B&K8500 300W load fail , Help needed please :)

[eevblogfan]

Hey

Nope it ain't mine , but I started to perform callibration for that unit . I remember the voltage range didn't let me test it above 20V or so .. I can't remember what I did but I think I managed to increas it to the full voltage range ,

sorry I am writing from my home and that case is open since 2 monthes or so . hence I can't remember the ranges of the unit ...

well .. so what's the fail ?

the unit doesn't draw current at all ,

* the display is fine ]
*the controls are responsive


I can't remember what else I've checked but nothing too obviuse here ...

so I asked for permission to open the device . I got green light and so I did ..

Inside there was no gate resistors blown , and no other *clear* vissualy harmed component ... not one I could see anyhow ..

can the fets be burned out , Although there was no power on the supply ? ( I think it aws set to 5V . and Current set to max 2A )

is it safe to put voltage between one of the fets and limit the current to few mA .. and then slowly raise the voltage to say 5V ? ..

I am asking because I don't have the schema In order to see id ther's something obviuse to be caution about ...

befor even that attempt ... I have meassured the gate(s) voltage(s) while setting the load to draw 0.5A or so .. and the voltages should be the max the driver can output here right >? ( nothing connected to the front binding posts .. )  and I got nothing but 0V ( or 30mV or so .. )

the menu is okay , so the Cpu is okay right ?
can someone please help me with new path to look for ?

service manual with full schematics is going to help here .. just saying

thank you in advance

[saturation]

Backtracking, you received the unit damaged?  Also can you post photos of the issues you wrote about, it'll make it easier to understand.