Amiga 600, boots, loads, but no picture.

Hi guys,

Sorry to be one of 'those people' who only register when they need help, but, errrr... I need help! Please.

So - a familiar story I'm sure - picked up a tatty Amiga 600 for 5 quid at a boot sale, no promise it worked, no PSU, blah blah blah.

So I bring it home, clean it up, plug it in with my old 512 PSU - Bingo! - I play a little Xenon, check some other disks, and then I get distracted by all the extras still in the box for Platoon and when I look up again - Black screen.

Haven't had a picture since either through RF, RGB or Comp. I know it's booting because I'm getting sound - just no picture.

ROM appears to be 37-300 and it's a PAL system.

Any ideas?

If you need any more info please ask.

Thanks in advance.

[ajk]

Time to grab the oscilloscope and start going through the video circuits It could be something like a bad solder joints. Another common problem are capacitors that have gone bad over time and need replacing. A high-res photo of the motherboard would be helpful, you will need to open up the case of course.

[majsta]

I would like to help but you need to provide more info. Maybe you can try to find some repairing tutorials on my website and investigate most of the problems on A600 motherboards.

[DDNI]

Hmm black screen after warm up. Sounds like a bad solder joint that is shifting with expansion. Leave the machine to go completely cold, then retry.

Thanks for the fast responses!

The machine is off now so should be nice and cold for a retry tonight, if that doesn't work I'll post a couple of shots.

I very much appreciate the help.

[Lord Aga]

Before trying again, be sure to open it up and check the capacitors.
Maybe some of them have leaked or exploded

[psygnosis]

5 quid thats a bargain

I've had her open already. Cleaned out a ridiculous amount of dust but other than the board looks fine, no sign of leakage or explosions.

There is some rust on the back plate and on top of the RF Modulator - I guess that might be a contributor?

Originally Posted by ajk

A high-res photo of the motherboard would be helpful, you will need to open up the case of course.

This is the best I can do:



All looks pretty clean to me (Apart from the RF Modulator being rusty) - but I'm far from the expert!

[demolition]

The RF modulator being so rusty is an indicator to me that the caps are leaking and have been for quite a while, so that would be the first thing to address. It has probably also eaten away a via or track in that area, causing the black screen.

[kipper2k]

Hi,

the caps underneath the RF modulator are dirty and probably slightly corroded so it should get recapped to start off with. Loss of picture could be caused by flaky caps not putting out.... (no comment or like DDNI mentioned, a cold solder joint. It's hard to see but it does look like some of the smaller alumininium caps do have a slightly rounded top also

[ajk]

Nothing appears horribly wrong, so yeah, it's probably time to remove the RF modulator and look under there, and start changing capacitors. You can find people here on the fourms who do repairs, if you don't want to try yourself (if you have previous soldering experience, it's not too hard).

There is a good [ Show youtube player ] about diagnosing an Amiga video problem. It's not quite the same, an A1200 and not completely blacked out, but might be interesting anyway.

Originally Posted by ajk

remove the RF modulator and look under there, and start changing capacitors.

I've ordered some capicitors (from AmigaKit) and when I break out the soldering iron I'll pull the RF off at the same time.

If that doesn't work, unfortunately, there will be one more 'Spares or Repair' Amiga on Ebay.

[Lord Aga]

They don't have to leak or explode. They can simply dry out and stop working properly. So recapping is surely a good thing to do. Thinking about doing the same for my A600. But it is a matter of funds