Big Red PSA: Power supply switch wiring

I recently picked up what I believe to be a later model big red 2 slot. It has an MV2F mobo, unpainted control panel, and the curved button layout, no memory card or headphone jacks exposed.

I also have what I believe is an older model big red 2 slot. MV2 mobo, mem card and headphone jacks, black control panel, offset button layout.

The power supply in the new cab was not original, it had an onboard switch, no external hookup. I ordered a replacement, but it was taking too long so I pulled the PSU out of my old cab in the mean time. When I hooked it up it blew the fuse. When I shorted the fuse it tripped the breaker.

What happened was the pin out from the power supply for the external switch was different. It was causing the hot to be connected to neutral.

On my original power supply, brown and black coming off the PSU are neutral and hot. Blue and white are the return neutral and hot respectively. I only found this out by opening the PSU.

So for the cabinet wiring, instead of red to red black and yellow to yellow black, the power switch had to be rewired to yellow to red, and yellow black to red black.

I will update this with more comprehensive information as I find it.

The new happ power supplies that have the remote switch connection do come with a pin out.

I too just picked up a big red cab! MVS-4-25 (ver. 3) If you need help identifying what cab you have, check out this site:

http://www.hardmvs.com/xml/usa/usCabs.htm

They also have the PDF manuals complete with pinouts and wiring diagrams.

Hope this is of some help to ya! This is my first cab restoration so I still have alot to learn!

If I am understanding this right sounds like the cab was re-wired for a different PSU than it should have. I would agree and hit up a wiring diagram to see how it should be correctly wired. Was the original PSU a peter chou? USP-11-150x is normally what they had. Happ sells both replacements with the power-switch built into the PSU or 4 pin external for cab mounted switches.