A1200 video problem, please help! :P

[Spordan]

Hi, I picked up an A1200 at a carboot sale today for a couple of quid (the seller had no idea if it worked or not, so I brought it on the presumption it was faulty).

I should mention this is the first amiga I have ever used (I was poor back in the early 90's ), and although it came with a bunch of stuff, a manual was not among them :0(

When I connected the power and RF cable to the TV, I saw the 'insert disk' screen, although very fuzzy (as you might expect from an RF cable), however, I had to turn it off and move the 1200 temporarily (someone else wanted to use the larger TV downstairs).

Since then, I can get no video output from the a1200, either with an RF cable or composite (I don't have a 15hz monitor to check the video).
When I power it up, the tv screen changes to black (indicating it is getting a signal), but the disk screen never appears.
The A1200 makes what I presume to be disk-checking noises every hmmm.. 10 seconds or so, but as I have no experience with these, I am not sure what is normal :0(

Does anyone have any idea what I might have done to it, and how to fix it?
I stripped it down to the motherboard and cleaned it (If it matters it is a 1D.4 version, though that's from memory) but this has made no difference.

If anyone can offer me any advice on what to try, or if you need any more information, please let me know, as it's a shame to find one with a lot of games and stuff, and then break it 5 minutes after getting it home

I thought perhaps something could have overheated/blown, since this is probably the first time it's been powered up this decade, but i'm hoping someone may know more about what to check.

Many thanks!
    Spordan

[Spordan]

Thanks for your quick reply, in answer to your questions:
There was no expansion modules plugged in at the bottom.
The green power light comes on, and the one above it flashes green (theres a chance it might be the power LED flashing, it's hard to tell as it's quite faint).
It has a seagate hard disk (the cable was slightly loose when I stripped it, but since I reassembled it firmly, it's hard to tell whether this has made a difference with the screen being black.
Is there anything else I can check?
Thanks for your help! :0)

[Spordan]

Okay, thanks for your help, I will try your suggestions and see if I can get it up and running :0)
Thanks again

[Spordan]

Hi, no, unfortunately I'm at home now, and the first tv set I tried it on was my girlfriend's fancy high definition set

I have tried stripping back to the motherboard and giving everything a good clean, and reconnecting floppy, trying that, reconnecting just the hard disk, and connecting them both and holding down the two mouse buttons.

The situation now is this:
I power on the 1200, the power led turns green, there is a click from the floppy drive, and the hard disk makes a typical hard disk noise (which it wasn't before, so that's a step in the right direction, I hope!)
the tv turns grey/black, so I know it is outputting a signal.
every 4 or 5 seconds, there is a flash of colour (purple, i think) then back to grey for 5 seconds. It keeps repeating this, so i think it might be the insert floppy disk screen, though i'm not sure.
Would it show the floppy disk screen if the hard disk was connected but blank, or damaged?
Should the A1200 output a video if I power up just the motherboard with no disks attached?
You mentioned to try holding the two mouse buttons in case it is in a different video mode - when I got the a1200 there was a VGA adapter plugged into the Video port, so presumably the seller used a monitor, I don't know anything about Amigas really, so is it possible it's in some sort of mode my TV cannot understand? I know amiga's need a 15hz monitor, so I can't use my PC one, but is there some sort of mode that would make it not display correctly on a TV?
Thanks again for the help!

[Spordan]

Right, just had another go with it, but still no luck, booting with both mouse buttons pressed doesn't seem to make a difference :0(
The power LED flashes 6 times, then a long flash, and repeats.
Does anyone know what this means? is it normal, or is it an error code?
Thanks

[Spordan]

is it possible that it keeps rebooting over and over again every few seconds?
what would make it do this? :0\

[Spordan]

Hi, thank you for your reply!

I think the a1200 is definitely resetting, i wasn't sure before as i'm not familiar with what I *should* be seeing

At the moment, having removed, then reseated the ROMs, I get a light grey screen for a few seconds, that then resets and this keeps looping.

Does this mean the ROMs are bad? Is there anything I can do about this? are they available to buy anywhere, or do I have to buy the blanks and use an EPROM programmer or something? :0(

[Spordan]

a little update: I just managed to get to a black screen that said "Software failure" in red (or something along those lines).
Does this fit in with the theory of bad roms?
I don't want to buy more if the actual motherboard is damaged or something

[Spordan]

I have only been able to get that 'software failure' screen twice, other times it just sits at a grey screen or reboots.

The same seems to be true without the hard disk connected.
 
It is a shame because the actual motherboard is surprisingly clean and new looking, but I can only guess there must be a bad solder somewhere, or one of the chips is damaged :0(

[Spordan]

Thanks for the reply guys.
Does anyone know if the error message I saw means the ROMs are okay?
If the chips were damaged, I wouldn't have been able to get that message, right? :0\
I will give the PSU a look at tomorrow morning with the 'meter, failing that, i'm not sure what to do!
If anyone knows where I can find information about the error codes, please let me know :0)
the power flashes 6 times and one long time.

If I can't repair it, i think i'll probably end up ebaying another one, as this one came with a lot of software, etc.

Cheers guys!

[Spordan]

Thanks for your replies, guys.

I have tried powering up just the motherboard with nothing connected, and I still face the same problem, I will check again today to make sure there are no visible shorts.

I have found a couple of web sites via google that describe using a PC ATX power supply to replace the Commodore PSU.

How easy is this? I have a spare 400W ATX PSU, is it simply a case of snipping the A1200 connector a few inches down and attaching the wires directly from the ATX PSU motherboard?

Does the A1200 use the same voltages a ATX PSU delivers? 12, 5, etc. Or is it different and i'll have to make up a PCB or something with resistors?

Thanks again! :0)