EEVblog #1245 - A Most Excellent REPAIR: IBM PCjr Keyboard

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Can you find the fault in the IBM PCjr wireless keyboard before Dave does?
A most excellent adventure in troubleshooting.

#Repair #IBM #Vintage

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"You don't want to get into reverse engineering it..."

Reverse engineers it, anyway.

Godzilla_Jesus

I love that you show all the futzing around, dead ends, and initial circuit misunderstandings. These are the lessons that give the new practitioners confidence that they too can attack these problems, and it's perfectly normal to follow a few fruitless leads before hitting the real problem. Well done Dave!

ksbs

Super interesting. Love the fact that you went through the whole process. I don't like it when people fix stuff very quickly based on experience (although i do respect them for it) and then assume that you have the same knowledge they do. At some point in their lives they had to go through this exact same procedure and find out for themselves the 'hard' way.
This is what troubleshooting is about: fumbling through it, retracing your steps, getting lucky sometimes, but all in a methodical manner. Thanks for the videos!

koffibanan

Great video, Dave. Reminded me of some of your older videos from a few years back. Always enjoy watching your videos regardless.

SolidStateWorkshop

Teardown + repair = *thumb up*, great vid Dave! Thanks!

famillePuces

I have been tinkering with electronics for 30 years but you still always manage to teach me something. Thank you.

dreggory

Tantalum caps are the devil.
Had one die in my dynamic signal analyzer that kept the crt from working; it was a dead short. Now another one has failed as well, same symptoms.
I had one fail in my spectrum analyzer also.
Finally, I got a dead Flir A40 that had a blown n-channel fet that burnt some traces because of a shorted tantalum cap; got that back up and running too.

paulmcgrath

I once had repaired some over/under voltage protection device, and found that voltage on a simple voltage divider wasn't what it should have been and ended up replacing every component in that part of the circuit (two resistors and comparator) and the damn voltage was still wrong. As the last effort I removed a tantalum that was parallel with R2 of the voltage divider and it worked! After I told my coworker what happend he said that I should try putting it back in beacause it was bizzare that the cap was the fault, and after soldering it back in, it still worked...
Ended up reporting it as "ghosts issues" hahah
Learned so much about troubleshooting from your videos, thanks Dave!

NKauzljar

Years of dumpster diving I finally found a working i7 like you with your planted finds.

Tech-NO-City

Gotta admit, when I first saw this guy I was put off by his voice. Now though, I not only have a great respect, but actually find him refreshing and entertaining!! Obviously knowledgeable and passionate. It great you give your time for us. Much appreciated, and keep ‘em coming !
Ps. How about telling us a bit about yourself? You’ve got a lot of fans out there

amandaporter

8:22 It's raining in Daves lab again ;)

perhansson

That Fn that was lit when Alt-Fn was pressed in DEC VAX times :)
What a great reminder that I'm almost 50 y.o. :) Thank you!

Vladimir-hqne

It's the tantalum. I hate those things. They're always failing on power supply boards.

_Hertz

That's an unusual failure mode. Most tantalum cap faults I've found were short cct. Sometimes blowing the top of the caps off which makes it a lot easier to find.

markcummings