Wednesday, March 26, 2014

Repairing a HP41CX

Our cat is only trained on algebraic entry system. I don't otherwise know how to explain why he threw my vintage HP 41CX on the floor. Doesn't he look frustrated and confused by RPN entry? Unfortunately after a dive from the table onto the floor, my HP41CX wouldn't boot.

This wasn't the first repair I've done to it. I originally rescued it from my Dad who was going to contribute it to his township's unneeded electronics drive.

VINTAGE CALCULATOR GOING IN THE GARBAGE? Sweet Baby Jesus. I love old calculators! Probably because once upon a time I used to work for HP in the calculator lab. This shabby treatment of a highly prized relic would not do, even though it was dead.

After cleaning the corroded battery compartment from long drained and oozing batteries, the foil touching the battery tips was eaten through. I inserted a strategic bit of aluminum foil to bridge the worn down battery contacts fired up to life!

That was about a year ago, and she was a trusty old friend until the cat incident. My poor old HP41CX has been sitting around again for a while, dead to the world and patiently waiting for me to get up the nerve to crack it open and see what was wrong. In light of my recent success repairing a sea-soaked Z10, I decided to give it a go.

First, I looked at the HP Calculator Museum on disassembly and repair tips. I popped open the battery compartment, removed the rubber feet, unscrewed the back, and pulled it apart.

The thing I was most worried about was broken screw posts, which seems to be a common occurrence with this model. However, everything looked in order--no broken posts. All the other components were solidly attached. There was still a lot of corrosion on the interconnect left over from my first cleaning. I cleaned that thoroughly with rubbing alcohol and a Q-tip, and then slightly squeezed the interconnect flex strip. That compression was to bow the contact strip outwards more, allowing it to more solidly touch when I reassembled the unit.

I put it back together, and it worked first time, another TINY VICTORY!

Maybe I should start an electronics repair company! Okay, maybe not. But I'm still quite happy that I've saved two of my devices from the landfill. Just so it won't happen again, I'll start teaching the cat how to use RPN. Wish me luck.

Saving a drowned Z10

The BB Z10 for all its great features is not waterproof nor saltwater-proof. This probably won't be a surprise to you, but it might be if you forgot it was in your pocket when you took a dip in the ocean. You probably see where this is going, and it's not good.

Other lessons to learn if your electronics has taken a swim: wash it right away in distilled water (or at least fresh water from the tap), and don't try turning it on until absolutely positively dry. Otherwise, if you did try to dry it and turn it on without rinsing it, you might get one or two random boots with the camera's flash LED blasting on and off erratically followed by nothing at all. Completely and unretrievably dead. Yes, despite knowing better, I made that mistake too.

However, even if you do everything wrong like I did, you'll be happy to know that there's still a chance you can get your device back to life. I had nothing to lose from completely disassembling it, giving it a good clean, and putting back together. Either that, or spring for a new phone. So once we were back from our Costa Rica vacation, here's what I did.

1) Acquire a very tiny Torq screwdriver - T4. In Ottawa, very few places carry it, but one that does and is super helpful besides is Canada Computers and Electronics. They have the iCAN32 toolkit, a handy little driver kit that has the needed T4 and a ton of other cool electronics bits for a mere $9. Peanuts compared to a new phone.
(Lee Valley is the first place I thought to go, but they won't have what you need. Their electronics screwdriver kit doesn't have the T4 or smaller bits. And Ottawa Fastener Supply is super cool, but they won't have a T4 either.)

2) Disassemble the Z10 according to these youtube videos:

I referenced both, but I preferred the first. I didn't pull the screen (it wasn't necessary)--just popped off the case and extracted the motherboard.

3) Scrub out all visible corrosion with rubbing alcohol and a Q-Tip. Even though it was just in the sea for a minute or two, there was quite a bit of surface rust, salt, and copper oxide. Most of it was around the battery contacts and camera, but it was on some of the shielded chips too. I was able to get most of it off, but not all.

4) Bathe it in distilled water. I gave it about a 10 minute soak and gently agitated it (swished it back and forth) in a small bowl of distilled water to try to get any salt that may have been underneath the shielded chips to dissolve.

5) Gently shake it off, then pack it in a bowl of white rice overnight to extract any excess water.

6) Reassemble it and plug in the battery.

I had my fingers crossed and held my breath for the seemingly long time before the screen lit up, but... IT WORKED! I ran the BlackBerry Virtual Expert and I only had one casualty--the camera. While the "selfie" camera worked, the main front-facing camera was completely dead. It was probably giving itself a nice shorting out while it going berserk flashing on and off after I turned it on. Whoops. (Anybody have an otherwise dead or defunct Z10 that I can salvage the camera from?)  

Everything else worked perfectly! Especially rewarding as I never backed it up, so would have lost everything on the internal flash.

The moral of the story is even if you soak your phone in a conductive sea-water bath, and try to turn it on and it's dead, you may still be okay with a little work and a lot of luck. Don't lose heart!