Amiga 2000 video problem

[QuikSanz]

What fuse? and which 12v line?

Read post #20 in above linked thread...

[QuikSanz]

"You know the A520 is good cause you have tested it.
To gain confidence regarding the A2000, simply but carefully measure the voltage while the A2000 is running on both sides of F5, should be +12V on the PSU side & 0V on Pin 22 side."

So I should connect positive connector of multimeter to the fuse and negative connector to the RGB's Pin 22, right?
Or positive connector to PSU 12V and negative connector to the fuse/Pin 22?
The fuse was fine since I remember :confused:

Easy way. Set meter for 12VDC and measure across the fuse, A fuse should be a short, 0 Volts. If open "blown" you will see 12VDC.

[QuikSanz]

@Rip,

Continuity check is not reliable in circuit, your meter could just be charging a cap. Must be removed, at least 1 end from the circuit for continuity to be reliable.

[QuikSanz]

The fuse for that device is good. the 12V is being interrupted else where.

[QuikSanz]

He was measuring across the fuse. If it's good he will get 0V, assuming there is 12V getting to the fuse. That's why I suggested measuring the voltage at the fuse from a ground point. A quick check for voltage on both sides of the fuse will tell him if the 12V is present and if the fuse is good.

Exactly. A fuse should be a short, if open 12v, if closed 0v.

[QuikSanz]

Yes, notice the second one has no FCC ID#, not a US product at all.

[QuikSanz]

Possible to measure 12/5V on the video port?

You probably could but, the pins are close together and you don't want to short them together since you have to test it "live". If you don't have it there you will still need to backtrack. Check between the fuse and ground first, at least you'll know if it's hot. Ground is always a big trace running around the perimeter with some traces going into the other devices. You can use battery ground.

[QuikSanz]

If the MB is not getting 5V it won't run. Start from the power supply and move thru it's path down the circuit. probably a broken solder/trace or wire somewhere.

[QuikSanz]

Interrupted between here and there, follow the path. Likely a cable or a solder gone flaky.

[QuikSanz]

The link Mike posted works here, Check again.

[QuikSanz]

Bottom Right of the schematic you linked, "User 5V" start there and trace back or forward to find the fault.

[QuikSanz]

Persistence pays off and patience is a virtue.