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   Strange buzzing noises from top of LZ64
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   Author  Topic: Strange buzzing noises from top of LZ64  (Read 469 times)
1333david
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Strange buzzing noises from top of LZ64
« on: Nov 13th, 2017, 11:54pm »
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Hi, I am hoping someone will be able to help me. Today I went to use my LZ64 which has not been used in a while.
 
When powered on using a freshly installed battery or mains (using Psion adaptor) I hear a horrible buzzing noise from the top of the unit. It functions correctly apart from the buzzing.  
 
I am worried that the unit (which is in pristine condition) is about to fail.  
 
Unfortunately, I'm not good at taking electronics to bits but I know some old computers need capacitors replacing.  
 
Any ideas on how I can correct the strange buzzing would be greatly appreciated.
Mikesan
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Re: Strange buzzing noises from top of LZ64
« Reply #1 on: Nov 14th, 2017, 11:40am »
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Possibly a capacitor and most likely to be on the interface board (the one that you see when you first open the Organiser's case).  http://archive.psion2.org/org2/techref/powerboard.htm
 
However, as you don't seem to have much experience with electronics, I'd suggest finding someone that you know who has and asking them to do it.
 
If you search for "capacitor" in this forum there are quite a few references, but this problem will probably need to be identified by measurement, rather than just looking for 'bulging caps' as they don't always bulge when they fail - IF that is even the problem.
jaap
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Re: Strange buzzing noises from top of LZ64
« Reply #2 on: Nov 14th, 2017, 12:13pm »
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In my experience it is only the LZ/LZ64 models that are affected by this problem, and not the CM/XPs. I have several LZs that emit these high-pitched whine and buzzing noises, but never had a CM/XP do it.

Jaap Scherphuis
https://www.jaapsch.net/psion/
1333david
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Re: Strange buzzing noises from top of LZ64
« Reply #3 on: Nov 14th, 2017, 2:20pm »
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Thanks for your reply Mike and Jaap.  
 
That's interesting it is only the LZ models. I was wondering whether I could replace the interface board from an older model CM but the keyboard ribbon looks fragile so maybe a bad idea.
 
Jaap, did you get to the bottom of why the LZs were emitting the high pitched whine/buzzing? - was it the capacitors?  If you didn't find out, are they still working (with the buzzing)?  
 
I might open up the case and see whether there is any obvious problem.  
 
PS I have just come across Jaap's JavaScript Psion emulator - great job and really useful.
jaap
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Re: Strange buzzing noises from top of LZ64
« Reply #4 on: Nov 14th, 2017, 2:52pm »
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on Nov 14th, 2017, 2:20pm, 1333david wrote:
Jaap, did you get to the bottom of why the LZs were emitting the high pitched whine/buzzing? - was it the capacitors? If you didn't find out, are they still working (with the buzzing)?

I haven't really looked into the problem further, but have always assumed it was some capacitor that was failing. I've not used those buzzing LZs much (I have 3 or 4), but they do still work for now. I may open one up and investigate.
 
Edit:
The noise is actually coming from the buzzer, so when you open the machine the sound stops. There were no visible defects that I could spot, to the capacitors or otherwise.
« Last Edit: Nov 14th, 2017, 6:21pm by jaap »

Jaap Scherphuis
https://www.jaapsch.net/psion/
MartinReid
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Re: Strange buzzing noises from top of LZ64
« Reply #5 on: Nov 14th, 2017, 7:35pm »
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Dear all
 
If remember correctly my LZ64 once started continually beeping - one long beep. Continued even after replacing the battery.  
 
I seem to remember running a beep(x%,y%) loop. Which if I remember correctly stopped it and it has been ok ever since.
 
In good faith
Martin Reid
starhawk
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Re: Strange buzzing noises from top of LZ64
« Reply #6 on: Nov 15th, 2017, 8:53pm »
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Capacitors can leak (ew) and explode (POP!!) and sometimes even catch fire (helloooooooo, tantalum caps... FOOSH.)... but they do not buzz.
 
