Rockford Fosgate 1500bd

[mike49504]

Perry,

Dont know what happen to my last Thread cant seem to find it probably overlooked it.

Anyway Ive replaced all of the ic's on the board again. Replaced all of the regulators,resistors for the regulators,all of the outputs, the mic4420's new emitter resistors.

Just finishing up on putting the last 2 ic's back in it.

Wondering is there anything else i should check before i power this up and test the output.

I dont want this thing blowing up for the 5th time

 

[Perry Babin]

Did you check the regulated voltage on the ICs that have been failing?

I hope you're putting the ICs in sockets.

 

[mike49504]

DO you mean The + - 15 volts? Or what do i check for on the IC'S

 

[Perry Babin]

Yes. It's ~±10v on this amp (don't expect ±15v). Set your scope to 2mS, 5v/div and DC coupling. touch it to the power supply pins and push on everything in the area to see if the voltage ever varies from the ±10v.

This amp doesn't have any pulldown resistors on the FETs so you should install the opto-coupler before applying power (or desolder the red/black wires on the power supply side of the board <-- this would be best way to prevent damage).

 

[mike49504]

I can already see this isnt gonna be simple.

I tryed powering it up and it draws 60 amps of current.

I took the mic 4420's out and it still draws excessive current.

Power supply problem?

 

[Perry Babin]

Can you easily desolder all of the outputs? If so, the amp will produce drive signals and you can check them with no chance of damaging the outputs. I know it's going to be somewhat time consuming but it may be worth it.

 

[mike49504]

Ok i unsolderd the outputs and the amp idles fine

 

[Perry Babin]

Reinstall all of the driver components and op-amps. Do you get a clean square wave on all of the gate pads?

 

[mike49504]

I will mess with this somemore in the morning i found 2 problems i had 1 output is shorted. And i put U17 in backwards (OPPPSS)

 

[mike49504]

Ok what would u iset me scope to ? To check for the square wave on the gates ? All outputs are taken out

 

[Perry Babin]

5v/div and 2mS/div to start. When you confirm that you have a signal, set the time base to 10uS/div to see if you have a square wave on all gate pads.

 

[mike49504]

pic 1 is off the first bank of fets pic 2 is off the second set

 

[Perry Babin]

The drive signal looks OK but the voltage isn't right. Is the scope set to 5v/div?

Is the center knob on the vertical amp control set to the full clockwise position?

If you center the trace and touch the probe to the B+ terminal of your power supply, does the trace deflect upwards ~2.5 divisions?

 

[mike49504]

If i set my scope to 5v/div and 10us/div and set the verical amp fully clockwise this is all i get on both sets of fets

 

[Perry Babin]

The inner knob needs to be fully clockwise. The outer knob needs to be at 5v/div (0.5v if the scope marking are for 1x probes and you have yours set to 10x).

 

[mike49504]

I have my scope set to .5volts/div and 10us i dont get a square wave on either bank. My probe isnt adjustable. If i set my scope to .2volts/div 10 us then i get a square wave on both banks

 

[Perry Babin]

If you have it set to 0.2v/div and touch the probe to the 12v terminal of the amp or power supply, how far up does the trace deflect (center on reference before touching to 12v).

 

[mike49504]

If i center it on the line and touch the B+ the trace goes off the screen deflects way high

 

[Perry Babin]

What if it's set to 0.5v?

What do you get instead of a square wave when you set the scope to 0.5v and touch it to the gate pads?

 

[mike49504]

Ok my probe is a 10x probe If i set it to 5volts/dive 10us/div.

The first pic is touching the B+ terminal with it set to the center line

next 2 pics is what i get if i touch the gate legs of the fets