Bad solder joints in Fender Deluxe VM - diyAudio
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Old 30th September 2011, 02:34 PM   #1
diyAudio Member
Join Date: Sep 2011
Location: Lititz, PA
Default Bad solder joints in Fender Deluxe VM

I just picked up a Fender Deluxe VM. It's a great amp but mine had a problem which I thought I would share just in case you run into one of these.

In my case, the overdrive channel occasionally became very noisy and the gain would drop out. It would still make a lot of noise even with the volume controls turned down completely. Tapping on the unit would make the noise change. Something was intermittent.

The clean channel made no noise. It worked perfectly.

I decided to isolate the circuit causing the noise as much as I could. I discovered that, if I plugged into the "Return" jack, the noise went away. So, I had the noise problem isolated to a small area of the circuit -- somewhere between the overdrive volume control and the "Return" jack.

I opened the unit and probed around. I found an IC U4 sensitive to pressure. Sure enough, this IC was in the circuit that I had already narrowed down. A close inspection revealed bad solder joints on the IC. It appears that there wasn't even a pad for one of the pins. I'm not sure if that was supposed to be like that or not. You could see that the solder on the adjacent pin had not flowed properly.

I reflowed the solder joints and now the amp works perfectly.
Here is a look at the circuit board prior to repair.
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Old 30th September 2011, 07:14 PM   #2
bigwill is offline bigwill  United Kingdom
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Join Date: Dec 2004
Location: UK
Some of those resistors look a bit suspect too - the ones to the left have an indentation around where the lead sits in the joint!
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Old 30th September 2011, 08:39 PM   #3
diyAudio Member
Join Date: Dec 2010
Location: Nottingham, NH
Bad day at the factory! lol. Listen to bigwill if you got it apart reflow as many joints as possible because you might not be able to see a cold solder joint. It be fine now but with time, heat, and vibration you can bet on another failing. I have pulled my hair out trying to fix noise problems because of faulty connections/pcb boards.
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Old 30th September 2011, 11:40 PM   #4
Enzo is offline Enzo  United States
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Join Date: Sep 2004
Location: Lansing, Michigan
And if it is recent production, they will have used the darned lead-free solder, which doesn;t make as reliable a joint either.

All it takes is a little contamination, and the solder won't wet well. Those parts are not soldered by hand.
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