512kB RAM expansion problem

[Richardsk]

I used a 512kb ram expansion card for my Amiga 500, that has been in storage and not used for 14 years, last used in 1994.

When it is switched on the screen changes Grey and white. Amiga works fine when the expansion card is switched off.
I have posted some pictures of the board, a small bit of white stuff has come out of the sides of the Varta 2.4v 100(don't know what this is)

Is there a common problem for these 512kb ram cards when they have not been used for so long? anyway to fix




The chip with white stuff comming out I clean it a bit



top view

[zipper]

Wow, I got a similar one that barfed the stuff out already 10 years ago - luckily I noticed it before the board was ruined. Yours probably is, the alkaline from that Varta battery has eaten/corroded something. Remove it immediately and inspect the surroundings with a magnifier to find contact problems.

[prowler]

Hi Richardsk,

Welcome to EAB, mate. I hope you find you like it here and stay around.

Thanks for including the pictures. That component marked 'Varta 2.4V 100mAh' is a 2.4V lithium battery. The 100mAh means 100 milliAmp-hours, which is an expression of its capacity. The white stuff indicates that some leakage from the battery has occurred and it must be replaced. This is the most likely cause of your problem with the card. These batteries are quite prone to leakage after a few years, especially when they become discharged.

Your first step should be to remove the battery using a soldering iron, and then check the board around and underneath it for damage to the printed circuit board (pcb) tracks. Let's hope they're OK!

If you've not used a soldering iron before, there is a thread here which may help you gain the confidence to give it a go. I'll have a look around and post a link here later to help you with that.

A replacement component should not be difficult to find now that you know what it is. Have a Google for it and see what comes up.

Manufacturer is not important, and neither is the capacity (the bigger, the better). The voltage must be an *exact* match. You will probably find many similar components on offer, but the voltage *must* be 2.4V and it will be easier if the dimensions are the same, so measure it up before searching for one.

The polarity must be observed too, so make sure the replacement battery is inserted with the + symbol inboard as shown in the pictures, and you should be OK.

I should say that I have neither an Amiga 500 nor a 512k expansion card, so I'm assuming everything shown in the pictures is correct and that the card has not been modified, nor the battery previously replaced.

Good luck with this.

prowler

P.S. I must say I disagree with zipper; the board doesn't look damaged to me!

[prowler]

@Richardsk:
Here is a link to the soldering hints thread, as promised:
http://eab.abime.net/showthread.php?t=28037

Have fun.

prowler

[Richardsk]

Originally Posted by prowler

@Richardsk:
Here is a link to the soldering hints thread, as promised:
http://eab.abime.net/showthread.php?t=28037

Have fun.

prowler

Hey thanks for the guide, I removed the battery, tried the board but it didn't work. There does appear to be some missing copper contacts underneath. I have read that the memory should still work without the battery.





To cover the missing copper paths I have a small bottle of "silver conductive paint". I will try it to paint over burnt contact and hope it is the right stuff to use.

[prowler]

Originally Posted by Richardsk

I removed the battery, tried the board but it didn't work. There does appear to be some missing copper contacts underneath. I have read that the memory should still work without the battery.

To cover the missing copper paths I have a small bottle of "silver conductive paint". I will try it to paint over burnt contact and hope it is the right stuff to use.

Well done so far.

Before trying the conductive paint, consider trying to bridge the broken tracks with solid tin-plated copper wire. If you could do this, it would make for a more reliable repair. Rather than laying the bare wire against the track it would be better to wire from pad-to-pad at each end of the track, and sleeving the wire in between. This is because lacquer may have been applied to the board, which would make it difficult to achieve good joints. Keep going until all the broken tracks are repaired.

It still doesn't look all that bad to me. I think you have a good chance of success.

[zipper]

Are the memory chips just pressed into their sockets? If yes, pry them a bit out and then push firmly back to revive the contacts.

[Richardsk]

Originally Posted by zipper

Are the memory chips just pressed into their sockets? If yes, pry them a bit out and then push firmly back to revive the contacts.

