Any Teletype ASR33 experts out there ? I have a couple
of problems with a teletype that recently came my way.
i) When I type a character from the keyboard in local
mode, something else gets printed. What gets printed
is not consistently the same character. I've watched
the selector mechanism while I hit rubout (all marking
codebars) and I can see that the codebars are not
being consistently selected betwee key presses:
sometimes I get 5 of them, sometimes 6 and
occasionally all 8. The high order bits seem to be
worst affected by this inconsistency. However if I
hold down the repeat key and select a character, the
right codebars are being selected. I punched a number
of characters onto tape to verify this and they seem
to be punching OK. This suggests to me that this isn't
an electrical problem since whatever code the keyboard
is sending is eventually being sensed correctly.
ii) In addition to i) above, even if I do get all the
codebars moving as required, the wrong characters are
being printed. I removed the carriage, cleaned and
oiled it and replaced it but this hasn't helped.
Any suggestions ? Are there any other diagnostic
procedures I can apply to figure out what's happening
here ? Right now the unit is not interfaced to
anything so any testing needs to be standalone.
Thanks,
Dave
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>
>
>Here, basically, is how the power switch should turn on the PSU.
>
>Turning on the power switch on the keyboard assembly brings pin 4 of IC
>5D low. Thus pin 6 goes high (check both of these).
>Pin 6 of IC 5D is connected to pin 9 of the same chip. Pin 10 (other
>input of that gate) should also be high -- it comes from IC2B in the
>power supply area, and shuts the machine down if the battery is too low
>(I think).
>So pin 8 of IC5D goes low. This is connected to pin 4 of IC5F. The
>output, pin 4, of this gate therefore goes high. This brings pin 2 of
>IC7E high, which makes pin 15 low, turning on Q8.
>
>I would now check all the pins I've mentioned. Something must be wrong in
>that area.
>
>
>
>>>
>>> As an aside, for those who maybe wondering why I'm bothering - I work at
>>
>>
>
>That question never occurred to me. The HX20 is a computer, so of course
>it should be repaired.
>
>
>
>>> If any one would be willing to supply photocopies of the relevant bits
>>> of the manual (schematic in
>>> particular) I would of course pay towards copying/postage/time.
>>
>>
>
>I will see what I can do...
>
Thanks for the above information - I have only just had chance to act on
it so here goes.
If I am reading the board correctly IC5D is a 4000 CMOS 2x3 input nor
and a not gate.
Checking round the pins, the inputs and
outputs are logically consistent but pin 4 does not go low when the
switch is turned on. Suggesting
that some thing is wrong else where on the keyboard board perhaps. (
Also if it is a 4000, then
pin 9 and 10 are on separate gates which doesn't agree with the above -
maybe you could confirm
that it is a 4000 )
However, the power supply voltage to the CMOS chips is very low -
bewteen 2.9 and 3.2
depending upon how long it has been plugged in which is right at the low
end of the operating range.
Unless I am mistaken the supply for a whole set of chips (presumably
those that run all the time
even when the machine is "off") is provided by Q10. If this is so, Q10
has 4.9V on the C (presumably the
main supply) and 3.3 V on the base but only 2.9 V on the emitter which
seems to be the
chip supply.
Is this inference correct and if so are the voltages right ?
Again, thanks for all your help,
Matthew Clemence
Hi
At the time I bought it, I believe I checked on this
and to break the rule, the numbers did correspond on
many of the relabeled Sharp calculators. I'll have
to admit, I never saw the matching Sharp for this
calculator but I had seen others that RS sold and
the only difference was the EC was changed from EL.
The numbers were the same.
Dwight
>From: "Eric Smith" <eric(a)brouhaha.com>
>
>Dwight wrote:
>> It is a radio shack model EC-4024 which I assume
>> is a relabeled Sharp EL-4024. I've been watching and
>> there just isn't anything like this in the stores.
>
>Typically Radio Shack model numbers do NOT correspond to the
>original manufacturer model numbers. At the moment, I can't
>think of any I've seen that actually did correspond, but
>perhaps there were some.
>
>
>
>
>
>From: "Dan Veeneman" <dan(a)ekoan.com>
>
>At 08:31 PM 11/9/02 +0100, you wrote:
>>My own favorite (otehr than my HP-16 ;-) is a CASIO CM-100 "computer math
>>calc".
>
>I too prefer the HP-16C, but the CM-100 is a nice design. I have a photo
>of one
>up on my Casio calculator page, http://www.decodesystems.com/casiocalcs.html
>
>A very similar discussion of hex-capable calculators occurred recently on
>Slashdot, along with a link to my page. As is to be expected, ClassicCmpers
>covered the same ground much more quickly. :-)
>
>>The nice thing is they have no batteries, just a "solar panel" and do not
>>seem to need much light to function properly.
>
>The CM-100 functions very well in surprisingly low light. However, when I
>need to
>do hex conversions (which I did for a while in developing code for a
>Motorola OnCore
>GPS chipset), I prefer the HP-16C.
