[R-390] Amelco R390A help, RT301 current regulator tube

[Studiumtelecom S.Rocha]

Thanks to all ! I used method number 4, with a solid jumper and a pair of
12BA6, I found a regulator tube for usd$28.00 here in Rio, so I think it
worths buying it also in the future.

The interesting point is that I have all spares tubes for this radio,
except the only which was defective!

Another question: should I replace the antenna connector for a SO-239 UHF
type?
Regards and a Happy New Year to all!
Sam Rocha

Em dom, 26 de dez de 2021 00:26, Jim Whartenby via R-390 <
r-390 at mailman.qth.net> escreveu:

> Sam
> It seems that Collins thought that the ballast tube was not necessary,
> according to the following passage.
>
> From page 15 of the R-390 Engineering Report, September 15, 1953
>
> "The ballasttube (3TF7) operates on a current of 290 to 330 mils and holds
> this current within ±10 mils for input voltage variations of ±15%. This
> reducedthe 15% variation to approximately 3%. There is some question if
> afilament regulator is necessary in these receivers since the
> oscillatorsare very good even without regulation. However, since the
> stability wasa big factor in this design and since the factor of tube aging
> was notknown, the regulator was included."
>
> Present day line voltages are quite steady when compared to what was
> available back in the 1950's or earlier.  When my 3TF7 fails, and it will,
> I plan to use either method 3 or 4 since I tend to be a bit "thrifty!"
> <grin>
>
> HNY, Jim
>
> Too much agreement kills a chat.  E. Cleaver
>
> -----Original Message-----
> From: Renee K6FSB <k6fsb.1 at gmail.com>
> To: Studiumtelecom S.Rocha <battcharger at gmail.com>; R-390 Forum <
> r-390 at mailman.qth.net>
> Sent: Sat, Dec 25, 2021 3:59 pm
> Subject: Re: [R-390] R390A help, RT301 current regulator tube
>
> I believe you are working on an R390A, to my knowledge amelco did not
> make the R390
> there are several methods
> 1. use 47 Ohm 5W (Sand) Resistor IIRC in the pins of RT301
> 2. build a current limiter using LM317 set at 300ma
> 3. use a 12BY7 (or similar) that still has functioning filaments...plug
> and play
> 4. use 12BA6 in both V505 and 707 and jumper the pins in RT301 solid
> wire jumper
> 5. there was someone making a SS replacemet
> 6. obtain a new/used ballast tube 3TF7
> 7. I am certain I left off a couple
>
> personally I used #2 all that was needed was a ground wire, i built it
> in/on a 9 pin tube base
>
> I think the Y2k manual may have this ...or is it Y3k by now?
> If you follow the schematics I am certain you will see what is needed.
> Merry Christmas
> Renée
>
>
> On 12/25/21 1:28 PM, Studiumtelecom S.Rocha wrote:
> > Dear members,
> >
> > I am restoring an  R-390 /URR Amelco serial 1596 and the V505 and  V701
> > 6BA6 do not have the filament voltage, so I would like to know how to
> > replace the RT301 current regulator tube.  Any other suggestion will be
> > greatly appreciated !
> >
> > Merry Christmas  and a much better New Year for all  !
> >
> > Regards,
> > Sam Rocha
> > Py1dkw
> >
> > Em sáb, 25 de dez de 2021 04:53, Larry H <larry41gm at gmail.com> escreveu:
> >
> >> I have updated our website's (r-390a.net) 'references' page.  I added a
> >> link to the Navy's R-390As tech ref of Apr, 1970 on  Nick England's
> >> website.  The link is at the bottom of the 'US Navy Manuals' section in
> >> our 'references' page.
> >>
> >> I have also added meter face files, a TIF file for the VU meter face
> and a
> >> Visio file containing 'white' faces for the VU and C/L meters.  All
> >> these can be found on the 'references' page on our website in the
> >> 'drawings' section.  They also have matching PDF files for viewing as
> the
> >> Visio and TIF files are only downloadable (oooops, I forgot the PDF file
> >> for the TIF file - I'll add it in soon).
> >>
> >> Happy Holidays.
> >>
> >> Regards, Larry
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