Another A500+ Motherboard - Part 1

So on the Amiga Facebook pages, a rather nice chap (hi Russell!) let me have an A500+ motherboard for pennies. This board, as per the majority of A500+ boards, has battery leak damage.

Green edge connector

This does not look good

Curse you Varta!

So, anyway. A quick power up and all I get is, rather unsurprisingly, a black screen. This would normally mean a CPU failure but given the extent of the battery damage, this is a bit meaningless.

First things first, I removed all the removable chips to check for damage to the sockets. Again, as is fairly typical with these things, the Gary socket was toast. A connector in the socket had already disintegrated due to the corrosion from the battery leak and Gary himself was looking a little worse for wear.

Alas, poor socket...

This will need replacing. The picture doesn't really show how green the contacts are across the whole socket.

On to Paula. Oh, dear. The bottom half of her socket is almost as bad as Gary but the top looks OK. This will still need replacing though.,.

Even Agnus did not escape unscathed. There were telltale signs of green on her 84 pins too which did not surprise me (no picture I'm afraid) so, as I precaution, I will replace her socket as well.

The other chips faired rather better. The two CIAs, Denise, the ROM and CPU were all unscathed so no socket replacements needed for these. It looks like I will need to replace at least one, possibly more of the logic chips that are in the are of the acursed battery. The chip U12, which is a 74LS244, took the brunt of the leakage. Fortunately, I have one of these in my box of bits. I don't have any others though, so I'm hoping everything else can get away with a bloody good clean.

First task, remove the Gary socket. Normally, I would just cut the old socket off and then de-solder the pins but, for some reason, I decided to be a bit more careful and I'm glad I did. Once I had the socket off I could check for any further damage (there was a little bit) and try to clean any other corrosion up.

Gary socket gone - some cleanup works carried out.

It was at this point I realised I had no sockets of the same size as Gary's (or Paula's). I did have some smaller sockets with the same style of pins so I hatched a cunning plan. I would clean up the plastic frame from the original socket and remove the pins from the small socket and place them in the big socket. This was a lot less fun than it sounded.

Half Completed Gary

Once I had replaced all of the pins I realised that I would have to do the same again for Paula. But that's for next time...

Sadstick 2 - El Cheapo

The second of my 'additional' joysticks is the cheapest of the cheap. Cheapo McCheap of Cheapland could not have made this any cheaper if he tried (even on a particularly cheap sort of day).

Did I mention it's cheap?

It worked when I plugged it in to my Amiga but the down direction was a bit sluggish and intermittent. After I unscrewed the one screw in the base it became obvious why and I thought it would be an easy fix.

Either a super ingenious enclosure or it's cheap.

The switches in this stick are formed from a piece of spring metal with four lugs cut out and bent upwards. As the joystick is pushed, the base of the shaft pushes a strip of metal against the lug, making a contact. The 'down' contact just needed to be bent a little bit closer to the metal strip. And then it fell off in my hand. Bugger.

Spring Metal Switches - Cheap

What I ended up doing was using a long bolt and some nuts to make a riser from the base. By drilling a hole for the bolt and then inserting the bolt through the hole, a contact was made to the metal. I added a piece of copper from an old piece of Amiga A500 edge connector I had and screwed that onto the top, bending it slightly so the it was roughly the same location as the lug had been previously.

Just call me MacGyver

My heath-robinson switch

I did have to remove part of the base retainer to make my mod fit.

The handle has no components other than two plastic switches that push down a plastic 'stick'. This presses down onto another piece of (cheap) plastic that then activates the fire button switch. Incidentally, the handle spins round on this joystick but as far as I can tell, there is nothing stopping it nor was there ever anything to stop this. Perhaps they were relying on the friction of the springy rubber block in the base to stop rotation but it doesn't work.

So there you go. My mod fits after a bit of butchery with a craft knife and, yes,it does actually work. If only it weren't so CHEAP.

Joystick Sadness (Sadstick?)

A few weeks ago I spotted a job lot of three joysticks on eBay for a very reasonable price. I was only really interested in one of them, and at the price I paid, the other two were a bargain.

Or so I thought.

The first of the additional sticks was a Cheetah Annihilator. If you are interested in retro gaming in any form then you will probably already know that this particular joystick could be described as the worst joystick in the history of mankind. If this was the last joystick in existence and I had to choose between the eternal fires of Hades or playing Sensible Soccer for an hour with this joystick then I'd be reaching for the suntan oil.

