Tuesday, April 28, 2009
Ibanez AD80 repair. Documenting a ghost in the machine.
YouTube via sounddoctorin. vox continental
"Bob Weigel of Sound Doctorin' ( http://www.sounddoctorin.com ) shows some of the interesting effects attainable from a classic digital delay unit, the AD80 by Ibanez, during a repair attempt. To clarify what I'm saying about the circuitry in the video, this pedal uses two FET's as alternating switches for the bypass or effect signals. A flip flop circuit turns on one of them at a time and toggles of course when the switch is depressed. I've never seen my breath have quite so much conductivity. I must be eating metal flakes in my diet. Because there are 1M resistors coming from the flip flop voltages (which were quite steady at about 10V on the FET that is supposed to be turned on during the cutting out effect you witness in the video) and attaching to .047uF filter capacitors (grounded on the other side) and to the cathode of a diode, the anode of which attaches to the gate of the FET switch. The voltage at the point where the filter cap is is what was collapsing to a few volts. Even at 8.some volts though there is enough current drain from the gate to shut off the FET switch. But I saw the voltage fall to just a volt or two when I was breathing on it. Well the clear cote (a super low conductive paint basically) seems to have done the job at protecting it from ...conductive air :-). If anyone has studied more into this effect let me know."
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It's AD not DD, hint
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