F5 power amplifier

[Sisyphism]

Thanks bobodioulasso.
I will remember that.

Can i use a 500W Variac? Is this enough power for start up?
On its specs i read 2A max. @ 230VAC.

[cetoole]

I was just getting ready to order parts to build one of these, and both Mouser and Digikey have no stock of FQA12P20 or FQA19N20C, and Fairchild's website shows both on the NRND list. Any suggestions for subs?

[bobodioulasso]

Originally posted by Sisyphism
Thanks bobodioulasso.
I will remember that.

Can i use a 500W Variac? Is this enough power for start up?
On its specs i read 2A max. @ 230VAC.

A bulb is nice to detect a problem at first run.

If all is ok the bulb enlights brievly and go dark again with pots at min.

The charging caps then nothing.

If the bulb stay lighting , switch off, there is a fault or pots are maximum.

I you do not start at a too low voltage, why not to use your variac in a

second time.

[Sisyphism]

Yes, pots at minimum = Zero Ohm.

First i have to put the PSU into the case,
and there are some questions about thermistors i should use.

Attached File:
This is something I DO NOT KNOW IF IT REALLY WORKS FINE,
How should i calculate those Thermistors ?
TH1 should be ok i think, but how about TH2 + TH3 ?

Please correct me, if there is something wrong.

[nigelwright7557]

Originally posted by Sisyphism
Yes, pots at minimum = Zero Ohm.

First i have to put the PSU into the case,
and there are some questions about thermistors i should use.

Attached File:
This is something I DO NOT KNOW IF IT REALLY WORKS FINE,
How should i calculate those Thermistors ?
TH1 should be ok i think, but how about TH2 + TH3 ?

Please correct me, if there is something wrong.

You seem to be using 3 thremistors where one would do the job.

I dont think you need TH1 just connect it to earth for safety.

If you put TH1 in series with mains you dont need TH2.

[udailey]

Those thermistors are calculated for you. Check the bottom of your schematic you posted and it tells values and part numbers for all of them.
When you fire it up you can use your variac but you can use this as well
http://www.antiqueradio.org/dimbulb.htm
This is the dim bulb tester they were talking about and it has saved a few of my amps.
500w is more than enough.
Uriah

[Sisyphism]

I made this file, and it seems to be wrong in some cases.

[Sisyphism]

If i understand it right, nigelwright7557 thinks this way is ok.

Thanks.

[nigelwright7557]

Originally posted by Sisyphism
If i understand it right, nigelwright7557 thinks this way is ok.

Thanks.

Yes, providing you can get a thermistor powerful enough to take all the current to both transformers.

[Jozua]

Hi

Has anybody done this comparison ?

I have a Aleph30 that sounds excellent. Would the F5 sound better?


Audio regards

Jozua