- Why are capstan wheels different size? - 21 Updates
- Gibson Les Paul classic of 2013 - 3 Updates
- Copper wire instead of fuses? - 1 Update
| DaveC <not@home.cow>: Mar 11 01:22PM -0800 Oh, smarter-than-I people, http://imgur.com/WPEoOu1 The 2 belt-drive capstan flywheels in an auto-reverse cassette mechanism are different sizes. (Motor drive pulley will be in the small loop end of the belt in illustration above.) How does that result in the same tape speed in both directions? Confused... |
| Jasen Betts <jasen@xnet.co.nz>: Mar 11 10:25PM > different sizes. (Motor drive pulley will be in the small loop end of the > belt in illustration above.) > How does that result in the same tape speed in both directions? do they have the same capstan diameter? -- \_(ツ)_ |
| M Philbrook <jamie_ka1lpa@charter.net>: Mar 11 06:08PM -0500 In article <0001HW.1C936E810003F2001244403CF@news.eternal- september.org>, not@home.cow says... > belt in illustration above.) > How does that result in the same tape speed in both directions? > Confused... Its been a while since I've seen the inside of a cassett drive. But memory tells me you have a pinch roller with pin shaft that governs the actual speed. Jamie |
| Les Cargill <lcargill99@comcast.com>: Mar 11 05:34PM -0600 M Philbrook wrote: > But memory tells me you have a pinch roller with pin shaft that governs > the actual speed. > Jamie Yep. -- Les Cargill |
| MJC <gravity@mjcoon.plus.com>: Mar 11 11:48PM In article <MPG.314d1a13f8dcab69989eb1@news.eternal-september.org>, jamie_ka1lpa@charter.net says... > But memory tells me you have a pinch roller with pin shaft that governs > the actual speed. > Jamie And I have long thought that with the small diameter of the capstan it must be the availability of excellent, and cheap, bearings for the shaft that made it possible to keep the wow and flutter down to acceptable levels... Mike. |
| Phil Allison <pallison49@gmail.com>: Mar 11 06:38PM -0800 MJC wrote: > must be the availability of excellent, and cheap, bearings for the shaft > that made it possible to keep the wow and flutter down to acceptable > levels... ** The vast majority use plain bearings and rely on a flywheel to do the rest. .... Phil |
| DaveC <not@home.cow>: Mar 11 07:49PM -0800 Jasen Betts asked wisely: > do they have the same capstan diameter? I was just about to say "Silly question!" but instead thought better... one 2mm, one 2.2mm I guess the difference is driven (c; by the fact (stated by Phil) that the flywheels are different diameters to discourage mechanical resonance. Thanks Jasen! |
| Tim Wescott <seemywebsite@myfooter.really>: Mar 11 10:35PM -0600 On Fri, 11 Mar 2016 13:22:09 -0800, DaveC wrote: > of the belt in illustration above.) > How does that result in the same tape speed in both directions? > Confused... Presumably the belt speed changes, or the capstains themselves are different diameters. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
| Look165 <look165@numericable.fr>: Mar 12 09:36AM +0100 One (the small one) is the motor capstan. The other one is the pressure capstan. Direction is given by the rotation of the first one and speed is servo-controlled. Generally there is a lever for the tension of the tape. DaveC a écrit : |
| stratus46@yahoo.com: Mar 12 12:42AM -0800 On Friday, March 11, 2016 at 1:22:14 PM UTC-8, DaveC wrote: > belt in illustration above.) > How does that result in the same tape speed in both directions? > Confused... Looks like my Nakamichi cassette deck. They used 2 different sdiameter capstans / flywheels running at different RPMs BUT the same tape speed closed loop drive (both pinch rollers always engaged). They said they did that so that the capstans won't slowly go in and out of phase which causes wow and flutter to go up and down. By running different RPMs they go in and out of sync so quickly we don't notice it. As the belt stretches and contracts around the flywheels, the lead capstan will alway run slightly faster (tape speed wise) than the trailing capstan which keeps the tape tension correct on an auto reverse machine regardless of the direction. My deck is only single direction and the wow/flutter is nearly imperceptible. Then I went digital so who cares about cassettes? G² |
| DaveC <not@home.cow>: Mar 12 01:39AM -0800 > Then I went digital so who cares about cassettes? Need a source to digitize the analogue media... |
| Adrian Caspersz <email@here.invalid>: Mar 12 09:48AM > faster (tape speed wise) than the trailing capstan which keeps the tape > tension correct on an auto reverse machine regardless of the direction. My > deck is only single direction and the wow/flutter is nearly imperceptible. I did initially think closed loop but then capstans would be revolving in opposite directions? It would be an extreme way to apply tension to a tape. -- Adrian C |
| mike <ham789@netzero.net>: Mar 12 02:34AM -0800 On 3/12/2016 12:36 AM, Look165 wrote: >> belt in illustration above.) >> How does that result in the same tape speed in both directions? >> Confused... The tape speed is controlled by the motor drive capstan. Doesn't matter which way the tape is going. The two flywheels are different sizes, but have the same rotation speed. That causes the belt to stretch on one side and compress on the other to account for the different sizes. That belt tension creates the tape tension. That's independent of the direction of the rotation. Tape speed across the heads is always controlled by the drive motor. |
| N_Cook <diverse@tcp.co.uk>: Mar 12 10:38AM On 12/03/2016 03:49, DaveC wrote: > I guess the difference is driven (c; by the fact (stated by Phil) that the > flywheels are different diameters to discourage mechanical resonance. > Thanks Jasen! May seem pedantic , but there is a rationale. Having been here before, to standardise to using a strobe to set tape speed, in the absence of a test tape of known goodness, ie not stretched, as the people wanting cassette players repaired these days tend to be musically on the ball as regards being perfect pitch. You'll probably find the spindle diameters are 1.99mm and 2.19mm . I got a precision mechanical engineer to measure a dozen or more random spindles and they were all *.*9 mm , presumably because the available bearings are *.*0 mm |
