16 Jun
2024
16 Jun
'24
12:51 a.m.
Seems this eBay seller let the magic smoke get out, then proceeded to power
it on again one hour later.
Litton Monroe OC 8820
https://www.ebay.com/itm/355793400092
See the description..
Don Resor
16 Jun
16 Jun
12:58 a.m.
On 6/15/24 21:51, D. Resor via cctalk wrote:
Seems this eBay seller let the magic smoke get out,
then proceeded to power
it on again one hour later.
Litton Monroe OC 8820
https://www.ebay.com/itm/355793400092
See the description..
Probably due to the failed film-in-oil (sometimes known as Rifa) line
filter capacitors--a very common failure and nonfatal.
My recollection of these machines is that they are a basic Z80 CP/M
box--I do have samples of these floppies in my archives.
So nothing special, AFAIK.
--Chuck
6:53 a.m.
I reached out to the seller and explained that it may have been AC line capacitors which
went up in smoke etc, and why it's always a bad idea to "just plug it in"
and power it on without some knowledge to remove the cover and make a visual inspect
first.
Yes, I found the same info searching online. It's a Z80 box which can run the
proprietary O/S which Litton-Monroe furnished or C/PM.
A nice looking piece of equipment but nothing special.
The cursor key layout could have been laid out in a more user friendly way.
Don Resor
-----Original Message-----
From: Chuck Guzis via cctalk <cctalk(a)classiccmp.org>
Sent: Saturday, June 15, 2024 9:58 PM
To: D. Resor via cctalk <cctalk(a)classiccmp.org>
Cc: Chuck Guzis <cclist(a)sydex.com>
Subject: [cctalk] Re: The magic smoke....
On 6/15/24 21:51, D. Resor via cctalk wrote:
Seems this eBay seller let the magic smoke get out,
then proceeded to
power it on again one hour later.
Litton Monroe OC 8820
https://www.ebay.com/itm/355793400092
See the description..
Probably due to the failed film-in-oil (sometimes known as Rifa) line filter capacitors--a
very common failure and nonfatal.
My recollection of these machines is that they are a basic Z80 CP/M box--I do have samples
of these floppies in my archives.
So nothing special, AFAIK.
--Chuck
7:09 a.m.
New subject: Cursor keys and the Inverted T layout, Was: The magic smoke....
On 16/06/2024 11:53, D. Resor via cctalk wrote:
*snip*
The cursor key layout could have been laid out in a more user friendly way.
Don Resor
Not a huge amount different to most contemporary machines. Cursor keys
were notoriously unergonomic before the introduction of the inverted T
layout present on the DEC LK-201, which became the industry standard
keyboard layout after IBM copied it for the Model M. Basically every
home microcomputer that had cursor keys, had them inline with each other
in a very unintuitive layout.
I imagine that DEC likely weren't the first to come up with the inverted
T, even if they were the first to place it on it's own between the main
QWERTY section and the number pad (which is also unlikely). Is anyone
aware of earlier examples of the inverted T, or at least similar layouts
to the LK201? Josh Rice
1:13 p.m.
New subject: Cursor keys and the Inverted T layout, Was: The magic smoke....
On Jun 16, 2024, at 7:09 AM, Joshua Rice via cctalk
<cctalk(a)classiccmp.org> wrote:
On 16/06/2024 11:53, D. Resor via cctalk wrote:
Great question. Not a direct answer but an example of user friendly cursor keys: PLATO IV
terminals have a main keyboard with some function keys mostly to the right -- keys with
labels like HELP and STOP. There are also operator keys to the left: plus, minus,
multiply, and divide signs. The shifted codes are roughly like on an ASR-33, for example
shift period is exclamation point. No numeric keypad nor dedicated cursor keys.
Instead, when cursor key functionality was needed, programs would by convention use the
keys surrounding "s" for that, and the keycaps are marked with 8 different
arrows. So not just up down left right, but also the diagonals in between. It makes
keyboard-operated graphics editing a lot easier. (These terminals didn't have a
mouse, though they often had an early touch screen.) So for user friendliness these are
hard to beat; the direction away from "s" is the direction of the movement you
get -- even more obvious than "inverted T".
paul
*snip*
The cursor key layout could have been laid out in a more user friendly way.
Don Resor
Not a huge amount different to most contemporary machines. Cursor keys were notoriously
unergonomic before the introduction of the inverted T layout present on the DEC LK-201,
which became the industry standard keyboard layout after IBM copied it for the Model M.
Basically every home microcomputer that had cursor keys, had them inline with each other
in a very unintuitive layout.
I imagine that DEC likely weren't the first to come up with the inverted T, even if
they were the first to place it on it's own between the main QWERTY section and the
number pad (which is also unlikely). Is anyone aware of earlier examples of the inverted
T, or at least similar layouts to the LK201? Josh Rice 
7:10 a.m.
It's a design feature.
They burn out self-destructively, clearing the fault and signalling the
loss of cable-borne RFI suppression.
On Sun, Jun 16, 2024 at 11:55 AM D. Resor via cctalk <cctalk(a)classiccmp.org>
wrote:
I reached out to the seller and explained that it may
have been AC line
capacitors which went up in smoke etc, and why it's always a bad idea to
"just plug it in" and power it on without some knowledge to remove the
cover and make a visual inspect first.
Yes, I found the same info searching online. It's a Z80 box which can run
the proprietary O/S which Litton-Monroe furnished or C/PM.
A nice looking piece of equipment but nothing special.
The cursor key layout could have been laid out in a more user friendly way.
Don Resor
-----Original Message-----
From: Chuck Guzis via cctalk <cctalk(a)classiccmp.org>
Sent: Saturday, June 15, 2024 9:58 PM
To: D. Resor via cctalk <cctalk(a)classiccmp.org>
Cc: Chuck Guzis <cclist(a)sydex.com>
Subject: [cctalk] Re: The magic smoke....
