24 Jan
2010
24 Jan
'10
7:14 p.m.
This is a long shot... On the other hand, there are people here who've
done all sorts of odd things, and the only silly question is one that's
not asked (or something like that).
As I mentioned yesterday (when I asked about zneer diode data), I've got
an HP2631B printer that's gone crazy. I had anohter quick look at it
today, and it appears that one problem is the shaft encoder on the right
hand end of the carriage leadscrew. This connects by a 10 way cable
(integral with the encoder) to the 'printer logic' PCB, 6 of the pins on
the connector sseem to be used, 2 grouds, 2 +5V and the 2 quadrature
output signals. Those 2 outputs are buffered by a couple of sections of a
'14, the outputs of that go to testpoints (and elswehere, of course).
Anyway, both those testpoints are low all the time (turning the leadscrew
by hand, I've not fixed the motor drive amplifer yet!). The outputs from
the encoder are high all the time (so the problem isn't the '14, more's
the pity), they are genuinely high, not floating. And there don't seem to
be any pull-ups on the printer logic PCB< so the 'high' is coming from
the encoder.
Anyway. Iv'e read the HP service manual (on http://www.hpmuseum.net) and
it appears you need special tools to remove and replace the encoder. The
encoder disk is epoxied to the neadscrew, you need a special puller to
break the bond and an alignment tool to get the encoder disk the right
distance insde the encoder housing when you refit it.
Of coruse I don;t ahve the tools...
Has anyone ever done this? Maybe the same tools, or something like them,
were used with THe shaft encoders that HP sold as loose componets. Any
thoughts?
-tony
25 Jan
25 Jan
7:01 p.m.
sounds like the lamp/led is off
Thanks!. I asusme the otuputs are high if the corresponding sensors are
dark, then.
This encoder is supplied in 3 piexes according to the manual. There's a
housing that scred to the ebaring cover plate in the printer. A slotted
encoder disk that's then glued to the leadscrew. And an end cover that
clips onto the end of the casing, this carries the light source (I assume
IR LEDs).
When I next work on the printer, I'll invesigate the powering and
operation of those LEDs.
-tony
9:19 a.m.
New subject: [personal] Shaft encoder in HP2631B printer
----- Original Message -----
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
To: <cctalk at classiccmp.org>
Sent: Sunday, January 24, 2010 7:14 PM
Subject: [personal] Shaft encoder in HP2631B printer
This is a long shot... On the other hand, there are
people here who've
done all sorts of odd things, and the only silly question is one that's
not asked (or something like that).
As I mentioned yesterday (when I asked about zneer diode data), I've got
an HP2631B printer that's gone crazy. I had anohter quick look at it
today, and it appears that one problem is the shaft encoder on the right
hand end of the carriage leadscrew. This connects by a 10 way cable
(integral with the encoder) to the 'printer logic' PCB, 6 of the pins on
the connector sseem to be used, 2 grouds, 2 +5V and the 2 quadrature
output signals. Those 2 outputs are buffered by a couple of sections of a
'14, the outputs of that go to testpoints (and elswehere, of course).
Sounds like it may be a HEDS or HEDL encoder as it's HP, any chance of a
photo or a p#.
Mike.
Anyway, both those testpoints are low all the time (turning the leadscrew
by hand, I've not fixed the motor drive amplifer yet!). The outputs from
the encoder are high all the time (so the problem isn't the '14, more's
the pity), they are genuinely high, not floating. And there don't seem to
be any pull-ups on the printer logic PCB< so the 'high' is coming from
the encoder.
Anyway. Iv'e read the HP service manual (on http://www.hpmuseum.net) and
Link to the manual ?
it appears you need special tools to remove and
replace the encoder. The
encoder disk is epoxied to the neadscrew, you need a special puller to
break the bond and an alignment tool to get the encoder disk the right
distance insde the encoder housing when you refit it.
Of coruse I don;t ahve the tools...
Has anyone ever done this? Maybe the same tools, or something like them,
were used with THe shaft encoders that HP sold as loose componets. Any
thoughts?
