Fetzilla Build Documentation

[meanman1964]

When I build my first FetZilla I had the same problem with that resistor also the first resistor on the positive side of the psu.Turn it off checked the board on shorts,cleaned the board to be shure and never had that problem again.There were other members with the same problem and also the first resistor on the positive side of the psu.Must say (red face)never used the lightbulb tester is this gonna prefent current draw?What wattage of bulb do I take for this tester?
Of this amp both channels R22 gets hot and burns up.
What is the purpose of D1-2 ?

 

[meanman1964]

What is the purpose of D1-2 ?

 

[rho]

I think these are a protection againt reverse voltages.
I you pull the ground up above V+ or below V- the diodes starts conducting.
If you mount them reverse they conduct and you will draw a fair amount of current from the supply and the output voltage would not go above 0.7V. Maybe you can check this. If the diode burns the problem will fix itself but the protection is gone. But in some cases a diode shorts which will worsen the problem.

 

[meanman1964]

I've soldered a second FetZilla using a seperate PSU.Set the bias but the voltage across bootstrap resistor R12 doesn't get lower then 28Vdc

 

[meanman1964]

Have to say I used for P3 a 200 ohm trimpot (schematic)in the BOM is P3 500 ohm

 

[meanman1964]

Problem solved used for P3 a 500ohm trimmer

 

[meanman1964]

Can I use for C1 2,2µF instead of 1µF?

 

[AKSA]

Yes, but no subjective increase to bass, which is very good anyway!
Hugh

 

[meanman1964]

My brother s FetZilla is alive and playing nice music.In post 130 you could read I'd some troubles but I took care of it and it was my own stupid fault.The first channel bad solder of R16 near T4.The second channel soldered D3 in the wrong direction.Pics will follow shortly

 

[ajst2duk]

Brilliant - nice troubleshooting !! What's the thoughts on the sound?
I'm just building a Pass B1 buffer pre for mine to see how that goes

 

[meanman1964]

It is my second FetZilla build and it stays an impresssive amp even after I bought a Naksa 80

 

[ajst2duk]

Ok that's good to know as I'm also keen on the Naksa 80

 

[meanman1964]

My brothers FetZilla

 

[AKSA]

Nice job, Patrick, looks very nice!

Hugh

 

[ajst2duk]

Here's mine with my newly build B1 buffer pre (remote control 4 inputs)

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[meanman1964]

Very nice build,how does it all sound?
What speakers are you using?

 

[rho]

Do you have some pictures of the internals of the amplifier?
What supply voltage do you use?
What's the impedance of the speakers you have connected?

 

[syklab]

My brothers FetZilla

Hi Patrick,
Is that a softstart you have next to the transformer ? Is it necessary for the Fetzilla?

Thanks

 

[meanman1964]

Hi Patrick,
Is that a softstart you have next to the transformer ? Is it necessary for the Fetzilla?

Thanks

Yes it is a soft-start.It allows you to use three kind of switches.A momentary,onoff and a trigger.It only cost 20Euro and I tought it wouldn't harm.

 

[AndrewT]

Hi Patrick,
Is that a softstart you have next to the transformer ? Is it necessary for the Fetzilla?.........

A soft start is used when one wants to limit the start up current flowing into the mains transformer.
The soft start has absolutely nothing to do with what load is applied to the output of the transformer.