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Old 21st May 2010, 08:40 PM   #1
tomchr is offline tomchr  Canada
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Default Recommended spacing for multiple 5AR4's


I'm building a power supply for a stereo amp. The supply will have two 5AR4 tubes in it for rectification. These tubes run rather hot during normal operation so I'm a little concerned of placing the tubes close together.

What's the minimum recommended spacing (center to center) of 5AR4 tubes?

The tubes are SOVTEK brand new stock.


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Old 21st May 2010, 09:15 PM   #2
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THe old Marconi-OSRAM data sheets sometimes gave separation specs. For instance, designers choosing the KT66, operated with 30W pounding the anode, and about 8,5W of heater, were invited to cut their hole-centres 3.5 inch [90mm] asunder.

The Sovtek drops only about 20V, but the rms current through it for its maximum 250mA of dc, is nearly 500mA when Cin is 50 .. 60uF. So you have about 10 anode watts and 10 heater watts, in a smaller bulb. I'd say the 3.5 inch would be about right here too.
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Old 24th May 2010, 06:04 PM   #3
tomchr is offline tomchr  Canada
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I was secretly thinking 3~4 inches (75~100 mm). So 3.5 sounds good...


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Old 25th May 2010, 02:45 AM   #4
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Default 5ar4spacing

A Hammond H100 power supply has the two 5AR4's spaced 4" apart, center to center, with a FP can cap in between. They were very careful to ground their caps to the appropriate part of the rectifier feeding it. Ground leads are explicit, bare, and very short. No ground current runs through the chassis, although it is at the same voltage as the returns.
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Last edited by indianajo; 25th May 2010 at 02:46 AM. Reason: define measurment
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Old 25th May 2010, 03:36 AM   #5
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Default Spacing

The only recommendation I've seen is one and a half envelope widths spacing for tubes........No notations for Rectifyer vs. Power tubes.

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