Coils can whine... it's the expansion and contraction as just barely too much electricity goes through them because the cheap Chinese power supply you just bought has really cheap inductors and operates within hearing range. Coils that sing you the song of their people (as the meme goes) are a hallmark of seriously nasty-cheap supplies. The louder and lower the whine, the cheaper the supply, and quite likely the more it will take with it when it pops.
 
...proper buzzing, however, is the sole domain of electromechanical elements. Something is dumping fuzz into your PSION's peizo disc... which is what passes for a speaker in the thing.
 
It's a little slice of quartz on a little slice of brass, with two bad solder joints and flying leads, and if you want to make electronic noise there is literally no cheaper way to do it -- nor is there any /crappier/ way to do it... peizo discs are the ultimate embodiment of lo-fi. Great for a cheap greeting card... less so in a proper computer. Unfortunately, real speakers are low-enough-impedance that properly fitting one to a PSION would be something of a bear...
 
Coincidentally, a batteryless electronic toy is possible with a peizo disc. I learned this off of a Forrest Mims challenge once, courtesy of MAKE: magazine. Wire the disc /directly/ to an LED (you do not need a resistor here! although some wires are OK) and put the disc on the back of a paper plate or the like, with something adhesive that's thin enough to transmit vibration. Get a ball or a badminton shuttlecock, and turn off the lights. Chuck your object of choice in the general direction of the paper plate, and if you hit near the disc, the LED will blink! Peizos produce thousands of volts at almost no current, and the LED's internal resistance is enough to drop that to "just enough to light up without cooking everyhing" levels... briefly.
thesourcerer
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Re: Strange buzzing noises from top of LZ64
« Reply #7 on: Nov 15th, 2017, 9:56pm »
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Where does the cheap Chinese power supply come in? David was talking about “with a freshly installed battery”.
starhawk
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Re: Strange buzzing noises from top of LZ64
« Reply #8 on: Nov 16th, 2017, 3:16pm »
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Coil whine is phenomenally common in cheap Chinese power supplies. It was an example.
Mikesan
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Re: Strange buzzing noises from top of LZ64
« Reply #9 on: Dec 17th, 2017, 12:14pm »
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1333david  I wouldn't worry TOO much about the ribbon.  It's awkward, due to the plated-through (PTH) holes in the PCB, so you'll need some form of solder removal - wick, or suction.  After that, just use ordinary ribbon or separate wires to replace it because the original does break easily.  I mention this because you'll really need to bend the ribbon about a bit in order to change caps on the interface board.  A little longer than the original is OK - I've found that even replacing it with wires twice as long caused no issues - just make sure that there is space.
Cosi
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Re: Strange buzzing noises from top of LZ64
« Reply #10 on: Dec 17th, 2017, 2:23pm »
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Hello, fellow Psioneers!
 
Like starhawk said, the speaker circuit, not a capacitor is the offender. That whining was driving me crazy (I heard that sound even after the computer had been switched off) so, out of desperation, I did something radical.
 
I noticed that the buzzing ceased when I was pressing the back side of the screen. When I opened the Organiser (three screws: two near the battery compartment, one underneath Datapak B), I saw that the speaker was attached to the metal cover exactly where my pressing had stopped the noise. After removing the springs connecting the speaker with the main board, the whining stopped completely and never came back
 
As I said, it was a radical solution - I'm no longer able to use sound on my Psion - but in my case it was a modest price for cutting off that noise.
jaap
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Re: Strange buzzing noises from top of LZ64
« Reply #11 on: Dec 17th, 2017, 4:59pm »
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What I believe is happening is that there are capacitors that are supposed to suppress the electronic noise (i.e. voltage fluctuations) generated by the processor,  and once they fail the voltage fluctuations leak into the circuits containing the buzzer, and so generate audible noise.
 
To stop the noise, you can either disable the buzzer, or replace the failing capacitors.

Jaap Scherphuis
https://www.jaapsch.net/psion/
Cosi
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Re: Strange buzzing noises from top of LZ64
« Reply #12 on: Dec 17th, 2017, 5:22pm »
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The latter is definitely better, no doubt, but it requires a multimeter and some skill. My solution is a "low-hanging fruit" for those who want to do it effortlessly and don't mind permanently muting their Psions
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