Amiga 500 help needed

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Amiga 500 help needed

Postby milkshakebot on Tue Apr 16, 2013 10:17 am

My girlfriend picked up an Amiga 500 for $10 at a school fair the other day. It came with the 520 modulator (sans cable), an external disc drive and a tonne of discs (including some labelled "Sam Fox Slideshow" and "digitized girls").

I'm waiting on a proper monitor, so in the meantime I decided to hook it up to the LCD via the monochrome port on the back using a standard yellow RCA cable.

It seemed to start up well. There was a sound from the internal disc drive on start up and the red power light came on and is continuous - no blinking. No disc light. Unfortunately all I'm getting is a grey screen, no workbench disc picture (I got the same when starting up with the workbench disc already loaded in the disc drive).

So I took this as an opportunity to open the amiga up and have a careful look around (and clean out the fifteen years or so of teenager fluff, ugh). No visible corrosion or leaking on the motherboard. There's a bit of corrosion on the expansion card battery, so I put everything back together and took the card out.

Same result as before, except now the green disc comes on and stays and the screen is completely black (apart from one start up when the grey screen reappeared). I get the same thing with the expansion card plugged back in.

I've opened it up again, made sure the floppy disc and keyboard connections are secure.

No regular click sound from the disc drive or the external disc drive (it only plugs in the back with one cable right? I don't need another one going to the serial port or anything stupid do I?) My assumption is that they're both buggered.

Any suggestions for further things to try would be greatly appreciated.
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Re: Amiga 500 help needed

Postby Carcenomy on Tue Apr 16, 2013 5:28 pm

Heck of a lot harder to diagnose when you don't have colour, believe you me - the Amiga uses a boot-time colour sequence to inform you of the condition. It should go light grey, white, disk prompt. But since you're in mono, you won't know if it's a grey screen or a yellow screen or a whatever unfortunately.

Leave the A501 out for the time being - get the Amiga running under its own power first. The 501s are notorious for having leaked batteries, it's one of those drum battery annoyances that most computers from the late 80s early 90s have.

The colours for errors are red for Kickstart ROM issue, green for chip RAM issue, blue for custom chip issue, yellow for CPU encountered an error before error trapping available, black for no CPU detected, grey for CPU test passed and white for CPU test failed. So as you can see, since you get a grey screen... it could actually be any of the colours of the rainbow! Recommend connecting via the A520's Video Out connector which should at least give you composite colour so you can see what it's up to.

Floppy light solid and no clicking can be the CIAs, but given that you're getting coloured screens I'd say start with that before worrying about drive activity.
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Re: Amiga 500 help needed

Postby natshaw on Tue Apr 16, 2013 5:38 pm

Hi there, are you in New Zealand? I have an Amiga-friendly colour monitor going dirt cheap. $10 and it's yours!
SC-3000H, SC-3000H, Amiga 500. Hobbyist electronics and programming.
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Re: Amiga 500 help needed

Postby Carcenomy on Tue Apr 16, 2013 5:39 pm

Boom! Is that the Philips one I heard mentioned? AFAIK they're more or less equivalent to the venerable 1084S (most of which were a Philips display anyway) so absolutely pearler for the job.
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Re: Amiga 500 help needed

Postby machinecoder on Tue Apr 16, 2013 6:45 pm

I dont no much about amiga's except that they have leaky batteries, and this may be
why they are "cheap as chips"

they only advice I can give is that when "googling" for help (if you do) dont forget
that the correct terminology is "disk drive" and "floppy disk", disc infers CD-ROM :wink:
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Re: Amiga 500 help needed

Postby Carcenomy on Tue Apr 16, 2013 6:52 pm

The Amiga 500 doesn't have a battery machinecoder - RTC was an add-on via the A501 memory expansion, so it's usually just the expansion that gets eaten. The Amiga 600 and 1200 equally don't have RTC, it's usually the bigger more expensive machines (2000, 3000, 4000) that had RTC straight away and suffer the worst, that and the Amiga 500+. But we don't talk about the 500+. ;)
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Re: Amiga 500 help needed

