reynhout@wpi.wpi.edu (Andrew Reynhout) (09/13/89)
I can tell you from experience that altering tape speed on a cassette deck to any useful degree is *NOT* as simple as lining a pot through the supply for the motor. Sure, you can do that, BUT... if you do, the possibility exists that it either won't work at all, or will work with adverse effects on the regularity of tape speed. (faster then slower, producing interesting but generally undesirable effects on the recorded material.) I was at a loss for years as to how to circumvent the adverse effects of slowing a tape deck. I mean, I knew that Sony did it, but couldn't figure out how to do it myself. Then, like an angel from heaven (OK, not really,) I happened across a cute little schematic in one of the major monthlies (Either RE or PE..don't recall exactly which one..) that detailed a circuit to solve this problem. I never tried it, so can't speak for its usefulness, but I suspect the reputation of the periodical speaks well enough for that. Basically, the circuit pulsed a full supply of operating voltage to the motor, at a rate high enough that the tape maintained a constant, but reduced, ips speed. So, I can either refer you to your library's most recent "Reader's Guide to Periodical Literature", or tell you that I will get that information to you as soon as I locate it (didn't bring my old copies of electronics mags to school with me, and I'm looking at October or so before I go home.) On second thought, skip the "Reader's Guide...", it probably wouldn't have a listing for Magnetic media recorders, motor speed control of. Just look through that last three or four months of Radio Electronics and Popular Electronics (and do it carefully...it wasn't an article, just a little 1/2 page thing, as I recall...) If no luck, let me know... Andrew (reynhout@wpi.wpi.edu)
kencr@haddock.ima.isc.com (Kenny Crudup) (09/14/89)
In article <3997@wpi.wpi.edu> reynhout@wpi.wpi.edu (Andrew Reynhout) says: > I can tell you from experience that altering tape speed on a cassette deck >to any useful degree is *NOT* as simple as lining a pot through the supply for >the motor. > Andrew (reynhout@wpi.wpi.edu) True. But, rest assured for permanent magnet type DC motors, there is some sort of speed regulation. Wow and flutter would be unbearable without any at all. They basically come in one of three varieties: - The "smart motor". This is a motor with a set of electronics in- side that regulates the motor speed. Look at the back of the motor. Is there a hole, possibly covered by a sticker? If so, there is your adjustment point. - The "speed governor". This motor has centrifugally mounted switches that open/close according to motor speed. These are a little bit harder to adjust, as what you have to do is open the motor, back in/out *both screws on the governor a little at the same time*, put it together, and try it. Can you say "trial and error"? I knew you could. I was desperate once with one of these; but it worked. - The "externally regulated" motor. Walkmans usually have these. There will be a pot in the motor circuit. You have to look for it, and trace the circuit back. Should be fairly obvious. Hope this helps. -- Kenneth R. Crudup, Contractor, Interactive Systems Co.(386/ix), Cambridge MA Not all men are fools; some are still single! Phone (617) 661 7474 x238 {encore, harvard, spdcc, think}!ima!haddock!kencr kencr@ima.ima.isc.com
cees@tamtam.htsa.aha.nl (Cees Keyer) (09/14/89)
In article <3997@wpi.wpi.edu> reynhout@wpi.wpi.edu (Andrew Reynhout) writes: > > I can tell you from experience that altering tape speed on a cassette deck to any useful degree is *NOT* as simple as lining a pot through the supply for >the motor. Sure, you can do that, BUT... if you do, the possibility exists >that it either won't work at all, or will work with adverse effects on the >regularity of tape speed. (faster then slower, producing interesting but >generally undesirable effects on the recorded material.) > I was at a loss for years as to how to circumvent the adverse effects of >slowing a tape deck. I mean, I knew that Sony did it, but couldn't figure out >how to do it myself. Almost all the cassette deck motors are equipt with a tiny printed circuit board in the motor casing. On this board there is a transistor (medium power transistor) which keeps the speed constant. If you take this board out you can control the speed by altering the resitance of the pot. The pot can mostly be reached trough a hole in the bottom of the motor casing. On some decks the motor speed control is outside the casing of the motor it self. No asid rain on my brain :-) -- DISCLAIMER: All the opinions expressed are my own. Cees Keyer, Algemene Hogeschool Amsterdam. department of electrical engineering. cees@tamtam.htsa.aha.nl cees@maestro.htsa.aha.nl UUCP: mcvax!hp4nl!htsa!cees