Trying to fix a Amiga A600HD

[Ioncannon]

So I got my first Amiga, a cheap A600. The reason it was cheap was it has a hardware problem. Basically, when you turn the power on, sometimes the screen is black, sometimes it's white. The Power LED is on, and so is the Caps Lock. BTW Caps doesn't blink. I tried removing the A601MA but it still does it.

[8bitbubsy]

First things first: Checked your PSU? Are you sure it gives stable output lines?
+5, +12, -12v... You can measure it (connect the PSU to your Amiga, turn it on, then measure from the inside pins of the Amiga) with a multimeter.
Keep in mind that measuring the PSU when it's not under load is nonsense, thus measure it when the Amiga is on.

Look around the motherboard for leaked capacitors or other signs of broken/smashed/missing components... Also look for bad solder joints... Also, try to squeeze the kickstart ROM a bit, to make sure it's in good place. ONLY with your hands (using tools might crack the chip!)
Another thing is to check if the upper metal shield (if you have it) is shorting some pins or components... Try to boot your A600 without the upper metal shield and any expansions.

[rkauer]

Start replacing all electrolytic capacitors on the motherboard, also check the voltage levels on the power supply while it is hooked to the Amiga (and turned on, obviously).

[Ioncannon]

Ok just turned it on again, and a green screen popped up. Read on another post this rules out the Kickstart and the CPU correct?

Going to look for my volt meter

[8bitbubsy]

Hencing the "unstable error code switching", it seems to me that the PSU is the reason...
It can of course be everything else, like bad solder joints... Or caps living their last moments.

The green screen means that the RAM test failed, or so (or that it's not accessable, can't remember). At least it means that the CPU is not dead.

[Ioncannon]

By unstable error code switching you mean it throwing random colors? Cause now I got teal, light green, dark green, etc.

How many capacitors are their on the mobo? I counted 18. Doesn't seem to be anything near them. What does a leak look like?

[rkauer]

A leak looks like an oiled surface or you'll spot green stuff on solder pads on components nearby the affected capacitor.

Some "fresh" leak will show as a slight discolouration on capacitor's solder pads.

[kipper2k]

Originally Posted by Ioncannon

So I got my first Amiga, a cheap A600. The reason it was cheap was it has a hardware problem. Basically, when you turn the power on, sometimes the screen is black, sometimes it's white. The Power LED is on, and so is the Caps Lock. BTW Caps doesn't blink. I tried removing the A601MA but it still does it.

You must live in Toronto, That was the Amiga i was trying to buy i think

[Ioncannon]

heh, yup that's me. Though that even if I couldn't get the thing working, at least I get all the peripherals! They guy gave me about 100 disks he found in his basement on his way here too.

I though today I'd take a break so packed the thing back up, and realized another thing, the DISK light also stays on, along with the power, and caps lights.

[TjLaZer]

Leave it on for a few hours and it might come alive. It's the caps...

[8bitbubsy]

Originally Posted by TjLaZer

Leave it on for a few hours and it might come alive. It's the caps...

Not to act mean, but how do you know?

[Ioncannon]

Maybe it's wishful thinking but the colored screens and black screen has stopped and now I am only getting a white screen. I am suspecting it's the PSU because the owner said he never opened the system, and the motherboard itself looks really clean. Will post pictures tomorrow.

[kipper2k]

Originally Posted by Ioncannon

heh, yup that's me. Though that even if I couldn't get the thing working, at least I get all the peripherals! They guy gave me about 100 disks he found in his basement on his way here too.

I though today I'd take a break so packed the thing back up, and realized another thing, the DISK light also stays on, along with the power, and caps lights.

If you can't get it working i'll do a trade . Your motherboard for a fully working Pal motherboard

[jbenam]

This reminds me in some ways of my old dead A600 mobo.

I couldn't ever get to pinpoint the real problem behind it, sadly
IIRC, my Reset Timer was pretty corroded by a leaking capacitor.
Also the PSU was almost dead. Too bad I discovered this after I had already changed it

First, try with another PSU, and then check well around every cap.
A lot of times you don't even notice that caps have leaked until you feel that "fishy" smell when desoldering them

[Ioncannon]

Wish I had another PSU to test with though. Is there anybody in the Mississauga / GTA area with a A600 compatible PSU who could test this Amiga?

Kipper: If the Motherboard is found to be the problem I might take up your offer!

[kipper2k]

Originally Posted by Ioncannon

Wish I had another PSU to test with though. Is there anybody in the Mississauga / GTA area with a A600 compatible PSU who could test this Amiga?

Kipper: If the Motherboard is found to be the problem I might take up your offer!

Did you measure the voltages on your PSU ? THe important one is the +5v
heres the pinout for the power supply

http://www.allpinouts.org/index.php?...in&redirect=no#

(you are looking at it with the cable in the back, and the ridge in the connector at the top between pins 3 + 4


I have quite a few ATX PSU's here that i have converted to Amiga, its not all that hard to do... you could probably run a few jumpers from an ATX power supply to test it

[Ioncannon]

Well found the volt meter. So the positive lead goes on +5, but what about the negative? Signal Ground? Just to get this straight the diagram is facing the front of the Amiga from the inside, right? Not looking at the port from the back? I am looking at the mobo, the smallest and lowest to the right line is +5v?

Nevermind got a good pinout. +5 is reading at 5v, but the 12V is reading at 24.4V!

[kipper2k]

Originally Posted by Ioncannon

Well found the volt meter. So the positive lead goes on +5, but what about the negative? Signal Ground? Just to get this straight the diagram is facing the front of the Amiga from the inside, right? Not looking at the port from the back? I am looking at the mobo, the smallest and lowest to the right line is +5v?

black lead to signal ground, or ground, they are normally tied together. The diagram is orientated so that you are actually holding the PSU connector in your hand, cable at the back and the ridge in the metal shroud of the connector is on top. Sometimes you may get correct readings under no load so you should also try the option below too.

plug it into the amiga... open the amiga and connect the black lead to any part of the metal shield and connect the red lead to the 4 pin floppy header on the left side, from left pin to right pin you should read 5v, 0v, 0v and 12v.
If the 5v is showing less than 4.7 then your power supply is no good (some people may challenge that number, its not cast in stone, depends on other onboard components).

[Ioncannon]

Scratch the above edit. Ok I am reading 5v, 0v, 0v, 12.3v

[kipper2k]

Originally Posted by Ioncannon

Scratch the above edit. Ok I am reading 5v, 0v, 0v, 12.3v

k, there are 3 possible options that i can think of, its either U7 (Odd CIA) or Gayle as they control the IDE and startup initialisation process, also, remove U6 (Kickstart rom) and then replace it firmly

If the problem is at the chip level there are not a lot of options you can do, you can try using a soldering iron and very gently go around all pins to try to resolder them or remove the chip completely, socket it, and replace one at a time, CIA chips are easy to find, not so for Gayle

Edit... Very important.... Dont put the kickstart rom in the socket on the far left. When its in place there is 1 empty row of socket pins on the left! I'm pretty sure you will toast the Rom if you put it in wrong