so in the original pictures of Francesca, the power tube heater wires do not run parallel, as in from lug 7 to lug 7,
is there a reason for this,
am i seeing it wrong
my concern is because of a lot of hum i am getting from the amp, and if this is the reason
heater wire swap
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HobbswheresCalvin
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Re: heater wire swap
Yeah, if anything could be that simple. Your hum is coming from elsewhere unfortunately. This little detail can be worth a 5% improvement from my experience if that, and you would probably not even hear the change.
But I will suggest measuring the AC voltage to the filaments. If you can measure 3.2? on one side and 3,2? on the other side to ground, you are looking pretty good. If there is an imbalance here, then do some work. Notably use the 100 ohm resistors to ground instead of the filament supply center tap. Some add a balance pot, sure, but metal film resistors are typically 1% tolerance upon measure, a pot is not that close.
Have you talked about this hum before here? If not, keep talking. There are plenty of helpful poeple here.
But I will suggest measuring the AC voltage to the filaments. If you can measure 3.2? on one side and 3,2? on the other side to ground, you are looking pretty good. If there is an imbalance here, then do some work. Notably use the 100 ohm resistors to ground instead of the filament supply center tap. Some add a balance pot, sure, but metal film resistors are typically 1% tolerance upon measure, a pot is not that close.
Have you talked about this hum before here? If not, keep talking. There are plenty of helpful poeple here.
Most people stall out when fixing a mistake that they've made. Why?
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HobbswheresCalvin
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Re: heater wire swap
Thanks, ill check thatvall out when ibtake it back into the shop tomorrow.
I just finished the amp yeterday, so im still fine tuning things. And had noticed that wiring difference
I just finished the amp yeterday, so im still fine tuning things. And had noticed that wiring difference
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HobbswheresCalvin
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Re: heater wire swap
Ac voltages on the filaments measured out to be 3.5 and 3.5, is that close enough with a center tap? Or should i try to 100ohm resistors
Re: heater wire swap
Are you getting much 60Hz hum?
If not I wouldn't worry about it.
But many times an artificial center tap can be quieter because it is better balance than the center tap.
Since you do have a center tap, you could try a humdinger circuit with a 100 ohm rheostat (wirewound) pot and connect the center tap to the wiper and the two outside lugs to ground.
Then you can roll it back and forth and select the quietest setting.
Also if your heater voltage is 7 volts or higher you may want to consider dropping that voltage a little as it will make your tubes last longer.
If not I wouldn't worry about it.
But many times an artificial center tap can be quieter because it is better balance than the center tap.
Since you do have a center tap, you could try a humdinger circuit with a 100 ohm rheostat (wirewound) pot and connect the center tap to the wiper and the two outside lugs to ground.
Then you can roll it back and forth and select the quietest setting.
Also if your heater voltage is 7 volts or higher you may want to consider dropping that voltage a little as it will make your tubes last longer.
Tom
Don't let that smoke out!
Don't let that smoke out!
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HobbswheresCalvin
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Re: heater wire swap
http://www.newark.com/ohmite/res100e/rh ... dp/64K5659
Is that the part your talking about?
The only noise i get gets stronger as i turn up the volume. Its a white noise. Its gotten better as we fixed a few not so clean lead dresses, but i wish it could be a little quieter, as i tend to turn the amp up to at least 2 oclock. Playing metal on this amp.
Is that the part your talking about?
The only noise i get gets stronger as i turn up the volume. Its a white noise. Its gotten better as we fixed a few not so clean lead dresses, but i wish it could be a little quieter, as i tend to turn the amp up to at least 2 oclock. Playing metal on this amp.