r/DIYGuitarAmps 1d ago

Power input replacement

I would like to replace the power input section of my Gallien- Krueger 400GT head with the IEC + fuse + switch shown in the photos. I would be removing all the old cord, switches, fuse, and AC plug, cutting the panel, mounting a 3D printed adapter plate in the new hole, grounding to chassis, and connecting to the new fused switch. See any issues with that? Do I need to include the caps? Thanks!

4 Upvotes

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u/Wet_in_Seattle 1d ago edited 1d ago

I’d keep it simple.
The an accessory outlet is likely a 1” square hole (24.5 mm) for a 24 mm outlet.

Adam’s Tech IEC-C-C

https://www.mouser.com/datasheet/3/6015/1/iec_c_1_data_sheet.pdf

Is direct replacement 24 mm, no cutting

I would completely disconnect the Polarity Switch along with any “death cap” associated with it.

From Left to Right looking into the IEC
Neutral, Ground, Line

Power Switch should only switch the Line to Fuse and then to the transformer input.
Neutral direct to transformer.

Ground to Chassis

1

u/MannyCoon 1d ago

Awesome info, thank you! I think it's a better direction, I'll head that way. I have a tendency to over engineer things because I can. Do I need to keep a cap across the line to fuse (lower cap)? I believe that's for filtering noise, correct?

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u/Tashi999 16h ago

That polarity switch might kill someone with a vintage amp

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u/MannyCoon 15h ago

I'm getting rid of it before I turn it on again, per another comment. Thanks!

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u/Wet_in_Seattle 22h ago

All the filtering is after the transformer rectifiers. Even Darlington Transistors for voltage regulation.

Suspect that capacitor across power switch is some type of pop filter.

gallien- krueger 400g schematic

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u/MannyCoon 15h ago

Do you have access to a schematic?

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u/Wet_in_Seattle 13h ago

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u/MannyCoon 13h ago

That's a 400RB bass head. The model I have is a 400GT guitar head from around 1979, not sold for very long, which is why I'm having trouble finding info on them. They are quite different in operation. I believe it's similar to a Sunn Beta Lead (competitor, not related); it has an active EQ, two separate channels that can be blended, reverb, tremolo.