A12 no sound buzz/hum help help please!

[jaymartinovich]

Hello,

That was really fun to build but..
I finished my first module and i am getting nothing but a crackling hum from my A12. I have a sc2520 and a cinemag.....

*checked solder joints
*J7 resistance is fine
*voltages are good a U1
*opamp is getting +/-20 (was at 15 so i turned up)
*j3 and j4 are jumpered at pins 2 and 3
*tried j5 with and without a shunt
* power and red diode are on...no smoke
all suggested tests are passed fine, just no sound except noise....

I also have the leads taped off, coming out of the last connector for my next module. Is that a problem? Should they be connected to something?

Thanks guys...

Jay

[tpryan]

What did you do at step 5? Are you using the load isolators? If not, you must solder jumpers in their place. Keep the jumper on J5 unless you have a good reason to not use it. Don't jumper J6. Let us know what you find.

[jaymartinovich]

That was it! sounds good. Distortion at +/-20, so i went down to +/-16 and it sounds great! On to the next one..


Thanks
jay