[Boatanchors] A "Glow tube (VR tube) question.

[wa4tukhr at comcast.net]

I agree you should monitor the B+ line in and the regulated voltage out.

Also, measure the series resistor to the VR tube to see if it has changed value. Then measure the voltage drop across the resistor to indirectly measure its current.  Total current through the VR series resistor should be in the normal range for the tube assuming not much current is supplied to the regulated load. The current should probably be in the 5 to 20 ma range for OA2's and the like and 10 to 30 ma for octals. If you have replaced the rectifiers with solid -state diodes and not included dropping resistors the B+ into the regulator could be much too high.

I've seen VR tubes in commercial products (broadcast transmitters) last in excess of 75,000 hours.  They sometimes glow between the envelope and plate when they are pulling excessive current. Some tubes will pulsate and are candidates for replacement. They don't last forever but they can last a very long time.

Some tube testers, (Hickok 539?) will allow you to vary the applied voltage to the VR tube under test and watch the regulated voltage output; otherwise, in circuit tests should tell you enough.

Pat
wa4tuk


> Phil,
> I would replace the VR tube and start monitoring the B+ line ASAP.
> The VR color change could be an indication of B+ intermittent excessive
> or lack of current somewhere.
> bob...w2ami
> www.qrz.com/callsign/w2ami
> 
> 
> ----- Original Message ----- 
> From: "Philip Atchley" <beaconeer at elite.net>
> To: <boatanchors at mailman.qth.net>
> Sent: Wednesday, May 12, 2004 11:41 PM
> Subject: [Boatanchors] A "Glow tube (VR tube) question.
> 
> 
> > Hi,
> > I have a Hallicrafters SX-71 that I completely overhauled/re-capped a
> couple
> > years back.  It has had "many" hours of reliable operation ever since
> then.
> > However, recently I've noticed that sometimes, not often, I'd get little
> > bursts of static or a crackle out of the speaker when I have the BFO on.
> To
> > date I've been unable to locate the source as I could never duplicate it
> > when it's on the bench (always the case in an intermittent).
> >
> > Anyway, I digress.  When listening I leave the lid propped up a couple
> > inches for better ventilation (runs a lot cooler.  Last night I was
> > listening to Shortwave and heard a brief "crackle" from the radio, sounded
> > like regular static.  I "normally" wouldn't think much about it figuring
> it
> > was atmospheric.
> >
> > However, I "thought" I saw a small flash of light inside the receiver out
> of
> > the side of my eye.  I looked into the top of the set and saw the VR tube
> > (VR-150/0D3) was glowing OUTSIDE the plate, towards the top of the tube.
> > Not a big section glowing, but on the outside none-the-less.  The NORMAL
> > pinkish/purple glow inside the tube's plate was still there.  After a
> couple
> > moments the outside quit glowing and everything looked normal again.  This
> > abnormal glow DID NOT seem to have any apparent effect on reception (set
> > didn't drift in frequency).
> >
> > QUESTION.  I don't think I've seen a VR tube do that before (glow on the
> > outside).  Is that indicative of a VR tube failing or should I look
> > elsewhere for a problem (like high B+ etc)?  I don't have a spare
> VR-150/0D3
> > to try out at this time.
> >
> >
> > 73 from the "Beaconeers Lair".
> > Phil, KO6BB
> >
> > DX begins at the noise floor!
> > Merced, Central California
> > 37.18N  120.29W  CM97sh
> >
> > _______________________________________________
> > Boatanchors mailing list
> > Boatanchors at mailman.qth.net
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> > ** List Administrator - Duane Fischer, W8DBF/W9WZE **
> > ** For Assistance: dfischer at usol.com **
> > $$ For vintage radio info, see the HCI web site $$
> > http://www.w9wze.org
> >
> >
> 
> 
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> ** List Administrator - Duane Fischer, W8DBF/W9WZE **   
> ** For Assistance: dfischer at usol.com **         
> $$ For vintage radio info, see the HCI web site $$      
> http://www.w9wze.org    
>