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Dictabelt speed
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Adrian Tuddenham
Sep 29, 2011, 10:07:40 AM9/29/11
to
Does anyone happen to know the official speed of a Dictabelt? It seems
to be around 6 inches per second or 30 belt revolutions per minute, but
there must be a proper specification somewhere.
to be around 6 inches per second or 30 belt revolutions per minute, but
there must be a proper specification somewhere.
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
N_Cook
Sep 29, 2011, 11:22:30 AM9/29/11
to
Adrian Tuddenham <adr...@poppyrecords.invalid.invalid> wrote in message
news:1k8d39l.icacwfv97jyN%adr...@poppyrecords.invalid.invalid...
If the Zapruder / Kennedy assassination recording is out there , is there
any repeated scratch/molding clicks to take timings off ?
Try posting to r.a.r.p ?
news:1k8d39l.icacwfv97jyN%adr...@poppyrecords.invalid.invalid...
any repeated scratch/molding clicks to take timings off ?
Try posting to r.a.r.p ?
N_Cook
Sep 29, 2011, 11:29:39 AM9/29/11
to
Adrian Tuddenham <adr...@poppyrecords.invalid.invalid> wrote in message
news:1k8d39l.icacwfv97jyN%adr...@poppyrecords.invalid.invalid...
news:1k8d39l.icacwfv97jyN%adr...@poppyrecords.invalid.invalid...
laser/tracking/servo technology
Jeffrey Angus
Sep 29, 2011, 11:36:42 AM9/29/11
to
On 9/29/2011 10:22 AM, N_Cook wrote:
> Try posting to r.a.r.p ?
That would be rec.antiques,radio+phono or is
> Try posting to r.a.r.p ?
that a different group you had in mind?
Jeff
--
"Everything from Crackers to Coffins"
N_Cook
Sep 29, 2011, 11:45:54 AM9/29/11
to
Jeffrey Angus <grend...@aim.com> wrote in message
news:j623aa$22l$1...@dont-email.me...
yep
To OP, would that use shaded pole motor and then fixed gearing?
news:j623aa$22l$1...@dont-email.me...
To OP, would that use shaded pole motor and then fixed gearing?
Jeff Liebermann
Sep 29, 2011, 12:52:48 PM9/29/11
to
On Thu, 29 Sep 2011 15:07:40 +0100,
adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>Does anyone happen to know the official speed of a Dictabelt?
Which maker and what model?
adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>Does anyone happen to know the official speed of a Dictabelt?
They followed the same speeds at record platters.
ips time
15 15 min
7 1/2 30 min
3 3/4 60 min
1 7/8 120 min
However, I'm not sure of the times. There were also versions that
offered 4 channels per tape, which decreased the run time. For
example, the Kennedy tapes were 4 channel mostly at 3 3/4 ips, but
only ran for 15-20 mins.
<http://whitehousetapes.net/info/kennedy-tapes-overview#TECHNICAL_NOTES>
More:
<http://www.videointerchange.com/audio_history.htm>
Scroll down to "Dictabelt 1947".
12" circumference, 15 minutes play time, 3.5" wide.
The problem is I don't know how how many tracks per inch across the
3.5" wide belt. If you have a device, you can measure tracks per inch
or calculate it from the gearing.
>It seems
>to be around 6 inches per second or 30 belt revolutions per minute, but
>there must be a proper specification somewhere.
0.5 rev/sec * 12 in/rev = 6 in/sec.
Close enough to 7.5 ips.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Adrian Tuddenham
Sep 29, 2011, 12:54:08 PM9/29/11
to
and a flat belt to the final drive roller shaft - so there's plenty of
slippage to give measurement errors.
Also, the machines I have seen in the UK have 60 c/s motors adapted for
50 c/s, which have very low torque and a high slip frequency on load.
(The only fixed gearing is between the drive roller and the leadscrew.)
Adrian Tuddenham
Sep 29, 2011, 12:54:08 PM9/29/11
to
reading project; but I don't do any optical playback myself.
