This is actually a piece of a thread on a Dumble-style preamp but that discussion petered-out on the circuit. This is specific to a problem I'm having with the relay activation on the footswitch so I thought I'd bring it over to the multi-disciplinary section of the forum.
The second attachment is a schematic with a block diagram of the preamp and of the footswitch. There are three relays activated by two DP3T stomp switches. OD is the overdrive, H is the HRM (OD with dedicated tone controls) relay and Both runs the regular overdrive back through the HRM overdrive. In the lower diagram, OD, H and Both are the negative side of the relay coil. They are 5v DC relays and I have about 6v available through a pretty stout supply -- but maybe not stiff enough. There is also a preamp boost (not shown) and an indicator lamp (also not shown) that pull some juice. I could easily use a different source for the indicator if needs be.
I tried to set this up so when I switch #1 only, only the overdrive is activated and the LED on that switch lights. That works fine. Stepping on #2 only activates the HRM relay, the Both relay and the OD relay. The LED on that switch is illuminated through the connection on the both switch. That also works fine.
The hitch is when I cut them both on at the same time. Both LEDs come on but the both doesn't have enough juice to activate the relay. I'm a bit surprised (confused is a better word) because in the two button configuration, the HRM relay is open so only the OD and Both are being used. I can short the relay to ground by touching it with a screwdriver held against the chassis which will hold the field until I cut the power but it can't turn on by itself. Unused relays on the board hold at 6.1 volts and that only sags slightly when one or two are kicked on.
I've tried three or four configurations and resistor values with the same result. The one you see is the latest.
Your comments and suggestions are most welcome. It might be something simple like changing some values in the supply. It could be that this is asking too much of things and a completely different approach would be better. I've gotten, "huh?" a couple of times too
Thanks for looking, Skip
PS The first attachment is the whole schematic if that helps, sh