It's been a long time since I have posted in this forum and this question really has nothing to do with modding but you guys have always be helpful and I have a dilemma I cant resolve. I have been restoring a Roland W-30 sampling keyboard with my son and recently tried to install a floppy emulator to replace the B drive that is stock. In doing so we made a complete mess and ended up having to solder every pin by hand on the floppy cable. Some of the traces were cut, solder pads ripped out etc. Anyway, we think we have it soldered correctly but when we were checking to make sure the cables were soldered to the correct parts using a DMM set to continuity we found that the +5.3V pads and the ground bus have continuity. Checking for resistance I find 28ohms. We have checked every solder joint over and over and can't find a short. It doesn't seem right to have continuity between the positive and negative rails. Looking at the schematic around r-21 it looks like positive and ground are connected via a 220uf cap. It seems that this would explain the continuity but I wanted to ask you guys first before I plug it in and watch the magic smoke. Any thoughts?
If you have low resistance between power and ground then there is a short and you will want to find it before applying power. The capacitor C1 should be an open circuit to DC voltages, and only allow transient signals the pass to ground. Your DMM should get an out of range error or read a very large resistance in megohms. A capacitor between power and ground is standard filtering on DC power busses. If the soldering lead to lifted traces it is potential that other components, not just the circuit board were damaged. Potentially you have a tough road of debugging ahead of you. Good luck.
Well after an exhaustive amount of checking, there were just no spots that were shorted so we fired it up. Sure enough it booted correctly with the floppy emulator. I was a huge PITA but in the end my son is ecstatic that he has a functioning 25 year old sampling keyboard. Now to get the SCSI drive working! Thanks for the feedback..