Adrian Tuddenham
Sep 29, 2011, 4:08:55 PM9/29/11
to
Jeff Liebermann <je...@cruzio.com> wrote:
> On Thu, 29 Sep 2011 15:07:40 +0100,
> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>
> >Does anyone happen to know the official speed of a Dictabelt?
>
> Which maker and what model?
> They followed the same speeds at record platters.
> ips time
> 15 15 min
> 7 1/2 30 min
> 3 3/4 60 min
> 1 7/8 120 min
I think you have misunderstood the type of machine I am enquiring about.
> On Thu, 29 Sep 2011 15:07:40 +0100,
> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>
> >Does anyone happen to know the official speed of a Dictabelt?
>
> Which maker and what model?
> They followed the same speeds at record platters.
> ips time
> 15 15 min
> 7 1/2 30 min
> 3 3/4 60 min
> 1 7/8 120 min
[...]
> >It seems
> >to be around 6 inches per second or 30 belt revolutions per minute, but
> >there must be a proper specification somewhere.
>
> 30 rev/min = 0.5 rev/sec. At 12" per revolution, that's:
> 0.5 rev/sec * 12 in/rev = 6 in/sec.
> Close enough to 7.5 ips.
It issignificantly below 7.5 ips. I need to know the manufacturer's
> >to be around 6 inches per second or 30 belt revolutions per minute, but
> >there must be a proper specification somewhere.
>
> 30 rev/min = 0.5 rev/sec. At 12" per revolution, that's:
> 0.5 rev/sec * 12 in/rev = 6 in/sec.
> Close enough to 7.5 ips.
specifications as I am developing a playback machine for archival work,
where comparison between the actual speed and the 'official' speed can
yield useful historical information.
Jeff Urban
Sep 29, 2011, 8:14:42 PM9/29/11
to
Interesting dilemma you got there. I searched the web but then it
would be unreasonable to think you hadn't. I found something called a
memobelt which was supposedly the same or similar.
However in thinking about it, being a scribing machine of sorts, and
given the time frame I would think two things, well one.....
It is unlikely that the unit used a capstan. Crushing the media would
not be desirable.
As such that means the media speed would vary as it accumulates on the
reel, which we really cannot call a takeup reel because of the lack of
a capstan and pinch roller. I guess it would be called a drive reel
then.
I don't imagine alot of problems with this, because some things can
just be figured out. Now I have gone into wiki and as you probably
know the JFK assassination is recorded on this medium. The article I
read also states that there are references due to police calls which
do denote the time one way or another, but that data are better used
in fine tuning, it seems that you need more of a ballpark figure right
now.
As such I would attempt to take a picture of a section of this belt
media. In fact I would do it at the beginneing of a reel as well as at
the end. Since the information is scribed, like a phonograph record
groove, you should be able to figure out the speed by the length of
the modulation in the "groove".
It is logical to assume that they used the minimum speed possible for
intelligibility, therefore figuring the minimum bandwidth for speech
what do we have ? I would think that 600 - 4,000 Hz would be enough.
Looking at the groove should then give you an idea. The high frequency
limit is the key,. And remember they didn't have high compliance
Shibata stylii when this thing was invented. You may need quite a
length of it, run it through something for film or whatever, and use
magnification. Find the shortest "wavelength" undulations in the
groove you can, and assume it's a couple of Khz. Then you can figure
the IPS from there.
I wonder how you intend to pick this up really. Optically or with a
stylus ? I mean would you somehow fit a magnetic phono cartridge to
this whatchamacallit or let some type of LED and optical sensor array
do it ?
This intrigues me just because it is different, and the fact that I am
stil a Beta dood. I even have a one inch vodeotape hiding in the
basement, still waiting for a machine that can play it. I used to own
a Cartovision !, but I did buy it used.....
Data preservation and restoration is a real field of endevor, I mean
people do devote their carreer to it. I myself would pay money to have
what I have recorded on Beta for example in the old days. In fact I
even worked on one of those Technicolor VCRs. Actually eight
millimeter but not the Sony type that was standardized about a decade
or so later......
Aaaa, the good old days.
J
would be unreasonable to think you hadn't. I found something called a
memobelt which was supposedly the same or similar.
However in thinking about it, being a scribing machine of sorts, and
given the time frame I would think two things, well one.....
