Power Acoustik OV2-1200

[m4ick]

I found a solder bridge on an op amp in this thing and fixed that.

My concern is that after I power it on in the vehicle the power led stays lit for about a minute or so after powering down. I unhooked it and brought it back into the house and the power LED is still pretty bright. Is that normal for these amps?

 

[Perry Babin]

It's driven by rail voltage so it's probably normal. It takes a while for the rail caps to discharge through the LED.

 

[fcruz]

I have the layout of the series of POWER ACOUSTIK OV2

 

[m4ick]

The HP/Full/LP switch was bad in this thing.

Now when I run it one channel sounds terrible in high pass mode and in low pass mode it sounds worse.

I've run the pots all the way down and all the way up and it still sounds just as bad. Could that be an op amp or morel likely dirty pots?

 

[Perry Babin]

If the channel never produces clean audio, it's not likely to be a switch.

Post a photo of the distorted signal with a speaker or dummy load connected. Confirm that there is no excessive DC (no signal) before connecting the load. Have all transistors clamped.

 

[m4ick]

Sorry, I don't have a camera on hand yet (it's been SLOW), but I will have a friend bring one soon to take a picture of the waveform.

The channel produces clean audio in full pass mode, distorted audio in LP/HP mode. The customer just informed me that the amp got wet while connected to power but not powered on, which led me to believe it was dirty pots.

The distortion seems to only occur in the lower octaves (when bass plays).

 

[Perry Babin]

Check the output of each of the op-amps in the preamp section. Do any have more than a fraction of a volt of DC on their output pins?

 

[m4ick]

I found 14.xV DC on a NJM072D but the inputs/output were not connected to any circuit.

In LP mode I could plainly see the distortion. I looked at the signal on the base of the outputs and traced it back until it was clean. I found a broken solder joint on the pre amp board.

I asked earlier about the power light turning off slowly. I have a same series 4 channel amp (they were a matched pair that got wet) and the power LED turns off much more quickly. Are these amps power LEDs more likely wired differently or more likely something is not discharging the rails on the 2 channel?