Componenets to Replace to Eliminate LZ Whine

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Arjayel
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Joined: Thu May 11, 2023 11:53 am

Componenets to Replace to Eliminate LZ Whine

Post by Arjayel »

My LZ has that annoying whine and I have read that it requires replacement of a specific capacitor. Does anyone know which capacitor and where it is located? Any help appreciated, thanks!
MartinP
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Re: Componenets to Replace to Eliminate LZ Whine

Post by MartinP »

Arjayel,
This article has a good photo showing the locations of the capacitors: https://bytemyvdu.wordpress.com/2018/12 ... lz-repair/
And I have reproduced the schematic of the power board, available at: https://github.com/martinprest/Psion-Or ... Schematics

I would start by replacing the 100uF, 6.3V cap (C3 in the schematic) as it's on the main supply and it has the lowest voltage rating. I think other people have reported this as the culprit, but seeing as most people seem to replace them all, it's difficult to say with much confidence.

Please let us know if you fix the whine and what you did.
Martin P.
Psion Organiser II XP power PCB schematic.PNG
Psion_Organiser_cap_layout.PNG
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Lostgallifreyan
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Re: Componenets to Replace to Eliminate LZ Whine

Post by Lostgallifreyan »

I have read that sometimes replacing caps fails to stop the whining, so it may be best to look specifically for low ESR electrolytics. Try to get them with high temperature tolerance too, 105°C instead of standard 85°C. They'll last longer, work better, and there's no point squeezing the margins of cost vs performance unless you're in business to produce lots of widgets.

Low ESR will give the best decoupling for noise, and unless such caps are found to cause high inrush currents, there's no reason not to use them. The only thing I can think of that might cause high inrush current surges is a Li-ion battery combined with lots of low ESR caps in the regulator. I doubt it will ever be a problem..

Low ESR caps are used as standard in modern computer power regulation and supply, so it's worth using them on general principle wherever an AC frequency on a power line is a risk in digital devices.
Zzoom
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Re: Componenets to Replace to Eliminate LZ Whine

Post by Zzoom »

Hi all ...Im looking at replacing the capacitors in some of the units in my collection .has anyone got a tried and tested list of what capacitors they have used . and where they have purchased them.the last thing I want to do is swap out components for ones that are not quite right or that will fail prematurely. :o o
amenjet
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Re: Componenets to Replace to Eliminate LZ Whine

Post by amenjet »

Zzoom wrote: Wed Mar 06, 2024 8:18 am Hi all ...Im looking at replacing the capacitors in some of the units in my collection .has anyone got a tried and tested list of what capacitors they have used . and where they have purchased them.the last thing I want to do is swap out components for ones that are not quite right or that will fail prematurely. :o o
To avoid capacitors of dubious provenance, I'd buy them from a large distributor, such as RS, Digikey or Mouser, that sort of thing. Ebay caps have a higher risk of not being as advertised, and the specs for ESR etc are quite often not available.

The whine actually comes from the beeper, at least on the units I looked at, and another way to stop it is to disconnect the beeper. That doesn't fix the problem, though, and supply rails won't be operating properly unless you swap the capacitors.
Lostgallifreyan
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Re: Componenets to Replace to Eliminate LZ Whine

Post by Lostgallifreyan »

Look for Panasonic FR series, because the size and specs are excellent. Ebay can be safe, but look for a seller in Europe, and check carefully to see they have stock in Europe, and are not a Chinese based seller operating in European location and law. Chinese sellers may be safe too, but not all, and the FR series caps are common enough that you don't have to take risks. If the seller shows pictures that indicate original RS packing and labelling, or similar, all the better... FR caps are black, so if the picture shows otherwise, the seller is an idiot. Avoid. Check the listing style and other items. It's not hard to see the difference between a scalper trying to get crazy prices, and a seller who has real inventory who is providing a service to electronics users on the basis of wanting to do exactly that.

Buying direct from RS is obviously safer, but you'll end up with LOTS more caps than you'll use because they won't sell single components. The same applies to Mouser, Farnell, Digikey, Arrow, etc, so Ebay is genuinely useful! It's how those with too many caps get rid of them and recover some money. :)
amenjet
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Re: Componenets to Replace to Eliminate LZ Whine

Post by amenjet »

Lostgallifreyan wrote: Wed Mar 06, 2024 1:00 pm Look for Panasonic FR series, because the size and specs are excellent. Ebay can be safe, but look for a seller in Europe, and check carefully to see they have stock in Europe, and are not a Chinese based seller operating in European location and law. Chinese sellers may be safe too, but not all, and the FR series caps are common enough that you don't have to take risks. If the seller shows pictures that indicate original RS packing and labelling, or similar, all the better... FR caps are black, so if the picture shows otherwise, the seller is an idiot. Avoid. Check the listing style and other items. It's not hard to see the difference between a scalper trying to get crazy prices, and a seller who has real inventory who is providing a service to electronics users on the basis of wanting to do exactly that.

