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.
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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. 
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Stevem
- Posts: 4568
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
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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
- Posts: 4568
- Joined: Fri Jan 24, 2014 3:01 pm
- 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.