On 3/28/09, joshdaigleusa put forth:
sound unusual. Off hand, I'd say you've accidently invented some
sort of theremin :)
I just took a quick glance at the circuit. Since this thing doesn't
appear to have any sort of clock, the first thing I would do is check
the power supply. Make sure all the DC voltages are correct. Check
the output of the voltage reference. Check the outputs of all the
op-amps, and make sure they are what they should be with no input,
0V, -5V, +5V, or whatever. If you have a scope, check for
oscillations around the power pins. Check the PCB for bad solder
joints or excess flux. Make sure that any unused logic pins that
should be tied high or low aren't left floating.
If the chip is socketed, I would try another chip. If it isn't, I'd
try adding bypass caps to the supply pins before unsoldering it, but
that's just me. If you do unsolder it, do not solder in a new chip
-- use a socket. Then if it still doesn't work with another chip,
you can replace the function of the mux by sticking little jumpers of
insulated solid wire. If it still doesn't work, then you know it's
not the 4053.
>Stranger still, there seems to be some sort of active "field" aroundAre you sure you aren't physically touching anything?? That does
>the lower 1/2 of the CD4053B there where the Maj/Min mode is supposed
>to be controlled (this isn't happening with any of the other chips and
>even not on the top 1/2 of the 4053). If I hold my finger close to the
>chip at this spot the control voltage output of the circuit gets
>unstable and distorts.
sound unusual. Off hand, I'd say you've accidently invented some
sort of theremin :)
I just took a quick glance at the circuit. Since this thing doesn't
appear to have any sort of clock, the first thing I would do is check
the power supply. Make sure all the DC voltages are correct. Check
the output of the voltage reference. Check the outputs of all the
op-amps, and make sure they are what they should be with no input,
0V, -5V, +5V, or whatever. If you have a scope, check for
oscillations around the power pins. Check the PCB for bad solder
joints or excess flux. Make sure that any unused logic pins that
should be tied high or low aren't left floating.
If the chip is socketed, I would try another chip. If it isn't, I'd
try adding bypass caps to the supply pins before unsoldering it, but
that's just me. If you do unsolder it, do not solder in a new chip
-- use a socket. Then if it still doesn't work with another chip,
you can replace the function of the mux by sticking little jumpers of
insulated solid wire. If it still doesn't work, then you know it's
not the 4053.