We use HEDS an HEDL's all the time, no special tools.
-tony
7:26 p.m.
New subject: [personal] Shaft encoder in HP2631B printer
Sounds like it may be a HEDS or HEDL encoder as
it's HP, any chance of a
photo or a p#.
It has a number QEDS8997 on the end cover (the part that carries the
LEDs). There may be a number on the other end of the housing, but I
can't remove it to check, the screws holding it to the bearing plate are
covered by the encoder disk that's emoxied to the eladscrew and which
needs the special tools (according to HP) to remove/replace.
I cna't easily provide a photo (no digital camera). If you've ever worked
on HP9000/200 machines, it's similar to the encoder used on the
twiddleknob on the keyboards of said machiens, but without he
spindle/mounting bush.
Anyway.
Iv'e read the HP service manual (on http://www.hpmuseum.net) and
Link to the manual ? We use HEDS an HEDL's all the time, no special
tools.
According to the manual, this encoder was supplied as 3 separate parts.
The housing, constianing the sensorts and with the cable fixed to it ;
the encoder disk; and the end conver containing the LEDs.
THey are fitted in that order, and removed in the reverse order.
The hub of the encoder disk doesn't have a setscrew or similar. It is
glued to the hend of the leadscrew with epoxy. One tool is used to remove
the disk (it hocks round the hub, and a screw then applies pressure to
the ned of the shaft to pull the disk off, breaking the epoxy bond. The
other tool is used to bet the disk back on the spindile, it, again, fits
round the hub and rests against the end of the housing, this getting the
disk the right distance inside.
What is not clear ffom the manual is wheter this procedure damages the
disk, or whether you can refit the old one if you want to.
My guessis that he other reply is correct, and that the LEDs are out. If
that's the case, I may not need to remocve the encoder assembly. The end
cover carrying the LEDs comes off anyway. The whould thing can be removed
from the printer complete with leadscrew, bearing, and
bearing cover
plate. And after doing that it's possible to unclip the cover
over the
cable and get to the edge of the snensoor PCB. Maybe that will be enough.
-tony
9:42 p.m.
New subject: [personal] Shaft encoder in HP2631B printer
-----Oorspronkelijk bericht-----
Van: cctalk-bounces at classiccmp.org
[mailto:cctalk-bounces at classiccmp.org] Namens Tony Duell
Verzonden: maandag 25 januari 2010 20:27
Aan: cctalk at classiccmp.org
Onderwerp: Re: [personal] Shaft encoder in HP2631B printer
The easiest way to get to it is to go to said site, then
naviage through 'printers' 'impact' 'hp2531' 'product
documentation'. You'll then see a serevice manaul (and a CE
manual) for the 2630B series listed. I think the encoder i
nthe 2531A is similar, the one in the 2631G is very different
(and, alas, looks a lot more repairable from the manual).
The HP 9000/200 series knob encoder uses a small bulb, witch I replaced for
a white LED (3mm type).
I had to remodel the LED a bit to make it fit.
-Rik
Sounds like it may be a HEDS or HEDL encoder as
it's HP,
any chance of
a photo or a p#.
It has a number QEDS8997 on the end cover (the part that
carries the LEDs). There may be a number on the other end of
the housing, but I can't remove it to check, the screws
holding it to the bearing plate are covered by the encoder
disk that's emoxied to the eladscrew and which needs the
special tools (according to HP) to remove/replace.
I cna't easily provide a photo (no digital camera). If you've
ever worked on HP9000/200 machines, it's similar to the
encoder used on the twiddleknob on the keyboards of said
machiens, but without he spindle/mounting bush.
> Anyway. Iv'e read the HP service manual
(on
http://www.hpmuseum.net)
and
Link to the manual ? We use HEDS an HEDL's all the time, no
special tools.
According to the manual, this encoder was supplied as 3
separate parts.
The housing, constianing the sensorts and with the cable
fixed to it ; the encoder disk; and the end conver containing
the LEDs.
