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Old 4th March 2005, 01:54 AM   #1
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Default Why?

...do diodes have 5V heaters rather than the typical 6.3 or 12? Enquiring minds want to know.

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Old 4th March 2005, 02:22 AM   #2
Colt45 is offline Colt45  Serbia
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So that Idiots dont use the 6.3v supply for other heaters as the supply for the diode's filament, therefore making all the heaters biased at +400v :P

Nah.. 5U4, 5Y3, etc are very old designs, back when most tubes used a 5v filament supply. I think.

I you get a diode with a cathode (damper for example) they use 6.3v heaters.
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Old 4th March 2005, 02:27 AM   #3
anatech is offline anatech  Canada
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Hey Colt45,
I like your first answer the best. Knowing your average human, you could be right! Just think how many tubes and lives were saved due to the difference.
Still, they make 5AQ5A's and the like.

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Old 5th March 2005, 02:29 PM   #4
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5AQ5s, 3AU6s, 7DJ8s, etc. were used in TVs with series heater strings. A bunch of tubes with the same heater current draw whose heater voltages totalled to 120 V. were wired together.

AMOF, the "A" seen in 7 and 9 pin mini type designations (6AU6A, etc.) indicates controlled heater warmup time. The "A" types are for series heater string service. Profit matters, you know. Save the expense of filament windings in the power trafo. Never mind that when any given heater fails, the whole string goes dark.
Eli D.
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Old 5th March 2005, 07:30 PM   #5
anatech is offline anatech  Canada
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Hi Eli,
Yes, and they are used in other things as well. Point is, a 5V heater may be waiting to make someone famous, posthumously. That's what Colt45 was poking fun at I think. There is always some truth in a joke, no?
I think I saw 5AQ5A's used on a computer based amp. Cool and scary at the same time. Computer guy + a couple hundred volts. Wow.

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