| MJC <gravity@mjcoon.plus.com>: Mar 12 10:45AM In article <c132015e-fe0f-4a70-be7a-d5bdeb18c48f@googlegroups.com>, pallison49@gmail.com says... > ** The vast majority use plain bearings and rely on a flywheel to do the rest. > .... Phil Sure, but my point was that any chatter in the bearings is just as bad as rotational variation and is not damped by the flywheel. So the plain bearings have to be accurate and long-lasting. Mike. |
| jurb6006@gmail.com: Mar 12 04:17AM -0800 Because of the thickness of the belt. |
| jurb6006@gmail.com: Mar 12 04:31AM -0800 >"I did initially think closed loop but then capstans would be >revolving >in opposite directions? It would be an extreme way to apply tension >to a >tape. " Do you understand mechanics at all ? It helps. Those things are turning in OPPOSITE directions and therefore that deck is NOT a true dual capstan. It has two but the other one is used to regulate tapes speed in reverse. That is all. It does not have the the qualitative edge over a single capstan deck at all, that part of the mechanism simply facilitates the reverse function. It is not dual capstan at all. To me, and anyone who knows tape, dual capstan means they both work at the same time, and in that the deck, THEY DO NOT. It is either one or the other, depending on if it it is in the forward or reverse mode. At no time are both pinch rollers engaged. Only one at a time. When it's running look and see, and you will see. |
| Phil Allison <pallison49@gmail.com>: Mar 12 04:31AM -0800 Look165 wrote: > Direction is given by the rotation of the first one and speed is > servo-controlled. > Generally there is a lever for the tension of the tape. ** You on crack ?? |
| Phil Allison <pallison49@gmail.com>: Mar 12 04:40AM -0800 MJC wrote: > Sure, but my point was that any chatter in the bearings is just as bad > as rotational variation and is not damped by the flywheel. So the plain > bearings have to be accurate and long-lasting. ** You have completely forgotten the damping effect of side-ways pressure from the pinch roller. .... Phil |
| Adrian Caspersz <email@here.invalid>: Mar 12 12:40PM >> >revolving in opposite directions? It would be an extreme way to >> apply tension >to a tape. " > Do you understand mechanics at all ? It helps. :) Those things are > turning in OPPOSITE directions and therefore that deck is NOT a true > dual capstan. Sorry, you can see I goofed up my sentence. Should have written "I did initially think closed loop but then capstans ARE revolving in opposite directions? (So not)" It has two but the other one is used to regulate tapes > it it is in the forward or reverse mode. At no time are both pinch > rollers engaged. Only one at a time. > When it's running look and see, and you will see. Agreed. -- Adrian C |
| Phil Allison <pallison49@gmail.com>: Mar 12 04:43AM -0800 > >tape. " > Do you understand mechanics at all ? It helps. > Those things are turning in OPPOSITE directions ** Self evidently false. Yawnnnnnnnnnn................ ... Phil |
| N_Cook <diverse@tcp.co.uk>: Mar 12 09:56AM Firstly "classic" moniker with battery and J202 FET inside? Unless I've misread the mini-pcb tracery , the boost switch is DPDT using 2 seriesed switch actions for increased unreliability? I would have paralleled for increased reliability of a simple switch action if using a DPDT perhaps because it is more mechanically robust than SPST or SPDT, or am I missing something? |
| "Gareth Magennis" <soundserviceleeds@outlook.com>: Mar 12 11:39AM "N_Cook" wrote in message news:nc0ouk$m1b$1@dont-email.me... Firstly "classic" moniker with battery and J202 FET inside? Unless I've misread the mini-pcb tracery , the boost switch is DPDT using 2 seriesed switch actions for increased unreliability? I would have paralleled for increased reliability of a simple switch action if using a DPDT perhaps because it is more mechanically robust than SPST or SPDT, or am I missing something? That's not the Series/Parallel switch you are looking at? Gareth. |
| N_Cook <diverse@tcp.co.uk>: Mar 12 12:31PM On 12/03/2016 11:39, Gareth Magennis wrote: > That's not the Series/Parallel switch you are looking at? > Gareth. Not my intended meaning, only 4 terminals are used of the 6 , but not in a DPST sense as 2 of those 4 terminals are bridged across by a trace, so the action is just a simple SPST, via 2 switch contacts. So one pole on or off to simply switch in/out a filter cap or something |
| "Gareth Magennis" <soundserviceleeds@outlook.com>: Mar 12 10:32AM Here's something I've not seen before. A Power Amplifier has binding posts which you are supposed to solder wire between, instead of fuses. This is on the low voltage power supply. The wire fuses go to the bridge rectifier/10,000uF caps, and supply the +/- 15v supplies. The PCB is inscribed "wire Cu 0.25mm" and also designated F2 and F3. And yes, there is (or was) thin copper wire soldered in place on both identical channels of this amp. (One side has melted both these wire fuses, as the caps are bad) Why would a manufacturer do this? I'd be inclined to put back wire ended fuses. I'm guessing 0.25mm means 0.25mm Cross Sectional Area rather than diameter, but it is not clear. The following table gives 6A and 15A for each possibility, which seems quite high for a low voltage supply. http://www.gxk.org.uk/info/wire.htm I took out a small remaining piece of the wire and it actually measured just below 0.5mm diameter, but this is not a reliable measurement as the wire has obviously suffered trauma. This is the amplifier in question: http://www.kv2audio.com/products/esr-series/esr2800.html Cheers, Gareth. |
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