autotek mean machine amx 100.2 repair

[grandam88]

i have a autotek mm series amx 100.2 i need to repair. I really want to bring this piece of car audio history back to life.

problem is protect light coming on as soon as power is received from remote wire, with b+ and ground hooked up. tried on multiple cars, same deal.

have already tested all output transistors (irf9540 and irf540) all are testing fine with similar readings across all transistors.

have tested all power side transistors (irfp064n) all are fine with no readings near zero.

only thing i cannot test or dont know how to test is the diodes (fmg-33r, fmg-33s).

have also tested all resistors in parallel with transistors, are seem fine.

need someone to point me in right direction, thanks

 

[Perry Babin]

If pin 16 on the TL494 is being driven above the voltage on pin 15, post the voltage on all of the pins of IC10.

IC10
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

 

[ppia600]

I have that amp with no heatsink lol and it powers up

 

[grandam88]

how much? u selling it?

 

[grandam88]

alright i have been doing some poking around on the amp and it looks as if a reavious repair was done with non oem component. This amp has irf9540's and irf540's. 4 of each on each side. one side has four irf540's and the other has 3 irf540's with a odd looking irfz24n. i have tested all fets with DMM all come out good, but this one irfz24n has differnt ohm readings than the irf540's and right leg/left leg tests .8 ohms(pretty near 0 if you ask me) other legs test 20-22 ohms. not only may this fet be bad, but i feel that it may not meet the specs to work right in the amp.
measurements of irf540 are
right leg, center leg/21ohms
right leg left leg/94.8 ohms
center leg, right leg/22.1

 

[Perry Babin]

You have center-right twice.

Remove the one that reads the lowest from leg 1 to leg 2 and recheck the rest.

 

[grandam88]

heres a link to both data sheets. the second link is the irfz24n. first is irf540

http://www.datasheetcatalog.org/datasheet/stmicroelectronics/9387.pdf
http://www.irf.com/product-info/datasheets/data/irfz24n.pdf

 

[grandam88]

sorry measurement for irfz24n
right leg,center leg:20.8ohms
right leg, left leg:.8 ohm
center leg, left leg:22.0 ohm

measurements for irf540 are
right leg,center leg:21.1 ohm
right leg, left leg:. 95 ohm
center leg, left leg: 114.9 ohm

also didnt understand

Remove the one that reads the lowest from leg 1 to leg 2 and recheck the rest.

the lowest reading is received from the irfz24n, all others read fine

 

[Perry Babin]

If removing the Z24 allowed the rest to read normally, the amp may power up and produce audio now. Clamp the transistors to the heatsink before applying power. Insert a 10 amp fuse in the B+ line.

 

[grandam88]

okay removing the z24 allowed amp to power up correctly. i have noticed this amp used heat transfer pads i guess you would call them, instead of heat sink compound. Are these reusable? they don't need to be replaced after removing board from heat sink?

 

[Perry Babin]

The sil pads can be reused. They won't work as efficiently as when new but will work well enough. I'd recommend using heatsink compound between the transistors and the sil pads. If the sil pads haven't been removed from the heatsink, you don't need to apply heatsink compound between the pads and the heatsink.

 

[grandam88]

k thanks