It is unlikely that the unit used a capstan. Crushing the media would
not be desirable.
As such that means the media speed would vary as it accumulates on the
reel, which we really cannot call a takeup reel because of the lack of
a capstan and pinch roller. I guess it would be called a drive reel
then.
I don't imagine alot of problems with this, because some things can
just be figured out. Now I have gone into wiki and as you probably
know the JFK assassination is recorded on this medium. The article I
read also states that there are references due to police calls which
do denote the time one way or another, but that data are better used
in fine tuning, it seems that you need more of a ballpark figure right
now.
As such I would attempt to take a picture of a section of this belt
media. In fact I would do it at the beginneing of a reel as well as at
the end. Since the information is scribed, like a phonograph record
groove, you should be able to figure out the speed by the length of
the modulation in the "groove".
It is logical to assume that they used the minimum speed possible for
intelligibility, therefore figuring the minimum bandwidth for speech
what do we have ? I would think that 600 - 4,000 Hz would be enough.
Looking at the groove should then give you an idea. The high frequency
limit is the key,. And remember they didn't have high compliance
Shibata stylii when this thing was invented. You may need quite a
length of it, run it through something for film or whatever, and use
magnification. Find the shortest "wavelength" undulations in the
groove you can, and assume it's a couple of Khz. Then you can figure
the IPS from there.
I wonder how you intend to pick this up really. Optically or with a
stylus ? I mean would you somehow fit a magnetic phono cartridge to
this whatchamacallit or let some type of LED and optical sensor array
do it ?
This intrigues me just because it is different, and the fact that I am
stil a Beta dood. I even have a one inch vodeotape hiding in the
basement, still waiting for a machine that can play it. I used to own
a Cartovision !, but I did buy it used.....
Data preservation and restoration is a real field of endevor, I mean
people do devote their carreer to it. I myself would pay money to have
what I have recorded on Beta for example in the old days. In fact I
even worked on one of those Technicolor VCRs. Actually eight
millimeter but not the Sony type that was standardized about a decade
or so later......
Aaaa, the good old days.
J
isw
Sep 29, 2011, 11:50:33 PM9/29/11
to
In article
<1k8djs5.mfwbsv10hentqN%adr...@poppyrecords.invalid.invalid>,
Any chance of there being any power-line hum in the recording? If there
is, that's your calibration. If not the fundamental, then maybe
harmonics ...
Isaac
<1k8djs5.mfwbsv10hentqN%adr...@poppyrecords.invalid.invalid>,
is, that's your calibration. If not the fundamental, then maybe
harmonics ...
Isaac
Jeff Liebermann
Sep 30, 2011, 12:31:54 AM9/30/11
to
On Thu, 29 Sep 2011 21:08:55 +0100,
in the early 1960's. I may still have a functional blue belt
Dictaphone, hand mike, and foot switch, somewhere in my mess.
As I understand it, the machine is something like this:
<http://www.videointerchange.com/images/Dictabelt3.jpg>
<http://www.gumtree.com/p/for-sale/dictaphone-timemaster-dictabelt-recorder-electronica/86424428>
<http://www.poppyrecords.co.uk/other/Dictabelts/dictabelts.htm>
<http://www.dpph.nl/content/radio_tv_audio/recorders/dictaphone/dictaphone0711.html>
If this is not the machine, it might be helpful if you would kindly
disclose some additional clues such as the maker and model numbers.
>It issignificantly below 7.5 ips. I need to know the manufacturer's
>specifications as I am developing a playback machine for archival work,
>where comparison between the actual speed and the 'official' speed can
>yield useful historical information.
Ok, I need to know the manufacturer, model number, and color of the
belt (blue or red). Please forgive me for not being able to guess
that information from your description.
To the best of my limited knowledge from 45 years ago, the nominal
speed of these devices used record speeds per the chart above. The
speed was settable and adjustable, but always followed the chart as
nominal speeds. If you have physical posession of a machine, you
should be able to measure it. If you have a clue as to the runtime of
the belt, you should be able to calculate it. The belt speed should
not have a huge effect on your playback device. If the belt contains
voice, you should be able to simply listen to the belt, and adjust the
drive speed until the speech is clear. You'll need to do that anyway
because many such dictation machines offer multiple speeds, any of
which might have been used for the recording.
