crate limo TX-50D not working

[feves]

I am posting this here after posting in the schematic request area to obtain schematic...thanks enzo!

The amp failed after the 15vdc wall wart was plugged into the 12vdc car adapter input. Amp would power up and make a few small pops and the LED would light brightly at first and then dim down to a faint glow. The amp would have no sound. I found that one of the opamps was bad when I tried it in a known good circuit. The others were fine. It was a 5534 that was bad. I didn't have another on hand so I replaced with TL082. Amp still does not work but now it oscillates when powered up. I suspected the power amp IC might be bad as it's data sheet says it's max supply is 18vdc and the 15v wall wart puts out over 20vdc with no load. Also, 4148 Diodes on the main board look good. I pulled the power amp IC out and everything looks good the power LED changes from Red to Yellow instead of blinking red and I get signal on the scope all the way to the power amp IC pin 1. However, when I replaced the power amp IC it is still not working. Back to where it was except the oscillation sounds a little different. Supply rails sag when either IC is in there. Any ideas? I was VERY careful not to give it too much heat when I put it in. The replacement is TDA1562QCD that I ordered from Digikey not sure the make. The original is just TDA1562Q made by Phillips
Thanks,
feves

[Enzo]

Look up the data sheet for the 5534 and compare it to the sheet for the TL082.

The 5534 is a single op amp, while the TL082 is a dual op amp. The two ICs pins are wired completely differently. A TL082 would work in place of a 5532 though. I am hoping 5534 is just a typo.

Your wall wart may put out 20v unloadedd, but it is a pretty safe bet it was not 20v when connected to the amp.

Chances are that you damaged something in the powr supply circuit. When you remove the power amp IC, you are also removing the major current user in the amp. Ther red/yellow light appears to be a low voltage indicator.

Are the batteries still connected? If so, disconnect them - note how they are connected - and try powering up the amp again. Possibly the battery is loading down.

[feves]

battery was disconnected during previous testing.
I meant 5532 sorry.
-Feves

[Mars Amp Repair]

Those amps usually won't blow if you try to run them from the charger input or visie-versie. It just won't supply enough power to run the amp.

My recollection is that these amps won't run without a good battery in them. The wall wart does not have the power to run them by itself. they will grunt & pop & generally act weird if the battery is bad, too. power led pulses. read the label on the back of the amp to tell you what the different LED indications mean.

The battery is used for most of the power drain, unless you are plugging a car power adapter (formerly known a cigarette lighter plug) from the car into them. g

[pontiacpete]

[QUOTE=feves;130226]
The amp failed after the 15vdc wall wart was plugged into the 12vdc car adapter input. Amp would power up and make a few small pops and the LED



A guy I use to play with did this, plugged the wall wart into the cig lighter input, blew something. He ended up taping off that jack and my limo is also taped off there, for the past 8 yrs. Why they put them so close to each other we'll never know?

I'm really interested in your repair, I have 2 broken ones here and will one day be delving into.
Good luck!
pete

[feves]

Thanks Mars,
I think you got this one right. I am charging the battery which is totally dead and I think it will probably work after that. Power IC was probably fine all along. The bad op amp was probably the culprit.