Buying direct from RS is obviously safer, but you'll end up with LOTS more caps than you'll use because they won't sell single components. The same applies to Mouser, Farnell, Digikey, Arrow, etc, so Ebay is genuinely useful! It's how those with too many caps get rid of them and recover some money. :)
I agree. You can use parts from ebay but you do need to know what to look out for. The big advantage with the RS type sellers is a datasheet for everything and always as good quality as anywhere else or better. You pay for it though...

Maybe the way to handle this is to buy the RS components at higher quantity and split the components into 'Whine Fix Kits'?

One thing I found when I did some of these fixes is that a desoldering tool is useful. The caps didn't really want to be removed easily and the PCb can be damaged by rough removal.
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Martin
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Whine Fix Kits

Post by Martin »

Hi Andrew

amenjet wrote: Wed Mar 06, 2024 7:04 pm
Maybe the way to handle this is to buy the RS components at higher quantity and split the components into 'Whine Fix Kits'?

That's not a bad idea. I could contribute by producing the 'how to' sheet if one of you electronics chaps can give me the gen.

MartinP has eluded to James post about his repair (here).

If we got a kit together we could put it in the shop here or maybe Peter would host it in his eBay store.

Luckily I haven't had the problem yet but if I did I wouldn't feel comfortable setting to with a hot iron on my treasured Organiser, I'd stiil need someone more confident than me to do it.

Martin
amenjet
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Re: Componenets to Replace to Eliminate LZ Whine

Post by amenjet »

I think the kit would be the capacitors that have already been mentioned and an instruction sheet, I can't think of anything else? I suppose some bags to put it all in.

I can buy some capacitors, any idea how many sets to buy for? Bit of a 'length of a piece of string question', I know.
Lostgallifreyan
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Re: Componenets to Replace to Eliminate LZ Whine

Post by Lostgallifreyan »

amenjet wrote: Wed Mar 06, 2024 7:04 pm I agree. You can use parts from ebay but you do need to know what to look out for. The big advantage with the RS type sellers is a datasheet for everything and always as good quality as anywhere else or better. You pay for it though...

Maybe the way to handle this is to buy the RS components at higher quantity and split the components into 'Whine Fix Kits'?

One thing I found when I did some of these fixes is that a desoldering tool is useful. The caps didn't really want to be removed easily and the PCb can be damaged by rough removal.
The whine-fix idea is good. RS sell the small 'FR series' caps needed, in sets of 10, likely for all relevant values, so the outlay isn't big. LePowerfulPierre (Sourcerer), being a man who sounds like a man used to pulling locomotives with his teeth, might find the haulage light enough. It's an ideal thing for someone already trading Psion gear to do, possibly. :)

As you say, getting the old caps out and the new ones in can be difficult. I used to use a desolder but those can prang the already hot copper pads and cause them to lift. In very confined spaces this method isn't possible at all. Braid can be awkward too. The method I use will scale up to hundreds of caps with reliability at 100%. I've repaired many Mini-ITX boards this way, where the room for manoeuvre can be extremely small.

Method:
1: Note cap position and polarity, then grasp the body with long-nose pliers, carefully pulling on it so the body comes away from the pins, which stay in the board. 'Walk' it from pin to pin while maintaining tension, if it's tough to grip it. (No squashing, that would just trap the pins in the cap).
2: Desolder each pin, pulling it away with the pliers, leaving the solder in place afterwards. Remove just enough to get a centred pit for drilling.
3: Use a cheap 'pin drill', with the supplied 0.7mm collet chuck and a 0.7mm drill bit, to manually drill out the solder. Use a light pressure and spin it moderately fast by hand till it goes through. Brush away debris.
4: Fit the new capacitor, maintaining its position by a tiny dab of superglue, or by bending the leads outward slightly.
5: Solder it in with thin resin-cored solder and trim the leads.

This method might need a couple of practise attempts on an old PCB so you get used to any awkwardness involved, but it's worth it because it's 100% effective, and can be repeated as many times as you'll ever need, unlike any method that damages the tracks or pads. The pin drill and bit are likely cheaper than a desolderer of any worth, and the waste lead (Pb) is much lower than any method that uses full desoldering. If through-hole boards are to be handled, then it may be better to use a 0.6 mm drill in the 0.7mm chuck, and to make sure by twisting a few times, that it runs free once it's drilled through. This will make a hole big enough for the lead while avoiding any damage to the plating in the hole, because that plating will always be harder, and of greater diameter, than the plug of solder the drill will be removing. Residual solder will protect the plating and give a firm guide to the new capacitor's leads when fitting it.

This may sound tedious, but it's not, it's the only method I can trust after the hundredth pin in a long session, I'd get tired and likely damage something with a desolderer, but drilling out the solder is much easier and safer. It reduces the time for exposure to harmful vapours too.
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