Good luck.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com je...@cruzio.com
# http://www.LearnByDestroying.com AE6KS
adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>Jeff Liebermann <je...@cruzio.com> wrote:
>
>> On Thu, 29 Sep 2011 15:07:40 +0100,
>> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>>
>> >Does anyone happen to know the official speed of a Dictabelt?
>>
>> Which maker and what model?
>> They followed the same speeds at record platters.
>> ips time
>> 15 15 min
>> 7 1/2 30 min
>> 3 3/4 60 min
>> 1 7/8 120 min
>
>I think you have misunderstood the type of machine I am enquiring about.
Maybe. As I see above, it's called a Dictabelt. I used to fix those
>Jeff Liebermann <je...@cruzio.com> wrote:
>
>> On Thu, 29 Sep 2011 15:07:40 +0100,
>> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>>
>> >Does anyone happen to know the official speed of a Dictabelt?
>>
>> Which maker and what model?
>> They followed the same speeds at record platters.
>> ips time
>> 15 15 min
>> 7 1/2 30 min
>> 3 3/4 60 min
>> 1 7/8 120 min
>
>I think you have misunderstood the type of machine I am enquiring about.
in the early 1960's. I may still have a functional blue belt
Dictaphone, hand mike, and foot switch, somewhere in my mess.
As I understand it, the machine is something like this:
<http://www.videointerchange.com/images/Dictabelt3.jpg>
<http://www.gumtree.com/p/for-sale/dictaphone-timemaster-dictabelt-recorder-electronica/86424428>
<http://www.poppyrecords.co.uk/other/Dictabelts/dictabelts.htm>
<http://www.dpph.nl/content/radio_tv_audio/recorders/dictaphone/dictaphone0711.html>
If this is not the machine, it might be helpful if you would kindly
disclose some additional clues such as the maker and model numbers.
>It issignificantly below 7.5 ips. I need to know the manufacturer's
>specifications as I am developing a playback machine for archival work,
>where comparison between the actual speed and the 'official' speed can
>yield useful historical information.
belt (blue or red). Please forgive me for not being able to guess
that information from your description.
To the best of my limited knowledge from 45 years ago, the nominal
speed of these devices used record speeds per the chart above. The
speed was settable and adjustable, but always followed the chart as
nominal speeds. If you have physical posession of a machine, you
should be able to measure it. If you have a clue as to the runtime of
the belt, you should be able to calculate it. The belt speed should
not have a huge effect on your playback device. If the belt contains
voice, you should be able to simply listen to the belt, and adjust the
drive speed until the speech is clear. You'll need to do that anyway
because many such dictation machines offer multiple speeds, any of
which might have been used for the recording.
Good luck.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com je...@cruzio.com
# http://www.LearnByDestroying.com AE6KS
Adrian Tuddenham
Sep 30, 2011, 4:10:01 AM9/30/11
to
Jeff Liebermann <je...@cruzio.com> wrote:
> On Thu, 29 Sep 2011 21:08:55 +0100,
> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>
> >Jeff Liebermann <je...@cruzio.com> wrote:
[...]
> On Thu, 29 Sep 2011 21:08:55 +0100,
> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>
> >Jeff Liebermann <je...@cruzio.com> wrote:
> As I understand it, the machine is something like this:
> <http://www.videointerchange.com/images/Dictabelt3.jpg>
> <http://www.gumtree.com/p/for-sale/dictaphone-timemaster-dictabelt-recorder-
>electronica/86424428>
> <http://www.dpph.nl/content/radio_tv_audio/recorders/dictaphone/
> <http://www.videointerchange.com/images/Dictabelt3.jpg>
> <http://www.gumtree.com/p/for-sale/dictaphone-timemaster-dictabelt-recorder-
>electronica/86424428>
>dictaphone0711.html>
Yes
> <http://www.poppyrecords.co.uk/other/Dictabelts/dictabelts.htm>
This was my set-up which I am now having to replace.
[...]
> Ok, I need to know the manufacturer,...
Dictaphone
> model number, ...
