A miracle cure

[naddy]

I just accidentally dropped my original HP-15C. Not from very high, so I didn't even think about it, but then it wouldn't turn on. Aww.

Let's jostle the batteries a bit.
Okay, it's on again. Phew.
Weird "0." display, though. I'll just run an ON/- reset.
That's better.
Just to be sure, let's run the ON/× self-test.
(... Wait, why is it showing "running" with a correct second "n"?...)
(... And didn't it just show 0.0000" with a complete fifth digit?? ...)
It's all there. All display segments are on. Including those two on the fifth digit that had been dead for many years.

I'm completely speechless.

[Ren]

Yes!
It is a miracle!
Get that booger down to the river and baptize it right away!
B^)

[naddy]

Seriously, I was making plans for a display transplant and have a donor 12C ready... and now it just fixes itself? Some sort of loose connection?

[Raymond Del Tondo]

I'd rather suspect a slight shift of one of the zebra strips between the LCD and the main board,
caused by the drop, so that the zebra strips between make contact again.

Nonetheless: Congrats for your drop-repair;-)

[Pierre]

In the 60s when the TV picture faded, my father would tap the top of the device and the picture would return to normal !
Would the shock be restorative?

[naddy]

In my excitement yesterday, I forgot that I had a picture that demonstrates the previous defect:
   

[AnnoyedOne]

(10-20-2024 12:00 AM)Pierre Wrote:  Would the shock be restorative?

"Thumping" intermittent things generally has one of three effects.

• None at all. Pretty common.
• The thumpee works for a while/permanently.
• The thumpee fails completely and is no longer intermittent.
  

Since there's only a 33% chance of a bad outcome thump it!

"Dropping" is a new technique to me. Perhaps it jolted a solder joint/conductive rubber strip/PCB trace just enough to make things work. Who knows.

A1

[brouhaha]

It's actually an old, well-known technique, called "percussive maintenance".

[badacktor]

As some who's been working in machining for years now, I cannot tell you just how valuable 'percussive maintenance' can be. I worked with a dork for a bit who called it something like 'chaotic vector entropic alignment'. I'm forgetting the specific phrase, I think...

[AnnoyedOne]

(10-21-2024 07:20 AM)brouhaha Wrote:  It's actually an old, well-known technique, called "percussive maintenance".

I thought that was more for mechanical things vs electronic.

Either way it worked for naddy.

A1

[Ren]

(10-21-2024 12:38 PM)AnnoyedOne Wrote:  

(10-21-2024 07:20 AM)brouhaha Wrote:  It's actually an old, well-known technique, called "percussive maintenance".

I thought that was more for mechanical things vs electronic.

FWIW, I read that an old Army Radar Maintenance Manual had a troubleshooting tip that if a certain problem presented itself a swift kick at a specified location on a certain cabinet/panel was warranted.
B^)

[twdeckard]

https://youtu.be/MvyBrX1eK4I?si=xJXdzuwEvuaBDTR2

3:20
"Manual says to kick it to get the rotors goin ..."

[naddy]

Alas, the miracle was short-lived and the two segments are off again. At least I've learned from this that it is a contact problem and the display itself is likely fine.

[Dave Britten]

(10-21-2024 12:38 PM)AnnoyedOne Wrote:  

(10-21-2024 07:20 AM)brouhaha Wrote:  It's actually an old, well-known technique, called "percussive maintenance".

I thought that was more for mechanical things vs electronic.

Hey, if it works, it works!

[vaklaff]

(10-29-2024 02:53 PM)naddy Wrote:  Alas, the miracle was short-lived and the two segments are off again. At least I've learned from this that it is a contact problem and the display itself is likely fine.

Time for another round of that percussive maintenance? With your experience and suitable specimen, you are in a unique position to develop a new standard operating procedure!

[AnnoyedOne]

(10-29-2024 04:32 PM)vaklaff Wrote:  Time for another round of that percussive maintenance?

How did that song go? "Drop it and drop it good"

https://www.youtube.com/watch?v=IIEVqFB4WUo

A1

[Geoff Quickfall]

Climbed to 35,000 feet in the 737-200 without the autopilot. At level off I reached up to engage the 2 Autopilot switches (single bar).

They would not engage. The last thing you want to do at 35,000 is fly an airplane without even a rudimentary autopilot for more than 1 hour.

I looked at the captain and he told me to kick the side panel on the mid console at knee level.

I did, then he said, try the switches again.

THEY WORKED.

Now for the reason. The switches were remote sending a signal to the solenoids. Over the years, dust encroaches on the solenoid contacts. By kicking the panel right were the solenoids live knocked the dust off the contacts and allowed the circuit to complete.

As an aside, no autopilot at 35,000 feet and asked to maintain that at plus or minus 100’ without the autopilot is akin to sitting on a large beachball and balancing for the next 5 hours. Can’t be done, having done it at 25,000 feet and for some reason it is no contrary to the FAA regs.

Cheers

[teenix]

Flying survey at 80 ft or so AGL is interesting enough but akin to manually flying an ILS for up to 6 hours. At night time above minimum safe, is really interesting without a horizon. Some of those old birds need a bit of a kick here and there too :-)

[AnnoyedOne]

(10-30-2024 12:07 AM)Geoff Quickfall Wrote:  I looked at the captain and he told me to kick the side panel on the mid console at knee level.

Are you going to "kick" your Sharp PC-1300S or other calculators if they develop a fault?

A1

[9aplus]

Kicking, knocking, heating, etc...
are almost normal search steps for cold solder joints....

Have recent experience on that for similar aged (mid 1980ties) technology.
One on my Sony ICF 2001D developed strange symptoms after cleaning some
"computer" 3V battery leak. The unit mimic blocked bands with all jumpers set
on all bands open. That influenced AIR band, FM band and HF band over 26.1 MHz.
That unit have 3V (2 x AA size) and 4.5V (3 x D size) power.

Lot of knocking and than heating on 100 C located the trouble
around two IC one shifter and one 4 bit CPU.

Finally cleaning and re-soldering of both IC resolved the trouble.
Here demo on finished unit, the right one, with clean white keyboard keys
=> https://youtu.be/2j6ofUqw6ww