Imagine my (non)surprise when I realised it was broken. The handle didn't centre properly, the fire buttons on the top of the handle didn't do anything and the handle itself wasn't screwed together properly. Once I undid the screws in the handle it became apparent why. The previous owner had deliberately screwed it together in such a way as to grip the shaft of the joystick (no sniggering at the back) thereby semi-concealing the fact it's buggered.

The second joystick is very much an el-cheapo generic joystick from the cheap end of cheapo land. This one at least seemed to make no pretence at being anything other than cheap. Did I mention it's cheap?

I tested both of them on my Amiga and, sure enough, the fire buttons didn't work on the handle of the Annihilator but the base fire button did. The directions all worked but nothing could hide the sagginess of it. El Cheapo worked but the shaft twisted rather unnervingly but that's for another post.

So, do I bother doing anything with the Annihilator? Of course. 

Opening the handle revealed two wires connected to two random pieces of metal. Also inside was a 'z' shaped piece of black plastic and another chunk of the interior. After puzzling over the bits for a while it suddenly became obvious what I needed to do. Bin it...just kidding.

Comprehensively Broken

The two pieces of metal formed the 'switch' for the fire buttons and the 'z' piece held them in place. The only snag was that one side of the area that holds the 'z' piece had snapped off. To solve this I used a tactic normally reserved for large, heavy parts of Warhammer models. PIN IT! Basically, drill a hole from the exterior of the handle through to the inside. I actually did two holes. Then, superglue the broken piece back where it should be and let it set. Once set, I got the drill out again and extended the two holes into the superglued part. Finally, two pieces of stiff wire (a paperclip) were cut to length and superglued into the holes and left to dry. Job done.

Two tiny holes betray the pins

Re-instating the switch was straightforward after that. The only tricky bit was ensuring that the pieces were the right way around. The way the switch works is this. If the top button is pressed the button pushes the spring metal down onto the other piece completing the circuit. If the trigger is pressed the the button presses the metal where it makes contact with the other piece, completing the circuit. Cheap and nasty.

Next up, in the base, the switches used for the directions are of the 'dome switch' type. These are the same as used in the original QuickShot and QuickShot II joysticks. In this case they were covered in a huge sticky sheet of clear tape that was also covered in what looked like sawdust. I had to remove the tape (yuk) and carefully take the domes of the sticky side. I cleaned them with isopropyl alcohol and re-attached with a few small pieces of sellotape. Easy. (Apologies there are no photos of this - phone camera let me down.)

The next problem was that the handle just rotated around the shaft because the plastic lugs inside the handle which normally slot into the joystick shaft had snapped off. This was solved relatively easily with a couple of bolts. I drilled a hole on each side of the handle and inserted bolts long enough to slot into the shaft. 

New anti-rotating bolt fitted

Finally, how to make it a bit less sloppy. This was more difficult but I had an idea of using a spring of some sort under the shaft. As luck would have it, I had a few single battery boxes used in small projects. The spring contact from one end of one of these boxes was just the right size and strength to fit under the main shaft. The result was more than acceptable and a darn site better than it was originally. Again, apologies for the lack of photos on this bit - I did it at the same time as the dome switches and, for some reason, no photos came out..

So for this joystick, the only signs of anything being 'different' are a couple of tiny holes on the handle near the fire buttons, and what looks like a couple of screw heads at the bottom. A small price to pay to make it work.

All repairs done - re-assembly in progress

Re-assembly complete and all tested

It's still a steaming pile of crap though...

A1200 Capacitor Trouble (again)....

So on the A1200 that I repaired the other week, I noticed a very slight flicker in the video output. It wasn't much but it was noticeable. It looked like the colour 'green' would disappear for a split second and then it would come back.

Strange.

I took the motherboard out and had a good look over the topside. Nothing out of the ordinary but I think that it definitely needs to be re-capped. In any case, there's nothing obviously wrong on the top.

Turn it over and look at the back. My attention is immediately drawn to this:

Ouch.

Holy crap. Another failed capacitor... This is a general power de-coupling cap that has clearly failed in a fairly spectacular way. I'm surprised I didn't see this when I did the previous repair but, to be honest, it could've happened after I did that.

Anyway, as it happens, I have a few of these value SMD caps in my box so I just replaced it:

Shiny.

Having put everything together, I plugged the A1200 back in and switched it on. This is what I got:

Now, I may not be an expert electronics engineer but this does not look like an improvement.

I dug the board out again and got the USB microscope on it for another survey, this time I was looking for ANYTHING that might look out of the ordinary. It didn't take long...

These two resistors have been replaced by someone:

361? 360 ohms? Are you sure?