Any Dictabelt model
>and color of the
> belt (blue or red).
I am constructing a playback machine for archival work, which needs to
be able to cope with any Dictabelt. There was a standard speed which
applied to all the normal models and all belts, so as to allow
interchangeability of the belts world-wide.
The basic machine was designed for 60 c/s mains, but there were
adaptations to allow the machines to run at the correct belt speeds on
50 c/s. Some special machines were also designed to run at half speed
for logging purposes . I have already encountered some belts which were
recorded on unadapted half-speed 60 c/s machines working from 50 c/s
supplies - and, no doubt, there will be others which were recorded at
different non-standard speeds for various reasons.
What I need to know is the manufacturer's specification for the standard
belt speed which was supposed to allow interchangeability between all
the machines. I can then calibrate the speed control on my machine to
show the %age speed variation from the norm, so as to deduce information
about the circumstances under which each belt was recorded.
Adrian Tuddenham
Sep 30, 2011, 4:10:01 AM9/30/11
to
running from stabilised mains supplies. Some Dictabelt machines were
battery-powered and some 'in the field' would have been run from
inverters or vibrator packs.
I need to know the manufacturer's standard speed in order to measure
the variations of individual belts from the norm.
Adrian Tuddenham
Sep 30, 2011, 4:10:01 AM9/30/11
to
Jeff Urban <jurb...@gmail.com> wrote:
> Interesting dilemma you got there. I searched the web but then it
> would be unreasonable to think you hadn't. I found something called a
> memobelt which was supposedly the same or similar.
>
> However in thinking about it, being a scribing machine of sorts, and
> given the time frame I would think two things, well one.....
>
> It is unlikely that the unit used a capstan.
This is a belt recording system, it was driven by being tensioned around
> Interesting dilemma you got there. I searched the web but then it
> would be unreasonable to think you hadn't. I found something called a
> memobelt which was supposedly the same or similar.
>
> However in thinking about it, being a scribing machine of sorts, and
> given the time frame I would think two things, well one.....
>
> It is unlikely that the unit used a capstan.
a pair of parallel rollers.
N_Cook
Sep 30, 2011, 4:11:30 AM9/30/11
to
Adrian Tuddenham <adr...@poppyrecords.invalid.invalid> wrote in message
of film so if any repeat noise/clicks on the belt would then be synced to
the film and a forensically accurate timing to determine the number of shots
or echoes
N_Cook
Sep 30, 2011, 4:21:17 AM9/30/11
to
Adrian Tuddenham <adr...@poppyrecords.invalid.invalid> wrote in message
news:1k8ehbi.1k8desl4ft1duN%adr...@poppyrecords.invalid.invalid...
Geo
Sep 30, 2011, 5:00:02 AM9/30/11
to
On Thu, 29 Sep 2011 21:31:54 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:
>If this is not the machine, it might be helpful if you would kindly
>disclose some additional clues such as the maker and model numbers.
Perhaps Adrian should have said that he has been working on these for
some time:-
e.g:-
http://cadensa.bl.uk/uhtbin/cgisirsi/x/0/0/5?searchdata1=CKEY6010012&library=ALL
http://www.poppyrecords.co.uk/other/Dictabelts/dictabelts.htm
wrote:
>If this is not the machine, it might be helpful if you would kindly
>disclose some additional clues such as the maker and model numbers.
some time:-
e.g:-
http://cadensa.bl.uk/uhtbin/cgisirsi/x/0/0/5?searchdata1=CKEY6010012&library=ALL
http://www.poppyrecords.co.uk/other/Dictabelts/dictabelts.htm
Adrian Tuddenham
Sep 30, 2011, 5:24:02 AM9/30/11
to
meanufacturer's designated belt speed.
Adrian Tuddenham
Sep 30, 2011, 5:24:02 AM9/30/11
to
deduce it from recordings which may have been altered or may not have
followed the standard in the first place.
As you can see above, it is not easy to be certain what the standard was
supposed to be, even when an actual machine is available.
