I hope I blew only the AMPs (again)

MIDIbox FM
1

I’ve been having trouble with my FM for some time, I had recently found out that my partially rectified current was not really working well (I thought it might have been adding noise, not to mention not being able to plug into a mixing board). So I decided to build a new PSU that used 9v regulators. Unfortunately though, I think that I blew my amps by just plugging in the 9+,gnd,-9 to my fm board; which ended up making my AMPs really hot.

Sooooo, once my new board was built (& tested for voltage as it had been before it plugged it in) my FM no longer makes any noise, not even the scratchy noise it made before.

Is just plugging in the bipolar supply a bad idea for the circuit? Does it somehow need the 5v to keep it from exploding or something? My CS and LCD and everything still come on and I can still upload midi.

2

Is just plugging in the bipolar supply a bad idea for the circuit? Does it somehow need the 5v to keep it from exploding or something?

Nah that shouldn’t break it… I dunno what happened :confused:

3

Crap, It’s strange as I only changed the PSU and nothing else, and that was tested.

4

Static, or dry joints+movement, could play a part there…

5

Aargh,

No sound still, and the first pair of amps are getting hot for no reason.

I tried to other amps and they’re not working either.

±8 volts is okay right? I remember hearing that once and it works better with the transformer I have.

Is there a decent way to test the Amps and or the rest of the circuit? I want to know if I need to replace the amps or just re-seat the smd.

6

Okay, I tested my amps by grounding both inputs and measuring the output. The value of a working amp should be close to 0 volts. So far I found three amps were

-6,-6,+7,-6

0,0,0,1

-6,-6,+7,+7

So I guess the second one is okay then? Has anyone else tried this method?

7

Clever!

For all I can think of that sounds right… I’m far from an expert on these things…

8

Both input pins ground -> ground at output is correct. Nice idea indeed.

9

WIKIMARKER

na’mean? That’s good stuff.

10

FYI I was correct, I ordered more amps and they are working fine.

Though for some reason channels 3 and 4 appear to be a lot less loud than 1 and 2.