fixing a mackie 1220

C

cello_pudding

Well-known member
so I got an onyx 1220 for 35 bucks. Yes, there's a catch. smoke came out of it its last use. He didn't power it on or take it apart since he didn't want to fry it even more, and it was his backup. He said the lights flashed and he powered off and unplugged.

So i found the thing that burnt out. could i just remove this one, find out what it is, and then replace it? or is this sort of a no turning back, it's got a very unique make and mackie will not give me one, type of thing?

if i had a beautiful camera the picture might look like this of a good one.

chips_3_bg_102602.jpg


since i don't...this is what you get. i circled the burnt one.

T5gp8.jpg
 
with a little more research.

it's an op amp.

a 4580 JRC one.

It says on it...

4580
53740
JRC

what would be the process of fixing this...is it as simply buying another and soldering it. this seems pretty delicate.
 
if its an op amp, it could be in a holder or solder to the board. if it can be removed buy pulling it out its simple just drop in a new replacement however if its soldered in you have to be careful not to fry the opamp when replacing it. do yourself a favor( if your not well informed about electronic repair) get your self a book. i learned with "Electronic Projects For Musicians"
 
Op amps are fairly common and standard, you can probably find one from a supply house for way less money than Mackie wants for it.
 
The crux of the matter is "Why did it fry?" If you simply replace it, you'll likely fry that one too. Check the integrity of the other components in that channel - the nice thing is you have other identical circuits nearby to help troubleshoot this one.

At the worst you have a mixer with 11 channels.
 
crazydoc,

yes. this is what i was also thinking.

i have no idea how to check what's up with the other parts of the channel. if rewiring is involved, i feel slightly intimidated by that. hopefully it's just like a light bulb burning out. it happens, and i don't have to rewire my house or dig through my yard to fix it. lightbulb is probably an inaccurate comparison. light switch, perhaps.
 
It's unlikely an op amp will go bad on its own in a destructive way. The power supply is probably OK, or it would have fried other channels too. Resistors seldom go bad. I'd check the capacitors in that channel first, to see if one is open or shorted. However, you'll have to remove or decouple them from the circuit to do this.

An alternative would be to turn it back on, and check voltages at different points, using another channel as a reference. Do you have a multimeter and know how to use it?
 
I would suggest that maybe the opamp fried because there was a Short , maybe somehow the bottom of the curcuit board made contact with the chassis which caused it ...... I would look on the bottom of the board and see if there are any shorts or any way the board could make contact with the chassis ..... if all looks okay , remove the opamp and before replacing it measure that +/- power pins and see if you are getting the correct voltage (probably between +/-12v and +/-15v DC) if you are getting the correct voltages then I would replace the opamp (it doesn"t have to be a JRC4580 and NE5532 any other bipolar opamp) then power it on and cross yer fingers ......
 
yeah. the guy gave me a few capacitors because he had one crap out on him on his other board. i looked at them, but frankly if there's no twisted wires and burn marks, i don't know. i'm really just a guy that has soldered stuff together a hand full of times that is reading up and seeking help.

The short suggestion makes some sense. the burn mark on the board seems like it goes from the mute of ch 2 to the op amp for ch 3, which is strange to me. i really have zero knowledge of what's really up with it. i bought the op amp, but am just waiting for it to come.

i think i can get my hands on a multimeter when the time comes.
 
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