Amiga 2000 motherboard repair

[retrostyle]

Hi

Any one in the uk repair amiga 2000 boards and a psu

The board shows a black screen i did remove the battery and cleaned the area also i have a psu from a 2000 system and the fuse keeps blowing not sure why

Albert

[B00tDisk]

Hi

Any one in the uk repair amiga 2000 boards and a psu

The board shows a black screen i did remove the battery and cleaned the area also i have a psu from a 2000 system and the fuse keeps blowing not sure why

Albert

Sounds like bad caps on the PSU motherboard.  I'd bet my bottom dollar.

[Oldsmobile_Mike]

Sounds like bad caps on the PSU motherboard.  I'd bet my bottom dollar.

Agreed.  I mis-read this and started typing up a different response (along the lines of "black screen + known battery leakage = probable corrosion in the CPU socket"), but I'd worry about the PSU first.

Make sure you have a clean and functioning power supply before moving on to the motherboard issues.  Easy option would be to just swap it for a replacement, but obviously we don't know your budget or skill level, or if you have available spare parts to swap with, etc.  OP needs to be prepared to post some pictures and do a lot more troubleshooting if they hope to solve this themselves.  

[retrostyle]

[attach]5676[/attach]

[attach]5677[/attach]

[Acill]

Hmm... At first look that leak doesnt look like it was very bad. Interesting thing is the CPU socket looks like its using header pins and the socket was replaced sometime back in its life.

[Castellen]

psu from a 2000 system and the fuse keeps blowing not sure why
Albert

The usual cause for this is at least one of the four diodes on the AC input bridge rectifier has gone short circuit.  They'll often be 400V diodes, which is fine for 230V mains (AC peak is +/- 325V), but voltage spikes in excess of 400V can cause sudden failure.

And sometimes the high voltage DC switching transistor (there will be one or a pair of them on a heat sink) may have gone short circuit, and in the process this can also damage the input bridge rectifier due to the high fault current that flows at power on before the fuse blows.

It's pretty much the same fault finding process for most switch mode power supplies.  I wrote this guide on A3000 power supply repairs - see the bottom of the page.

[orange]

check traces, have a look at this:
http://www.amiga.org/gallery/index.php?n=2390

have you tried the psu with dummy load?

[retrostyle]

Hi

Whats a dummy load?

[Pat the Cat]

Basically a resistance that simulates the computer, the bit being powered by the PSU. A set of resistors that simulate the resistance of the various voltage rails of the power supply.

It's a lot safer than using the real computer to trouble shoot the power supply - if it starts kicking off weird and wonderful voltages, your real equipment doesn't get damaged.

https://en.wikipedia.org/wiki/Dummy_load

[darkage]

Best not to attempt fixing your power supply by yourself unless you absolutely know what your are doing.  Need to make sure caps are fully discharged and of course unit is unplugged before work.   might be easier/quicker to replace the powersupply, especially if you have a spare ATX powersupply around the house.  You can get ATX adapter.

http://amigakit.leamancomputing.com/catalog/product_info.php?products_id=998


For the reason why the fuse blows, could be powersupply or what ever is connected to it. (motherboard, etc).   Might be a good idea to check with the motherboard schematic and go through the affected area with a test meter to test for continuity.

http://www.amigawiki.de/doku.php?id=en:service:schematics

Inspect for obvious shorts. i.e. -  metal case, or rogue screw touching somewhere it shouldnt on motherboard etc..

[retrostyle]

Hi

yes i will buy a atx adapter thanks for info

[orange]

Hi

yes i will buy a atx adapter thanks for info

you can build one yourself:

http://www.amiga.org/gallery/index.php?n=1637