THey are fitted in that order, and removed in the reverse order.
The hub of the encoder disk doesn't have a setscrew or
similar. It is glued to the hend of the leadscrew with epoxy.
One tool is used to remove the disk (it hocks round the hub,
and a screw then applies pressure to the ned of the shaft to
pull the disk off, breaking the epoxy bond. The other tool is
used to bet the disk back on the spindile, it, again, fits
round the hub and rests against the end of the housing, this
getting the disk the right distance inside.
What is not clear ffom the manual is wheter this procedure
damages the disk, or whether you can refit the old one if you want to.
My guessis that he other reply is correct, and that the LEDs
are out. If that's the case, I may not need to remocve the
encoder assembly. The end cover carrying the LEDs comes off
anyway. The whould thing can be removed from the printer
complete with leadscrew, bearing, and bearing cover plate.
And after doing that it's possible to unclip the cover over
the cable and get to the edge of the snensoor PCB. Maybe that
will be enough.
-tony
26 Jan
26 Jan
6:36 p.m.
New subject: [personal] Shaft encoder in HP2631B printer
The HP 9000/200 series knob encoder uses a small bulb, witch I replaced for
a white LED (3mm type).
I had to remodel the LED a bit to make it fit.
HP must have used several different encoders, then. I have 4 HP9000/200
machines with the twiddleknob -- an HP9826, an HP9836A, an HP9836CU and
an HP9816. I also have an HP9817, but I use a standard HP46020 keyboard
with that, so no know :-(
Anyway, all 4 machines use the same encoder, and the light source is a
pair of IR LEDs with the LED chips driectly mounted ona timy PCB on the
end cover. They're wired in series to 2 little wire sockets on the board.
There are 2 wire pins sticking up from the housing thac connect to these
-- one is a noraml wire to ground, the other is actually a 100 Ohm (or
so) resistor with one ende osldered to the +5V line, the other end goes
into the +ve pin socket on the LED board.
If I had to replace the light source in an encoder and I couldn't get a
suitable bulb, I'd try an IR LED first. The sensors are almost vertainly
sensitive to IR. Filaments bulbs give off a lot of IR (particularly if
underrun). of course some is absorbed by the glass envelope [1] but enough
gets out to operate the sensors.
[1] I once worked on an IR spectrometer which used a Nernst glower as the
light source. THis is a rod or coil of rare earth oxides, and you'd think
it eas a good electircal insualtor. At room temperature it is, but get it
hot, and it'll conduct (the reisstance drops with increasing temperature,
in fact it can thermally 'run away'). Anyway, the nernst glower was
connected in series wiht a ballast lamp across the mains. To get it
started you used a bit of cototn wool soaked in ethanol and ignited to
heat the glower, once it got hot, it would glow quite brightly. Of course
the advantage is that the nernst glower runs in air (it can't exaclty
oxidise, so you don't have a glass bulb to absorb any IR emission.
The nernst lamp was actually proposed for electric lighting at one point
(with an electical heater coil to start it), the advantage being that you
don't have to have an evauated bulb, and you can just replace the glower
when it fails, not the whole lamp. But they're less efficient than vacuum
or gas-filled filament lamps for producing visible light (the golwer runs
cooler than a tnngsten filament).
-tony
27 Jan
27 Jan
5:17 a.m.
New subject: [personal] Shaft encoder in HP2631B printer
Tony Duell wrote:
<snip>
[1] I once worked on an IR spectrometer which used a Nernst glower as the
light source. THis is a rod or coil of rare earth oxides, and you'd think
it eas a good electircal insualtor. At room temperature it is, but get it
hot, and it'll conduct (the reisstance drops with increasing temperature,
in fact it can thermally 'run away'). Anyway, the nernst glower was
connected in series wiht a ballast lamp across the mains. To get it
started you used a bit of cototn wool soaked in ethanol and ignited to
heat the glower, once it got hot, it would glow quite brightly. Of course
the advantage is that the nernst glower runs in air (it can't exaclty
oxidise, so you don't have a glass bulb to absorb any IR emission.