Jeff Liebermann
Oct 1, 2011, 11:52:19 PM10/1/11
to
On Fri, 30 Sep 2011 09:10:01 +0100,
adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>Any Dictabelt model
I just tore apart many boxes of junk that I haven't seen for 20 years,
but didn't find my Dictaphone or belts. Sorry. I think asking in the
rec.antiques.radio+phono
newsgroup might be more productive in finding someone with a working
Dictaphone machine.
>I am constructing a playback machine for archival work, which needs to
>be able to cope with any Dictabelt. There was a standard speed which
>applied to all the normal models and all belts, so as to allow
>interchangeability of the belts world-wide.
>
>The basic machine was designed for 60 c/s mains, but there were
>adaptations to allow the machines to run at the correct belt speeds on
>50 c/s. Some special machines were also designed to run at half speed
>for logging purposes . I have already encountered some belts which were
>recorded on unadapted half-speed 60 c/s machines working from 50 c/s
>supplies - and, no doubt, there will be others which were recorded at
>different non-standard speeds for various reasons.
That explains the strange errors in apparent belt speed. I would have
expected South Africa to use the same standards as UK (230V 50Hz).
>What I need to know is the manufacturer's specification for the standard
>belt speed which was supposed to allow interchangeability between all
>the machines. I can then calibrate the speed control on my machine to
>show the %age speed variation from the norm, so as to deduce information
>about the circumstances under which each belt was recorded.
If that's the situation, you may need to handle a fairly wide range of
belt speeds. I suspect that it might be easier to setup a servo
controlled motor, external belt tensioner, and stylus attached to a
linear actuator. In effect, a belt recorder implimented mostly in
software. That should give you control over speed and head position,
which should also solve the track skipping problem. It would also
allow you to run at some high speed (i.e. 15 ips) and slow down the
playback in software.
Good luck. Sounds like an interesting project.
adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>Any Dictabelt model
I just tore apart many boxes of junk that I haven't seen for 20 years,
but didn't find my Dictaphone or belts. Sorry. I think asking in the
rec.antiques.radio+phono
newsgroup might be more productive in finding someone with a working
Dictaphone machine.
>I am constructing a playback machine for archival work, which needs to
>be able to cope with any Dictabelt. There was a standard speed which
>applied to all the normal models and all belts, so as to allow
>interchangeability of the belts world-wide.
>
>The basic machine was designed for 60 c/s mains, but there were
>adaptations to allow the machines to run at the correct belt speeds on
>50 c/s. Some special machines were also designed to run at half speed
>for logging purposes . I have already encountered some belts which were
>recorded on unadapted half-speed 60 c/s machines working from 50 c/s
>supplies - and, no doubt, there will be others which were recorded at
>different non-standard speeds for various reasons.
expected South Africa to use the same standards as UK (230V 50Hz).
>What I need to know is the manufacturer's specification for the standard
>belt speed which was supposed to allow interchangeability between all
>the machines. I can then calibrate the speed control on my machine to
>show the %age speed variation from the norm, so as to deduce information
>about the circumstances under which each belt was recorded.
belt speeds. I suspect that it might be easier to setup a servo
controlled motor, external belt tensioner, and stylus attached to a
linear actuator. In effect, a belt recorder implimented mostly in
software. That should give you control over speed and head position,
which should also solve the track skipping problem. It would also
allow you to run at some high speed (i.e. 15 ips) and slow down the
playback in software.
Good luck. Sounds like an interesting project.
Adrian Tuddenham
Oct 2, 2011, 11:13:33 AM10/2/11
to
Jeff Liebermann <je...@cruzio.com> wrote:
> On Fri, 30 Sep 2011 09:10:01 +0100,
> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>
> >Any Dictabelt model
>
> I just tore apart many boxes of junk that I haven't seen for 20 years,
> but didn't find my Dictaphone or belts. Sorry. I think asking in the
> rec.antiques.radio+phono
> newsgroup might be more productive in finding someone with a working
> Dictaphone machine.
