x
This website is using cookies. We use cookies to ensure that we give you the best experience on our website. More info. That's Fine
HPC:Factor Logo 
 
Latest Forum Activity

hp Jornada 720 IRDA repair - success!

chiark Page Icon Posted 2005-06-15 11:46 AM
#
Avatar image of chiark
H/PC Sensei

Posts:
1,325
Location:
North of England
Status:
Hey folks, I thought I'd share my frustration and eventual joy at getting my 720's IRDA back working.

A while back, my IRDA packed up. It was working absolutely fine, and just stopped with no warning or apparent reason. The strange thing is reception was still working, but the transmission was definitely gone. I knew this from experimenting with "Remote Control" from WinCESoft - you can't just try to receive a contact or something from another device, because the protocol is bidirectional so it'll just stop working. Remote Control will "learn" IR commands, but not replay them - a weird situation to be in!

I stripped my Jornada down to see if there was anything obviously broken like a solder joint. It all looked good. To make matters nigh-on impossible, the IRDA lamps are surface mount, and are just next to the power supply so are really quite difficult to get at with a soldering gun. Besides, googling for the component number returned nothing

I borrowed another 720 motherboard (thanks Chris, and indirectly Niteman1969 I think!), and compared the two...



The first one is mine, the second is the working one. It's hard to see (blame the shoddy XDA 2s camera) but there's a black lump missing on the first one!

On the top of the motherboard, above the lamps, the working 720 had an extra surface mount component, labelled 6R2 - a 6.2 ohm resistor, in a 2mm package. Mine had a pair of solder pads, and evidence that something had fallen off- dull pitted solder paste.

6.2 ohm is not a standard value for resistors... nearest is 5.6, or 6.8. I went with 6.8, possibly on the misguided assumption that higher resistance will draw less current - but that could be wrong.

Farnells sell just the thing, for 2 pence, in multiples of 50. The part number is 3217814. So, one shiny pound later, I had a very small resistor which might or might not fix the problem.

A passing engineer at work is a hardware nut, and was happy to hack at SMT stuff. I'd never worked on it before... Clean the landing pads by applying a dab of solder, then using a solder sucker pull the residue off. Hold the resistor (I used a pen knife blade point pushing down), apply a tiny dab of solder and heat to either end, and you're done. It's a two person job unless you have the dexterity of a very dextrous person!

Reassemble, and.... Voila! It works!

Thanks to Chris for providing the motherboard which was the inspiration, and Pete Holland (the engineer) for the steady hand with the soldering iron!

So if your IRDA isn't working, it might be an easy fix. If anyone wants a resistor, let me know as I've got 49 of 'em spare

Cheers,
Nick.
 Top of the page
C:Amie Page Icon Posted 2005-06-15 12:03 PM
#
Avatar image of C:Amie
Administrator
H/PC Oracle

Posts:
15,647
Location:
United Kingdom
Status:
Great going, glad you got it sorted.

Chiark now has 49, 6.8 Ohm resistors - any takers on hpcBay?
 Top of the page
Jake Page Icon Posted 2005-06-15 3:04 PM
#
Avatar image of Jake
Moderator
H/PC Elder

Posts:
2,233
Location:
Choking on the stench of ambition in Washington DC
Status:
That's an amazing story. Well done!

Jake
 Top of the page
Snappy! Page Icon Posted 2005-06-15 3:27 PM
#
Avatar image of Snappy!
H/PC Elder

Posts:
1,712
Location:
New Mexico, US
Status:
cool! Keep the HPCs going ...
 Top of the page
chiark Page Icon Posted 2005-06-16 4:04 AM
#
Avatar image of chiark
H/PC Sensei

Posts:
1,325
Location:
North of England
Status:
Cheers folks

IRDA is apparently a common failure on these things. I do wonder if this is the common failure mode... Hmmm...
 Top of the page
hpc:factor« View previous thread · Hardware Support · View next thread »
Jump to forum:
Seconds to generate: 0.082 - Cached queries : 62 - Executed queries : 8
Server Time now is: Wednesday, 14 April 2021 - 15:22