[Amps] HIGH FILAMENT VOLTAGE

[Jim Hargrave]

There are several ways to fix this one. I mentioned Diodes because I know it works. It may not be the best solution, but is a simple way to obtain a volt or so drop. A bridge rectifier takes up a small chassis space and a 50 amp block will support 2x3-500 or 2x4-400 tubes. They are in the $3 +/- range

 

Here is an example.

http://www.newark.com/multicomp/gbpc5006/bridge-rectifier-single-phase/dp/51T1789?MER=sy-me-pd-mi-alte

 

 

73, Jim – w5ifp at gvtc.com

 

>> -----Original Message-----

>> From: w8hw at comcast.net [mailto:w8hw at comcast.net]

>> Sent: Sunday, December 11, 2016 2:08 PM

>> To: Jim Hargrave <w5ifp at gvtc.com>; 'amps'

>> <amps at contesting.com>

>> Subject: Re: [Amps] HIGH FILAMENT VOLTAGE

>> 

>> 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 –  <mailto:w5ifp at gvtc.com> w5ifp at gvtc.com

>> 

>> >> -----Original Message-----

>> >> From: Amps [ <mailto:amps-bounces at contesting.com> mailto:amps-bounces at contesting.com] On Behalf

>> Of

>> >>  <mailto:w8hw at comcast.net> w8hw at comcast.net

>> >> Sent: Saturday, December 10, 2016 6:41 PM

>> >> To: Mike Waters < <mailto:mikewate at gmail.com> mikewate at gmail.com>;

>>  <mailto:amps at contesting.com> amps at 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:  <mailto:amps at contesting.com> amps at 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

>> >>  <http://www.w0btu.com> www.w0btu.com

>> >>

>> >> On Sat, Dec 10, 2016 at 5:58 PM, kenneth Johnson

>> < <mailto:wa6rtp at hotmail.com> wa6rtp at 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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