Hey.
I just finished putting together a nice Asteroid. (still trying to come up with a simple name... wondering about Halley).
Anyways, the 6,3V heaters were too high, but a couple of 0,1R/5W'ers brought them down precisely to 6,3V.
However, the 5V's are high too, sitting about 5,95V.
I wonder if this is a bit problematic like the 6.3V heaters, and whether I should bring them down in similar way?
Regards
Anders
5V heaters high - dropping needed?
Moderators: pompeiisneaks, Colossal
Re: 5V heaters high - dropping needed?
It's a good idea for long tube life to run power tubes at just their specified heater voltage.
The story for preamp tubes is complicated.
The story for preamp tubes is complicated.
"It's not what we don't know that gets us in trouble. It's what we know for sure that just ain't so"
Mark Twain
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Stevem
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Re: 5V heaters high - dropping needed?
The accepted range for heaters is + or - 10%, and your at + 16%.
You will also have somewhat higher V+ due to this which may or may not be a issue dependant on the excess voltage rating you may have on your power supply filters.
A increase in V+ may also kick your preamp gain structure up more than you where shooting for .
If you have resistors on hand you can bring it down, of just resign yourself to having 6% less rectifier life, which to me really does not sound too bad, especially if you are running a 5U4 recto with its massive cathode and plate structure!
You will also have somewhat higher V+ due to this which may or may not be a issue dependant on the excess voltage rating you may have on your power supply filters.
A increase in V+ may also kick your preamp gain structure up more than you where shooting for .
If you have resistors on hand you can bring it down, of just resign yourself to having 6% less rectifier life, which to me really does not sound too bad, especially if you are running a 5U4 recto with its massive cathode and plate structure!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: 5V heaters high - dropping needed?
Or use a 6V rectifier tube: 6AX5GT, 6BY5GA are octal base - check the pin-outs
He who dies with the most tubes... wins
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Stevem
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Re: 5V heaters high - dropping needed?
Just note that the 125 ma rating of a 6AX5 is barely good enough for running 2 6v6 tubes and 4 or 5 ax7s.
Last edited by Stevem on Tue Jun 27, 2017 4:13 pm, edited 1 time in total.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: 5V heaters high - dropping needed?
I'll go ahead and state the heresy - two silicon diodes and a power resistor make a very convincing replacement for a tube rectifier. Better yet, this setup doesn't care if it's heater voltage is 5V or 50V. 
"It's not what we don't know that gets us in trouble. It's what we know for sure that just ain't so"
Mark Twain
Mark Twain
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Stevem
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- Joined: Fri Jan 24, 2014 3:01 pm
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Re: 5V heaters high - dropping needed?
Run both!
With this you will still get some good sag , and if the recto ever blows you can replace the fuse , yank out the blown recto and Just play on!
With this you will still get some good sag , and if the recto ever blows you can replace the fuse , yank out the blown recto and Just play on!
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When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: 5V heaters high - dropping needed?
Indeed. But if the 5V winding is rated for 3A, you run run two 6AX5 in parallel.
He who dies with the most tubes... wins
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Stevem
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- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: 5V heaters high - dropping needed?
Lol, oh ok!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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billyz
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Re: 5V heaters high - dropping needed?
What about a bucking transformer. Solve all your high voltage issues.