But i think the first step is to accurately quantify the instability in the existing circuit. One could buy a higher freq oscillator and divide it down. Here where to buy an high precision oscillator with the correct frequency: what do you think ? Is it possible to get those data somewhere ? those data will help to improve this circuitry maintaining the old fashion estetic. Then I have even a question: what's the frequency of the oscillator ?Īnd also: what is the ratio of this synchro motor ? I mean: If I drive it with 50 Hz, how many turns per minute I will get ? 500 ? 5 000 ? 600 ? 6 000 ? Not clue. the engine rotates supposing that it's own speed stills constant all the time. so that it was possible since early '70s. At that time, there were photocells and lamps. as a turn counter made by otpical disk for instance. in order to compensate little changes in rotation, it's needed to have some kind of feedback that here in the ST-11 there is not. it means that some kind of precision is reached. but consider that Peterson still producing turning wheel tuners for professional use. it's interesting to change this oscillator with another one more stable.Īll the problematics you told are true. but just wanting this instrument, for fashion, and just to have fun. There are probably far more talented people than I, so I thought I would suggest the project.Ĭlick to expand.Hi Enzo indeed you're right. There are a lot of ST-11's out there so I think it would be a good update. Thus retaining the original value of this old classic. Without making permanent modifications to the unit. So a new board could be easily installed. The good thing is that the oscillator circuit is all on one module which is removable. Maybe even with a center detent which locks the oscillator to dead-on 440 HZ concert pitch, since most people want to calibrate it for perfect pitch. I'm hoping someone can help to devise a nifty circuit that retains the adjustability, yet is very stable. It outputs 146.66666 khz when calibrated so it's not an off-the-shelf frequency.Īctually the line frequency is used just as a reference to calibrate the oscillator. The oscillator circuit probably needs to be redesigned. The oscillator circuit is TTL and is unstable no matter how long your warm it up. I've actually worked on quite a few of these units.
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