[time-nuts] 6CW4 Nuvistors on eBay...

paul swed paulswedb at gmail.com
Sun May 2 22:11:59 UTC 2010


Well just one O those days.
Heavens knows why but I had 7 nuvistors and I don't have any idea when I
picked them up.
6CW4s and a few other types. But lo and behold one 7587.
Plugged in getting signal and osc locked. Its definitely not a hot tube but
it proved the tube was indeed the issue.
Checked several ugly looking caps but they were actually good. ESR and
value.
Will replace any how so I can cause myself some real trouble.
Thanks


On Sun, May 2, 2010 at 6:01 PM, J. Forster <jfor at quik.com> wrote:

> And the 7587 even has a plate cap! LoL.
>
> There might be RF chokes in the Nuvistor filament line. Worth a look.
>
> FWIW,
>
> -John
>
> ===============
>
> > Indeed there are.
> > And even 7587s thats the TRF frontend. In one of the units V3 appears bad
> > all Rs are good voltage high on plate, 0 cathode current. But oddly when
> I
> > swap v1 into position same effect so somethings odd. Or my methods not
> > correct.
> > The other units working. Had to replace a shorted 6.2 V zener.
> > The 100 kc vco /lock osc is awful touchy.
> > Pretty amazing the units pretty hot sensitivity wise -80 dbm.
> > Interesting afternoon. Way in the deep corner of the basement I think I
> > may
> > have a nuvistor or two. Time to see what they are.
> >
> > On Sun, May 2, 2010 at 4:14 PM, Burt I. Weiner <biwa at att.net> wrote:
> >
> >>
> >> For what it's worth, I just took a look and found a bunch of 6CW4's on
> >> eBay.  See:
> >>
> >>
> >>
> http://shop.ebay.com/i.html?_adv=1&_nkw=6CW4+Nuvistor&_in_kw=1&_ex_kw=&_sacat=See-All-Categories&_okw=6CW4+Nuvistor&_oexkw=&_udlo=&_udhi=&_ftrt=901&_ftrv=1&_sabdlo=&_sabdhi=&_samilow=&_samihi=&_sadis=200&_fpos=Zip+code&_fsct=&LH_SALE_CURRENCY=0&_sop=12&_dmd=1&_ipg=50
> >>
> >> Burt, K6OQK
> >>
> >>
> >>  From: paul swed <paulswedb at gmail.com>
> >>> Subject: Re: [time-nuts] schematics for a HP117a please
> >>>
> >>>
> >>> Thanks everyone.
> >>> Indeed the nuvistors will be a challenge.
> >>> Don't know if between the 2 recvrs I have enough or if they are good or
> >>> bad...
> >>> But if need be a bit o redesign may be in order.
> >>> I am currently using a fair size copper tune loop/preamp on a tracor
> >>> 599H.
> >>> So thats a good start. But I will dig in and see whats cooking (Or not)
> >>> Noticed one has the creeping ground lug oxidation. Time for a drill.
> >>>
> >>> Regards
> >>>
> >>> On Sat, May 1, 2010 at 1:02 PM, J. Forster <jfor at quik.com> wrote:
> >>>
> >>> > Have you tried Dave at Artek Media?
> >>> >
> >>> > A couple of things on the 117A:
> >>> >
> >>> > The antenna is a roughly 1 meter diameter loop, but has a very
> >>> frequency
> >>> > selective pre-amp built in. Early versions used two Nuvistors and a
> >>> 60
> >>> KHz
> >>> > mechanical filter. Later versions used FETs I think. The amp in the
> >>> unit
> >>> > also uses three Nuvistors. These devices are getting scarce and
> >>> expensive.
> >>> >
> >>> > The coax between thr receiver and antenna has DC on it to power the
> >>> loop
> >>> > preamp.
> >>> >
> >>> > The paper for the stripchart is getting hard to find also.
> >>> >
> >>> > FWIW,
> >>> >
> >>> > -John
> >>>
> >>
> >> Burt I. Weiner Associates
> >> Broadcast Technical Services
> >> Glendale, California  U.S.A.
> >> biwa at att.net
> >> K6OQK
>
>
>
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