Amiga 500 plus showing white screen

[Viserion]

So here we are with yet another A500 plus that doesn't work.

The difference with this one is that there is no visible battery leak

I got this several months ago, so can't check the battery any more to be absolutely certain, as it was delivered for recycling.

It looks pretty good, the best looking A500 MB I have seen. So there is not any obvious reasons why it won't boot any more(as it did boot when I first got it).

I've tried to change all the removable IC with spare ones, but it makes no difference.

The only thing is that the C913 broke one of the legs when I was trying to clean it up a bit.

The unit failed to boot before this happened, but some of the MB paint got removed while removing rest of the capacitor.

I have ordered replacment caps, but they haven't arrived yet. Also I have changed the sound capacitors on C303 and C304.

The power unit I use is an A 1200 Magic pack one, and I have used this to power everything from other A500s to accelerated A1200s, without any problem.

So this should not be an issue.

What happens when I power it up is that the "no source" text when nothing is powered on disappears, but screen remains black. After 2-3 second it becomes white.

It's connected through the DB 23 connector via a scart to hdmi adapter. Used the same setup for other Amigas, so I know this works well.

The power led stays on all the time, and I can see no blinking.

There are some pictures of the Mb on this link.

So where do I start to track this error(s) down. I have a multi meter but no real experience of using it, as I assume this has to be used at some stage to track this down.

[Viserion]

Can see from a other thread it could be the angus socket.

Will try that since there is no other advice.

I do have one of the USB camera/microscopes, but the software that was included was, if one is generous, not very good.

So does any one at least know of good, preferable free software I can use to get a more detailed view of the A500+ board.

[kipper2k]

lots of pictures here...

http://www.bigbookofamigahardware.co...List.aspx?id=1

[Viserion]

I was looking for better software, so I could look at the MB through the USB microscope to see if there is faults that are not visible to the naked eye.

[Viserion]

There is some good news, and some bad news regarding this.

The bad news is that I am blind, and the good news is that on R309(1 Ohm) I found a burned resistor.

As luck would have it, I have another A500 plus with the R401(4.7 OHM) problem where a burned resistor causes the mouse not to work in port 1, so I bought a resistor kit where among others a 1 Ohm resister was included.

So I have changed both both resistors, and the operation was a success in both cases

[Viserion]

I was happy a bit to early.

While it boots, it still is terribly unstable. I get guru 8100 00FF all the time until I changed the Angus IC.

I also had artefacts on the left side on the screen sometimes when WB is loaded before the games start.

This has not occurred after the Angus switch, but haven't tested it that much yet.

After the switch I only get an occasionally Guru, but still far more often that I should.

I assume that still have something to do with Angus, maybe a broken socket, but any pointers would be welcome.

[Viserion]

I've worked on this a bit more, and the curious thing, is that the board works if I connect my ACA500 to it.

It then worked well apart from the clock replacement I bought from Amigakit.
Clock was simply not found.

I found 2 of the capacitors had red "marks" on them and thought that they might be bad.

Both where 100uF 16V so I replaced them with 100uF 50V(C812 and C814).

Got my hopes up, that this fixed the problem but soon it was back to Guruing left and right.

I also tried changing the cpu, but it made no difference.

Connected the ACA500 again, and I can boot to Amiga os 2.1 via the CF card.

Problem now is starting games. The WhdLoad window comes up, and it start getting recoverable Gurus. Every time I click the left mouse button, a new Guru replaces it within a second or two.

It might be the kick start rom in /devs/kickstarts is corrupted, because sometimes I get an error telling me that there is a wrong version of the kick34005.A500 rom. It worked fine before.

When trying one of the games from adf files via my Gotek drive, it worked perfectly.

Another odd thing is that after changing the capacitors, the clock suddenly gets detected.

So I assume there is something with the logic surounding the processor that is the problem, and I have replaced the resistor at R309.

So is there anywhere I can measure, and if yes, what value should the measurements have?

I'm crap at reading schematics, so they won't tell me much.

[kipper2k]

Not sure about what i am saying is correct here, but when you boot from the ACA500 i think you are using the builtin rom from the aca500 so your onboard rom is not in use.... therefore there may be a problem with either the onboard rom or traces from the rom that feed the bus. Try removing the rom and cleaning the legs with sandpaper, check that the rom socket is not dirty or has oxide buildup on it and also check all traces , even a touchup with a soldering iron wouldnt hurt.

For the clock... the onboard clock of the a500+ may still have control so your new clock (not sure how its hooked up) may not be seen because of it

[Viserion]

Forgot to mention that when using the ACA500 I use the 3.1 rom on the MB and not the ones built in to the ACA500.

Reason is of course that I want as much memory available to run WHDLoad as possible.

Instead of the rom, it's possible it is the cpu socket that is the problem.

The clock replacment is soldered on where the old one was removed, so it is the same logic.

[Viserion]

Looks like Kipper2k was right after all.

Changed the 3.1 rom to a 2.05 rom and it is now a lot better stability wise.

What makes me baffled is that the 3.1 rom worked more or less fine when using the ACA500(booting from the on board 3.1 rom) but was completely unstable when using local CPU, despite trying several different CPU.

Now, with the amount I have tested it works fine with or without the ACA500.