F5 power amplifier

[fritz39]

[QUOTE=Nelson Pass;1949901]Is it the output or the distortion that looks symmetric?

I'm looking at the output waveform on an oscilloscope. I don't have any way
to measure distortion.

[Zen Mod]

Originally Posted by fritz39

.....
I'm looking at the output waveform on an oscilloscope. I don't have any way
to measure distortion.

then nothing to worry about ......

[Russellc]

Originally Posted by Beftus

You can use IRF9240P's and IRF240N's instead.

Thanks for the reply. I ordered the kits from Tech-Diy with the IRF devices, and also ordered 2 pairs of the Fairchild devices, so I should be covered.

Russellc

[fritz39]

Originally Posted by Zen Mod

then nothing to worry about ......

I also forgot to point out I have a tin ear!

[Melon Head]

Originally Posted by chrismercurio

I like my battery powered B1. (try that too)

Yes I will.
I will try everything. Switch mode is more interesting to me though, mainly because of the hatred people have toward it.
I love the underdog.

[juma]

Originally Posted by fritz39

Speaking of the Fairchild parts...

I was looking at the threshold voltage of the FQA12P20 vs the FQA19N20C and
noticed there is about a 1V difference. That wasn't the case with the original
MOSFETs. When you adjust the bias to get 1.3A one pot will be higher than the
other. Doesn't that make the gain on one side of the input fets higher than the
other? Does that make any difference or does the feedback take care of it?

I also noticed on one of the pictures from an F5 review that a 2.2 ohm resistor
was put in parallel with the 0.47 ohm resistor on the N-Channel side. Does this
have anything to do with the difference?

P.S. I haven't matched anything and the output on an oscilloscope looks very
symmetric. I just don't understand why.

Thanks.

You obviously didn't read the whole thread. The issues that you mention are already discussed at length (in some other threads too).

[westend]

Originally Posted by Russellc

I'm only to page 222, so sorry if I havent got there yet, but was wondering what everyone is going to do now that FQA19N20C and FQA12P20 are discontinued? I ordered a parts kit from Tech-DIY, but was wondering if there is a replacement?

Thanks, back to the thread,'


Russellc

Russel, the Tech-diy kits are avaiable with the Fairchild FQA12P20 and FQA19N20C MOSFET's. I received these within the last couple of weeks.

[westend]

While I'm in the posting mode, a quick question, if I might. I have the Cviller boards and at looking at the location of the LED through holes I noticed resistor #35 location. Is this the location of the resistor for the LED ?

[max426]

Originally Posted by westend

While I'm in the posting mode, a quick question, if I might. I have the Cviller boards and at looking at the location of the LED through holes I noticed resistor #35 location. Is this the location of the resistor for the LED ?

yes it is

[fritz39]

Originally Posted by juma

You obviously didn't read the whole thread. The issues that you mention are already discussed at length (in some other threads too).

Actually I have read most of the thread and don't remember any mention of my
specific questions. How about giving me post numbers or just a short answer. I
have read quite a bit about the lack of need for matching, but not why.