According to the A1200 schematics for Revision 1 type boards, these resistors should be 2000 ohms, not 360 ohms.


R217 is very badly soldered and looks like it has been messed with:

 Bad Solder Joints

R345 has been replaced:

681? 680 ohms? Are you sure?

According to the A1200 schematics, R345 should be 22,000 ohms. Yes, that's right, someone has replaced a 22K ohm resistor with a 680 ohm resistor. What the hell? If anyone has any idea why somebody would do this, feel free to comment below.


 This one (and another nearby - close to the op-amps for the audio) have also been replaced:

Correct - but REALLY badly soldered..

This last one (and it's pair) are part of a known fix for the audio on these earlier models. The original schematics had these at 1.5k ohms but that value is too high for the op-amps and the sound comes out distorted. 681 - or 680 ohms is the correct value. Soldering standard sucks though..

Finally, this:

Caps

This little group of three 1206 size components are capacitors. They should all be exactly the same as they are part of the de-coupling circuits on the video encoder, with one capacitor each on the Red, Green and Blue inputs. So why are there three different colours and why are they all soldered differently? Bottom one looks like factory, second one up is a reasonable manual attempt and top one has way too much solder on the right side. Could this be the cause of the video problem?

Fortunately, these are all 22nF which just so happen to be the only value of SMD caps that I have (and was also the same as the one I replaced at the top of page!). So, out came the soldering iron again. And now we have this:

More new shiny...

And that completely cured the video problem. Rock solid. I left Frontier playing its demo for nearly six hours and no problems. Another great result.

Just waiting for the 'real' caps to arrive so I can do a complete job on this A1200 now. :)

The Scarlet Amiga - Part 2

Sooooo. The Scarlet Amiga is working. It's a KS1.3 early(ish) A500 with a Samsung keyboard, a tidied up A501 half meg memory expansion and, following a lot of careful calibration, a working floppy drive. But we still have that awful sloppy red paint to deal with.

Following a few test scratches, the paint has two or three distinct layers. On the top is the red oil based gloss paint. I suspect that this is the same as some might use to paint skirting boards. Underneath that is a softer white-ish layer that I think may be some sort of spray paint, presumably used as an undercoat. In some areas there is also a dark green 'smudge' of what might be paint but could equally be wax crayon...

I googled 'remove paint from plastic'. One suggestion was to use vegetable oil on it, which should lift the paint from the plastic without causing any damage. I did actually try this as it would be non-destructive and if it worked would have been very cheap.

It didn't work. It just made the case oily.

Next up, isopropyl alcohol. This was a long shot as it's more a de-greaser than a paint remover.

That didn't work either. It just made the case shiny.

Next. Nail varnish remover (acetone basically). Mrs Crashed has (or had) a bottle of purple nail varnish remover which, to be honest, was a bit stronger than I anticipated. I put some across the top part of the case, near the AMIGA logo and within 10 seconds the paint had shrivelled and cracked. A quick scrape and a hug swathe of red paint was gone. BUT, where the acetone touched the bare plastic, the plastic started to melt and deform (she puts this stuff on her finger nails??) so, despite the promising results, I didn't continue with this.

By now we have a case that looks like this:

And so it starts...

More work has been done here - mostly around the inside of the keyboard

While trying to pick out the Amiga logo my hand slipped and, despite my best efforts, I failed to injure myself but I did put a large scratch in the paint. It was immediately apparent that large areas of the paint could be scraped off relatively easily using a handy scalpel with a flat square blade. This is the result of a couple of nights of scraping:

Getting there....

A smaller blade allowed me to get into the vents to some degree and soon, almost the entire top was back to an almost normal colour. A few more nights scraping and we've reached this point.

Vents waiting to be cleared

Almost done...

Fun fact. Do you know how many small ridges there are on the back of an Amiga A500 case? Seventy five. SEVENTY FIVE. S E V E N T Y  F I V E. Each one had to be scraped out by hand. 

It took over a week to get all of the solid red paint out of those ridges. If I'm honest, had I started by doing these ridges first it would have gone in the bin and I would've been searching ebay for a new case. But that would be cheating. :)

Red Gloss GONE

I realised some time ago that this case is not going to be suitable for selling. Even if I'd managed ti get all the paint off with no scraping or melting plastic, it was still in relatively poor condition.  Anyway, after all the effort I have put in I have decided that I will keep it for myself. 

There is still a lot to do on this case before I consider it finished. I intend to sand it down to remove the last bits of white/red paint and then I shall look at polishing it. This means it will lose it's customary patterned finish but, what the hell. It's my Amiga. :)

More updates soon..