The nernst lamp was actually proposed for electric lighting at one point
(with an electical heater coil to start it), the advantage being that you
don't have to have an evauated bulb, and you can just replace the glower
when it fails, not the whole lamp. But they're less efficient than vacuum
or gas-filled filament lamps for producing visible light (the golwer runs
cooler than a tnngsten filament).
-tony
I wonder if one of those Nernst glowers emits many electrons. I've had
this pipe dream lately to build a triode to operate in open air, and
I've been pondering what to use for a filament/cathode. Googling so far
has not revealed anyone else this crazy. ;)
Later,
Charlie C.
8:08 p.m.
New subject: [personal] Shaft encoder in HP2631B printer
I wonder if one of those Nernst glowers emits many
electrons. I've had
this pipe dream lately to build a triode to operate in open air, and
I've been pondering what to use for a filament/cathode. Googling so far
has not revealed anyone else this crazy. ;)
You are going to have problems. The mean free path of an electron in air
at atmospheric pressure is pretty short (I forget how short, but it can
be looked up). You need to have the overal distance between the
electrodes to be less than that.
There was a proposable to make field emitting triodes (rather than
thermionic ones) using eteched silicon structures. Those would work
without a vacuum due to their small size. The reuslt would be
radiation-hard chips.
-tony
28 Jan
28 Jan
6:43 a.m.
New subject: [personal] Shaft encoder in HP2631B printer
Use a light beam, an analog optical gate and a photocell
Regards
Rod Smallwood
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Tony Duell
Sent: 27 January 2010 20:09
To: cctalk at classiccmp.org
Subject: Re: [personal] Shaft encoder in HP2631B printer
I wonder if one of those Nernst glowers emits many
electrons. I've had
this pipe dream lately to build a triode to operate in open air, and
I've been pondering what to use for a filament/cathode. Googling so far
has not revealed anyone else this crazy. ;)
You are going to have problems. The mean free path of an electron in air
at atmospheric pressure is pretty short (I forget how short, but it can
be looked up). You need to have the overal distance between the
electrodes to be less than that.
There was a proposable to make field emitting triodes (rather than
thermionic ones) using eteched silicon structures. Those would work
without a vacuum due to their small size. The reuslt would be
radiation-hard chips.
-tony
7:55 a.m.
New subject: [personal] Shaft encoder in HP2631B printer
Tony Duell wrote:
Yes, and I'm sure that's not the only problem I'd have. :)
Maybe my next dream will be better...
Later,
Charlie C.
I wonder if
one of those Nernst glowers emits many electrons. I've had
this pipe dream lately to build a triode to operate in open air, and
I've been pondering what to use for a filament/cathode. Googling so far
has not revealed anyone else this crazy. ;)
You are going to have problems. The mean free path of an electron in air
at atmospheric pressure is pretty short (I forget how short, but it can
be looked up). You need to have the overal distance between the
electrodes to be less than that.
There was a proposable to make field emitting triodes (rather than
thermionic ones) using eteched silicon structures. Those would work
without a vacuum due to their small size. The reuslt would be
radiation-hard chips.
-tony
9:03 a.m.
New subject: Paper tape reader in the UK
For those few lurkers over here in the UK there is a spool feed Textron
papertape reader on Ebay in the UK, from a Bridgeport CNC machine.
Ebay listing 120523596119.
I'm not connected to the seller, auto searches found it.
Best regards,
Mike Hatch
Web - www.soemtron.org
PDP-7 - www.soemtron.org/pdp7.html
Email - mike at soemtron.org
Stock sale - www.soemtron.org/stockdisposalmenu.html
Looking for a PDP-7 (some hope!)
5448
days inactive
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11 comments
6 participants
participants (6)
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ard＠p850ug1.demon.co.uk -
csquared3＠tx.rr.com -
dave.thearchivist＠gmail.com -
hp-fix＠xs4all.nl -
mike＠brickfieldspark.org -
rodsmallwood＠btconnect.com