Cviller's F5c

[thor61]

Do I use R111 & R112 as bias test points ? See pic >

[coils]

Originally Posted by thor61

Do I use R111 & R112 as bias test points ?

Those are the correct r's for monitoring the bias current, actually, any one of the 11, 111, 12, 112 will work, with well matched parts, the volt drop across them will be the same, so you can just monitor one. If you have multiple dmms, monitor an n and a p simultaneouly, and with another monitor the dc on the output of the channel.

[coils]

Originally Posted by thor61

Cviller, Thanks for the quick reply ! I have all of your pcb's F4, F5, and F5c. My I'm not sure as to which one to build as I'm looking for 60 wpch or better @ 4 ohms. Can't find a lot on the F4 or the F5c which is the one I hope to build. My heat-sinks are 0.26 c/w and I plan to use copper heat spreaders... My transformer is a Antek AS-4218 2x18v @ 400Va And the psu caps are 40v 15,000uf x 12. I plan to use 6 each per channel via Chipamps.com's psu pcb's giving me a total of 180,000 uf ! Any help instrumenting a build based on this info would greatly help..... Thank-you

If you want 60wpc, I would build the F5c. You wont need to cascode with your 18 v xfmr though (uless you have enough secs to series them). And at 400va, its not really for a hot rod F5, unless you have two of them, one for each channel. Your xfmr is perfect for a stock F5 though.

How many sinks per channel are you going to use? They look like you will need two per channel. I dont think one per channel will work at a respectable bias level.

When you build it, and are ready to bias it, just let your sinks decide. Slowly start to bias it, letting it warm up as you go. If your sinks get too hot, you can back off some. The biasing procedure is the funnest part of the build, and it offers a lot of flexibility to adapt to your sink capabilities.

[Rixsta]

Ok Ive been reading about this PCB and have a little confusion as the wording used about it is diferent to nelsons PDF.

the F5c boards, will make the double output F5 Turbo, Ill end up with 50w F5 ? will it also make Version two ? can i make V2 work with this board ?

[coils]

Originally Posted by Rixsta

the F5c boards, will make the double output F5 Turbo, Ill end up with 50w F5 ? will it also make Version two ? can i make V2 work with this board ?

Yes, the F5c boards can make F5Tv2, and can easily achieve 50 watts class a into 8 ohms, if you have the rail voltage and enough sink to bias it. You will have to hard wire P3 and the parallel source diodes.

here is a pic of mine. It is not cascoded, and I did not install P3. Its not difficult to build it this way, or you can wait for turbo boards.