>
>
Hi
I have a pocket calculator that I would love to replace
with a newer one ( because this one is dying ). It is a mix
of solar/battery or one can use it in low light as well.
I've replaced the battery twice since I've owned it.
It doe very convenient Dec/Hex/Binary/Octal conversions
as well. It doesn't seem that these types are being made
anymore. It is a radio shack model EC-4024 which I assume
is a relabeled Sharp EL-4024. I've been watching and
there just isn't anything like this in the stores.
Dwight
>Trying to use CD-RW is asking for trouble. They have a lower contrast
>ratio than CD-R, so even DVD players that can handle CD-R may not be
>able to handle CD-RW.
You would think, but from what I found when researching why mine couldn't
play CD-Rs, it is actually VERY common for a DVD Player to fail to play
CD-Rs, but plays a CD-RW just fine. So common, that apparently, it is the
norm for a DVD Player that can play home brew VCD's will only work with
CD-RW, unless is specifically mentions that it works with CD-R. At least
this was true a few years ago when I was looking for info.
And beyond research, in my informal polling of friends and their DVD
players (mix of old and new models)... I found the fact holds true. Out
of about a dozen DVD players I have ready access to (ie: I can go to
someone's house, and try a disc). One could not play any kind of VCD. Of
those that could, I think there were 3 that only played commercial
stamped VCDs, the rest could play home brew VCDs. In all cases where they
could play home brew VCDs, all could play CD-RW, and 2 could play CD-Rs.
The two that could play CD-Rs both specifically mentioned that they
handled CD-R media. One was a multi-format, multi-region unit, and the
other was a brand new one that even did MP3 audio CDs (which was kind of
cool).
And interestingly with one player, it had problems playing discs created
by my computer, but no problems with one created with my VCD burner (it
could play either, but the computer made one wasn't recognized every
time... sometimes you had to eject the disc, and reinsert it a few times
before the DVD player would accept the disc).
-chris
<http://www.mythtech.net>
>On Sat, 9 Nov 2002, Dr. Ido wrote:
>
>> Several old games systems used the 2650 and it's related display chips 2636
>> and 2637:
>>
>> The Emerson Arcadia 2001 (and it's many clones by Sheen, Hanimex and
others)
>> The Radofin 1292/1392 (and it's many clones by Fountain, Grandstand,
>> Hanimex and others)
>>
>> If you just need some 2650 CPUs you could remove them from these consoles.
>
>Except that those consoles are not like the Atari 2600, i.e. they are
>scarce. Arcadia 2001 systems go for at least $50 on eBay.
I've seen the genuine Arcadia 2001 get high prices, but clones can be
cheaper. Sometimes they are not listed as Arcadia 2001, the carts are not
interchangable and they look totally different. The radofin consoles don't
seem to attract the same interest, one I sold went for around AU$40 and
that was with a stack of boxed games.
At 07:17 PM 11/8/02 EST, you wrote:
>On Sat, 09 Nov 2002 (downunder time); you posted to classiccmp:
>
>> I've picked up a DECmate III and a DECstation 3100 that I'd like to get
>> running, but I don't have monitors for either.
>
>> Does anybody have the pinouts for the video ports so I can make up some
>> adapters?
>
>I can help with the DECstation 3100. I am going to paste several files to
>the end of this and that should provide you with some info to get started.
>
>I noticed the 'optus' in your email address. Out of curiosity, do you work
>for Optus or is that just your ISP? I ask as I made two trips to Australia
>to conduct training classes at Optus. It so happens they were using DEC
>equipment for what I was dealing with.
>
>Hope this helps,
Thanks, should have at least one monitor here that will handle once I make
up a cable.
Optus is only my ISP, I don't work for them. I guess they could use some
more training though, with what they consider "service" at times.
I've picked up a DECmate III and a DECstation 3100 that I'd like to get
running, but I don't have monitors for either.
Does anybody have the pinouts for the video ports so I can make up some
adapters?
>I've used both brands without any problem for Data, Music, and VCD.
>Although when using them for VCD I can't get either brand to play in our
>good JVC progressive scan DVD player :^(
This may be a DVD Player issue. I'm assuming that your DVD Player plays
Video-CD's in the first place. If so, try using a CD-RW disc (if your
burner supports them).
I have a Toshiba DVD Player that plays commercial VCD's, or any that I
make as long as I use a CD-RW disc. This is apparently not uncommon.
-chris
<http://www.mythtech.net>
The auction now has a part list attached (I've not
followed this thread too closely, so sorry if it's
been mentioned before).
>BTW if anyone knows of a decent NN-NNNNN-NN style
>part number look up utility or website, let me know.
I picked a few of the larger quantity part numbers and
threw them into google. The first hit was a large list
(or set of lists) of DEC part numbers. All the ones I
looked at (1000+ off items) were lamps or cables.
The number of actual boards may not be that much. It's possible
that some of the part numbers were complete systems or large
subassemblies, but I must admit my brief scan through left
me somewhat unimpressed (given the $3500 reserve!)
But don't let me put anyone off ... there are plenty of
parts to check out!
Antonio
