no power to motherboard

[rvo_nl]

Hi guys, could use some help. Foe years I've had a nice working a1200t. With a lot of expansions, all working in harmony. But for some reason, my motherboard stopped working. After finally finding a new (recapped!) one, I was installing my expansions one by one. This all went perfectly fine. Until I plugged in my PPC + Bvision and hit the power button.

Nothing. Just the HD spinning up. Basically no power to the motherboard. No keyboard led. No output to my television (was still using RF output at this point). Removed PPC, and all expansions one by one. Same result.

What is wrong here? tried with another PSU, same result. It is driving me mad. I've waited for months and now still have no working Amiga I'm an electronics n00b, can not do any measurement. How can I proceed? Does anyone have a similar experience? Name anything you can think of, because this one is not so straight forward I'm afraid.

[Blizz1220]

Your signature looks scary enough , maybe post some pictures of motherboard inside the tower ?

When you say you unplugged everything you meant IDE cables too?

If you still have original brick PSU maybe try just that on bare motherboard?

[mechy]

Hi guys, could use some help. Foe years I've had a nice working a1200t. With a lot of expansions, all working in harmony. But for some reason, my motherboard stopped working. After finally finding a new (recapped!) one, I was installing my expansions one by one. This all went perfectly fine. Until I plugged in my PPC + Bvision and hit the power button.

Nothing. Just the HD spinning up. Basically no power to the motherboard. No keyboard led. No output to my television (was still using RF output at this point). Removed PPC, and all expansions one by one. Same result.

What is wrong here? tried with another PSU, same result. It is driving me mad. I've waited for months and now still have no working Amiga I'm an electronics n00b, can not do any measurement. How can I proceed? Does anyone have a similar experience? Name anything you can think of, because this one is not so straight forward I'm afraid.

Strip it down to a bare board, start with only the motherboard and power, no HD,accelerator or addons. etc, If that doesn't power up, it has to be a problem on the motherboard. If it does work, start adding items back one by one until it quits.

do you have any details on the recapping of the board?

Mike

[danbeaver]

Step One (1): Buy a multimeter
Step Two (1): Google basic use of a multimeter
Step Three (3): check voltages a) Out of PSU, b) In at motherboard (FDD connector)
Step Four (4): Try another motherboard -- a stripped MB with voltages reaching it and no response needs evaluation and then repair by someone with more than a multimeter.

[rvo_nl]

Thanks all for replying.

I've tried without IDE and floppy, yes. There is not much more I can disconnect. Here's a pic of installation without ppc/bvision and prelude:



I have a multimeter. But also no idea what I'm doing. The two dont match. And I dont think Googling around is going to change that.

[rvo_nl]

Okay, what about that Ratte monitor switcher that I have attached top-left (not in the pic). Could that cause this issue? It's a very fragile thing and now that it's connected I'd rather leave it in. It breaks easily.

[paul1981]

From what I've read it looks as though your ppc turned bad, blowing your motherboard and again, blowing your replacement motherboard. I hope not though, I'm hoping your motherboard will spring to life somehow. Please give us some hope!

[rvo_nl]

good thinking, but Im quite convinced the ppc had nothing to do with the broken old motherboard. since it broke down when the ppc wasnt connected. will do some testing tonight.

[rvo_nl]

so uhm..



it's alive! again!

your guess is as good as mine. took out the motherboard. powered on. worked first time. curse you, old computers!

seriously, I think I know what needs replacing:



right now I'm very happy its still working. and even more happy that my ppc is not faulty

[Matt_H]

Hooray! It's always the last thing you expect...

[mechy]

so uhm..



it's alive! again!

your guess is as good as mine. took out the motherboard. powered on. worked first time. curse you, old computers!

seriously, I think I know what needs replacing:



right now I'm very happy its still working. and even more happy that my ppc is not faulty

Could something on the board be shorting to the back of the tower case when it is installed? maybe cap leads sticking too far out of the back? or was it something to do with the cabling in the above picture?

[danbeaver]

Not to be contrary, but that wiring harness is for an A4000D and I assumed you had an A1200.

[rvo_nl]

@mechy indeed, I havent ruled that out yet. I also had lots of troubles getting output from the indivision until I placed it inside the tower. something's still not quite right. but I need that cable anyway, its falling apart.

@danbeaver yeah they dont have the a1200 cable listed on their website at amigakit, so had to use this one. good thinking though, thanks

[scuzzb494]

I'll tell you a funny story. I have this 1200 with an Apollo and with the case open all worked perfect. Then as soon as a closed the case the machine stopped functioning. Open the case all was fine, shut and stopped working. I had checked everything. Then I noticed that when I touched the case in one area the machine came to life. The fault was a rogue pin and it was obviously shorting. But it was enough to cripple the whole machine.

Next up I have a 4000T which was working fine when I went to pick it up. When I got home it just wouldn't work. Like you I removed all the expansion cards and even the hard drive. I struggled for a couple of years and determined the machine must be broken. Then one day I gave it one last try. And I was pressing on the Cyberstorm and she came to life. My goodness did I wake the neighbours with my scream of delight. Still working.

All I can say is when you get your computer running smoothly do not mess with it. With age they really do start to get very fragile.

No help, but in truth, never give up. But my advice is never mess with too much on a computer that is working fine. Tiny steps. Tiny steps.

Well done by the way. I was so pleased all worked out in the end.

[rvo_nl]

Thanks for the encouragement. you can be sure I am not giving up. I know for sure I can get this cable fixed and hopefully that will solve my issues. Will update this thread when I know more.