My mistake on the F5

[erez1012]

Hi all
Firs of all thanks to all the gays here that help me so much to build this amp.
This is the best sound I hear ever !
The circuit is so simple, this is masterpiece.
I have a lot of mistake in this pcb, all the time the 2sk/j burn me and I don’t know way.
After I replace 5 from the 2sk and 5 irf that I burn I decide to Retire, and I buy some chip amp kit on eBay. Then I find my mistake:

My PS including 2 transformer, one for + and one for -.
The thing is that I power on the + and then the – because if I turn both of them together I burn the fuse.
Another mistake is that the + was 33vdc and the – was 29vdc.
I think this is the problem because the new kit from eBay burn too.
After change back to regular PS: one transformer and one power button the amp works!
So I think I back to the F5.

Thanks to everyone here.
erez

 

[FastlaneAudio]

Nice to see you got your working, I burned up one channel of mine by shorting it out when I was re-biasing it.

Dave

 

[erez1012]

Hi
My F5 steel don’t work, I just assume this is the reason.
Even its not working, this is so simple. Just remove 4 transistor and check.
After replace my 4 transistor and check the resistance my F5 burn again, its have to be the PS.
I buy some chip transistor from eBay until the amp work normally and then I move to match pair again.
The thing is that my amp work fine after replace the semi, but when I put more volume in the input I see DC in the output.

and i remove the protaction stage, so now its more simple

 

[bear]

33v and 29v is too high.

The power supply SHOULD be turned on so that both plus and minus starts at the same time.

The two transformers need to be *identical*.

There needs to be a connection between the two in order to create the CENTER point which is referenced (connected) to GROUND.

When you turn on the amp, you should have a light bulb (incandescent) connected in series with one of the AC mains leads. Ideally one would use a Variac (variable auto-transformer) to bring the AC power up slowly from a low voltage to full voltage. Just flipping the switch is an invitation for disaster.

The lightbulb gives some degree of protection. In your case a small lightbulb might be preferable, like 30watts or 20 watts...

Perhaps you might want to post some clear sharp images of your amplifier's internal wiring?

_-_-

 

[erez1012]

thank bear.
this is my PS
i hope its the PS that cause all the problems.

but now i back to regular PS:
one transformer with 4 wire. 2-ac-21v and more 2-ac-21v.
each of them connected to bridge and the cap

 

[Zen Mod]

never connect secondaries directly in parallel , unless you are certain that manufacturer made them for that .

connect rails in parallel after diode bridges , without harm

of course , that calls for each secondary having own diode bridge

 

[erez1012]

what do you think about my new PS?
this is one transformer with 4 wire in the out:
2 wire 21v and another 2 independent of 21v

thanks

 

[Zen Mod]

that's correct

all you need is to read schematic Papa already posted , if you're already going to make project by them

 

[bear]

Pretty safe to parallel secondaries of a transformer with dual secondaries that are identically rated and spec'd by the mfr. Imo.

But 21vac in will not give 21vdc out.
You will get 1.414 x 21vac since you have a "cap input" filter on the output.
So you'd expect 29vdc - which again is too high. Very much on the edge of what you would want to run given the input devices - the outputs are fine. Probably will work ok, but you also have to account for slightly higher AC line voltages...

_-_-

 

[erez1012]

hi
Few month ago when I start to build the F5 I have 2 transformer: 16ac and 21ac.
After read Mr. nelson PDF about turbo F5 I realize that I can use the 21ac with no change in the ver.2 pcb from DIY (the first F5).
So I connected the F5 to 33vdc !!

its wrong?
Maybe this is the reason for burning the F5 all the time?

Thanks all