Ok, since a few of you have expressed interest in this mod here's how it's done. Sorry the pcb pics aren't better. There are a few extra resistors on the BM board that should be left eventhough they aren't on the JTB schematic, the ones labeled pulldown and LED. They don't have any effect on sound. Also, the BM uses two power supply filter caps (C13) instead of the one in the Bender. This shouldn't really make much if any difference but you can change those if you want to as well. Lastly, I show that a trace should be cut. That's optional I don't think it matters. If you cut it and it doesn't sound right then reconnect it. EH was nice enough to put to empty holes right where that cap (C9) goes. I don't know why, maybe they anticipated us wnating to do this mod
. Other than that it should be straight forward. Remove all the parts labeled for removal and compare all the resistors with those in the schematic to find the ones that need to be changed. Small differences like 470pF vs 500pF or 470K vs 510K probably don't make much if any audible difference. Tolerances in components could make them be about the same in the end anyway. As far as using mylars for the .1 caps, that's just what the original Jumbo used. Use electrolytics or polystyrene or whatever you want. I forgot to label C10 and C11 on the pic, but they don't change anyway. Ok, that's it, feel free to ask me if you have any questions.
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. Other than that it should be straight forward. Remove all the parts labeled for removal and compare all the resistors with those in the schematic to find the ones that need to be changed. Small differences like 470pF vs 500pF or 470K vs 510K probably don't make much if any audible difference. Tolerances in components could make them be about the same in the end anyway. As far as using mylars for the .1 caps, that's just what the original Jumbo used. Use electrolytics or polystyrene or whatever you want. I forgot to label C10 and C11 on the pic, but they don't change anyway. Ok, that's it, feel free to ask me if you have any questions.Invalid Link Removed
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...well I checked the orientation of my transistors, and found out that I had them in wrong. The Fairchild BC184C's are CBE (when looking at the flat face), where as some other transistors are EBC. My PCB was orientated to EBC. I should have known something was up, as it sounded okay but didn't quite have the gain or volume that I expected. It sounds much better now, with more volume and fuzz.
