5F6A 18343 Output transformer question ?

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JTM
Junior tube assistant
Posts: 85
(2/2/04 6:47 pm)
 5F6A 18343 Output transformer question ?
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 I have a question about the secondary wiring in Doug's 5F6A layout.

The 18343 transformer secondary has an 8 OHM Green/Yellow,a 4 OHM Green, a 2 OHM White, and a Common Black wire.

The layout shows the Green 4 OHM tap going to the 27K resistor on the board.

My question is,
does the 4 OHM Green tap stay connected to the 27K resistor regardless of what tap is used for the speaker?
Or does the tap needed for the speaker take it's place ?

Thanks for any help.

Tim

 
Rotting27
Junior tube assistant
Posts: 103
(2/2/04 7:55 pm)
 ReL
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 The feedback circuit is always connected to one and only one tap. Of course, you could wire it so that the feedback sources from whichever tap you select (with a switch) for different tones.

For stock purposes, hardwire the feedback to one tap (the four ohm in this case) which stays connected no matter which tap the speaker is connected to.
 
GroundhogKen
Forum Moderator
Posts: 2238
(2/2/04 8:52 pm)
 Re: ReL
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 "The layout shows the Green 4 ohm tap going to the 27K resistor on the board."

True, BUT...

...the proper feedback arrangement for a Bassman is 27K from the 2 ohm secondary. I believe the wire color in Doug's layout refers to the 022855 output transformer which only has a 2 ohm output--Black common and Green ( 2 ohm ).

If you use a 27K with the 4 ohm tap you will have twice as much negative feedback and the amp will be pretty stuffy sounding. If for some reason you must use the 4 ohm tap for NFB, use a 47K resistor.


Ken
 
JTM
Junior tube assistant
Posts: 86
(2/3/04 6:20 am)
 Re: ReL
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 Thanks for the help guys.

I'll just use the 2 OHM tap from the 18343.  


Tim
 
 
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