Blues Briefcase

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

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crgfrench
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Re: Blues Briefcase

Post by crgfrench »

Replaced the 125 Ohm 8 Watt bias resistor with a 150 Ohm 12 Watter.
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JMPGuitars
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Re: Blues Briefcase

Post by JMPGuitars »

crgfrench wrote:
Thu 07/25/19 1:08 am
Replaced the 125 Ohm 8 Watt bias resistor with a 150 Ohm 12 Watter.
Those are good resistors. I have the 20W version on my EL34 36W Superlite TMB.
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crgfrench
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Re: Blues Briefcase

Post by crgfrench »

crgfrench wrote:
Wed 07/03/19 7:43 am
There is room for another OT in the briefcase so I'm thinking of adding a Classictone 40-18031 or a Hammond 125ESE like this:
20190703_082112.jpg
...So I'm finally getting back to my briefcase project after it sat on the back burner all summer. I'm just ordering the 125ESE now.
One issue I see with my dual OT concept is: i believe ithe setup in my schematic would result in 2 in-phase signals being combined when the switch is set to the single-ended position. This could be problematic? I'm going to try it anyway unless you guys all think it would blow up my workbench...

EDIT: I meant to say, "I believe it would result in 2 out-of-phase signals going into the same side of the transformer when in SE mode. This could be problematic?"
Last edited by crgfrench on Sun 09/01/19 11:12 am, edited 1 time in total.
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geoff 1965
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Re: Blues Briefcase

Post by geoff 1965 »

have a look at this schematic,he has the power section switchable between single end and push/pull with the same OT but LTP but you might be able to improvise!
p18sc02.jpg
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crgfrench
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Re: Blues Briefcase

Post by crgfrench »

geoff 1965 wrote:
Sun 09/01/19 11:08 am
have a look at this schematic,he has the power section switchable between single end and push/pull with the same OT but LTP but you might be able to improvise!
p18sc02.jpg
Thanks Geoff. The switching on this and on mine is all after the PI so the PI type probably doesn't matter. The ampmaker one is interesting, works by turning off one output tube which would also significantly lower the Wattage. Mine keeps both output tubes running and would keep similar Wattage in double ended or single ended mode.
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crgfrench
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Re: Blues Briefcase

Post by crgfrench »

Glacial pace continues, got the 20 gauge wires soldered to the board today, everything but the shielded input lines.
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Re: Blues Briefcase

Post by crgfrench »

Finally decided it's too tight to shoehorn the 5E3+ PCB into this Hammond 1444-10 chassis. Would not have even had room for my second input jack. Now I'm working with my V2 Fullerwell protoboard ...much better fit! Also not sure I need shielded input lines with only a 3" run from the jacks to the sockets, but this cable is fun to work with.
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