Dead A1200

[taunusand]

Through time I have been given several broken commodore/amiga computers. Recently my interest in theese came back :-)

I have several working systems, that I intend to keep, but I hope that I can repair some of the broken computers, some of them will probably be sold, but some of them I would sergently like to keep.

Most of all I would like to repair 2 Amiga 1200's. Same symptoms. Power lead lights op, but the screen keeps black. No expansions, power supply ok (testet on other computer) where should i start to find out what the problem is? Or hint to replace component?

BTW: no click from drives or reaction when disk inserted.

Thanks  :-)

[AmiBoy]

I have exactly the same problem with my spare 1200

Power light on but no activity from disk drive and screen stays black.

I hope we can get an answer

[Amiga4k]

Suggest you install a known working set of ROM chips. Black denotes failed CPU or CIA. In the A1200 that might present a problem.

[rkauer]

 The machines have a HD? If so, it could be only the re-validation process acting up.

 To keep it simple: turn the machine on and wait for a couple of hours.

 Usually when you have a validation problem, the machine don't boot. It lits both leds (hard drive and power) for time needed to re-validate the system.

 Bad socketed ROM could be an issue, too. Open the Amiga and press gently, but tight, the ROMs into the socket.

[taunusand]

rkauer wrote:
 The machines have a HD? If so, it could be only the re-validation process acting up.

 To keep it simple: turn the machine on and wait for a couple of hours.

 Usually when you have a validation problem, the machine don't boot. It lits both leds (hard drive and power) for time needed to re-validate the system.

 Bad socketed ROM could be an issue, too. Open the Amiga and press gently, but tight, the ROMs into the socket.

I will try it :-)

[pan1k]

rkauer wrote:
 The machines have a HD? If so, it could be only the re-validation process acting up.

 To keep it simple: turn the machine on and wait for a couple of hours.

 

Or just open the case, unplug the HD and power it on and see if you get a kickstart screen, that's what I do!

[taunusand]

pan1k wrote:

Or just open the case, unplug the HD and power it on and see if you get a kickstart screen, that's what I do!

No harddisk installed, clean machines :-)

[pan1k]

Then you should see a kickstart screen after half a minute or so. If that doesnt happen.. i'd go with new ROMs as suggested. I *may* have ROMs that you can have for postage, they are 3.0 ones but hey ...

[Plaz]

CIA chips were always a common failure on Amigas. When one goes bad, floppies could fail or the whole machine might not boot. After all the common fixes like... power supply, memory, battery corrosion, expansion hardware, resetting connectors and chips in sockets, have all been eliminated as the problem, I would recommend the following trouble shooting to some one with very good solder skills. (U7,U8, U28 and U29 are surface mount)

Replace U28 and U29 (They're cheap). If those chips were to fail, they could keep the floppy from working or the machine from booting by tying up CIA U8. If no change, then it's time to remove U8. With U8 removed, power up and see if the symptoms change. If so U8 is probably bad. If no change, replace U8 and remove U7. Again look for any change in the symptoms. If it looks like one of your CIAs are bad, I don't know that there is a source for replacments. But if you have two machines, you might be able to come up with enough good chips to get one running again.

FYI, carefully using a basic heatgun works well for doing surface mount parts.

Picture of CIA on A1200/A4000

Plaz

[taunusand]

pan1k wrote:
Then you should see a kickstart screen after half a minute or so. If that doesnt happen.. i'd go with new ROMs as suggested. I *may* have ROMs that you can have for postage, they are 3.0 ones but hey ...

Very kind of you :-)

I have a working A1200 that I have ordered 3.1 chips for at www.vesalia.de .
When I recieve theese, I will try to replace the ones in the dead A1200's with thoose 3.0 that I KNOW works 100%

But.. I have left one of them on, just to see if it comes back to life :-)

[taunusand]

-> Plaz

I am an electronics mechanic.
I think I spelled that incorrectly, I'm an idiot at typing anything other than dahish..  :roll:

8520 are easy to replace, but hard to desolder and use again.

I wonder where I can get thoose.

[taunusand]

-> Plaz
IC 8520PL, CIA (PLCC) for Amiga 600/1200/4000(T) [391078-01] www.vesalia.de

You are right, they are cheap  :-D

I think that I'll but some when I have some more to order, just in case :-)

[Plaz]

I think I spelled that incorrectly, I'm an idiot at typing anything other than dahish..

You're doing great. I'm an idiot in any language. :lol:

In US english we call you a technician. Mechanic is used for those who work on machinery.

Nice job finding those CIA chips at Versalia. I wonder how many they have? Supplies have to be limited since they probably haven't been made in 10 years.

Plaz

[taunusand]

Even danish i spelled incorrectly  :lol:

It is typical, I have 8520 chips, but the "standard" ic, used in A500/2000/CDTV... But those will probably be nice to have sometime.