Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: okguitarman on June 04, 2019, 07:43:40 pm
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Why not chose a lower voltage or is there a reason to use all those dropping res.
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That's just not the messy booger way. :icon_biggrin:
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I'm trying to figure out how to change it Voltage @ what ma. without them.
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Well you still need a high voltage PT to give you 430V for the node A (probably output plates). Then you need a resistor to drop down to the 344V needed at node B (screens).
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just seems real high for 4x el84
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Not when you consider the screens are running at 342V.
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Ok got it thanks!
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1) Once a box of 47 Ohm resistors fell off a truck in the road by my house. For years I was using strings of 47r for *everything*. Maybe M-B had a heap of 365r to use up.
2) That string is running 0.2W per piece, so can use 1/2W resistors, which used to be the cheapest type. In fact an odd value like 365, it might be they found an overstock cleared-out at a penny a bucket.
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In addition, they probably figured that 11 small resistors was probably cheaper than one big power resistor for the mass production. Plus, they could squeeze in an extra 10u in the middle of the string, to make the supply filtering better (making up for the lack of a choke).
Things you normally don’t have to consider as a DIY:er...