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Tape deck / turntable adjustable motors - how do they work?

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PKTKS:
For the record..

Capstan belt drivers run at fixed speed
The capstan mass is order mag bigger

Dedicated ics keep capstan belt at proper speed regardless  tape used

Not true for VCRs

Paul

tooki:

--- Quote from: Benta on May 29, 2022, 09:24:24 pm ---
--- Quote from: tooki on May 29, 2022, 01:35:46 pm ---Techmoan is hands-down the authoritative channel on obsolete and obscure AV media formats, an absolute gem of a channel. VWestlife does a lot of repairs of old stuff, also a good channel.

P.S. Flaky means “undependable” (as in a person who may or may not do something that they promised). It does not mean “imprecise” or “vague”.

--- End quote ---
@tooki, Thank You for correcting my imperfect language. Swiss precision rules!

--- End quote ---
American former technical writer/translator, to be precise! :p (But I agree, Swiss (and German) precision does rule!)


--- Quote from: Benta on May 29, 2022, 09:24:24 pm ---No, I haven't played with or repaired casette tape decks, my preferred tape player was a Revox A77.

--- End quote ---
Great sound, no doubt. A bit bulky for pocket use, though!  ;D

tooki:

--- Quote from: PKTKS on May 30, 2022, 08:21:16 am ---For the record..

Capstan belt drivers run at fixed speed
The capstan mass is order mag bigger

Dedicated ics keep capstan belt at proper speed regardless  tape used

--- End quote ---
Not in all cassette decks. Many use motors with integrated speed control. Others use external control. Only the best used quartz PLLs and whatnot to maintain precision speeds. Either way, the mass of the capstan flywheel serves to stabilize it.

The tape used doesn’t have any effect on capstan speed, since the spool speeds are independent from the capstan speed. The capstan’s rotarion provides a stable linear speed at the point where the tape is pinched between the capstan and pinch roller.

Zero999:

--- Quote from: tooki on May 30, 2022, 03:14:53 pm ---
--- Quote from: PKTKS on May 30, 2022, 08:21:16 am ---For the record..

Capstan belt drivers run at fixed speed
The capstan mass is order mag bigger

Dedicated ics keep capstan belt at proper speed regardless  tape used

--- End quote ---
Not in all cassette decks. Many use motors with integrated speed control. Others use external control. Only the best used quartz PLLs and whatnot to maintain precision speeds. Either way, the mass of the capstan flywheel serves to stabilize it.

The tape used doesn’t have any effect on capstan speed, since the spool speeds are independent from the capstan speed. The capstan’s rotarion provides a stable linear speed at the point where the tape is pinched between the capstan and pinch roller.

--- End quote ---
Here's the data sheet for the type of IC used inside one of those motors.
https://industrial.panasonic.com/content/data/SC/ds/ds4/AN6652_E_discon.pdf

In cassette players the motor needed to be reversed and run at different speeds, so an external controller IC was more commonly used.
https://industrial.panasonic.com/content/data/SC/ds/ds4/AN6657__E_discon.pdf

tooki:
Depends on the deck, but generally speaking, the capstan motor never changes direction. On cassette mechanisms without auto-reverse, there’s no need either way. And in auto-reverse mechanisms, generally both capstans are always turning (in opposite directions), with only one pinch roller being depressed.

On the other hand, the reel motor is often controlled in wild and wacky ways (but its speed does not need to be controlled accurately at all). In most logic controlled cassette mechanisms, those motors not only wind the takeup reel at multiple speeds (for playback/recording and FF/rewind, often at multiple speeds to be gentle on the end of the tape, plus an extremely gentle low speed just to take up slack to prevent tangles before ejecting), but use pulsed high speeds in both directions to use centrifugal force to change directions, operate cams, etc. that (i.e. engage things that don’t at lower speeds), but also to overcome the friction in clutches and slip rings (i.e. to escape things that engage at lower speeds). This drives all the movements of the heads (including rotating the heads on auto-reverse units) and pinch rollers, reversing the reel direction, etc. (High-end decks use more motors and solenoids to make them faster.)

In Walkman type portable players, they often use one single motor to do all of this. It’s absolutely fascinating that one motor can literally do it all. The downside is that it makes them rather slow, and you hear the various clicky sounds as they sequence the motions to reverse the playback direction at the end of the tape, or go from FF/rewind to playback, for example. (Attached is the relevant page from the service manual of my Sony WM-EX508 Walkman, which I’ve owned since around 1997, which vaguely explains how the mechanism works.)

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