Capacitors

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
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RMartins
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Re: Capacitors

Post by RMartins »

1024Mak, I was not replying to your message :)
In fact, I only saw it after I postted mine.
I replied to a message on the previous page.

I agree, with everything you said.

I use 7.5 because my regulated power supply gives me exactly that plus a tiny bit (7.58v), and guarantees the lowest power dissipation as heat.

As you say, regulated 8V is hard to find, so 9V is a good option.
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1024MAK
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Re: Capacitors

Post by 1024MAK »

No worries :D

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MonkZy
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Re: Capacitors

Post by MonkZy »

Many thanks for all the great technical advice.

I tested my iron on some scrap PCB's and it is woefully inadequate. It takes way longer than the two second melting threshold, on PCBs with thick tracks it is more like 10 seconds it seems. It is a simple 18w Antex iron, without any temperature control. Right now I do not know any techs who have the soldering skills needed.

The spectrum initially seemed very reliable during an initial 3-4 hour session loading games using .wav files. The next session was not so good. The machine suffered 'lock-ups', the screen had no screen corruption/artifacts but there was no keyboard input on any keys. The new membrane is working and connected perfectly, so I fear some other issue. For now I have stopped powering the old machine up. No capacitors have swelled or leaked. After a cool-down I did a swift power-up/keyboard check and things seem fine. No acrid smells or magic smoke, fortunately.

Can anyone offer comment on these two £60 solder stations from Maplin?

https://www.maplin.co.uk/p/60w-mains-lc ... tion-a55kj

https://www.maplin.co.uk/p/48w-mains-so ... tion-n34fb

Would these be good for general PCB work? The next price band is around £200, which is a bit too much for me. I have watched several speccy repair videos on You Tube and I am confident with a suitable iron I would go ahead and do a re-cap.
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1024MAK
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Re: Capacitors

Post by 1024MAK »

What type of bit are you using on your iron? A chisel tip is what I recommend. Is the tip clean? Did you "tin" it?

For normal tracks/pads, an 18W Antex should be okay. But is not very useful for the thicker tracks, like those used for the power supply or ground (0V) circuits.

I use a Antex TCS 50W iron. The one I have is now over 20 years old and is discontinued. But Antex have a new version.

Details of my old TCS (now discontinued) follow link

Hackaday review of the new TCS iron
CPC sells them
link
but they are also available elsewhere. Antex will also sell them direct, but for a lot more money :shock:

Or you can go for a Chinese made soldering station. If you do, fit a suitable bit, not the pointy type that are often supplied. Also do a safety check, specifically, check that the mains cable, plug and fuse, and that the earthing inside is okay.

I'll have a look at the links you posted later...

Mark
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Ast A. Moore
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Re: Capacitors

Post by Ast A. Moore »

In Bill Lumbergh’s voice, “Yeah . . . Um . . . I’m gonna have to go ahead and sort of disagree with you there, Mark.”

An 18-watt soldering iron is not going to be enough on its own, especially on thicker tracks/leads. With good technique, I’d opt for a higher-wattage iron—it melts the solder faster, so there’s less linger time.

As for these Maplins, well, they look a little dodgy. Then again, they might work all right. The advantage of any (decent) soldering station is that it can maintain the tip temperature. As the joint sucks heat away from the iron, the station will up the heat to the tip accordingly. Other than that, you can do almost any soldering job with a simple unregulated soldering iron. My main one is about 40 years old. It has a bare simple copper tip with no plating. I just tin it well and try to keep it clean. Ahem, okay, maybe not that clean, as this picture demonstrates:

Image

If you really need a decent soldering station, the Hakko FX-888D is a good choice. You can get it for around £100, although it comes with a pointed tip, which I personally never cared for. But you can get any tip you want for it.

Oh, and another tool you should definitely consider is a solder sucker.
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1024MAK
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Re: Capacitors

Post by 1024MAK »

Yeah, I never said that the 18W iron was ideal for repair work :lol:

Both those irons available from Maplin are I believe, Chinese irons. Maplin has been selling them for many years. Not having tried one of these, I can't say how good they are. However, it has been found that some so called temperature controlled soldering stations from China are not quite what they appear to be. Instead of showing the temperature of the bit, some only display the temperature that you have set it to. Or they show the tip temperature while it is getting up to the set temperature, but as soon as it goes past the set temperature, they switch to showing the set temperature and not the bit temperature. Why does this matter? Well, with the heating element switched on, the tip temperature will overshoot the set point. The heating element will switch off. Then the tip temperature will start to fall. If you then use the iron, the tip may cool quite a lot before the element switches on again. But the temperature display will be rock steady still showing the set temperature!

The most important design feature for a soldering iron is not the Wattage. But instead it's ability to transfer heat from the bit to the joint. I have a Chinese 60W "temperature controlled soldering station" that is okay, but when I want to desolder items on PCBs that have large tracks and pads, I fit a large chisel tip to my Antex TCS iron. This does the job a lot quicker than the Chinese "temperature controlled soldering station" iron (admittedly I don't have such a large chisel tip for it).

For desoldering on the cheap, there is this desoldering iron. They are also on eBay etc. I have not however tried one.

Here you can see the difference between a small bit I use for fine work, and the large chisel tip I use when a lot if heat is needed:
Image

Here is my good old Antex TCS upgainst a younger Chinese 60W iron:-
Image

And here are two Antex tips next to the tip from the Chinese 60W iron:-
Image

Mark
:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :dance
Looking forward to summer later in the year.
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MonkZy
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Re: Capacitors

Post by MonkZy »

I will check my local Maplin as they apparently have some TCS 50w irons in stock. I am not sure if they are the old type or the new push button models. I like the size of the iron and I already have a good old Antex iron stand, the other stations on offer are far more bulky.
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Guesser
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Re: Capacitors

Post by Guesser »

I have one of these which isn't perfect (had to replace some wiring inside after my dad left it turned on all day and burnt out the iron), but works fine for everything I've thrown at it.
https://images-na.ssl-images-amazon.com ... L1024_.jpg

It's been discontinued though and even if it hadn't I wouldn't buy anything from Maplins now.
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