[NJARC] Philco 37-650 RF Question

Sun Feb 26 23:19:32 EST 2006

Harry- Thanks for the reply: I was pretty certain the
color is grey- really odd, however... The place I got
them doesn't even carry that value! It is definitely
not silver. I just this moment took another look, and
compared it to another resistor of a known value, and
then rechecked it with a multimeter: It is not
3,300,000,000 as previously suspected: the band which
looked grey to me, actually is a wishy-washy brown,
bodering on tan: which puts it at 330 ohm... colors
look diferent in different light... Now I feel
dumb...lol... So, that reverses the situation! Is it
possible something may have been damaged by too little
resistance in that part of the circuit?(#46)

Thanks again: Glad I took a 42nd look... Now I have
useful spares for a later job.

Scott

--- Harry Klancer <klancer2 at comcast.net> wrote:

> Visit our web site - See http://www.njarc.org
> _______________________________________________
> Scott,
> 
> A couple of comments.
> 
> I don't think your resistor was orange-orange-grey
> because 3300 Meg is not a standard value and
> grey is not used as a multiplier anyway. Was it
> silver?
> That would make the resistor 0.33 ohm - unusual,
> but probably available.  If it was the resistor that
> connects one of the output tube grids to the bias
> voltage, which is the only place I see a 330K in the
> schematic, and it was 0.33, I doubt any damage
> was done. Anyone else want to comment?
> 
> As for the 9K. What using a 10K would do is slightly
> raise the voltage at the 2nd grid of the 6A8
> tube - probably 2 volts or so. This grid essentially
> operates as the oscillator plate and runs at a
> couple
> of hundred volts, more or less, so it probably
> wouldn't
> make a lot of difference. It would also lower the
> screen
> voltage of the first 3 tubes, but again, not by
> much.
> 
> Also, you asked about the wire before. Skin effect
> at such low frequencies is negligible, so stranded
> vs. solid doesn't really make a lot of difference.
> 
> Since it's not the 16A padder, have you checked the
> dc resistance of the bc oscillator coil itself? That
> could
> definitely affect the operation of the oscillator,
> although if it was
> much out of spec, the oscillator wouldn't work at
> all.
> 
> Guess we're all still assuming it's the oscillator.
> Any
> other symptoms?
> 
>                              Harry Klancer
> 
> 
> At 02/26/2006 02:35 PM, you wrote:
> >Visit our web site - See http://www.njarc.org
> >_______________________________________________
> >My problem with the resistor wasn't the age- I
> >replaced all of them- it was the wrong band... It
> was
> >supposed to be a 330k ohm, which has an
> >orange-orange-yellow band arrangement. What got put
> in
> >place was orange-orange-grey, or 3,3 and 8 0's- or
> >3,300,000,000ohm! 3,300M ohm! Which was a little
> high
> >resistance...
> >
> >I can confirm what you say about age, however: I
> have
> >a box of NOS resistors from the 1950's/1960's, and
> >while many are still very near correct, and within
> >tolerance, many more are out of spec to a great
> >degree. These usually donate their leads to little
> >projects... These are all carbon comp resistors.
> >
> >Now, another resistor question. I replaced one of
> the
> >power resistors, a wirewound 9k ohm/2watt(#61) with
> a
> >combination: a 4.3k/2watt and a 4.7k/2watt, both
> metal
> >oxide. I also replaced a neighboring(#60) 10k ohm,
> 2
> >watt with a 10k/2watt metal oxide. I replaced #60
> >again with a 10k/5watt wirewound power resistor,
> but
> >not #61, as I could not find a 9k ohm. Would a 10k
> ohm
> >wirewound power resistor be a better one to put in
> >place, and could this have anyting to do with my
> >problem?
> >
> >Thanks
> >Scott
> >
> >--- Mbeeferman at cs.com wrote:
> >
> > > Visit our web site - See http://www.njarc.org
> > > _______________________________________________
> > > Having done a little research in this area, I
> tend
> > > to agree with Jim.  A
> > > rating is a rating, and functional differences
> > > between a 1-watt carbon composition
> > > and 1-watt film resistor should not exist. 
> Problems
> > > at high frequencies come
> > > into play only with wirewound substitutions.
> > > I tend to believe that Bob's problem may have
> been
> > > in another area.
> > > The problem with carbon composition resistors,
> > > especially NOS, is related to
> > > how critical a tolerance is required.  The
> process
> > > that creates carbon
> > > composition resistors leaves them under stress.
> > > Over the years, this stress is
> > > eventually relieved (I won't go into the
> physical
> > > details) and the resistor can be
> > > left significantly out of tolerance.  As an
> > > experiment, randomly select 10 NOS
> > > carbons from your junk box that are greater than
> > > 20-30 years old and take
> > > some measurements...you might be surprised.
> > > In any restoration project, I always`use the
> same
> > > philosophy...it might take
> > > some extra time, but it is surely worth it....
> > > 1.  Verify what you install and don't depend on
> the
> > > markings.
> > > 2.  Verify what you remove (unless the component
> is
> > > completely destroyed) and
> > > ensure it makes sense with regard to the circuit
> or
> > > the schematic.
> > > 3.  Don't make any more than 3 replacements
> without
> > > firing up the set to
> > > ensure that you're not introducing more problems
> > > than you're trying to fix.
> > >
> > > _______________________________________________
> > > NJARC mailing list
> > > NJARC at mailman.qth.net
> > > http://mailman.qth.net/mailman/listinfo/njarc
> > >
> >
> >
> >"War is an ugly thing, but not the ugliest of
> things; the decayed and 
> >degraded state of moral and patriotic feelings that
> thinks nothing is 
> >worth war is much worse. A man who has nothing for
> which he is willing to 
> >fight, nothing he cares about more than his own
> personal safety, is a 
> >miserable creature who has no chance of being free,
> unless made and kept 
> >so by the exertions of better men than himself."
> John Stuart Mill, 'The 
> >Contest in America', Feb. 1862
> >
> >
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