memphis 1000

[mike49504]

Amp goes into protection. If i pull both driver boards amp will power up normal.

But both not just 1 of the driver boards for the outputs needs to be out for it to power up normal

 

[Perry Babin]

If there is no DC on the tabs of the output transistors when the driver boards are out of the amp, there's a good chance that you have a defective LM361 comparator.

Did you get your scope back?

 

[mike49504]

theres no dc on the outputs with boards removed. Wheres the lm361 located on this amp?

 

[mike49504]

My scope isnt back yet i dont what the heck the guy is doing ill call them tommrow and see where its at

 

[Perry Babin]

There are likely two DIP ICs on the board behind the RCA jacks. The 14 pin IC is the LM361. Give me the DC voltage on all 14 pins.

LM361
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:

 

[mike49504]

lm371
1=12.42
2=0
3= -.02
4= -.06
5=0
6= -12.68
7=0
8=2.92
9=.01
10= -1.90
11=0.62
12=0
13=2.93
14=2.93

 

[Perry Babin]

That doesn't look defective.

Plug one driver board in at a time and see if the tabs of the output transistors swing towards the rails.

 

[mike49504]

when i put 1 in at a time the output readings are leg 1= 0 middle 25.38 for 1/10 of a second last leg 0

 

[Perry Babin]

There's something wrong. The tabs of all of the outputs on each side should be directly connected (confirm).

If that's correct, the rail voltage is on the last leg and has to be greater than or equal to the voltage on the center leg. I wouldn't think it possible that the rail voltage could get back down to 0v so quickly that you couldn't measure it. Use the secondary center tap as the reference.

 

[mike49504]

im gonna put this aside for the night i have to fix another one before the guy comes picks it up

 

[mike49504]

ok i checked the rail voltages on outputs its doing the same thing for 1/10 of a second it reads 25.38 then 0 the red and grenn power lights are flashing back and fourth wondering what i should check next?

amp does this crazy stuff even if all outputs are removed and i only put 1 board in at a time.

 

[Perry Babin]

What's in/out of the amp (outputs, driver boards...)?

 

[mike49504]

All of the outputs are removed. If i try to power the amp up with only 1 driver board in at a time amp still does the same thing (goes into protection) red and green lights flashing back and fourth . And amp meter on my supply goes crazy
(between 2amps and 20 amps)

 

[Perry Babin]

It still draws excessive current with no driver boards and no outputs?

 

[mike49504]

It idles fine and the relay kicks on with no outputs and no driver boards in the amp.

With no outputs in the amp and only 1 driver board in the amp doesnt matter which one thats when it trys drawing current from 2amps to 20 back to 2 then 20 and so on

 

[Perry Babin]

Are there any solder bridges on the pads for the outputs?

 

[mike49504]

Ok did a lil checking into this amp . The problem is both of the driver boards have something shorted on them. I pulled a driver board out of the memphis 500 i have here and put it in the 1000 in both locations and the amp powers up fine. I try using the driver boards that were in the amp then i get problems again

So im probably gonna have to rebuild both driver boards from the looks of it

 

[Perry Babin]

Post what defective parts you find. As far as I know, there's nothing that can cause the driver boards (with no outputs) to cause the amp to draw excessive current.

 

[mike49504]

Ok guess i was wrong the amp still does the protection thing with the new driver board.

I also replaced the board behind the rca jacks (the one with the lm371) and still have that crazy stuff going on. Wondering what i sholud look at next?

 

[Perry Babin]

Does it come on and idle (never going into protect) with no audio driver boards in the circuit?