[R-390] 6T4F

[Glen Galati]

I lloked in my NAVSHIPS manual for the R-390A and it shows onlythe 3TF7 for
RT-501. I tend to believe that the 3TF7 was the predecessor to the TJ311M01
which is contrary to the FEDLOG as explained below. We nood some real
AMPERITE experts to explain the 'THRESHOLD VOLTAGE'
and WHY the 220ma spread vs the 20ma spread in operating currents. I have
Date codes on the 3TF7 of 5/66 & 9/66 vs 7/69 up to 1/81 on the TJ ballast.
DC Resistances vary on th TJballast from 10.8 to 14.5 ohms using a Fluke 87.
Of course I would rather measure this using a 4-wire set up to get better
accuracy. Does anyone out there have a AMPERITE CATALOG on these  Current
Regulating Resistors or Ballasts?

73,
Glen Galati           eldim@att.net
Tacoma, WA
----- Original Message -----
From: Norman Ryan <nryan@intrex.net>
To: Glen Galati <eldim@worldnet.att.net>; <r-390@mailman.qth.net>
Sent: Wednesday, July 24, 2002 9:39 PM
Subject: Re: [R-390] 6T4F


> Hi, Glen,
>
> Nice research!
>
> I have an Amperite TJ311M01 that measures cold at 13.3 Ohms DC
> resistance on my Fluke DMM 8024B.  I'm patiently waiting for it to
> exhaust so I can replace it with a 3TF7.  :-)
>
> All seriousness aside, the above ballast doesn't carry the designation
> "3TF7."  Thus the FEDLOG may have assigned a different NSN when the 3TF7
> appeared.  (I'm assuming 3TF7 is a newer designation for Amperite's
> catalogue number TJ311M01.)
>
> It came out of a spare IF deck.  I'm too lazy to pull my working R-390A
> out of its case to do voltage checks and substitution with a 3TF7 to see
> if the regulated tubes are getting similar voltage, but expect it's
> close enough for government work.
>
> The lettering is that notorious stuff that wipes off easily.  I couldn't
> make out that any lettering is gone.  What's there is is there-- that
> is, no smudges.
>
> Hope this helps.
>
> 73 de Norman KG4SWM
>
>
> Glen Galati wrote in part:
> >
> > Here is some interesting info on the the 3TF7 Current Limiting Resistor
as
> > specified for the R-390 Series. The FEDLOG description specifically
> > identifies this as Application = R-390/URR,  AC/DC, 0.040 to 0.260
Amperes,
> > 10.2 Volts Threshold,  9-Pin Miniature with T-6-1/2 envelope. NSN
> > 5905-00-259-1964, and was last procured $118.27. Measured DC Resistance
is
> > approximately 12-12.75 Ohms.
> > Now, here is an interesting twist to the story.  Amperite PN: TJ311M01,
NSN
> > 5905-00-681-4707; DC, Current Range 0.31 to 0.33 Amperes, 8.0 Volts
> > Threshold,  9-Pin Miniature with T-6-1/2 envelope. The FEDLOG states
"WHEN
> > EXHAUSTED USE 5905-00-259-1964" which is a 3TF7.  Hmmmmm! Makes you
> > wonder-What we really need here is to do a close scrutiny of the TM/TO's
for
> > the R-389, R-390, R-390A. and R-391 Part List and see what part number
and
> > stock number was listed.
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