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   LZ Repair Dewhistling
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   Author  Topic: LZ Repair Dewhistling  (Read 147 times)
hiddenevil
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LZ Repair Dewhistling
« on: Dec 14th, 2018, 10:49am »
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Hey guys
 
I finally got around to popping open my LZ and as promised I'm putting together a how to guide for replacing the caps.
 
I'm just waiting on the new caps arriving, but thought I'd share my progress thus far.
 
https://bytemyvdu.wordpress.com/2018/12/14/psion-ii-lz-repair/
MartinReid
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Re: LZ Repair Dewhistling
« Reply #1 on: Dec 14th, 2018, 6:47pm »
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Dear James
 
Let me start by saying I looked at your blog and it looks interesting.
 
I hope you don't mind my suggestions..
 
(Para 2) four column display.... perhaps... 20 column 4 row display (usually 20 character 4 row display)
 
(Para 3) Sadly the LZ64 suffers from... Perhaps you could put... Sadly my LZ64 suffers from.... I have 6 on the go and none of them have any such issues.
 
Yours sincerely and in good faith
Martin
 
 
 
 
hiddenevil
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Re: LZ Repair Dewhistling
« Reply #2 on: Dec 14th, 2018, 11:12pm »
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Hello Martin
 
Glad you like the site! Hopefully I'll have the next part up before Christmas! As I know I'm not the only person on the forum with a noisy LZ, I think it's reasonable to assume there are still more out there with this issue.
 
Sounds like you've been lucky with yours. However it's more a case of when, not IF the caps will deteriorate. The more time that passes, the more of these units will likely need recapping. The whistling is a convenient way of warning you to crack the unit open and get those suckers out before trace damage occurs.
 
Thanks for your input and Merry Christmas! :-D
hiddenevil
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Re: LZ Repair Dewhistling
« Reply #3 on: Dec 20th, 2018, 12:22pm »
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Hmm so some progress on the recap and a set back.
 
I've soldered in new caps and the unit doesn't turn on. Something was getting warm inside do I took the battery out.
 
Does anyone know what the black cap like component is directly above the contrast pot, beside comm port on the main board?
 
It looks like a coil wrapped in black plastic.
« Last Edit: Dec 20th, 2018, 12:28pm by hiddenevil »
Mikesan
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Re: LZ Repair Dewhistling
« Reply #4 on: Dec 21st, 2018, 11:39am »
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Check for shorts.
 
The black component is just a choke - it's part of the charge-pump circuit that gives you the 21v necessary to 'blow' the data onto the EPROM in the Datapak.  The top slot interface is on this site, maybe in the reference section, but it is a pretty poor scan of a scribble that Psion sent me many years ago!
 
If you have a solder bridge somewhere, that could cause it - maybe a break.  If another component were out of spec, that could be the problem, however, capacitors are the most likely culprit over time, so change them all out!  Ceramic caps (tiny square ones directly on the PCB) are fine, unless they break, whereupon they can become open, or short - test, it's the electrolytic ones, including the Tantalum beads that you need to swap-out 99.9% of the time.
Cosi
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Re: LZ Repair Dewhistling
« Reply #5 on: Dec 25th, 2018, 1:11pm »
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hiddenevil: I love your blog! I'll be following it - if only to find out how you eventually solve the problem
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