[R-390] My 'new' '67 EAC is now "on line" 8^) Ballast Tube question.

[Joe Foley]

I agree on the ballast tube, normal function is to
come on bright at first then go dim so only a few
places are lighted.

Not sure what your problem is though too much current
draw sounds right.

Joe





--- Barry Hauser <barry@hausernet.com> wrote:
> Phil wrote:
> 
> >Well, it looks like all the trials and tribulations
> associated with this
> PTO
> >are over.
> 
> That's good news!  Now that your skill-sets are at
> their peak, let's
> everybody send Phil a Cosmos to fix 'n tweak.
> 
> >The receiver alignment went very well,
> 
> By now the radio probably feels bad about running
> you through the ringer, so
> went easy on 'ya.
> 
> >..a new 3 wire power cord
> > has been installed and the unit placed in its
> CV-979 cabinet.   The
> >alignment was already very close and just needed a
> light tweaking.  A
> modest
> >improvement in gain was noted when some of the Xtal
> oscillator trimmers
> were
> >adjusted.
> 
> >Only one minor glitch was noted during alignment. 
> The 28 MHz band was
> dead,
> >removing its Xtal and tightening up the pins of the
> socket cleared that
> >problem.  Whew, thought I had a bad Xtal at first.
> 
> I've found the same thing as well as some bad xtals
> here and there.  The
> crystal sockets vary, but not the greatest in the
> later receivers.  Probably
> the stamped cupped type. Not much contact area and
> metal is none too
> springy.  Fix is easy.  You probably just staked
> them down a bit.  Was it
> just the 28 MC band?  Is that the one solo crystal
> -- usually two or three
> bands are involved.  Anyway its fixed.  They tend to
> loosen up when the
> radios are moved or shipped and the crystals
> actually wobble in those
> holders.  Further compromised as a tiny bit of
> oxidation will cut them out.
> 
> <snipped>
> >BALLAST TUBE QUESTION:  In all the R-390A's that
> I've had previously (that
> >still had the ballast tube) I seem to recall the
> filament having just a
> dull
> >glow in only a small part of the filament.  This
> one glows fairly brightly
> >over nearly the entire length of the filament and
> makes me feel uneasy in
> >that I'm afraid it's nearing the end of its
> lifespan (seems I recall
> reading
> >that was an indicator).  No, my line Voltage is
> under 120 VAC, especially
> >this time of day with everybodies A/C running.  Do
> I have cause for
> concern?
> >Perhaps I should start looking for a 12BH7 tube (I
> did the 12BH7 mod
> >while recapping the IF strip).
> 
> My experience is that they don't glow much after
> power-up.  The ballast may
> be good but you may have excessive current draw. 
> Since you replaced nearly
> everything else that could affect that, I strongly
> suggest you check the two
> tubes involved -- especially the one in the PTO. 
> Yes -- lightning
> (element/filament shorting) does strike twice, (Phil
> found the previous PTO
> tube shorted).  Two possible reasons,  offhand --
> continued bumping/moving
> of the PTO as you were adjusting the linearity
> and/or the replacement tube
> may have come from the same lot with a latent
> defect.
> 
> Now that things are settled in, test those tubes
> again in the tester.
> Normally it's not best practice to leave them in the
> tester too long, but
> let them sit and tap as you go through the shorts
> test.  Another
> possibility -- something in the wiring harness. 
> Maybe you should measure
> the current draw with the ballast in place.
> 
> Do others agree about the bright ballast situation?
> 
> Barry
> 
> 
> 
> 
> 
> 
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