Soundcraft DCP 100 PSU schematic

[bce]

Hello,
I have a Soundcraft DCP100 PSU which is creating a hum. R5 is burnt out and unreadable, it is connected in parallel with a cap between chassis ground and 0v. Has anyone got schematic or have a look inside one or give me an idea of a value from experience of this part of a PSU.
Any help greatly appreciated
thanks
bce

[Jazz P Bass]

It may be a 100 ohm resistor between circuit ground and chassis ground.

That resistor being open should not 'create' a hum.

Check each supply voltage for excess Vac ripple.

If they are steady then the PSU is more than likely not the problem.

(Sounds like you had a ground loop issue that took out the resistor)

[bce]

Thanks,
because of its age I have already replaced all electrolytics in the psu with new ones, it ran quiet for a few hours, then when hum started I noticed R5 burnt out. I rechecked board for shorts etc and all is ok. I ran the desk with a known good PSU (not a DCP100) and all was quiet. The only bands on R5 that I can see are a red at one end and gold at the other, then all is burnt black in the middle.