help with MOSFET AMP

[averasjr]

Hello everyone,

I'm new here. I joined this group hoping a help from someone.
I'm an electronic enthusiast. And i love assembling amps (from kits). I have assembled 2 amps (100w) being used for my band. a guitar and bass. so i decided to assemble one again for my keyboard.

but this time, when i follow the same schematics from my old amps, my kit (particularly the resistors) keep burned up. i can't figure the error. i'm sure i have followed the biasing. I have busted most of my speakers because when i turned my amp on, the resistors burnt up and smokes emits at my speakers too.

I suspect the grounding is an issue. another problem i have is when my amp works, i level up the volume at 9 o clock and my mosfets easily gets hot. so its either i have to check my grounding.

is there an issue if you are using a transformer with two secondary (50 0 50 and 36 0 36)? i,m using the +/-50 for the amp kit and +/-36 to power up my tone kit.

Please help.

Thank you so much.

vic

[Xoc1]

Welcome to the Forum
Please fill in your profile details. It helps to know which part of the world you are from!
Can you post any schematics of your amp, or a link to them if they are on the web.
Are you using the right type of mosfets?
A 50 0 50 transformer is a high AC voltage for an 100w amp!

[ervinl]

Before using 50-0-50 and 36-0-36, try using lower voltage, e.g. 15-0-15.
Start bias from 100 mA. Check Vgs voltage around 3-4 volt. May be disconnect alll MOSFET in final stage while measuring the voltage (after driver)/at Vgs. Make sure that GDS is correct, usually GDS can be swapped to GSD (e.g. 2sk 1058 vs IRFP).
Don't forget polarity and of zener dioda in VAS/LTP regulator, CCS, Elco, and pin out of small transistor (some time can be swapped EBC or CBE).

Can you post the schematic here?

Ervin L