Amiga 1200 Black Screen - Green Led NO FLASHING

Hi! First of all I want to thank the people on this forum..... For all the info you gave here, I used it a lot for the installation! But mostly for keeping the Amiga alive!!!

So, to the problem:

Some months ago I bought an Amiga 1200 PAL, a rather difficult / impossible to find here in Argentina...

I also bought from Germany an Memory Expasion Board (Mikronik RA1208) an 8Gb CF Card with IDE adaptor, a PCMCIA Network Card and a G-Lock from G-Valley. Installed all in my Amiga, etc.

Everything was running smooth... I do VJing so I started to use it with a Video Switcher.

Last night I left the Amiga turned on and when I came back it was frozen.

I turned it off and then on. It started with Validation errors in some blocks so I used DiskSalv but it frozen some minutes later. Tried that a couple of times.... Frozen a couple of minutes after DiskSalv started again and again.

So I opened the Amiga, took out the CF and checked it in my WinUAE. The installation was perfect, no errors.

When I put the CF again and turned on the Amiga, it didn't boot.

It started with 11 Green Power Led flashes and Black Screen (I cant see colors until I start the G-Lock software, so I don't really know if it's black or another dark color)

So I started to take all the connections out: CF Card, IDE adaptor, FDD, Mikronik Board, PCMCIA.... The Amiga was just connected to the PSU and Composite video to a monitor.

Turned it on again an this time there was no Green Led Flashing. It is stable, without flashes, and of course, BLACK SCREEN.

Tested the PSU output:
+12v = 12.3v
+5v = 4.9v
-12v = 10.9 to 11.2v

The -12v is a little low but according to my investigations, it's just for RS232 and Audio!

What else did I tested:
- PCMCIA pins are OK, none of them are forced, etc.
- Visually there are no inflated caps or leaked, but I'm not an electronic ingeneer.
- Visually I can't see any of the chips unsolded
- Kickstarts are on their place, very difficult to take them out. Tried but they just pop a little out, I don't really want to force them out!

And finally: Tested the voltage in the FDD socket: 5v OK... 12v are NOT PRESENT. It reads 0v volt to 0.2v or something like that.

Tried to close it, and tur it on: The green power led flashed 6/7 times, black screen. Don't know what that means... After that, again just green steady light when turned off->on.

The worst thing is that I was invited to a TV show here to do a Demo with the stuff I'm doing on Wednesday! Of course I called them to cancel but maybe and only maybe I have the hope you can help me to solve the problem!

Thanks in advance for helping !

[Marmes]

Hi!
Try to measure on lf347 or tl084 . one or other pin 3 or 4 should have +12v and pin 11 or 12 should have -12v. If Not check if 4.7 ohms resistors are OK. Remove the board and check for burned tracks on bottom.

Originally Posted by Marmes

Hi!
Try to measure on lf347 or tl084 . one or other pin 3 or 4 should have +12v and pin 11 or 12 should have -12v. If Not check if 4.7 ohms resistors are OK. Remove the board and check for burned tracks on bottom.

Pins checked: Ok.

Didn't checked for burned tracks but I will tomorrow.

Seems like there is a cap (the first one in the +12v rail) that doesn't work....

But seeing at the mother schematics, seems like +12v is only used in FDD, RGB port, audio filters and rs232. So, if that's true, I must ask: Does the Amiga can't start / boot without those +12v? If the answer is NO, why?