zapco ag 350

[genes66]

help with zapco ag 350 will not power up and does not blow fuse either no burn marks etc.

[Perry Babin]

Change the fuse to a 10 amp fuse (added protection in case something goes wrong). Leave the transistors clamped to the sink. If you've already removed the clamps, replace them.

Look up the datasheet for the power supply driver IC (SG3525) so you can see how the pins are numbered.

Connect the black meter lead to the ground terminal of the amplifier. Set your meter to DC volts. Power up the amp (including remote) and measure the voltage on each of the pins of the SG3525. Don't slip and short between pins

Post the voltages like this (copy and paste this):

Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

[genes66]

the only readings are on pin 11:0.07 and on pin 14 0.02

[genes66]

fets dont even warm up

[genes66]

center pin on irfz46n n- channel mosfets read 13.75v if that helps at all but they dont even get warm why?

[genes66]

Pin 1: o.oo
Pin 2:0.00
Pin 3:0.00
Pin 4:0.00
Pin 5:0.00
Pin 6:0.00
Pin 7:0.00
Pin 8:0.00
Pin 9:0.00
Pin 10:0.00
Pin 11:0.07
Pin 12:0.00
Pin 13:0.00
Pin 14:0.02
Pin 15:0.00
Pin 16:0.00

[Perry Babin]

What's the DC voltage on the second and third legs of the 2n6714 transistor (Q30) near the IC? If the third leg has ~12v but the middle leg has ~0v, check the diode DZ5 to see if it's shorted.

If there is no voltage on the transistor... There are 2 diodes near the FETs. Do they have ~12v on both sides?

If not, there are 2 10 ohm resistors next to the diodes. Do they have more than a volt across them? If so, remove power from the amp and measure the resistance across them.

[genes66]

I did some voltage checks to 2n6714 no voltage on second leg but 13 volts on third leg voltage on zener diodes has voltage on 1 side only.but when i tested i forgot to hook up remote wire to amp and when i did i rechecked voltage on 2n6714 and there was less than 1 volt on it second leg and third leg

[Perry Babin]

It sounds like there is either excessive current flow through the transistor (would likely be causing transistor to overheat) or there is excessive resistance in the circuit feeding the transistor.

With the amp powered up (including remote), measure the voltage on the center leg of the FETs. If it's near 12v, measure the voltage on each side of the 10 ohm resistors.

[genes66]

i also tested dz5 and it had a reading one way only