Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Ledzepp007 on April 17, 2017, 06:29:58 pm
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Hi,
I am rebuilding one of my early attempts at a tube amp... a Marshall Plexi SLP that I built from a Mojotone kit. I did a... poor job. It worked (most of the time), but it was time to redo it, Hoffman style. I did not like the Mojo layout, but I am having difficulty visualizing the layout for the Hoffman style. Attached is a draft of what I thought might work. If you all wouldn't mind giving me feedback, that would be very helpful.
Instead of using a bridge rectifier, I used a two 1N5408 setup in my example with the PT center tap grounded. Can these two diodes handle the rectification duties of a 100W amp?
My PT has the following specs:
178/0/178 @ 300ma
103V Bias tap
3.14/0/3.14 @7.5A
Thanks!
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> My PT ...178/0/178 @ 300ma
That PT and that rectifier will give 250V DC.
I don't think this is what you want.
I also have concern about the all-around-town path through rectifiers to first cap. But let's figure the base circuit before fretting the routing.
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the PT you have requires a full wave bridge for that application.
you need to use a full wave bridge with CT. you can build the bridge with 4 x 1N5408 diodes, or just buy a bridge module rated for 800V or higher.
copy the model 2203 marshall PS and layout - no need to re-invent this. :icon_biggrin:
http://el34world.com/charts/Schematics/files/marshall/Marshall_2203%20JMP%20Master%20Volume%20Lead%20100watt.gif (http://el34world.com/charts/Schematics/files/marshall/Marshall_2203%20JMP%20Master%20Volume%20Lead%20100watt.gif)
--pete
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This is what I figured. I'll have to mix the original power supply with the Hoffman style layout.
Thanks for the help.
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Hoffman has info on the 100W Plexi power supply right here. Look around. It's not always easy to find.