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Author Topic: Taming my Shack Voltage From 252Vrms to 240Vrms  (Read 22666 times)
N1UK
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Posts: 2219




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« on: May 14, 2014, 01:42:14 PM »

I was surprised to see that the 240V 30 amp supply to my shack is actually sitting at 252 Vrms.  This is causing the filament voltages and HV values to be out of specification for my amplifiers.

I am seriously thinking of installing a buck auto transformer to tame the voltage back to 240V.


http://www.jeffersonelectric.com/s3/site/catalog/buckBoost.pdf

http://www.galco.com/buy/Jefferson-Electric/416-1181-000

The 416-1181-000 transformer would be excellent overkill I think

Do people think that this will be a worthwhile exercise.

Mark N1UK

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AA4PB
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Posts: 15017




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« Reply #1 on: May 14, 2014, 02:05:28 PM »

The voltage is only 5% over. What is the spec on the amp?
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Bob  AA4PB
Garrisonville, VA
N1UK
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Posts: 2219




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« Reply #2 on: May 14, 2014, 02:26:16 PM »

Tentec doesn't seem to give a figure and Kenwood says 10% but I am already out of spec on the Kenwood filament voltage range of 5%


Mark N1UK
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K6AER
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Posts: 5689




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« Reply #3 on: May 14, 2014, 02:37:47 PM »

I take it you are using an amplifier with 3-500's. What is the actual filament voltage at the tube pins?
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N1UK
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Posts: 2219




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« Reply #4 on: May 14, 2014, 03:06:52 PM »

I took some measurements...the amp is sitting on the kitchen table so no rf at this stage


HV no load              3320 Vdc
HV at Ip=160mA     3105Vdc


240V input..amp off   253.5Vrms

Tube 1 Vfil  idling  5.53Vrms
  at Ip 160mA       5.48 Vrms

Tube 2   idling  5.50 Vrms
at Ip 160mA    5.45 Vrms

http://www.eham.net/ehamforum/smf/index.php/topic,96806.0.html

Mark N1UK
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W8JX
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Posts: 13268




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« Reply #5 on: May 14, 2014, 03:50:02 PM »

I took some measurements...the amp is sitting on the kitchen table so no rf at this stage


HV no load              3320 Vdc
HV at Ip=160mA     3105Vdc


240V input..amp off   253.5Vrms

Tube 1 Vfil  idling  5.53Vrms
  at Ip 160mA       5.48 Vrms

Tube 2   idling  5.50 Vrms
at Ip 160mA    5.45 Vrms

http://www.eham.net/ehamforum/smf/index.php/topic,96806.0.html

Mark N1UK

I would not be concerned but you could merely add about .03 ohm of wire to each tube.   
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
N1UK
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Posts: 2219




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« Reply #6 on: May 14, 2014, 04:34:01 PM »

OK I will leave well alone for now

Mark N1UK
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W1AN
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Posts: 23




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« Reply #7 on: May 15, 2014, 06:58:44 AM »

You are sizing the transformer way too big. For a buck/boost transformer you need only consider the voltage decrease/increase and the max current for the transformer.
I wouldn't be too concerned about a little increase over recommended filament voltage for the tubes. Just make sure you are using the correct primary taps transformer on the amplifier.
Most line voltages I've seen recently are about the same as yours or more.
73, John, W1AN
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KD0REQ
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Posts: 2364




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« Reply #8 on: May 15, 2014, 09:01:45 AM »

uh, Variac?  constant-voltage transformer?

or maybe two aspirin.  that's not outlandish a rise.  bad enough retuning as you sweep the band, but one hand on the Variac all the time is not impressive unless you're reshooting the Frankenstein movie.
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N1UK
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Posts: 2219




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« Reply #9 on: May 15, 2014, 09:17:14 AM »

Quote
You are sizing the transformer way too big. For a buck/boost transformer you need only consider the voltage decrease/increase and the max current for the transformer.

Yes I see but I was figuring that a bigger transformer would provide a stiffer supply, give me plenty of head room and run cooler.


Mark N1UK
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W3RSW
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Posts: 606




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« Reply #10 on: May 15, 2014, 09:51:59 AM »

All rigs I've known for US market have 240 as the upper limit tap.

Anyway, down here we have two main voltage seasons.  AC season where voltage drops to 230 and heating season ( natural gas) where voltage is closer to 240.

I leave stuff at the 240 tap.
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Rick, W3RSW
N1UK
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Posts: 2219




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« Reply #11 on: May 15, 2014, 10:07:18 AM »

Quote
Anyway, down here we have two main voltage seasons.  AC season where voltage drops to 230 and heating season ( natural gas) where voltage is closer to 240.

I will measure my 240V but I imagine that my voltage is going to be pretty constant. I have my own 240V 400 amp drop to the house fed by what I believe is called MV at around 13KV I think.


Mark N1UK
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WA5VGO
Member

Posts: 69




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« Reply #12 on: May 15, 2014, 05:59:49 PM »

What's wrong with contacting your power provider and asking them to adjust the voltage? They don't want excessive voltage anymore than you do. 

Darrell
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KI6LZ
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Posts: 738




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« Reply #13 on: May 15, 2014, 06:10:43 PM »

Duh. Why didn't I think of that. The power company should be able to fix that.
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KH6AQ
Member

Posts: 7769




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« Reply #14 on: May 15, 2014, 07:23:02 PM »

252 VRMS is within the voltage tolerance limits of ANSI C84.1, range A. Range B allows 254 VRMS.

http://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/voltage_tolerance.pdf
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