The memory chips are difficult to remove so I left them but they all seem okay.
Since I removed the battery and added the ram expansion the screen now boots and turns Yellow. It use to just boot up grey/white and continuously reboot.
When you removed the battery on your board years ago did you connect the missing pins where the battery was. If you look at the last picture I posted above I don't know whether I need to connect any of the contacts.

[prowler]

Hi Richardsk,

I'm guessing what you mean, because my browser hasn't loaded your pictures for some reason However, from what I can remember of the last picture when I last saw it, I should imagine that a lot of those holes were originally plated through the pcb and this plating may have been damaged either by corrosion resulting from leakage of the battery electrolyte or by lifting out with the battery wires when they were removed.

See if you can insert a pair of dummy wires in the holes left vacant by removal of the battery and solder them to the pads on each side of the board to make good the original connection between them.

If this doesn't cure the yellow screen at boot up, repeat the procedure for some, perhaps all, of the adjacent pads and holes which appear to have suffered damage.

I'm sorry I can't help more than this just now. It might be better to wait until zipper is again online to see what he can suggest.

Don't rush in. I'm sure that with a little patience you can sort this out.

Good luck,

prowler

[Richardsk]

Here's the picture that didn't show up. I put some silver conduct paint over the connectors where the battery was.(it's easy to remove if it;s wrong).

[coze]

it doesnt look right to me. everything is connected. there should be 5v and gnd seperate. you're probably shorting something.

[zipper]

I just desoldered the battery out and got an external clock cartridge, which stopped to work years ago.
The two lonely pads seem to be the positive ones, so it's probably not shorted. Give the memory chips a really hard push on a sturdy base. Expect some crackling sounds as they seat down.

[prowler]

Hi Richardsk,

It still didn't help when you posted another copy of the latest picture. Something must have tampered with my browser settings. So I've had to log off, disconnect from the internet, flush my system cache, reconnect and then log in again. It's fixed now.

Originally Posted by coze

it doesnt look right to me. everything is connected. there should be 5v and gnd seperate. you're probably shorting something.

Yes, it now looks like the battery, if it was to be re-inserted into the place from where it was removed, would now be shorted by the array of interconnections between the pads, some of which couldn't have been there originally.

It is difficult to tell which connection(s) might be the culprit(s), as unfortunately, the first and fourth pictures in the series, which show more of the area under the battery than the others before your paint job was carried out, do not show this region very clearly.

I think you're going to have to wait for zipper's verdict on this, since it sounds like he's still got his card and can give you the most accurate picture of the required track connections.

Sorry, but it would appear that I can help you no further at this point.

I shall keep an eye on this thread for further developments, if and when zipper is able to make a further contribution. He's your best hope now.

prowler

[Richardsk]

Guys these were the three pins the battery was connected to



Now Pins 1 and 2 are not connected. pin 3 is.

I just found another .05mb expansion card on Ebay
http://cgi.ebay.co.uk/Amiga-500-1-2m...QQcmdZViewItem
so I will buy this.

[prowler]

I had not realized that the positive end of the battery had two wires attached to those pads. I had thought that a single wire at this end was connected to the pad between them and just a little outboard. Hence my belief that the array of pads shown in the fourth picture was shorting the battery connections.

A thought: "Experience may not be worth what it costs, but I can't seem to get it for any less."

[rkauer]

Did you ever notice the green stuff on the chips's legs? That thing is corrosion!!!

Take the memory chips out and inspect the copper traces under the sockets.

Here is an edited picture:

[prowler]

@Richardsk:

Originally Posted by rkauer

Did you ever notice the green stuff on the chips's legs? That thing is corrosion!!!

Take the memory chips out and inspect the copper traces under the sockets.

I second what rkauer has said. It would be a shame to see this card binned when it might still be possible to get it working again. So lift out the chips carefully (note their orientation) and have a look underneath.

Good luck,

prowler