Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rsr on February 22, 2018, 11:49:54 pm
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For reference, i have these for a starting point
standby switch
http://el34world.com/charts/SwitchDPST.htm (http://el34world.com/charts/SwitchDPST.htm)
bjr conversion wiring diagram
http://el34world.com/Hoffman/files/Hoffman_BluesJunior.pdf (http://el34world.com/Hoffman/files/Hoffman_BluesJunior.pdf)
I am using the original input transformer from the bjr amp and a 3 position standby switch as above.
So to wire up the input transformer and standby switch....
- the IT has 2 red wires that go to the corners of the bridge rectifier. I assume it doesn't matter which wire goes to which corner right?
- the IT has 2 brown wires which i think are shown as yellow in the wiring diagram and those go to the bias diode and to the same ground lug as the power cord ground. Again, i assume it doesn't matter which of the brown wires goes to which.
- the IT has 2 green wires. forgetting about the standby switch for a minute, is the wiring diagram saying to
take one of the green wires -> 180Ohm resistor -> LED
-> 47 Ohm resistor on tube board -> tube socket pins
and the other green wire goes -> other end of the LED -> to the other 47 Ohm resistor on the tube board -> tube socket pins
Do i have that close to right? Could someone clarify how the IT green wires are supposed to be connected?
And, ultimately then, how would this be adjusted to incorporate the standby switch?
The picture has labels for "AC In", "PT Primary" and "HT in" and "HT out" on the switch.
Is "AC In" the black or white wire from the power cord?
I guess "PT Primary" is the black wire from input transformer and that rather than connecting the white power and IT wires directly, one or both go to whatever "HT in/out" are. But what are "HT in/out".
Heaters maybe? But which is in, and which is out? I'm confused.
I think this is the only part of the wiring that i don't get. The output transformer bit seems clear.
So if i can straight this out, i think i'll be good.
Thanks for your help here
roger
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Refer to page 2 of Hoffman's document... And pretend that the four lug power switch is really the power/standby switch. Remove both white wires from the right side of the switch. Connect the white wires together and insulate.
The picture has labels for "AC In", "PT Primary" and "HT in" and "HT out" on the switch.
Is "AC In" the black or white wire from the power cord?
Neither. "AC in" will be the wire from the fuse to the switch. "PT Primary" is the black wire from the PT. "HT In" will be the top red wire labeled "to Bridge AC". "HT Out" will be an additional wire that goes to the board and connects to one of the AC terminals on the bridge. (The lower red wire labeled "to Bridge AC" will still go to the board and connect to the other bridge AC terminal.)
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Nomenclature police alert! The tranny is a Power Transformer (PT). An Input Transformer is for signal entering an amp.
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Thanks sluckey,
i think that is exactly what i needed to know
much appreciated.
rsr
Refer to page 2 of Hoffman's document... And pretend that the four lug power switch is really the power/standby switch. Remove both white wires from the right side of the switch. Connect the white wires together and insulate.
The picture has labels for "AC In", "PT Primary" and "HT in" and "HT out" on the switch.
Is "AC In" the black or white wire from the power cord?
Neither. "AC in" will be the wire from the fuse to the switch. "PT Primary" is the black wire from the PT. "HT In" will be the top red wire labeled "to Bridge AC". "HT Out" will be an additional wire that goes to the board and connects to one of the AC terminals on the bridge. (The lower red wire labeled "to Bridge AC" will still go to the board and connect to the other bridge AC terminal.)
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Sorry sluckey, just one more thing here.
When you say "top red wire" and "lower red wire"...
They're both red. Does it matter which is which, and if so, how can i tell them apart?
Thanks
Neither. "AC in" will be the wire from the fuse to the switch. "PT Primary" is the black wire from the PT. "HT In" will be the top red wire labeled "to Bridge AC". "HT Out" will be an additional wire that goes to the board and connects to one of the AC terminals on the bridge. (The lower red wire labeled "to Bridge AC" will still go to the board and connect to the other bridge AC terminal.)
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When you say "top red wire" and "lower red wire"...
They're both red. Does it matter which is which, and if so, how can i tell them apart?
Referring to Hoffman's drawing, it's easy to tell top from bottom. But when you actually get inside the amp you'll have to flip a coin. :wink:
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Well, since only one of the wires is long enough to reach over to the BR, i'll say that one is "heads".
But, what are the consequences if it's wrong?
When you say "top red wire" and "lower red wire"...
They're both red. Does it matter which is which, and if so, how can i tell them apart?
Referring to Hoffman's drawing, it's easy to tell top from bottom. But when you actually get inside the amp you'll have to flip a coin. :wink:
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There is no wrong.
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There is no wrong.
Ok, phew.
Thanks.