Sir.Byrd's F5 build thread

[Sir.Byrd]

I'll do it after a lunch break, gotta have my brain working.
What is the next step that I need to do?

 

[Sir.Byrd]

Measured across R11 and R12? Adjust trimpots to get it there?

 

[Woody1911a1]

yes but you also need to be measuring dc offset at the speaker terminals , keeping them near zero . .

just bias up one channel at a time slowly

 

[Woody1911a1]

turn each pot a half a turn each until it starts reading on r11 +12

 

[Sir.Byrd]

okay, I'll have to go borrow some meters, I just have one.
First I'll need to jumper the ground to the output ground though.

 

[Woody1911a1]

once you start reading voltage the magic starts to happen . get it up to say .40 v and let it cook for awhile . you should start feeling heat eventually from your mosfets and sinks . if alls well and no smoke just leave it and go to the other channel .

 

[Woody1911a1]

you really only need 2 meters , one on either 11 or 12 and the other on the speaker terminal

 

[Woody1911a1]

g'nite komi

 

[Woody1911a1]

another thing is that you can't bias up with the variac , you need full voltage . if you bias up with the variac at say 3/4 power , then you connect direct to mains expect smoke .

 

[Sir.Byrd]

I don't plan to do the biasing with the variac, I only had planned to see the effects of the trimpots at a lower voltage.
I'll do full voltage for the bias for sure.
I'm getting help locally with it tonight in a few hours.
Thanks for all of your help.

 

[specialidiot]

get three meters, it will bias up a lot easier. If you don't understand what a turn on one pot does to the other with respect to the DC offset at the speaker terminal, it will take you forever.

 

[Sir.Byrd]

Got it!
Biased both channels to roughly .59 ±.005
DC offset within 10mV of 0V
To say the least it works, to say the most it sounds phenomenal!
I got 26 watts out of it into an 8 ohm load, and 42 watts into a 4 ohm load.
Now I just need to attach the faceplate and it's done

 

[marantzfan]

Got it!
Biased both channels to roughly .59 ±.005
DC offset within 10mV of 0V
To say the least it works, to say the most it sounds phenomenal!
I got 26 watts out of it into an 8 ohm load, and 42 watts into a 4 ohm load.
Now I just need to attach the faceplate and it's done

Awesome Will!! Welcome to the F5 fraternity.

 

[specialidiot]

you are supposed to set it to .4 and let it run for a while.

good job getting it going.

 

[Sir.Byrd]

We did it at .4 then let it run, then my mentor cranked it into class AB to get it heated up, then we put it back in idle until it was more stable and I honed it into the final setting of about .59 with no trouble.
I'll post photos and listening impressions soon, but I can't listen to it until tomorrow afternoon at the earliest.
Thanks everyone for your help, I had just about lost it today when I reached a hitch.
Without the support I receive on here I don't know where I'd be!

 

[skywave-rider]

:thmbsp:
Congratulations.

 

[Sir.Byrd]

Now I just need to finish the preamp/DAC.

 

[Sir.Byrd]

It only took 8 months, 18 days!

 

[marantzfan]

It only took 8 months, 18 days!

I'm pretty sure I still hold the record. But, it was a good run at the title Will.

 

[Sir.Byrd]

We'll see how long the preamp takes. Should be a neater build now that I have some build experience and know what NOT to do...