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if you're talking about the little hand-cranked ones, I think what is happening is there are vibrating tines in the base, and they are made to vibrate all the time by the cranking movement, but a metal wheel sits on the tine and stops it from making sound. When the hole in the paper comes by, the wheel can lift up slightly into the paper hole, which allows the note to ring for a moment. Slots in the paper allow for longer notes. This is my guess based on the pictures I can find.
Nice work. Glad it was helpful for you. If you can make room for a bigger fan, that would help make it quieter.
I agree, 0.3A is very low. I would not use something so low next time. I haven't had any issues with it though, running several pedals. The thing is, it can deliver more than 300mA, but the voltage at the transformer secondary may drop lower than 18V AC, but there is a lot of voltage headroom in the design.There's really no chance for an issue until the transformer overheats to the point of failure, which would take some doing.
Can you explain more?
I attached some PDFs I found, might be useful for you.
Or just adjust the ISO to compensate.
Looking at my pictures, I count 4 potentiometers total. I imagine there could be high/low sensitivity or limit setting pots, but I suspect the one near the metal can (which I believe is an operational amplifier) could be a gain-adjust. I suggest tuning that one until you have linearity in readings, then adjust the others to try to get the right values at high and low EVs. If this is just for you and your linearity is fine but the reading is simply off, maybe identify the error and mark it on the unit so you can do quick math in your head? ie. adding 1/2 an EV to each reading to correct for the error.
Hi John, looks like you did a fantastic job on it. I'm glad to hear you managed to make use of the information I provided.
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