I have just turned off the second channel. I don't think I should go into much detail but both channels started up without blowing the 3A fuse on the 500VA toroid transformer. I tested both channels separately. The results are pretty much similar. Loaded rails voltage stands still at 21.5VDC, DC on output 0.000VDC at 2V position on the multimeter while both source resistors have around 6.2VDC across them. That is for both channels. Input J-fets (170/74) are matched, nothing else is. I will still need to put both PSU sections and amps with heatsinks together and build some kind of box around them, but I deliberately placed the heatsinks on their back to get the worst possible heat releasing capacity and measured (again, the same on all four output devices) 65 degrees C on the plastic housing of the transistor, 50-51C 10mm from the transistor (on the heatsink) and about 40-45C on the edges of the heatsink. The 25W 0.22resistors in the filter and the 2.2K resistors remain cold (not ice cold, though). both amps were on the table for about three and a half hour and the temperatures and voltages remained pretty much constant/stable after the first 30 minutes. The maximum DC variation on the output went to 0.005V for short time (couple of seconds) and slided back. At the same time, the voltage across the source resistors did change at benign levels, from .599 up to max .620 in extremes. I am very pleased to say it all went very smooth from the very first moment. I hope it will serve my ESLs with the same stability to my complete pleasure. So, if anyone is reading this, I must also say that this was my very first attempt to build an amplifier that requires adjustment and also my very first attempt to build a solid state amplifier that works in Class A. Mister Nelson Pass, thank you for designing this amplifier and sharing it with DIYers, thanks to Zen Mod for intensive support and not turning the phone off, Mr. Borko who provided the design for PCBs and my lucky star for not letting me start a fire in our living room...
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spavleski said:I just hope that instrument on the left is connected as it should be............... . ...............Ok, that was a JOKE. I'll stop it here. Hope the sound of F5 will pay off the effort of completing F5 in 10 days including hard work and stress.
yup , that's even more decent work - including his illness (minor problems with lungs) ;
fortunately , that's just temporary ....... not like permanent short circuit between headphones , which is certainly bigger issue for our friend Stein
Zen Mod said:
I just hope that his Hungarian is as good as his English
I can, at least read und fersten alles von diese seite:
www.ret.hu
Can you?
stein2 said:
naturlich
meinen ersten Schatz Name - Lydia ......... heisse Madjarica
Mosfet question
Hello
I'm planing to put together a F5 amplifier before the F6 comes out .
I have a question can I use these mosfet-s together because only I found these type IRFP9240 in the local store .
In case it degrade the sound I would rather order from US fairchild mosfet . I not even know which company produced the SEC type mosfet ??? It cost me almost $6CAD each , I bought 5 PC so I can (found hopefully two the same)
Mr. Pass would you be so kind please let me know , I want to know your opinion . But any one else who has experience with these mosfet !! Thanks a lot .
Mr. Pass thanks for your time and the opportunity we can have such a good quality amps .
Greetings
Hello
I'm planing to put together a F5 amplifier before the F6 comes out .
I have a question can I use these mosfet-s together because only I found these type IRFP9240 in the local store .
In case it degrade the sound I would rather order from US fairchild mosfet . I not even know which company produced the SEC type mosfet ??? It cost me almost $6CAD each , I bought 5 PC so I can (found hopefully two the same)
Mr. Pass would you be so kind please let me know , I want to know your opinion . But any one else who has experience with these mosfet !! Thanks a lot .
Mr. Pass thanks for your time and the opportunity we can have such a good quality amps .
Greetings
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gaborbela said:
SEC nowadays is short for Shanghai E-Comp., but if you go to secccn.com you'll see that they manufacture only weenie MOSFETs.
The IRFP9240 you have was manufactured by Samsung, must have been lying on the shelf quite a while but not a fake.
(Fairchild and Samsung have been playing corporate takeover ping-pong over the last 30y)
I would like to announce that my F5 clone is well and working. No need to bother ya with all the details because there is nothing I can teach you, but would like to comment on assembly issues... I had my own issues but none with this amp. Took me about ten days to put everything together (including building the box and gathering the parts) and with shear pleasure I can say that the only detail that is not really as Mr. Pass said, is the assembly and adjustment. It was much easier than it appeared after reading the service manual. Now the F5 is connected to my Fostex horns and really no noise or nasty things during power up or warm-up period. The next are the panels, but first I have to make some order in the living room... It's a mess... 
