help request: my amiga 1200 tower don't boot

Hello,
i have get some amiga stuff, but they don't work.
the first amiga is an a1200 put into the infinitiv tower with the micronik a1200 board (6860 rev 5.44) and a picasso iv (v 1.2).

i have try to connect it either lg flatron m1921a and a commodore 1084s with the amiga video output and with the vga picasso output, but nothing happen.

i have test (without any load) the power supply (a sky hawk) and i see that the red line is 5v, the white line (could be the power good line??) is -3v and both the yellow and blue line is 8.7v, the yellow line should be 12v? is the power supply broken??

anyone can help me?

[rkauer]

Figures you have a busted PSU. It is a common AT PSU (or custom)?

The "normal" wiring code is:

red = 5V (4.85 ~5.05V)
yellow = 12V (must be on 10.5~12.1V range)
blue = -12V (diddle, but negative, of course)
white = -5V (-4.85 ~ -5.05)
orange = power good (PG), 5V when the PSU stabilize
black = ... zero, of course

Oh, and the PSU must have at least 2A of load in the +5V rail to regulate all the other voltages!

[alphonsus]

Infinitive towers have a custom wiring that doesn't have standard colours. They're also an adapted AT design with a hard power switch. They don't have a 'power good' line.

[rkauer]

So no orange(A.org), thanks God!

Thanks to everyone,
my power supply is not a standard at psu. anyone know if can i use an old at psu and just replace the "2 motherboard connectors" from at psu with the connector of my broken psu?
on this page: http://www.ianstedman.co.uk/Amiga/am..._supplies.html i read is necessary connect the orange (power good) wire on the +5v line, is it right and/or safe?
this is my broken psu:
http://eab.abime.net/attachment.php?...1&d=1216758225

and this is the connector for the micronik a-1200 board:
http://eab.abime.net/attachment.php?...1&d=1216758225

regards

[rkauer]

Originally Posted by conte0

Thanks to everyone,
my power supply is not a standard at psu. anyone know if can i use an old at psu and just replace the "2 motherboard connectors" from at psu with the connector of my broken psu?
on this page: http://www.ianstedman.co.uk/Amiga/am..._supplies.html i read is necessary connect the orange (power good) wire on the +5v line, is it right and/or safe?

Perfectly safe. It must be done or the PSU will not work. And my recommendation is exactly this: re-use the older Micronik power connector/wires.

this is my broken psu:

Could you please repost the pictures? Those are too dark/out of focus.

All you need to do is open the Micronik PSU, desolder the wires (taking note the corresponding voltage of each colour).

Originally Posted by rkauer

Could you please repost the pictures? Those are too dark/out of focus.

All you need to do is open the Micronik PSU, desolder the wires (taking note the corresponding voltage of each colour).

i have update the images, thanks for your help.

[rkauer]

So, can you please measure the voltages on the connector with it attached to the motherboard (or just to a pair of HD/floppy/other molex devices)?

There is no PSU who regulates itself with nothing "sucking" some current from the +5 (or +12V) rail.

Originally Posted by rkauer

So, can you please measure the voltages on the connector with it attached to the motherboard (or just to a pair of HD/floppy/other molex devices)?

There is no PSU who regulates itself with nothing "sucking" some current from the +5 (or +12V) rail.

hello,
without load on hd connector i read 5.04v (black/read) and 8.48v (black(yellow).
with a load (a 12v 21w light) on the 5v line the light is shining and i read 5.03v and 11.84v.
with the some load on the 12v line the light is almost off and i read 2.30v and i hear a fizz from the power supply. i think it going in protection.

thanks in advance

[rkauer]

Yeah, bad PSU. Still regulating OK, but busted.

Now you know that red is +5 and yellow +12, measure the remaining pins (blue and white) with a load in the +5V line.

After that, dessolder the power cable and install it in a new PSU (AT or ATX, it's your choice).