Repairing A500 PSU - how to crimp new earth cable?

[sirlemonhead]

Hi,

My A500 was sitting in my parents attic for a few years. They had some work done on their boiler and not long later I discovered my A500 PSU's power lead was now only around 6 inches long! Someone had cut the cable off.

I found the rest of the wire... which is now part of the new boiler :\

Anyway, I want to replace the power lead in the PSU and was wondering, does anyone know what exactly I'd need to get to crimp a new screw in lug for the earth lead? It looks like a little round hoop crimped to the end of the earth wire that's then screwed to the PSU.

Bit of a long shot but I'd like to repair it properly without splicing wires!

[prowler]

It's called a crimp tag. PM me your name & address and I'll send you one FOC.

You'll either have to bend it around the wire, squash it with pliers and then solder it, or I could just send you a solder tag with a hole which accepts the wire and this will only need soldering. Or I could send you both if you're not sure.

[sirlemonhead]

Thank you! I'll PM you now!

[prowler]

Reply sent.

[prowler]

Hi sirlemonhead,

I have sorted you out a crimp tag for the earth wire on the new mains lead you will be fitting to your A500 PSU.

I'm assuming that it's one of the heavy PSUs, because the light ones have all three mains lead wires soldered directly to the circuit board.

The tag has a slightly shorter shank but the same size spade as the one you will be replacing. However, it's meant to fit a 2BA thread, so the hole will be a little larger than the 4mm screw which secures it to the board, but not enough to be a problem.

The crimping tool you have would probably do a reasonable job of crimping the tag to the mains earth wire, but the tag could also be soldered to the wire instead if you don't feel confident that it would be good enough.

If you do decide to solder it instead, I would suggest that you first tin the shank inside and out by resting your soldering iron on a level surface and gripping the spade of the tag in a pair of thin-nosed pliers. Present first the solder to the iron until it flows over the tip, then touch the tip of the shank to the iron and present the solder to the shank until it flows through and all around it.

At this point, release the shank from the pliers so that it drops into an old jam jar from high enough to remove the excess solder from the tag leaving a clean, shiny surface all over and inside the shank. (You may have to repeat this a few times until you get the hang of it.)

Next, slide the sleeve I have provided a little way up he wire (apply some petroleum jelly or Baby Oil to the wire if necessary), then strip the insulation from the earth wire to leave just sufficient bare wire to fill the shank and protrude very slightly from the other end and check that it's a good fit. Finally twist the stranded end of the wire between your fingers until it is a good, tight fit when inserted in the shank of the tag and leave it there.

Now support the mains wire so that the earth wire and shank end up horizontal and a little above the workbench, grip the soldering iron with one hand and solder with the other, touch the solder to the iron until it flows and apply first the iron and then the end of the solder to the spade end of the shank until the solder just starts to flow into the copper strands and up the shank. With the correct preparation, this process should take only three or four seconds, consuming very little solder to produce a good joint and avoid melting the insulation on the earth lead too.

Job done! Now all that remains is to slide the sleeve down to cover the shank and solder the live and neutral wires in their respective places on the circuit board.

There is no visible means of fixing the mains lead in the strain relief grommet on my A500 heavy PSU, so I'm assuming is it glued. This will be easier if you make sure that your replacement lead is a good fit in the grommet.

That's all, and Good Luck!

It'll be on its way to you tomorrow.

If you have any questions, just come back here.

PS. If you don't have provision for a wetted sponge on your soldering iron stand to clean the bit, you will find this job much easier if you use a ball of wetted cotton cloth to wipe the end of your iron regularly to prevent a build-up of lead oxide and resin gum from contaminating your work.

[sirlemonhead]

Thanks Prowler! that all sounds doable I'm handy enough with a soldering iron so that shouldn't be a problem. Would you recommend using some hot glue or superglue to secure the cable in the strain relief?

Thanks again, this is really appreciated!

[prowler]

I wouldn't use superglue myself, although that would certainly be easier to apply, because I don't think it works best with dissimilar materials or where there is more than a very narrow gap to bridge.

Hot glue sounds a better option, but I have no experience with it, so I would invite the opinion of one of the many members here with case modding experience to advise you on that.

Myself, I would probably end up using araldite or other epoxy resin adhesive applied, Blue Peter style, with a narrow strip of plastic cut from an old ice cream carton or other container. It's not as if you'll be wanting to take it apart any time soon.

By the way, I sent your crimp tag, complete with sleeve, this afternoon. I imagine you'll receive it on Saturday.

I hope you'll stick around on our forum when you've completed your repair and rekindle the Amiga enthusiast in you.

[demolition]

To secure the cable in the strain relief, I normally use a cable tie tightly around the cable on the inside which will keep it from being pulled out. Normally it is not a problem that it gets pushed in.

[Daedalus]

Hot glue is an awesome thing for many situations It will do a great job for securing a cable or fragile solder joints, and can easily be removed with gentle heat that doesn't affect the plastic.

[prowler]

Thanks, Daedalus. That sounds so much better than using araldite.

[turrican9]

Originally Posted by sirlemonhead

Hi,

I found the rest of the wire... which is now part of the new boiler :\

Lol! Was this done by an electrician? I work as an electrician and would never steal a cable like that. Especially not from an Amiga

[sirlemonhead]

Thanks guys, I'll probably go with a combo of a cable tie (great idea!) and a small bit of hot glue

Thanks again prowler This time I'll hopefully get the 500 up and running and stick around for a bit. It's kinda been an on and off project over the years but since it was free I was usually happy enough to give up. I think I've a few more tools and repair experience now though! I've already repaired the tank mouse it came with by soldering on some new switches but unfortunately I've misplaced the mouse ball and screws over the years! argh!

It's hard to tell if it was an electrician or not, possibly just a plumber or the guy who put the boiler in! Not sure how legit any of the people my parents use actually are

[sirlemonhead]

Hi prowler,

Received the crimp tag today (no post on weekends here) and job done! Thanks again so much!

Gone from this:


To this:

[prowler]

Great job!

And you're most welcome.