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   LZ Repair Dewhistling
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   Author  Topic: LZ Repair Dewhistling  (Read 462 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
hiddenevil
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Re: LZ Repair Dewhistling
« Reply #6 on: Feb 3rd, 2019, 11:20pm »
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Greetings all!
 
I return with great news! I've fixed my LZ and rid it of the annoying whistling! Huzzar!  
 
Bare with me as this post will be a biggy
 
As suspected the culprit behind the buzz / whistle that ails some LZ / LZ64 IS due to failing electrolytic caps. Given the age of the Psion II, these caps are well past their expected life span. In fact it is a testament to Psion there aren't more users complaining about this fault.  
 
Just to put in to perspective, over Christmas I had to recap an original 2003 Xbox due to failing and very leaky caps. Thats 2003! not 1989! When I opened it up I had to deal with acid leakage and trace corrosion. There was no such issue with the LZ, that's not to say it doesn't happen. Electrolytic caps do have a habit of leaking when they get old and begin to fail. I can only surmise that Psion didn't cheap out when it came to components, unlike Microsoft :-P
 
So after popping open the LZ, replacing the caps. It didn't work and there was an acrid smell coming from the main board. I later discovered part of the ribbon cable had come away from the keyboard PCB. I guess because the keyboard wasn't present to draw power from the main board, it resulted in some components getting a little warm. Choosing to replace the ribbon cable, I linked the boards together with fresh wire. Ugh what a pain in the butt this was, seriously folks be gentle with your Psion II. Replacing the ribbon cable is a thankless task and not one I wish to repeat any time soon.
 
With the guts of the Psion II on my workbench, I hooked up a 9v using some crocodile clips and tried to power on. Much to my delight the screen came alive! Better yet there wasn't a trace of a whistle from the speaker.
 
I think we can say with some certainty that the dreaded whistle has been thwarted.
 
Pictures to be posted to my blog later.
 
Many thanks for all the comments, I hope this information will be useful for other users.  
 
starhawk
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Re: LZ Repair Dewhistling
« Reply #7 on: Feb 4th, 2019, 4:19pm »
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Here's what almost certainly happened to your XBox.
 
https://en.wikipedia.org/wiki/Capacitor_plague
hiddenevil
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Re: LZ Repair Dewhistling
« Reply #8 on: Feb 4th, 2019, 11:52pm »
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Thank you, it hardly surprises me. Owning as much old electrical equipment as I do, replacing caps has become par for course lol. When I first heard the LZ whistle, I guessed it would be cap related. The Sega Game Gear sometimes suffers from a similar problem, too often it fails all together, resulting in no sound what so ever. SMD caps are usually more prone to failing than through hole caps.
 
Anyhow I hope the info on the website helps someone.
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