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Read Robliz thread. I am also a "multimeter, and read the schematics" kind of guy, myself. I already tried the "open it with a dremel" deal. It is "potted" on the inside with a material that prevents its re-usage. The bulb is burned out, at least, and is of a special proprietary value, not replaceable by conventional grain-of-wheat incandecents. We have replaced them with LED's for the light source, coupled with a custom value chosen, light dependent resistor. The thread, also has a "so called" diect replacement" for the OEM unit. Don't believe it. This modern unit also uses an LCD as a light source, instead of an incandescent), and the amp does not perform properly.
I don't understand the circuit theory, but the tremolo circuit fluctuated/oscillated voltage to a tiny lamp on and off, which in turn, shined on a little light dependant resistor, causing the resistor's value to rise and fall. This rising and falling resistance is used to modulate/attenuate the volume, by alternately, grounding out, then insulating, the audio signal to ground.....like a volume control.
The problem is, the led substituted in the circuit, allows a bit of "gain drain" by allowing too little resistance between the audio signal and ground. With the "LED/LDR combo", (an "opto isolator") repair method, the Reverb channel will sound weak, all the time, because the peculiarities of the circuit will cause the volume to be "padded down" all the time, because of this leakage/attenuation of the audio signal, to ground. This is true, even with the tremolo intensity control all the way down at 0, (tremolo off), or if using a foot pedal, to ground out the tremolo. The "NON vibrato" volume will always be low and weak, unless switched out of the circuit.
You are better off not fixing it, or you can do what i am going to do.....replace the dead OEM unit with the Silonex part from Allied Electronics, (as referred to in the prior thread), and replace the OEM intensity pot, (25 K ?). with a similar value pot having an on/off switch. With the on off switch, you can figure out a way to eliminate the pesky attenuating trem circuit from the equation completely!
I have experimented with every possible voltage/amperage grain of wheat bulb, teamed up with a carefully selected LDR, in an effort to replicate the "innards", of the little square black box that was OEM.
No results were satisfactory. Many grain of wheat bulbs, would not even light or even fluctuate, with the available voltage of the circuit. The best choice is the silonex part used instead. It is not worth wrecking the volume of the reverb channel
I don't understand the circuit theory, but the tremolo circuit fluctuated/oscillated voltage to a tiny lamp on and off, which in turn, shined on a little light dependant resistor, causing the resistor's value to rise and fall. This rising and falling resistance is used to modulate/attenuate the volume, by alternately, grounding out, then insulating, the audio signal to ground.....like a volume control.
The problem is, the led substituted in the circuit, allows a bit of "gain drain" by allowing too little resistance between the audio signal and ground. With the "LED/LDR combo", (an "opto isolator") repair method, the Reverb channel will sound weak, all the time, because the peculiarities of the circuit will cause the volume to be "padded down" all the time, because of this leakage/attenuation of the audio signal, to ground. This is true, even with the tremolo intensity control all the way down at 0, (tremolo off), or if using a foot pedal, to ground out the tremolo. The "NON vibrato" volume will always be low and weak, unless switched out of the circuit.
You are better off not fixing it, or you can do what i am going to do.....replace the dead OEM unit with the Silonex part from Allied Electronics, (as referred to in the prior thread), and replace the OEM intensity pot, (25 K ?). with a similar value pot having an on/off switch. With the on off switch, you can figure out a way to eliminate the pesky attenuating trem circuit from the equation completely!
I have experimented with every possible voltage/amperage grain of wheat bulb, teamed up with a carefully selected LDR, in an effort to replicate the "innards", of the little square black box that was OEM.
No results were satisfactory. Many grain of wheat bulbs, would not even light or even fluctuate, with the available voltage of the circuit. The best choice is the silonex part used instead. It is not worth wrecking the volume of the reverb channel
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