Yet another A500+ revival

[RobTurbo]

Quick back story, I had an amiga 1200 many moons ago, when I moved on to PCs it was given to my older sister, some time later it apparently "went pop" and she threw it away (I really hope someone rescued it), I forgot all about amigas and carried on with life, until last week, for some unknown reason I remembered cannon fodder and decided to look for an emulator, when I saw my dad I told him, and to my surprise, he told me he had an amiga 500+ in the loft that he bought at an auction for £5 years ago but couldn't connect it to the TV so put it away!

He got it out, I connected it up to the TV, turned it on, and you guessed it, black screen, off I went to google and quickly found out about the battery leaking issues. I took it home and cracked it open to find a leaky battery and lots of green that shouldn't be there. I removed the battery and cleaned the board up then tried turning it on again just in case, of course I wasn't that lucky! I got the multi meter out and started checking continuity, there appeared to be a lot of broken traces, I removed the gary socket and replaced it with a new one, then started patching up traces.

Using photos on this forum (thanks!) I checked continuity and soldered/added jumper wires where needed until all of the connections in the surrounding area were connected, cleaned up the pins on gary, then tried again, same result!

I checked all the other socketed chips were clean and correctly seated, still nothing, occasionally I'll get a different colour screen if I keep turning it off and on, sometimes white, sometimes a sort of black and blue flicker, once it was yellow!

What area of the board can cause the black screen? Is it just the area above the battery and to the left of the battery? The 74ls244 nearest the battery was badly corroded and a few of the traces were broken, I've read that if it is damaged it can cause a black screen, they are cheap so I think I'll replace that first, I might get a few just in case others are damaged as well. I've also read that if gary is damaged it can cause a black screen so that will be the next thing I try, I'm looking for another amiga, preferably a 1200, but would settle for a 500/500+ or 600, if I get one sooner rather than later I'll be able to swap the garys to test, I'll probably not get one that soon and end up buying a replacement. Other than those, is there anything else that can cause a black screen? It could end up being an expensive and time consuming fix if I try replacing every single component!

I believe the area to the right of the battery is audio? The CIA chips only stop certain things working? I've tried swapping them around and it was still the same.

Any help would be much appreciated, I know they don't cost the earth and they're not that rare, but I'd like to save it, it'll sort of make up for the loss of the A1200 that probably only needed a new power supply!

Thanks,
Rob

[eXeler0]

I know the feeling. Sometimes we buy tools and components for more money that it would cost to buy a full replacement, however A500+ are actually not that common anymore so its probably worth saving. I can promise you won't find a new one for 5 bucks ;-)
Anyhoo A full recap is usually recommended in any case and if you check eBay you'll see kits with capacitors for appropriate Amiga models and board revisions.
For your specific black screen problem, I suggest you check these forums because others have already had these problems so maybe you'll get lucky.
With leak damage it's difficult to say, could be some pesky resistors, diodes or something not as obvious as a faulty Gary chip.

Anyway, good luck. Now I'll return to my man-cave (out of reach for the kids ;') and continue my A500 mod.

[RobTurbo]

I've just won an auction (sooner than I expected!) for an A500, that's working, so at least I can get my fix of amiga action!! Will the gary chips be interchangeable between the two models? Assuming it's the OCS A500 and ECS A500+, I can't find any info on about chip compatibility between the two.

I've also ordered a few 74ls244s, before the auction for the A500, otherwise I would have waited in case it was the gary chip!

[eXeler0]

I'm not entirely sure if Gary was updated for ECS.. Never swapped Gary *And I have regular A500s no + but I've modded it to use more chip ram) but it is mostly a glue logic chip for boring stuff like bus control etc. Denise and Angus were changed for sure in ECS. (And obviously ROM and ChipRAM).
Also, different mobile revisions of A500 might have some variations.
And knowing the motherboard revision is essential because various hacks are done differently depending on revision.
Have you compared the Gary chip versions between A500 and 500+. Different numbers?

Edit: Had to Google different Gary revisions and according to this site, same Gary is used in A500 and A500+
(Gary 5719)

http://www.bigbookofamigahardware.co...t.aspx?id=1491

[TjLaZer]

Cap replacement are not needed as much on older models! SMD caps are the ones that fail. (A600/1200/4000/CD32)

[RobTurbo]

I haven't picked the A500 up yet (I'm getting it later today) so couldn't compare the two or try them, thanks for confirming they are the same.

