HIFONICS ZXi 1008 car amp has output on one channel only

[tfs2015]

Dear Forum Members,

I have the above listed amp that a friend of mine dropped off for me to look at. He said that only one channel of the two had output signal to speakers. I tested the amp and found this to be the case. I don't have a schematic for this amp so I am a little at a loss here.

Things I have checked so far:

I Got +40, -40 volts dc on the supply rail to the output transistors which are C4467 and A1694

The op amps are MJM4588L's. I can't find a pin out for these to tell if any of them are bad.

If I am understanding the supply rail voltage correctly then the power supply part of the amp is functioning OK.

Any help would be greatly appreciated.

Thanks
Tom

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

I made a mistake op amps are 4558L

[diif]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

This should be the datasheet.

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

Thank you.

A friend of mine made the suggestion to me that one of the inputs is not being grounded properly, but without a schematic I don't believe there is a way I can test this. So any help would be greatly appreciated.

Thanks
Tom

[diif]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

Check for shorts, check the voltage going in, you have the good side to compare against.

[stj]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

how about some inside foto's?

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

Here are some photos of the component side of the board. looks like the photos got rotated 180 degrees for some reason

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

can someone tell me how to upload photos without them getting rotated 180 degrees?

[stj]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

they arent rotated by the forum, that's your photo's!!

[stj]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

o.k. car unit - parallel output design.

you need to resolder all those big white resistors that burned the board,
you need to check all the BIG transistors for shorts between the 3 legs.
and you need to check all the gray resistors with a meter.
i assume you have a meter & know the colour codes?

[SteveNielsen]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

Use a graphic editor and rotate the pics, save and then upload.

[diif]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

Windows photo viewer will rotate the photos, open the photo, click the rotate right or left icon then close the viewer. The rotated photo is saved automatically.

[stj]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

better yet, dont hold the camera at that angle when you take foto's
i'll assume it was a smartfone with a gyro in it - some of those re-orientate the image based on the angle of the fone.

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

That black stuff around the resistors is a coating of some kind

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

I can trace the audio signal out of the op amps after that I am not sure where it goes. I wish I knew how to turn my computer into an o scope so that I can see the input and output signals better. I appreciate all the help I can get to get this working for my friend.

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

Am I going to have to pull all the power transistors off of the board to test them?

[stj]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

not unless you detect a short in more than one

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

All I am able to tell is that there is rail voltage getting to them but I. Am not getting any out from them and no shorts across the legs. Could a bad ground be causing no output from the big white resistors on the board?

[stj]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

no.

are any outputs shorted to ground?
btw - have you got an esr meter?

[tfs2015]

Re: HIFONICS ZXi 1008 car amp has output on one channel only

no I don't have an esr meter and no none of the outputs are shorted to ground. I did find if I turn the input up to a real high level that I can get just a little bit of output on the bad channel but the power transistors on the bad channel never warm up.