The Scarlet Amiga

I saw this Amiga on eBay. I could not let it go. I had to save it...

A package arrived. Cautiously, I unwrapped it and, miracle of miracles, it had survived the journey with MyHermes. Good show!

A Mysterious Package

Bubble Wrap Goodness

Who can see what's not quite right?

First things first. Does it have a trapdoor expansion? Yes, an A501 still in it's shield. This almost certainly means the battery is still attached. This has to be dealt with first. Batteries that are in equipment this old will leak and they are not known for containing nice neutral compounds that are safe on PCBs and components. They contain chemicals that destroy PCBs so I have to get inside this and quick.

A501 With Shield (and Evil Battery)

I tried to de-solder the shield properly but my iron could not get hot enough given that the whole shielding acts like a huge heat sink. I resorted to cutting it off. Sure enough, the battery was still there and there was some corrosion. It wasn't too bad though, and a quick splash of vinegar (no lemon juice available) and a gentle scrape with a screwdriver got rid of the green stuff.

Battery Removed & Corrosion Cleaned

The Affected Area - I've seen worse...

Next, clean the 'slightly' grubby keyboard. This thing was filthy, with a capital 'fetch me Kim and Aggie!'. It looked like it had been under somebody's bed for a good number of years given the amount of dust and fluff and other crap that caked the whole thing. I first used a small screwdriver to scoop off the biggest bits of fluff (nice) then prised off each key carefully.

Flufftastic

Number Pad & Cursor Keys Removed

It doesn't get much better with the rest of the keys removed...

By now I had realised that this is an unusual type of keyboard. Most A500s have a Mitsumi manufactured keyboard but this one is actually different. It does not have the usual spring under each key - which are very easy to lose - rather the spring is under the plunger of each key. Also, instead of a single membrane connector this is the rather unusual double membrane type. The keys are also a very subtly different shape, being a bit more angular at the edges (and they are also made of thinner plastic - especially the space bar). As I understand it, this type of keyboard was manufactured by Samsung.

Normal A500 Keyboard by Mitsumi

Samsung Keyboard - note the double membrane connectors

This Samsung keyboard makes me far happier than it should do. It may not be that rare but it is unusual and so it makes me happy. :)

Each key was washed in warm, soapy water then left to air-dry thoroughly before being put back onto the keyboard. This is not my favourite activity, after all there are over 100 keys on these things... It also gave me the chance to put a few things right. Firstly, the 'Tab' key was upside down. Also, the bottom row of keys were in the wrong order. Instead of the usual 'zxcvbnm' they were arranged as 'zvcxbnm' so someone had clearly been messing around with this Amiga.

Keys. Lots of them.

All back together and CLEAN!

At this point, I'm ready to try and switch this thing on. Trapdoor expansion? Check. Keyboard? Check. Floppy drive? Check. Hideously painted top case hidden out of view? Check.

And....... red screen. ROM fault. Bugger.

I have a spare 1.3 ROM so I thought that this would be an easy fix. It turns out that it was even easier than that. The previous user had obviously been inside the case and, for reasons unknown, had taken out the ROM chip. And then put it back. The. Wrong. Way. Round. A quick switcheroo and try again.

Success! We have a Kickstart 1.3 boot screen. Now to try and boot workbench. But then the next problem rears its ugly head. The workbench disk is not recognised by the floppy drive. This IS a big problem. This symptom normally means that the heads need to be aligned which is no easy task. It requires that the screws holding the heads (or head motor - depending on drive model) need to be loosened and the heads moved by a fraction of a fraction and then the screws tightened again before testing to see if there's any difference. Repeat until the end of time...

Inside the Floppy Drive

Adjustment screws either side of the main motor

Fortunately, a chap called Thomas Richter (who is still active on the Amiga forums) created a clever program to assist with this. What happens is that a blank disk is written with a series of basic sound tones across several tracks with the highest pitch being track zero. Between the tracks is just noise (or silence). The small utility then reads the disk and outputs the sound based on the location of the heads on the disk. While the disk is spinning the heads are adjusted until the tone from track 0 can be heard and then locked into place. It sounds great in principle but does it work in practise?

Yes, is the short answer. The longer answer is that it took a lot of patience and a fair bit of too-ing and fro-ing but, ultimately, I got the floppy in this Amiga to read disks. It took about an hour or so to get it 'just right' but, at the end of the day, it was time well spent. The drive now reads all disks including the Workbench, all original games and even some floppies that last saw the light day about 15 years ago.

So that's the basics covered. Now, what the hell am I going to do with that awful paint job?