All the caps look ok, no bulging or leaks, I know that doesn't mean they are definitely working, but good enough for me to hold off replacing them until I've tried replacing the bits that look damaged.

I picked up some more goodies from my dads yesterday, he'd been back in the loft and got a couple of boxes of my old stuff out, nothing amiga related, there's an atari 2600 with a couple of games but no cables, a sega master system with 4 games and the power supply but no joypad (I turned it on and it worked, just can't play anything!) and a commodore vic 20 with 2 cassette decks, power supply, a few game cartridges and some game cassettes, I haven't tried it yet, it needs a good clean before I do anything with it!

[RobTurbo]

I've been and collected the A500, had a quick play around to make sure it worked ok, then opened it up, put the A500+ gary in, turned it on and got a black screen, so I tried the A500 gary in the + and got a black screen with purple lines, I put it back in the A500 and it still works fine, so it looks like gary is part of the problem. I'll try again when the 74ls244 gets here.

On the plus side, I tried the + keyboard and floppy drive in the A500 while it was open and they both work, in fact the floppy drive is quieter than the original!

[RobTurbo]

The 74ls244s came today, I'll get them fitted tonight after work.

If it still doesn't work I'll try swapping all socketed chips one at a time, I believe the only one that won't be a straight swap is the rom, which needs a jumper between two pins IIRC, I'll look into it properly if I get that far.

If all the chips work on the other board I'll abandon it and get a rev6 board and upgrade it with bits from the plus.

[eXeler0]

Originally Posted by RobTurbo

The 74ls244s came today, I'll get them fitted tonight after work.

If it still doesn't work I'll try swapping all socketed chips one at a time, I believe the only one that won't be a straight swap is the rom, which needs a jumper between two pins IIRC, I'll look into it properly if I get that far.

If all the chips work on the other board I'll abandon it and get a rev6 board and upgrade it with bits from the plus.

what ROM are you putting into it 3.1? I tried a 2.05 ROM from an A600 in a A500 not long ago but that didn't work. Needs some hacking ;-) But it didn't wanna solder on the legs of the ROM so I got some ROM sockets from Amigakit to mod. (they are cheap like €1 a piece)

[RobTurbo]

It was the 2.04 rom from the A500+ that I tried in the A500 (with a wire soldered between pins 1 & 31) and it worked. One of the CIA chips doesn't work but the other does, denise works, paula works, I already knew gary didn't work.

I tried fat agnus and it didn't work, but I did some reading and found that they are not interchangeable between the A500 and A500+.

I tried all known good chips in the A500+ and now I get a flashing power led (constantly pulsing, not a set of flashes) and sometimes the screen randomly flashes colours, many more than I've seen meanings for. Next I started tracing the connections from the even cia (the one that didn't work) and found a via that didn't connect through the board, it's too late to be playing around with it so I've marked it and put everything away for the night, that will be my first job after work tomorrow!

[eXeler0]

Originally Posted by RobTurbo

I tried fat agnus and it didn't work, but I did some reading and found that they are not interchangeable between the A500 and A500+.

Fat Agnus 8371 from a500 won't work in A500+ as it only supports 512kb ChipRAM but Fatter Agnus (8372a from A500+) will work fine in an A500 so strictly speaking they are somewhat interchangable :-) , (but you usually need to do some additional hacks. (in pal territory you need to isolate one pin or it defaults to ntsc etc...))

[kipper2k]

Hi,

A common problem with the a500+ fix is it is not just the traces that get corroded. The vias and also the traces at the point where it connects to the chip pads also corrode. If you remove a chip then before you put it back in you will need to scrape the legs in order to remove the oxides that have built up over the years, it may look like a good connection but the oxides will cause a problem... Dont remove Fat agnus unless you have tried all other alternatives,... they are a bitch!!!. I did provide a picture with the traces mapped out on the forum here somewhere, that is an excellent tool.

One other thing is dont forget expansion port as that is probably bad too. Adigital camera with close up macro is a very valuable tool

Have fun

[Jope]

Originally Posted by eXeler0

Fat Agnus 8371 from a500 won't work in A500+ as it only supports 512kb ChipRAM but Fatter Agnus (8372a from A500+) will work fine in an A500 so strictly speaking they are somewhat interchangable :-) , (but you usually need to do some additional hacks. (in pal territory you need to isolate one pin or it defaults to ntsc etc...))

