[Boatanchors] Acceptable filament voltage range

[Rick Poole WA1RKT]

Good afternoon, Alex.

Well, that can't be done with any of these three 516F-2's I have here, of widely varying vintage, powering two different KWM-2A's.  All of them show a low filament voltage, anywhere from 5.95 to 6.1.  They all show high LV (300-315) and HV (900-910 no-load / receive mode).  This is with an input voltage, out of the wall, of nominally 118 VAC.  This is with one analog meter (Simpson 260) and three different DMMs.

I could boost the input AC but that would also boost the LV and HV which people here are saying is already excessive.

Rick WA1RKT

----- Original Message -----
From: "Radio AI2Q" <ai2q at roadrunner.com>
To: "Rick Poole WA1RKT" <wa1rkt at comcast.net>, boatanchors at mailman.qth.net
Sent: Friday, January 9, 2015 12:00:30 PM
Subject: Re: [Boatanchors] Acceptable filament voltage range

Rick, when K9BWI and myself serviced Special Forces KWM2A transceivers 
during the war in Vietnam, we noticed that low filament voltage resulted in 
partially inoperative sets and low output sets.

Keeping filament voltage at 6.3 vac, to my thinking, is mandatory.

Vy 73, AI2Q, Alex
Member: ARRL, FOC, RSGB, CWops, QRP-L, Antique Wireless Association, the 
Southern Maine Area Amateur Radio Team (formerly the New England Radio 
Discussion Society), DXCC Honor Roll, 16ØM DXCC, 8ØM DXCC
http://ai2q.org

----- Original Message ----- 
From: "Rick Poole WA1RKT" <wa1rkt at comcast.net>
To: <boatanchors at mailman.qth.net>
Sent: Thursday, January 08, 2015 10:13 PM
Subject: [Boatanchors] Acceptable filament voltage range


> Anybody know what the average acceptable filament voltage range is for 
> most small receiving tubes as in, for example, a KWM-2?
>
> I've checked some of the data sheets and they only give a nominal 6.3V 
> range, they don't specify the minimums (or the maximums).
>
> Each of my three Collins 516F-2 power supplies gives from about 6.0 down 
> to occasionally as low as 5.9 volts RMS to the filaments at the radio, 
> which is around 5% under spec (this, by the way, is with the power supply 
> plugged into the wall without a variac or bucking transformer).  I can't 
> find any specifications that tell me if this is too low, or not.
>
> Thanks...
>
> Rick WA1RKT
> Londonderry, NH
> Catch me on 14.300 MHz Intercon / MMSN most days
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