Postby natshaw on Tue Apr 16, 2013 7:03 pm

machinecoder wrote:I dont no much about amiga's except that they have leaky batteries, and this may be
why they are "cheap as chips"

they only advice I can give is that when "googling" for help (if you do) dont forget
that the correct terminology is "disk drive" and "floppy disk", disc infers CD-ROM :wink:

Lordy. Didn't the A501 expansion have a battery soldered to the circuit board?
SC-3000H, SC-3000H, Amiga 500. Hobbyist electronics and programming.
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Re: Amiga 500 help needed

Postby Carcenomy on Tue Apr 16, 2013 7:30 pm

natshaw wrote:
machinecoder wrote:I dont no much about amiga's except that they have leaky batteries, and this may be
why they are "cheap as chips"

they only advice I can give is that when "googling" for help (if you do) dont forget
that the correct terminology is "disk drive" and "floppy disk", disc infers CD-ROM :wink:

Lordy. Didn't the A501 expansion have a battery soldered to the circuit board?

Yes. Drum type NiCd. Common conversion if they're not already corroded is to install a coin battery holder.
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Re: Amiga 500 help needed

Postby Carcenomy on Tue Apr 16, 2013 8:16 pm

Yeah she did... a friend recently took up the challenge of completing Samantha Fox Strip Poker on my C64. He was most displeased to discover that the wildly pornographic picture you are rewarded with (a low res black and white half-toned photo of her posing...) is shown to you as the opening graphic! :)
Just the local Commodore hobo and middle-aged PC hoarder.
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Re: Amiga 500 help needed

Postby milkshakebot on Tue Apr 16, 2013 8:56 pm

natshaw wrote:Hi there, are you in New Zealand? I have an Amiga-friendly colour monitor going dirt cheap. $10 and it's yours!


Thanks a bunch, but I'm picking up a monitor tomorrow.
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Re: Amiga 500 help needed

Postby milkshakebot on Tue Apr 16, 2013 11:34 pm

Lol I opened her up again because I got paranoid I'd put the floppy connector around the wrong way (I hadn't). But I pulled out and put the connectors back and now, from what I can hear, the disk drive is making whirring sounds like it's trying to access the disk. The grey screen is now back. I should have a colour monitor tomorrow so I can start to diagnose the problem. What fun.
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Re: Amiga 500 help needed

Postby Carcenomy on Wed Apr 17, 2013 5:42 pm

Just plug in your A520 and use its video out connector to get colour and find out what colour the screen is.
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Re: Amiga 500 help needed

Postby milkshakebot on Wed Apr 17, 2013 5:59 pm

I've got the A500 hooked up to a monitor and the colour of the screen is ... grey. Or at least it was. I turned it off and on again and it was displaying red!

Opened her up and reseated the CIA, GARY, DENISE AND ROM chips ... back to a grey screen.

I must admit I'm scratching my head at the moment.
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Re: Amiga 500 help needed

Postby Carcenomy on Wed Apr 17, 2013 7:21 pm

Grey screen is CPU OK, red is Kickstart failure... I'd be inclined to think if it's staying grey the Kickstart isn't initializing. Pop the Kickstart ROM out and try it, see if you get a nice solid red screen. I have a dead A500 I can harvest a ROM from if you need one.
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Re: Amiga 500 help needed

Postby milkshakebot on Wed Apr 17, 2013 10:48 pm

Carcenomy wrote:Grey screen is CPU OK, red is Kickstart failure... I'd be inclined to think if it's staying grey the Kickstart isn't initializing. Pop the Kickstart ROM out and try it, see if you get a nice solid red screen. I have a dead A500 I can harvest a ROM from if you need one.


ROM is popped out ... and grey screen.

I'm wondering if it's possibly something to do with the monitor as well? There's no change on screen when I turn the computer on. Although I'm certain it's in working condition.
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