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About that GI-7b.

Takes closer to 2kV to get any real power gain from it. A sweep-tube box that uses a full-wave doubler for B+ won't achieve that easily.

An amplifier that used a full-wave bridge to get 800 or 900 Volts can be reconfigured to use a full-wave doubler and get enough B+ for that tube. But only if the higher voltage doesn't exceed the insulation on the transformer's windings.

Easy enough to tell in advance. Take the HV winding's wires loose and put a couple of kV on them. If the insulation holds up, you're probably good to go.

That's how we converted this Eagle 525 for that tube.

It's a pretty invasive mod.

This one proved that it's more work than it's worth.

73

<blockquote data-quote="nomadradio" data-source="post: 651622" data-attributes="member: 22">About that GI-7b.Takes closer to 2kV to get any real power gain from it. A sweep-tube box that uses a full-wave doubler for B+ won&#039;t achieve that easily.An amplifier that used a full-wave bridge to get 800 or 900 Volts can be reconfigured to use a full-wave doubler and get enough B+ for that tube. But only if the higher voltage doesn&#039;t exceed the insulation on the transformer&#039;s windings.Easy enough to tell in advance. Take the HV winding&#039;s wires loose and put a couple of kV on them. If the insulation holds up, you&#039;re probably good to go.That&#039;s how we converted this Eagle 525 for that tube.<img src="https://imageshack.com/a/img96/8093/eagle525hvboardsm.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" /><img src="https://imageshack.com/a/img152/3244/eagle525inputcircuitsm.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" />It&#039;s a pretty invasive mod.<img src="https://imageshack.com/a/img256/21/eagle525naketsm.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" />This one proved that it&#039;s more work than it&#039;s worth.<img src="https://imageshack.com/a/img137/9559/eagle525topviewsm.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" />73</blockquote>

[QUOTE="nomadradio, post: 651622, member: 22"] About that GI-7b. Takes closer to 2kV to get any real power gain from it. A sweep-tube box that uses a full-wave doubler for B+ won't achieve that easily. An amplifier that used a full-wave bridge to get 800 or 900 Volts can be reconfigured to use a full-wave doubler and get enough B+ for that tube. But only if the higher voltage doesn't exceed the insulation on the transformer's windings. Easy enough to tell in advance. Take the HV winding's wires loose and put a couple of kV on them. If the insulation holds up, you're probably good to go. That's how we converted this Eagle 525 for that tube. [IMG]https://imageshack.com/a/img96/8093/eagle525hvboardsm.jpg[/IMG] [img]https://imageshack.com/a/img152/3244/eagle525inputcircuitsm.jpg[/img] It's a pretty invasive mod. [IMG]https://imageshack.com/a/img256/21/eagle525naketsm.jpg[/IMG] This one proved that it's more work than it's worth. [IMG]https://imageshack.com/a/img137/9559/eagle525topviewsm.jpg[/IMG] 73 [/QUOTE]

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