GX4000 - Has 12v power but no output

[P5ychoFox]

A GX4000 I recently acquired powers up using the 12v PSU and just shows a black screen.
Using the 5v from the CM14 monitor it won't even power up.
I have gone over the board and re-soldered all chips but no change.
Is the thing beyond repair?

[IanS]

I've never used one, but it looks like the GX4000 was supplied with an 11V power supply http://www.cpcwiki.eu/index.php/File:GX4000_09.jpg. It was never intended to be powered from 5V from a CM14.

Did you have a cartridge in when powered on?

[IanS]

Turns out I was wrong - http://www.cpcwiki.eu/index.php/File:GX4000_06.jpg. It can be powered from a CM14.

[Bryce]

Is L1 present on the board? Measure the resistance from the 5V plus input to the power switch input. It should be pretty close to zero. After the power switch both the 11V and 5V supply share the same route, so the problem can only be at the 5V power socket or the inductor.

Bryce.

[P5ychoFox]

Sorry, yes the PSU is 11v not 12v. Thanks I'll open it up again and do more testing.

[P5ychoFox]

Is L1 present on the board? Measure the resistance from the 5V plus input to the power switch input. It should be pretty close to zero. After the power switch both the 11V and 5V supply share the same route, so the problem can only be at the 5V power socket or the inductor.

Bryce.

Thanks Bryce. Just got time to have a look at the board. L1 is present and resistance from 5v to power switch input is .79 Ohm (resistance between 11v socket and power switch input swings around 100 Ohm - not sure if that's normal). The inductor shows good continuity but could be faulty I assume. Any advice as to how to fix the console is welcomed.

[Bryce]

That all sounds fine. There must be something wrong somewhere else. You can send me it if you want me to take a look at it, but I doubt that financially makes sense, you can pick them up very cheaply these days.

Bryce.