Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: PharmRock on April 02, 2022, 11:38:29 am
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In the final stretch of getting this EF86/18-watt "hybrid" finalized. I am looking at several schematics, and unless I'm reading them wrong, they don't match up with respective layout.
For example, Sluckey's 18-watt files seems to be the only schematic and layout I've found that are properly "matched" as far as how the speed control lugs are wired: Lug 3 (left-most lug) goes to ground; Lugs 1 and 2 are connected to the R24 (470k).
https://sluckeyamps.com/18w/18w.pdf (https://sluckeyamps.com/18w/18w.pdf)
However, when looking at the other layouts and schematics I've come across either in the schematics library here on EL34 world or on 18watt, the schematics are all consistent, but the layouts all have the speed control Lug 1 wired to ground, and Lugs 2 and 3 connected to R24.
Schematic: https://el34world.com/charts/Schematics/files/Marshall/Marshall_18watt_schem.pdf (https://el34world.com/charts/Schematics/files/Marshall/Marshall_18watt_schem.pdf)
Layout: https://el34world.com/charts/Schematics/files/Marshall/Marshall_18watt_layout.pdf
So is this a layout error that was just perpetuated when builders tweaked/modified the circuit?
If anyone can shed some light on this and help me figure this out, I'd appreciate it.
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Ain't no big deal though. Just swap the two wires if the pot works backwards.
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Ain't no big deal though. Just swap the two wires if the pot works backwards.
Yeah there's not much too it if its the other way around. The chassis I have has a folded "lip" that goes over the tops of the pots, so its a little tricky to get in there if I have do undo anything. Guess I'll find out soon enough.
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Ain't no big deal though. Just swap the two wires if the pot works backwards.
Well I got it all wired up today, and it looks like I'll be swapping the wires around, as the speed is at its highest rate when its on zero.
The intensity sounds great, but I'd like to widen the range of the speed to get a little slower than it it is right now on its slowest setting. Something a little more "swampy".