www.diyaudio.com/forums/showthread.php?postid=1324572#post1324572