Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: FREYES_7 on March 06, 2025, 06:52:40 am
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Hello all!
I'm building a 5F1 from scratch, as there are no available kits in my country, using the stewmac guide and rob robinettes how tube amps work page,
PT input is 220V @50Hz, Hammond 291AEX
I'm running the electrical tests now, stewmac says DC output from the 5Y3 should be 479V and I have 464V, it seems right but
Preamp voltages should be 1.65V in cathode and 235V in both preamp plate
I have 6.8V, 264V in plate 2 and 414V in plate 1 :D :help: :dontknow: :BangHead:
I haven't connected the output jacks, so there is no earth connection in the triode 1's cathode. Also I added a 22uF cap in parallel to the 1.5k cathode resistor, as Rob's suggest 25uF and 22uF was the option I had at local store
Both 100k resistors are ok, the 10k and 22k resistors seems to be ok too,
I don't think I broke the thermodynamics law, so any insight on why is plate 1 voltage and cathode voltage values are so high, will be appreciated
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Don't worry. Voltages will get right when you install the input jacks.
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Cool, thanks!