dos wrote: ↑
April 26th, 2020, 9:06 pm
Does anyone know how to fix ground loop monitor interference on these? I just got one imported from China and it had a 220v to 110v step down transformer installed and the earth ground wire severed before the transformer (China is on 220). I'm in the US and we have 120V power so I removed the transformer. Using the original two prong power cable resulted in the cab itself becoming "hot", giving small shocks when you touch it, so I fixed the ground wire and installed a 3 prong cord (following the schematic in the manual, but using the cord's built in ground instead of Japanese standard separate ground prong). Cab is no longer hot but I see the typical ground loop wavy lines onscreen. On my NAC this is simply fixed by removing the grounding wire from the monitor frame but on this cab I don't see any obvious ground wire attached to the frame. Multimeter confirms the frame is tied to ground, it's my first metal cab, I assume the body itself is tied to ground and so is everything touching it including the frame?
Fixed by tying field ground to logic ground on the PSU, oldest trick in the book but I initially thought it was not necessary since there was continuity between them, picture is nearly perfect now except for a mild version of the exact same jailbars on the left as this user
, so I'll be recapping/reflowing the chassis when I can.
e: as this is the U4 owner's thread, might as well post a pic:
The panel is yaton's repro, the blue is too dark so I'm on the lookout for an original. The side stripes and memory card/headphone surround seem to be original, I added repros of the rest of the decals. It has obviously been repainted at some point and not very well and it has some dents. Yaton or somebody replaced the original fluorescent with a not very nice bare LED panel and I prefer original equipment so I'm also on the lookout for the entire fluorescent fixture. The wire for the MV-LED PCB was missing but it fired up once I added one. The quick disconnects for the controls were crimped on to the terminals or something and disintegrated when removing the green fake sanwa buttons and zippy sticks he had in there to put in original seimitsu parts, so now I'm waiting on some .110 and .187s so I can actually play. The sound wiring was changed from MVS stereo to JAMMA standard mono so I need to fix that, as with a proper MVS board sound only comes from the left speaker. Overall I'm pretty happy with it considering I've wanted one for years and they're pretty hard to find in the US.