Another Amiga 500 Plus repair thread!

[gizmo1990]

Hi all. I finally got round to opening an old Plus I have to try and get it working. Upon opening I checked the battery state and it didn't seem too bad but was definitely leaking. So I've removed that and used a little diluted lemon juice around the area followed by some isopropanol.

Inspecting further there appears to be some damage to one of the 74LS244N chips. I don't know what these are, memory chips? There also seems to be some slight battery leakage on Gary too. Powering the board on I get nothing on the monitor. The green power led comes on and interestingly, the orange drive led lights up after around 2 mins? I thought that was odd?

I've done the finger test on all the chips and from what I can tell they all seem to be slightly warm. Except that is Gary, it stays cold.

Does anyone have any advice on what my next steps should be? I'm no electronics wiz but I'm keen on learning. If the two chips I mentioned are faulty, is there a way to test that? Are they even replaceable now if need be? Is it a situation where I'd have to source old parts?

Any advice greatly appreciated.

[Jpor]

Originally Posted by gizmo1990

Hi all. I finally got round to opening an old Plus I have to try and get it working. Upon opening I checked the battery state and it didn't seem too bad but was definitely leaking. So I've removed that and used a little diluted lemon juice around the area followed by some isopropanol.

Inspecting further there appears to be some damage to one of the 74LS244N chips. I don't know what these are, memory chips? There also seems to be some slight battery leakage on Gary too. Powering the board on I get nothing on the monitor. The green power led comes on and interestingly, the orange drive led lights up after around 2 mins? I thought that was odd?

I've done the finger test on all the chips and from what I can tell they all seem to be slightly warm. Except that is Gary, it stays cold.

Does anyone have any advice on what my next steps should be? I'm no electronics wiz but I'm keen on learning. If the two chips I mentioned are faulty, is there a way to test that? Are they even replaceable now if need be? Is it a situation where I'd have to source old parts?

Any advice greatly appreciated.

SHG had something similar on his YouTube channel. His was a Gary issue.

Worth a look here to give you an idea on what he ended up doing to get his 500 and 500+ systems working;

[ Show youtube player ]

This is part 2. Worth having a look at part a on cleaning up the board with white vinegar etc.. good luck

[gizmo1990]

@Jpor thanks a lot for the reply. I'm checking out the vid. He already seems to have had a torrid time. Pity he can't video closer in, it's hard to see what he's actually doing at times for a beginner like me!

Regarding spare parts, where are people getting them? Is it a case of Amibay (which seems down currently..)/ebay etc? Or are there other reputable online sellers around?

[Vypr]

U12 and U13 buffer and latch some of the memory lines So if there is an issue with them then the common symptom is a green screen What you'll probably find is the traces underneath these chips are damaged/broken.

What I would do:

Clean the area with white vinegar to neutralize any remaining battery liquid then wipe down with IPA

Remove Gary, and clean the legs.
Replace the Gary socket, it's probably corroded so much it's useless.

Remove U12 and U13, the chips are probably fine and will work if you give the legs a good clean. Check the area under these chips, this is where the memory data lines go and this is where I find battery damage happens most often in a 500+, the lines go under these two chips and are usually the first to break. bBeak out a multimeter and use the continuity tester to check the lines. Best to fit sockets in there place.

[Jpor]

Originally Posted by gizmo1990

@Jpor thanks a lot for the reply. I'm checking out the vid. He already seems to have had a torrid time. Pity he can't video closer in, it's hard to see what he's actually doing at times for a beginner like me!

Regarding spare parts, where are people getting them? Is it a case of Amibay (which seems down currently..)/ebay etc? Or are there other reputable online sellers around?

You are looking at EBay for parts. Analogic seem to sell spares here in the U.K. Individual Computers in Poland also. Check out Amigakit as well.

[gizmo1990]

Thanks a lot for that guys.

Originally Posted by Vypr

Remove Gary, and clean the legs.
Replace the Gary socket, it's probably corroded so much it's useless.

Remove U12 and U13, the chips are probably fine and will work if you give the legs a good clean. Check the area under these chips, this is where the memory data lines go and this is where I find battery damage happens most often in a 500+, the lines go under these two chips and are usually the first to break. bBeak out a multimeter and use the continuity tester to check the lines. Best to fit sockets in there place.

@Vypr Excellent just what I was looking for, thank you. Regarding the removal of the sockets and soldered chips, are there reliable methods used for this that don't include a de-soldering gun? All the youtubers I seem to find who do this seem to use them? And even the cheapest knock off chinese ones are a little out of my price range currently! Without one is it just a matter of using a solder sucker/de solder braid and hoping for the best?

[Jpor]

Originally Posted by gizmo1990

Thanks a lot for that guys.



@Vypr Excellent just what I was looking for, thank you. Regarding the removal of the sockets and soldered chips, are there reliable methods used for this that don't include a de-soldering gun? All the youtubers I seem to find who do this seem to use them? And even the cheapest knock off chinese ones are a little out of my price range currently! Without one is it just a matter of using a solder sucker/de solder braid and hoping for the best?

You can use a solder sucker and a soldering iron plus desoldering wick. It will take you a while. The thing here is getting rid of the old solder. Ideally you want to add new solder first then remove. The use of solder flux would benefit if doing it the manual way. Be careful with heat as too much can lead to removing pads off the board. Been there, done that, got the T-shirt

[Vypr]

Originally Posted by gizmo1990

Thanks a lot for that guys.