Be careful, a 512 and 1MB agnus are somewhat interchangeable (mainly the PAL/NTSC pin modification is needed), but the 2MB agnuses will not interchange with 512k and 1MB agnuses. The 2MB agnuses are not even interchangeable amongst themselves every time. The a500+ Agnus will not directly work in a motherboard less than revision 8.

[RobTurbo]

Well I give up!

There was a slight glimmer of hope after I sorted out the broken via that I found last night, fitted known good cia, gary, paula and denise chips, I know the rom works, I can't test the fat agnus but there was no corrosion anywhere near it, when I turned it on I now get a steady power light, the screen starts grey then flickers and turns white (just like the working A500) and the floppy drive starts clicking, but that's it, no kickstart screen, if I put a disk in the drive it doesn't do anything, doesn't spin or seem like it's trying to do anything, just stops clicking! This doesn't happen every time, sometimes I just get a black screen still, it doesn't seem to make any difference if I press on anything or not, if I just keep turning the power on and off sometimes it's a white screen with clicking floppy, other times it's just plain black.

After that I checked every via on the board, I've downloaded the A500+ service manual and tested every connection anywhere near even the slightest hint of corrosion and everything checks out.

I'll hang on to the working chips, case, floppy drive, power supply and expansion card and throw the rest away, I'm sick of the sight of it!

[eXeler0]

The thing with this old stuff is that you can never be sure it will ever run again. After all we are talking about 25 years old electronics.
But at least you gave it an honest try and you probably learned something in the process. Take that experience with you and move on. Regular A500s are cheap and relatively plentiful and easy enough to mod to A500+.

You can probably still sell faulty Amiga parts and someone else will give it a go ;-)

[RobTurbo]

I'm not happy that I couldn't get it working, if I had another A500+ to try the fat agnus in I wouldn't give up just yet, without knowing if that's ok I could replace everything on the board and still get nowhere. But as you say, I've learned a lot about amigas because of it, all I knew before was I used to play games on one when I was younger!

Also, if it wasn't for my dad having it in his loft I wouldn't have the A500 either.

The A500 has a 512k expansion with space for a RTC, I suppose I could take the components from the A500+ and remember not to leave a battery in when I put it away!

Just need to find a hard drive adapter and more ram for the A500 and I'll be set.

[eXeler0]

Originally Posted by RobTurbo

I'm not happy that I couldn't get it working, if I had another A500+ to try the fat agnus in I wouldn't give up just yet, without knowing if that's ok I could replace everything on the board and still get nowhere. But as you say, I've learned a lot about amigas because of it, all I knew before was I used to play games on one when I was younger!

Also, if it wasn't for my dad having it in his loft I wouldn't have the A500 either.

The A500 has a 512k expansion with space for a RTC, I suppose I could take the components from the A500+ and remember not to leave a battery in when I put it away!

Just need to find a hard drive adapter and more ram for the A500 and I'll be set.

A600/1200 have IDE on the mobo, so adding a CF is really easy.. on A500 OTOH... not quite as easy..
but either get a second hand solution or you can check out Kippers RAM board.

http://kipper2k.com/a500fastmem.html

Or.. if you can wait a few months, there will be a Vampire 500 v2 card that will give you features you didn't know were possible ; -)
(it will give the A500 a cpu that is roughly twice as fast as a 060, 128MB RAM and HDMI out for RTG modes.)

[RobTurbo]

I knew about the 600/1200 having IDE, but I can't really justify buying an A1200.

I've also seen Kippers ram board and must say I'm tempted, at some point I'll look into the cost of getting one shipped to the UK, I prefer things in DIY form where possible so I'm going to look into making something myself, the downside is I have no idea where to start with designing circuits, so I'll need to find a circuit that does what I want first, when it comes to making a pcb, soldering and programming chips I don't have a problem.

I think the vampire will be overkill for my needs, a couple more MB ram and a small CF card will do me fine!

[eXeler0]

There's also the ACA 500 from individual computer that pretty much does what you are looking for and price is decent and possibly lower shipping cost than kippers board... However, if you're more of a DIY guy then maybe you can start by looking at these docs here:
http://aminet.net/package/docs/hard/a500ide