Maybe just because of the last few post even if same of those are not realy exact to the third decimal place.
I don't know, but might depend on how your pots are connected/oriented
when setting pots at 'zero' start proceedure, you should measure on the bypassing resistors right next to it
if I remember correctly, bypass resistors should measure lowest value when pots is at zero bias
your dc depends on a balance act between the two bias pots
with every bias change you make, you should finish adjusting the balance for minimum cd
I woulds suggest that you focus primarily on good dc balance
ok, I kind of figured out what messing up my bias settings.
I checked r3 + r4 on the other board that properly biases and they are both ~ 60ohms.
I spun up pot P2 to reach ~ 60 ohms on r4, but I kept turning P1 and reached a max of about 35ohms.
I'm not sure what's wrong...
Arg, I thought I had this fixed, not just yet!
I checked r3 + r4 on the other board that properly biases and they are both ~ 60ohms.
I spun up pot P2 to reach ~ 60 ohms on r4, but I kept turning P1 and reached a max of about 35ohms.
I'm not sure what's wrong...
Arg, I thought I had this fixed, not just yet!
I hope that's with no power on
before power on, you need to set pots to low bias
measure across R3/R4
adjsut pot to low value measure on R3/R4
then you are ready to power up
please note which way the pot is turned
so that you always know if your are turning bias up or down
also note that dc can be either negative or positive
maybe thats what is confusing you to turn the wrong way
Lift one end of the fixed resistors and check the resistance of each. While they are lifted check the max and min resistance of the bias pot.
Another F5 built. Isn't it getting boring?
First of all, a little prayer for F15 who lost its life given birth to her first child - named F5 in her honor. Amen.
Biasing the mosfets was easy although those trimpots have too many turns for my liking. So far no DC on speaker's terminals. Heatsinks are doing a great job - no excessive heat. Hmmmm...what else.....oh, it sounds great ( almost forgot
).
Thanks to Nelson and to all those who helped me.
* The story about the bleeders was a little boring... anyway with no bleeders resistors installed the leakage paths suck the juice out of the caps in ~ 30 seconds. Big deal.
The pics. The plastic connector will be removed later on.
First of all, a little prayer for F15 who lost its life given birth to her first child - named F5 in her honor. Amen.
Biasing the mosfets was easy although those trimpots have too many turns for my liking. So far no DC on speaker's terminals. Heatsinks are doing a great job - no excessive heat. Hmmmm...what else.....oh, it sounds great ( almost forgot
).Thanks to Nelson and to all those who helped me.
* The story about the bleeders was a little boring... anyway with no bleeders resistors installed the leakage paths suck the juice out of the caps in ~ 30 seconds. Big deal.
The pics. The plastic connector will be removed later on.
Attachments
Cassiel..... nice looking amp--but aren't the heatsinks, front panel, enclosure (and it's design) all from the Musical Fidelity amp, that came out in the mid-1990's? In any case, nice job in "repackaging".
Did the F15 Class A die on you? If I recall, they used to retail for about $2,700 (US)....
Did the F15 Class A die on you? If I recall, they used to retail for about $2,700 (US)....
You have excellent taste, amigo.
http://www.diyaudio.com/forums/pass-labs/166784-pictures-your-diy-pass-amplifier.html
Nice catch, Al-Var-O-Madrileno.
British moms, keep your pretty daughters at home, send your ugly ones to Spain instead, there's a ravisher on the loose and he's single.
(really pretty heatsinks, if that front plate was covered with epoxy-glued sea shells and shiny stones, it would make a pretty Gaudi amp)
No, it was in good working conditions. It's a funny story... initially I was going to do a recapping job that turn out to be too complicated. I had to remove almost everything to access the bloody caps so I thought, hey why not build a new one?
OK, the chassis is a bit expensive
D) but the DIY F5 is cheap sooo... and the F15 was getting too old. I'm happy, a new amp and much better sounding. Hehe. Best of both worlds. A great looking chassis with a great circuit inside.Yep, I'm single and dangerous.