On 6/15/24 21:51, D. Resor via cctalk wrote:
Seems this eBay seller let the magic smoke get
out, then proceeded to
power it on again one hour later.
Litton Monroe OC 8820
https://www.ebay.com/itm/355793400092
See the description..
Probably due to the failed film-in-oil (sometimes known as Rifa) line
filter capacitors--a very common failure and nonfatal.
My recollection of these machines is that they are a basic Z80 CP/M box--I
do have samples of these floppies in my archives.
So nothing special, AFAIK.
--Chuck
7:29 a.m.
I remember in the Xerox DSBU lab the phrase was often used, "That's not a bug,
it's a feature!"
Don Resor
-----Original Message-----
From: Adrian Godwin via cctalk <cctalk(a)classiccmp.org>
Sent: Sunday, June 16, 2024 4:11 AM
To: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org>
Cc: Adrian Godwin <artgodwin(a)gmail.com>
Subject: [cctalk] Re: The magic smoke....
It's a design feature.
They burn out self-destructively, clearing the fault and signalling the loss of
cable-borne RFI suppression.
On Sun, Jun 16, 2024 at 11:55 AM D. Resor via cctalk <cctalk(a)classiccmp.org>
wrote:
I reached out to the seller and explained that it may
have been AC
line capacitors which went up in smoke etc, and why it's always a bad
idea to "just plug it in" and power it on without some knowledge to
remove the cover and make a visual inspect first.
Yes, I found the same info searching online. It's a Z80 box which can
run the proprietary O/S which Litton-Monroe furnished or C/PM.
A nice looking piece of equipment but nothing special.
The cursor key layout could have been laid out in a more user friendly way.
Don Resor
-----Original Message-----
From: Chuck Guzis via cctalk <cctalk(a)classiccmp.org>
Sent: Saturday, June 15, 2024 9:58 PM
To: D. Resor via cctalk <cctalk(a)classiccmp.org>
Cc: Chuck Guzis <cclist(a)sydex.com>
Subject: [cctalk] Re: The magic smoke....
On 6/15/24 21:51, D. Resor via cctalk wrote:
Seems this eBay seller let the magic smoke get
out, then proceeded
to power it on again one hour later.
Litton Monroe OC 8820
https://www.ebay.com/itm/355793400092
See the description..
Probably due to the failed film-in-oil (sometimes known as Rifa) line
filter capacitors--a very common failure and nonfatal.
My recollection of these machines is that they are a basic Z80 CP/M
box--I do have samples of these floppies in my archives.
So nothing special, AFAIK.
--Chuck
10:42 p.m.
Chuck Guzis wrote:
Probably due to the failed film-in-oil (sometimes
known as Rifa) line
filter capacitors--a very common failure and nonfatal.
I never "just turn on" equipment that's been out of service for an extended
period of time ... until I ...
Over the years, I've had good luck "reforming" electrolytic capacitors.
Very simple and easy to do, basically:
- Disconnect at least one side of the cap.
- Connect a variable voltage supply to the cap, through a few hundred ohm
serial resistor (this both limits current in case the cap has actually failed, and makes
it quite reasonable to do this to several caps in parallel (in this case, either make
sure if you left one side connected that it's common (and not the lead from
the supply that has the resistor) - or just disconnect both sides.
- Start low (a volt or so) - let the cap sit at that voltage for some time
(I usually do a few hours - more if the cap is really old/disused)
- Make sure cap charges to set voltage and is not drawing current
- repeat, raising voltage by a volt of two each "cycle" till you get to just
above the normal operating voltage of the cap.
When I was more active in collecting/acquiring old system of indeterminate
state. I built a little gadget to do this automatically - so I could leave it to do
it's
thing overnight.
Dave ::: https://dunfield.themindfactory.com ::: "Daves Old
Computers"->Personal
10:58 p.m.
On 6/16/24 19:42, Dave Dunfield via cctalk wrote:
Chuck Guzis wrote:
Point taken, but in this case no amount of "reforming" will fix those
old 'Rifa" filter caps.
--Chuck
Probably due to the failed film-in-oil (sometimes
known as Rifa) line
filter capacitors--a very common failure and nonfatal.
I never "just turn on" equipment that's been out of service for an
extended
period of time ... until I ... 
11:34 p.m.
Yes, those Rifa, Wima, and so on, mains-bypass paper caps in clear epoxy always fail,
they're notorious. Over time the epoxy cracks letting in moisture which degrades the
paper. They may be rated to fail without bursting into flames, but they sure make some
smoke.
Replace on sight, with an appropriate X/Y-rated part.
-Dave Wise
________________________________
From: Chuck Guzis via cctalk <cctalk(a)classiccmp.org>
Sent: Sunday, June 16, 2024 7:58 PM
To: cctalk(a)classiccmp.org <cctalk(a)classiccmp.org>
Cc: Chuck Guzis <cclist(a)sydex.com>
Subject: [cctalk] Re: The magic smoke....
On 6/16/24 19:42, Dave Dunfield via cctalk wrote:
Chuck Guzis wrote:
Point taken, but in this case no amount of "reforming" will fix those
old 'Rifa" filter caps.
--Chuck
Probably due to the failed film-in-oil (sometimes
known as Rifa) line
filter capacitors--a very common failure and nonfatal.
I never "just turn on" equipment that's been out of service for an
extended
period of time ... until I ...
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days inactive
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days old
9 comments
7 participants
participants (7)
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Adrian Godwin -
Chuck Guzis -
D. Resor -
Dave Dunfield -
David Wise -
Joshua Rice -
Paul Koning