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Re: [Amps] HIGH FILAMENT VOLTAGE

To: "Jim Hargrave" <w5ifp@gvtc.com>, "'amps'" <amps@contesting.com>
Subject: Re: [Amps] HIGH FILAMENT VOLTAGE
From: <w8hw@comcast.net>
Reply-to: w8hw@comcast.net
Date: Sun, 11 Dec 2016 15:07:43 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Caution... Yes you can but... In the case of 3-500 tubes each diode would dissipate 8.5 watts (14 amp * .6v) so for Continues use, you would need 15 watt or better yet 25 watt diodes and that would be chassis mount. They are not cheep. Less than that, they could short and you would never know it as the amp might still work, just the fill voltage issue not fixed. Additionally voltage spikes can happen causing the diodes to fail where 18 ga wire survives.

73, Bruce, W8HW


-----Original Message----- From: Jim Hargrave
Sent: Saturday, December 10, 2016 23:38
To: 'amps'
Subject: Re: [Amps] HIGH FILAMENT VOLTAGE

You can reduce the voltage with parallel back to back diodes in series with each tube filament.
20 amp/40v diodes are cheap and do not present a mounting challenge.

73, Jim – w5ifp@gvtc.com

-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of
w8hw@comcast.net
Sent: Saturday, December 10, 2016 6:41 PM
To: Mike Waters <mikewate@gmail.com>; amps@contesting.com
Subject: Re: [Amps] HIGH FILAMENT VOLTAGE

Mike is correct. I have used 27 inch of #18 wire on 3-500 tubes many
times and got voltage down to 4.97 volts for each tube. The wire is
just one big resistor and gets warm, but works fine. The life of 3-500
drops real fast with high filament voltage.

73, Bruce, W8HW
========================

-----Original Message-----
From: Mike Waters
Sent: Saturday, December 10, 2016 19:15
To: amps@contesting.com
Subject: Re: [Amps] HIGH FILAMENT VOLTAGE

No need to use #12. Smaller wire = more compact. A shorter piece
of #16 (or maybe even #18), would do fine.

Depends on the current.

73, Mike
www.w0btu.com

On Sat, Dec 10, 2016 at 5:58 PM, kenneth Johnson
<wa6rtp@hotmail.com> wrote:

> I used # 12 wire …total of 24 inches long  wound in a two inch coil
> placed in each filament lead .
> this  droped  the voltage on my henry 2k-3  filaments into
specifation.
> your problem is finding enough room to get the coil in there.  at
any
> rate …a length of wire is the way to go.
>
>
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