9308 FatMan, board contact with case bottom

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9308 FatMan, board contact with case bottom

Post by PAiA-Scott »

John Woelfl wrote:
> I did something really stupid. I unpacked the kit and saw the protective coating on the bottom of the case. It looked bad and removed it. About 6 months later I built the kit. After checkout and trying to calibrate the kit I installed the bottom. This shorted the digital area and the unit no longer responds to the midi inputs. It does randomly start emitting tones.
> What would you recommend?
> John Woelfl

Hello John.

The plastic film is not supposed to remain to prevent contact with the board soldering, but to protect the finished aluminum surface. It should be removed once the kit is built.

But, as you have noticed, the way the board folds over the wiring in the case, it can push it up to where it can contact the metal bottom if extra care is not taken to prevent this. The back area of the board near the VCF and VCA circuits sticks up most and is more likely to touch than the digital and MIDI Input section. Since you are hearing some sounds, maybe the damage was from force against the taller parts (voltage regulators) on the top side of the board as it folded over and now this is a short-circuit between them and/or other parts, or, the printed-circuit-traces have released from the board and broken.

If everything looks OK in the voltage regulator area, and the soldering and printed-circuit-traces below, go through the tests and checks in the attached tips and suggestions for measuring the dc power supply voltages.

FatMan trouble-shooting tips&suggestions:
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Here is an image showing the way stick-on rubber bumpers can be used to press against the board as the case-bottom is attached, preventing contact between the soldering on the board and the case bottom.


Notice these are are a hexagonal 3M type, doubled-up, but anything of comparable size should work.

DO NOT use the black foam used to hold the ICs in the kit. It is conductive and would work like a resistor between the solder joints and the case bottom. Save it for making a force sensitive resistor by sandwiching it between two metal plates with wires to each.
Scott Lee