[R-390] R-390A IF deck caps in T501 or T502

[Larry H]

Dave, it was more of a process of elimination.  After determining that the
2nd stage gain was erratic, I started with the tube, then the bypass caps.
Then the voltages on the tube.  Then the output transformer, so I checked
to see if the 2 slugs were still at their peak.  One was and the other not,
and it would not peak.  I measured the coil resistance and examined it for
damage and loose wires.  All ok there, so it had to be the caps.  Since I
don't have a cap checker, I removed both.  This is one time I wish I had an
accurate cap checker, then I would have checked the mica first.  Replacing
both confirmed one of them was bad.  Reinstalling the ceramic with a new
200 pf mica confirmed it was the mica.

Regards, Larry

On Wed, Jan 23, 2019 at 7:51 AM dog <agfa at hughes.net> wrote:

> I mean the bad ones, how did you determine they were bad?
>
> On 1/23/2019 07:23, Larry H wrote:
> > Dave, I tested the new cap only for leakage at the rated voltage (500 v)
> > before installation.  After installation, for correct operation during
> warm
> > up.
> >
> > Regards, Larry
> >
> > On Tue, Jan 22, 2019 at 12:09 PM dog <agfa at hughes.net> wrote:
> >
> >> Larry, how did you test the 200pf caps? Did you test the actual cap? I
> >> haven't replaced mine yet, procrastinating.
> >>
> >> Dave N3DT
> >>
> >> On 1/22/2019 00:14, Larry H wrote:
> >>> I received the 200 pf caps today that I ordered from Just Radios.  I
> put
> >>> the original 39 pf cap (with -30 tempco) back in, that I had removed,
> and
> >>> installed the new 200 pf.  It's working great.  IF warm up shows very
> >>> little drift and good stability.  The size is very good for good fit
> with
> >>> ample room in T501.  Both coils peak with ample tuning on both sides.
> >>>
> >>> Regards, Larry
> >>>
> >>>
> >>> On Wed, Jan 16, 2019 at 1:20 PM Larry H <larry41gm at gmail.com> wrote:
> >>>
> >>>> Hi Dave,  Sorry your posts are not getting through.
> >>>>
> >>>> The 5% are fine as long as it will peak on adjustment, which it
> should.
> >>>> Does 1 or both coils not peak in yours?  The easiest way to check is
> to
> >> rx
> >>>> in cal, tune to signal, measure dc on diode load.
> >>>>
> >>>> Regards, Larry
> >>>>
> >>>> On Wed, Jan 16, 2019 at 7:20 AM dog <agfa at hughes.net> wrote:
> >>>>
> >>>>> Larry,
> >>>>>
> >>>>> For some reason my replies to the 390 list are not getting through. I
> >>>>> might have to re-register, don't know. Anyhow, I've been having the
> >> same
> >>>>> gain problem. I traced the jump in gain to T502 after much fiddling,
> >> but
> >>>>> didn't get much farther, I sorta got burned out just finding that. I
> >> had a
> >>>>> thread on it last summer. I have a bunch of dipped SM caps but
> they're
> >> 5%.
> >>>>> Is it that important they be 2%? I thought that was what the
> >> adjustment in
> >>>>> the coil is for? Oh, I see I've got a 200pf  5% 500V one. I may have
> >>>>> another if I look through the pile. Most of what I have are 270pf.
> The
> >> 200
> >>>>> is fairly small too, only 3/8" at the widest.
> >>>>>
> >>>>> Dave N3DT
> >>>>> On 1/16/2019 00:02, Larry H wrote:
> >>>>>
> >>>>> Still Holding.  I ordered 20 of the 200 pf from justradios.   Hope
> >> they get
> >>>>> here soon.
> >>>>>
> >>>>> Tomorrow I celebrate with Kielbasa and cold brewsky.
> >>>>>
> >>>>> Regards, Larry
> >>>>>
> >>>>> On Tue, Jan 15, 2019 at 6:21 PM Tisha Hayes <tisha.hayes at gmail.com>
> <
> >> tisha.hayes at gmail.com> wrote:
> >>>>>
> >>>>> Yea, at the prices for mica caps you definitely do not want to be
> >>>>> shotgunning the replacements of those things through the deck.
> >>>>>
> >>>>> *Ms. Tisha Hayes, AA4HA*
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