MB DR (3 channel ) Schematics, missing parts
- Thread starter weeest
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There doesn't seem to be much missing. The schematic sucks though in it's depiction of the lm3914. The LM3914 receives a voltage on pin 5. Depending on how much voltage there is either pin 1 or pin 17 has voltage going through it. That voltage enables either channel 1 or channel 3. When there is no voltage to the LM3914, no voltage is going out to any pin. The LM3914 is a voltage meter diode driver. Basically that fancy level indicated on your old sterio used a chip similar to that. The more voltage in, the more led's light up. Mesa used this to enable switching on more than one channel. The road king and nomad's uses this same chip.
I think the part 2 of the switching schematic is actually the voicing page. The foot switch is very similar to the foot switch the nomad series uses. I've simulated the schematic below and it seems like it fills in the missing segments of the released schematics.
I think the part 2 of the switching schematic is actually the voicing page. The foot switch is very similar to the foot switch the nomad series uses. I've simulated the schematic below and it seems like it fills in the missing segments of the released schematics.
msi said:
Let's say Mesa switching designs are... unconventional. Their muting circuit is stolen from other amp-makers and patented on the sly. Mesa wanted the footswitch pedal to change channels using a single wire, and they used the LM3917, an led bar driver. Not the way I'd do it nor would any other manufacturer, but I guess it works. The reason they didn't draw the rest of the LM3917's connections is because they're pretty straightforward. Those jacks aren't the only things missing off the schematic...
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