ADS 850MX

[mike49504]

I just got another one of theese in for repair..

The boards look nothing alike at all.. Must be 2 different versions of this amp..


I opened this amp up and transistors fell out of it..


Wondering if anyone knows a good replacement for the following transistors..


First one is marked : K214

2nd one is marked: J77

They are both T0-220 AB package

[Perry Babin]

How are those being used? The datasheets that I found indicate that they're only rated for 1/2 amp of current.

[mike49504]

Im guessing the drivers for the outputs.. Here is a pic of the board and i put an arrow to thoose transistors..

[Perry Babin]

Are they shorted?

[mike49504]

The legs are broken

[Perry Babin]

I don't have any suggestions for anything similar. If no one else does, try an IRF540 and and IRF9540. I'm assuming that the supply voltage in this amp isn't greater than ±50v.

[RiLoWa]

It would appear that MCM has both original part numbers in stock.

[mike49504]

Does anyone know thw the value of C13 and C14 ??


The amp is missing them..

[mike49504]

Or any ideas what may work in C13 and C14 locations ?

C13 the negative side of the cap connects to the 3rd leg of the power supply fets - IRFZ34

C13's positive side connects to the middle leg of the IRFZ34



C14 does the same but in the other power supply of the amp..

[mike49504]

Ok i think i might have figured out the value of them..


Next thing is this amp has 4 power supply in it ..

1 supply per 2 channels..


There is also 4 banks of rectifiers in this amp 1 bank per 2 channels..


When trying to power the amp up it will draw excessive current and the outputs will heat up..

If i remove all 4 banks of rectifiers the amp will power up and idle perfectly..

if i try to put just 1 bank of rectifiers in it no matter what supply i put them in the amp goes back to drawing excessive current and the outputs heat up within 5 secs..

Any ideas what to check?