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Post subject: Mustang II V2 Feedback Issue
Posted: Fri Feb 22, 2019 8:19 am
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Joined: Fri Feb 22, 2019 7:49 am
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I'm hoping folks may be able to help diagnose an issue I'm having with a Mustang II V2. The core of the problem is the amp's occasional tendency to feedback extremely loudly in an oddly specific lower register of notes. About 50% of the time when I turn the amp on and begin playing, a very specific range of notes will cause the amp to drastically increase volume and sustain. I can be playing at a normal volume and pick a note on E or A string, usually round the 6th or 7th fret and suddenly pictures on the walls are shaking and the speaker begins to crackle as if it is about to blow. I attempted to capture this on video to upload, but the feedback is so low it won't even register on the video. The other 50% of the time it behaves normally as expected and sounds great. But when it's acting up, playing is nearly impossible.

I've read a good amount of threads and tried troubleshooting in the following ways: changing position of the amp, my position while playing, different guitar cables, took the amp apart and cleaned it with electrical contact cleaner and checked the solders and tightness of the screws, cleaned the input out, tried different outlets in the house, surge protectors

Any recommendations?


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Post subject: Re: Mustang II V2 Feedback Issue
Posted: Mon Mar 11, 2019 8:48 pm
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Aspiring Musician
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Joined: Thu Aug 07, 2014 3:25 pm
Posts: 988
See if it is affected by temperature. If you leave it in a cold garage overnight and it works, it might be a bad solder joint from lead free solder. It looks good, but isn't bonded electrically. Start resoldering around the 8 pin op amps.
Conversely, you can heat it up with a blow dryer to see if one of the big ic chips is heat sensitive.
One way to isolate which end of the amp is affected is to plug into the aux in jack. If it seems stable there, then its upstream in the preamp and digital sections.


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Post subject: Re: Mustang II V2 Feedback Issue
Posted: Tue Mar 12, 2019 8:46 am
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Joined: Fri Feb 22, 2019 7:49 am
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Thanks for the tip.

Since this was posted, I got my hands on a different guitar and a different amp (a cheap old Peavey solid state amp that came with a beginner guitar set). I tried every combination of guitar, cable, and amp imaginable and the problem was repeatable about 50% of the time in each scenario although not nearly as drastic as with the Mustang. This leaves two constants that could be the source: me and the electricity to the house (house built in the 80's in a relatively rural area). I picked up a Furman AC power conditioner. I'll report back if it works.


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