Another Amiga 500 Plus repair thread!

[gizmo1990]

Well the heat gun works wonders! U12 finally removed.

I've started desoldering the Gary socket but run into a few snags again. The ground pin is yet again hugely frustrating to desolder but I presume the heat gun will shift it.

However, how do you remove the solder from the 2 legs which have been bent over? Does anyone have any tips for those. I've tried looking for video which cover this exact socket desolder but found nothing.

[IMG][/IMG]

[gizmo1990]

I've had some time to get back on this.. I'm about to solder a socket onto U12 but I had to scrape away a little of one of the trace's coating to check that there was a good connection, which there is.



Before I solder the socket on I feel I should coat the trace's bare copper with something to stop it oxidising(?) or somehow coming into contact with the 2 holes either side of it. It's extremely tiny so I guess it would need to be applied with a small brush? A lot of people suggest using nail varnish but others say it can have a low melt point and isn't suitable. Can anyone suggest what I should be using and perhaps a link to it? Something UK based?

Any advice really appreciated.

[gizmo1990]

Looking into this some more. Could I simply add flux to the trace and then apply a small amount of solder to cover the exposed trace's copper? That should protect it shouldn't it?

[Nbdy]

Or solder a wire on the down side of the board from the pin to the hole ...

[gizmo1990]

Thanks for the reply @nbdy. I got some solder mask and a cheap uv torch.

Looking around my board further there some white deposit around the oscillator. Does anyone know what this may be? What could have caused it? Could there be an issue with it now?

[gizmo1990]

Time for another update! I powered on the board for the first time, after:

1. Replacing Gary's socket with a new one.
2. Replacing the Gary chip for a new one
3. Installing sockets for U12 and U13
4. Replacing U13 chip for a new one. U12 looks ok with no crustiness.
5. Checked all the lanes from the chips mentioned checking for continuity.
6. Checked all the lanes around the battery for continuity.

And I'm still just getting the power light (green) come on. I get nothing from the monitor either. No screen flashing or colours. Effectively no signal.

Does anyone have any further suggestions for how I should proceed? How should I troubleshoot this? Any videos which deal with this exact issue? I feel like many must have come across this, I'm just not managing to find them. All my YouTube searches just throw up Amiga green screen problems. Whereas I'm not even getting to that stage I just get the power light come on.

Any help really appreciated.

[gizmo1990]

A further update which might be of use is that I've noticed that there is the tiniest electrical flicker on the monitor as I switch the psu on, but that's it. Also, the floppy drive doesn't spin or make any sound at all and that caps lock on the keyboard illuminates fine when the key is depressed.

I also have a spare internal floppy drive I hooked up and that doesn't make a sound either.

[nocash]

Looking at your pictures, the green corrision on the IC and resistor legs doesn't look too healthy. There are darkened PCB wires where the acid has crept underneath of the solder stop layer, I would scratch off the solder stop and corrision until the blank copper becomes visible, if there's any. For the cold gary chip, make sure that it is still having intact connections to VCC and GND. I would also desolder the oscillator and look underneath for corrision, and try to measure if it does output a clock signal; without an oscilloscope, you should probably see something like 2 volts on the clock output pin using a multimeter. Unplug and reinsert all socketed chips, and look for corrision on the contacts, and of course remember which chip was where, and which side is pin 1.

[gizmo1990]

@nocash Thanks a lot for that. I've checked the Gary chip and all the connections check out ok with a continuity test. I'll get on with your other suggestions and report back.

[Nbdy]

Check also the rom and the CPU ....

Try lifting them and reseating ...

Even look beneath them for broken or corroded wires ....

[gizmo1990]

Thanks @Nbdy, I'll do that. Doing to take off all the socketed chips anyway as I think I need to give the whole board a wash down.