MMATS D2000.2

[S Merlington]

Got this amp in and it does some strange things..

First off the power light will not light up at all in this amp..

When hooked up the amp will have sound for a min then fade away then come back real quietly then go back out and will continue to repaet the cycle..

This is a HIP4080 Based amp..

Someone has switched the outputs in it before The outputs that are in the amp right now are IRFB4710's


Any ideas ??

 

[Perry Babin]

Was the supply cycling on and off as well?

Did you get a good rail to rail square wave (0-80v) on the output transistors at all times or was it cycling also?

 

[S Merlington]

I dont think the power supply is working correctly ..

When i first powerd it up i got 5 volts on the Gate leg for the fets now i get 0.02 volts


The rail voltages keep cycling as well...


But the amp has output for a few seconds then fades in and out

 

[Perry Babin]

Did you get a good rail to rail square wave (0-80v) on the output transistors at all times or was it cycling also?

 

[S Merlington]

I got good rail to rail oscillation ...


With just power ground and remote hooked up I get rail to rail oscillation and its steady never cycles..

 

[Perry Babin]

If you drive a signal into the amp does it shut down?

You stated that it fades out. Doesn't it have a relay? Does the relay engage/disengage?

 

[S Merlington]

Amp has no relay..

If i send a signal into the amp and increase the signal the output will fade out even faster..

Heres what i have on the SG3525

Pin 1:0.34
Pin 2:5.15
Pin 3:0.00
Pin 4:0.46
Pin 5:2.02
Pin 6:3.81
Pin 7:1.93
Pin 8:0.38
Pin 9:6.00
Pin 10:1.19
Pin 11:0.00
Pin 12:0.00
Pin 13:13.12
Pin 14:0.00
Pin 15:13.12
Pin 16:5.15

I get hardly any rail voltage

Heres what i get on the 4710's

Leg 1:7.03
Leg2:5.12
Leg 3:2.64

 

[Perry Babin]

Pin 10 (The shutdown pin) has too much voltage on it. It needs to be very near 0v DC.

 

[S Merlington]

Pin 10 goes to Pin 8 of the Driver IC (AD826AN)

The voltages i have on the driver IC are

Pin 1:0.00
Pin 2:13.11
Pin 3:0.00
Pin 4:0.00
Pin 5:0.00
Pin 6:0.00
Pin 7:0.00
Pin 8:0.00

http://pdf1.alldatasheet.com/datasheet-pdf/view/48430/AD/AD826AN.html


So what do i need to look at since the voltage on Pin 10 is to high??

 

[Perry Babin]

A couple of issues...

Pin 8 of the 826 has no voltage. I'm assuming that it should be near 12v.

Pin 8 is a power supply pin for the 826 and wouldn't be connected to the shutdown pin.

 

[S Merlington]

Ok sorry Pin 11 of the 3525 gos to Pin 8 of the driver IC

 

[Perry Babin]

So what connects to pin 10?

 

[S Merlington]

Ok found 1 problem the Driver IC is in a socket and as soon as i wiggle the IC around in the socket it gets voltage on PIn 8 and the power light comes on..


Im gonna order a new driver IC and remove the socket since the legs are ready to break on the IC

Amp still does crazy stuff with the output..


Wondering Should i order the IRF3710Z's For this amp and replace the IRFB4710's to see if that cures the output problem since this a HIP4080 based amp..

Pin 10 connects to the collector of a MMBT4401

 

[Perry Babin]

Do you know if the amp was working properly with the 4710s?

It would be a lot of work to replace them and should be left as a last resort.

You should be able to get the op-amp connected well enough to do further troubleshooting. If so, you'll have to determine if the power supply is being shut down when the audio fades out.

 

[S Merlington]

Not sure if the amp was working correctly with the 4710's or not since the guy who brought it to me said he outputs and the power supply fets were blown and he just replaced them and couldnt get the amp to work

 

[Perry Babin]

You'll need to determine what is shutting the amp down (a real fault that's triggering one of the protection circuits or a fault in the power supply that's not keeping it on).

 

[S Merlington]

How do i tell which way the 826 is suppose to sit in the board???

It was in 1 way when i got the amp but the markings on the board shows it goes the other way any ideas?

 

[Perry Babin]

I would expect pin 4 to connect to ground.

 

[S Merlington]

Right now Pin 7 connects to ground

If i reverse the direction of the op-amp pin 3 would be connected to ground

Heres the datasheet i found..

AD826AN pdf, AD826AN description, AD826AN datasheets, AD826AN view ::: ALLDATASHEET :::


So which would be correct Pin 7 connected to the amps ground terminal or Pin 2 connects to amps ground termianl ??

 

[Perry Babin]

I don't have any information on this amp so I didn't realize it initially but you appear to have an op-amp in place of a driver IC. Pins 11 and 14 will connect to pins 2 and 4 on the 8-pin IC which should probably be a TC4424 or an MIC4424. If that's true, pin 3 would be ground. Pins 5 and 7 would drive the FETs.