@Vypr Excellent just what I was looking for, thank you. Regarding the removal of the sockets and soldered chips, are there reliable methods used for this that don't include a de-soldering gun? All the youtubers I seem to find who do this seem to use them? And even the cheapest knock off chinese ones are a little out of my price range currently! Without one is it just a matter of using a solder sucker/de solder braid and hoping for the best?

I have a desoldering gun but I only use it for big jobs, one of these is much simpler to use and doesn't break the bank:
https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1

Use the solder sucker to get the bulk of the solder off, then use plenty of flux and desoldering braid to get the last remnants of solder out of the holes, most chips and sockets will just fall right out at that point although you may have to give the legs a little nudge with a hot soldering iron to break them loose..

[r.cade]

Also all those traces going under and around where the battery was look bad to me. They will need to be patched up.

Also, see all the little black dots where it says "audio filter". Same thing... If they aren't already open, they will be gone soon.

[gizmo1990]

Thanks again everyone. Really great advice. I feel more like theres some objectives to complete now.

@Vypr Would you believe, great minds think a like! I'd ordered that exact one last night!

@r.cade I'll get the multimeter out and check the continuity on them.

I thought I'd try and source some 20 pin sockets in readiness. Apparently there's 2 types of ic socket, turned and standard. Turned being a bit more reliable and easier? Is that what people here would suggest getting? Size wise they'd fit too?

[gizmo1990]

I need to get some 20 pin sockets for U12 and U13. Does anyone know if these through hole sockets will fit? I can't figure out the dimensions that are mentioned in the data sheets! I'd like to use through hole as apparently they are better when removing and replacing chips and the connections are more reliable.
https://uk.rs-online.com/web/p/dil-sockets/1831566

[Vypr]

Yes, those will be fine. 2.54mm is the correct pitch.
Turned pin sockets are more generally recommended for parts that don't see a lot of replacement as they d give better contact but they can be a bit of a a pain when inserting chips into them, especially ones you have de-soldered.
Make sure you have completely removed any solder blobs from the removed chips and get a pair of needle nose pliers to make sure the legs are completely straight

[gizmo1990]

Originally Posted by Vypr

Yes, those will be fine. 2.54mm is the correct pitch.
Turned pin sockets are more generally recommended for parts that don't see a lot of replacement as they d give better contact but they can be a bit of a a pain when inserting chips into them, especially ones you have de-soldered.
Make sure you have completely removed any solder blobs from the removed chips and get a pair of needle nose pliers to make sure the legs are completely straight

Thanks for that @Vypr They arrived and they look like they'll fit fine.

I've been trying to desolder the U12 and U13 chips and boy, is it tough to melt the ground pins! I've got some flux on order so I'll see how that helps.

One thing I thought I'd ask, does anyone have any suggestions for a good solder make? Links? There's all types of stuff around but I'd like one that perhaps is well regarded, good quality and easy to use. I'm currently using some lead solder I got a few years back but I'm rnuning out and always worry about the fumes. I've made a little fume extractor from 2 large pc fans and some filters. And it pulls the fumes away well, but whenever I catch an occasional whiff it sets my alarm bells off! Anyway, some good lead or lead free solder suggestions would be appreciated.

[r.cade]

Originally Posted by gizmo1990

Thanks for that @Vypr They arrived and they look like they'll fit fine.

I've been trying to desolder the U12 and U13 chips and boy, is it tough to melt the ground pins! I've got some flux on order so I'll see how that helps.

One thing I thought I'd ask, does anyone have any suggestions for a good solder make? Links? There's all types of stuff around but I'd like one that perhaps is well regarded, good quality and easy to use. I'm currently using some lead solder I got a few years back but I'm rnuning out and always worry about the fumes. I've made a little fume extractor from 2 large pc fans and some filters. And it pulls the fumes away well, but whenever I catch an occasional whiff it sets my alarm bells off! Anyway, some good lead or lead free solder suggestions would be appreciated.

The smoke and fumes are mostly from the rosin core burning, not the lead or tin, but still it can irritate the eyes and lungs and could cause asthma if you were exposed heavily for a long period of time (years). A fan is always good to use.

[gizmo1990]

Originally Posted by r.cade

The smoke and fumes are mostly from the rosin core burning, not the lead or tin, but still it can irritate the eyes and lungs and could cause asthma if you were exposed heavily for a long period of time (years). A fan is always good to use.

Thanks for that @r.cade

I've posted the following in the soldering thread, but thought I'd put it here too in case no one is reading that much now!

Could someone give me some advice for removing stubborn icu's? I'm trying to desolder U12 and U13 and they are proving so difficult.

I've a good solder sucker and it seems to have removed the solder from the underside of the chips. However when I look at the top side there still seems a lot of solder caked around the pins. Which probably explains why the chip still won't budge.

So my question is, how do you remove the solder which is applied to the pins on the top side of the board?

[cpiac64]

first cut all pin
second remove all pin
3° remove solder with sucker

[gizmo1990]

I'd rather not destroy the chips. They might be completely fine.

[cpiac64]

create a huge drop of tin on each side of the chip and lift the chip

[gizmo1990]

I've given in and got a cheap heat gun. Will post how it goes!

[pandy71]

Better to use hot air soldering station or pre heater and regular temperature controller soldering station - not so expensive i think - for easy desoldering there is pain free method with special low temperature melting de-soldering alloy from for example Chip Quik (but i think you can find similar alloys with not so famous brands - they are based on Bismuth and melting point is bellow 150C deg).