I have a working Dictablet machine (in addition to the one I have
> On Fri, 30 Sep 2011 09:10:01 +0100,
> adr...@poppyrecords.invalid.invalid (Adrian Tuddenham) wrote:
>
> >Any Dictabelt model
>
> I just tore apart many boxes of junk that I haven't seen for 20 years,
> but didn't find my Dictaphone or belts. Sorry. I think asking in the
> rec.antiques.radio+phono
> newsgroup might be more productive in finding someone with a working
> Dictaphone machine.
cannibalised to make the archival player). That is how I know the
approximate speeds. What I do not know is the manufacturer's specified
speed. For a number of reasons, the speed I have measured on my
machine may not be the same as the specified speed.
What I really need is the manufacturer's written specification (which
might be found in either an internal works document or a decent workshop
manual). Somebody somewhere must have worked on those machines and will
know what the speed was supposed to be.
> >I am constructing a playback machine for archival work, which needs to
> >be able to cope with any Dictabelt. There was a standard speed which
> >applied to all the normal models and all belts, so as to allow
> >interchangeability of the belts world-wide.
> >
> >The basic machine was designed for 60 c/s mains, but there were
> >adaptations to allow the machines to run at the correct belt speeds on
> >50 c/s. Some special machines were also designed to run at half speed
> >for logging purposes . I have already encountered some belts which were
> >recorded on unadapted half-speed 60 c/s machines working from 50 c/s
> >supplies - and, no doubt, there will be others which were recorded at
> >different non-standard speeds for various reasons.
>
> That explains the strange errors in apparent belt speed. I would have
> expected South Africa to use the same standards as UK (230V 50Hz).
half speed on 60 c/s - and were running it on 50 c/s. The speed was 17%
below half speed.
>
> >What I need to know is the manufacturer's specification for the standard
> >belt speed which was supposed to allow interchangeability between all
> >the machines. I can then calibrate the speed control on my machine to
> >show the %age speed variation from the norm, so as to deduce information
> >about the circumstances under which each belt was recorded.
>
> If that's the situation, you may need to handle a fairly wide range of
> belt speeds. I suspect that it might be easier to setup a servo
> controlled motor, external belt tensioner, and stylus attached to a
> linear actuator. In effect, a belt recorder implimented mostly in
> software. That should give you control over speed and head position,
> which should also solve the track skipping problem. It would also
> allow you to run at some high speed (i.e. 15 ips) and slow down the
> playback in software.
My experience suggests that it is better to allow the stylus to follow
> >What I need to know is the manufacturer's specification for the standard
> >belt speed which was supposed to allow interchangeability between all
> >the machines. I can then calibrate the speed control on my machine to
> >show the %age speed variation from the norm, so as to deduce information
> >about the circumstances under which each belt was recorded.
>
> If that's the situation, you may need to handle a fairly wide range of
> belt speeds. I suspect that it might be easier to setup a servo
> controlled motor, external belt tensioner, and stylus attached to a
> linear actuator. In effect, a belt recorder implimented mostly in
> software. That should give you control over speed and head position,
> which should also solve the track skipping problem. It would also
> allow you to run at some high speed (i.e. 15 ips) and slow down the
> playback in software.
the grooves, rather than being rigidly fixed where the groove ought to
be. That way, belts which wander across the faces of the rollers don't
cause the stylus to skip. The leadscrew of the machine drives the
playback head carriage, but the head swivels freely to adjust itself +
or - 1/8" from the central position set by the carriage.
At present I am using the machine's existing motor with the two sets of
stator coils driven in quadrature from a pair of high voltage amplifiers
by signals from a 4-phase oscillator. As well as providing variable
frequency, the system has to control the current through the motor
windings so as to gives adequate mechanical torque but not saturate the
iron and give rise to excessive hum harmonics in the playback head. The
motor will work over a speed range from 20 to 70 c/s if the phasing and
currents can be correctly maintained.
It may be possible to put a toothed wheel and magnetic sensor on the
drive roller shaft, which would be used to control the motor drive
frequency so as to compensate for slippage in the rubber idler and drive
belt and the motor slip frequency. That way, the drive roller speed
would be accurately controlled and the only discrepancies would come
from the very slight slippage of the recorded belt on the roller.
Another way of specifying the speed would be to count the drive roller
revolutions. Off-load, it seems to be spot-on 120 rpm, so perhaps that
is how the manufacturers laid down their standard.
> Good luck. Sounds like an interesting project.
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