I've seen plenty of these caps fail (a nearby ham has a pair of
419A's on RTTY) but have never seen one burnt to the point where
you could see or smell it. Instead, the shunt caps that go to
ground on the radio side (not the antenna side) change value and
detune the filter, causing in-band swr to skyrocket.
When a failure occurs we just routinely replace those two caps,
without even testing them. So far, all of the failures have
occurred on 10 and 15 meters. What we are going to try now is
replacing those caps with a parallel combination of three caps,
instead of just two caps. We will use 3x220uf on 15 instead of
2x330. We will use 3x180uf instead of 2x270uf on 10 meters. The
caps will be CDE CDV16 series. Hopefully, the reduced current
through each cap will improve reliability.
After replacing the caps, we squeeze or spread the coil using a
rubber-gloved hand at 10 watts, tuning for min swr.
These capacitors get hot enough to boil spit at 100W.
Dave Hachadorian, K6LL
Big Bear Lake, CA
-----Original Message-----
From: N2TK, Tony
Sent: Wednesday, July 20, 2011 9:54 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] ICE 419B schematic
Someone gave me a tip a number of years ago about checking out
419 filters.
He said to take off the cover and stick your nose in the box and
see if you
have a burnt smell. And look at the color of the caps and see if
some are
quite dark in color from excessive current.
Now use W3NQN transmit and receive filters. Overall seem to work
much
better.
73,
N2TK, Tony
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of K1TTT
Sent: Tuesday, July 19, 2011 6:15 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] ICE 419B schematic
Again, its probably not the voltage but the current that is the
problem...
See my last message.
Also on mine the capacitors on 20m hadn't 'failed' they had
shifted value...
It was obvious to see using a minivna to sweep the filter that it
was still
there, it just wasn't resonating where it what supposed to any
more. In
mine the 10m section had one of the shunt caps shorted, the
others were ok,
but I replaced them all anyway. The 20m section had one of the
shunt caps
changed from 1000pf to 247pf on a handheld dmm, my mfj 269 reads
it as 614pf
at 2mhz but is highly frequency dependent where the good one is a
stable
1040pf or so over a wide range.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: Mark Ketchell [mailto:k5er@arrl.net]
> Sent: Tuesday, July 19, 2011 21:48
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] ICE 419B schematic
>
>
> Okay, I'll ask too...
>
> The 20 meter section of my ICE 419b failed - infinite SWR.
>
> I removed cover from relay and polished contacts, eliminating
> it as the
> possible failure point.
>
> Inductors - still same size and shape, can't be them.
>
> Pulled the 3 caps and took to elec supply store. All 3
> checked good on
> their tester (had them check twice). Took to friend with HP
> meter. The two
> shunt caps (.001 @ 2kv) each checked fine - the 270 pf (+/-
> 5%) checked as
> 251 pf - about 7% off. Would have thought it was close enough
> to find a
> resonate point, but it would not.
>
> I simply replaced all three and it works just like new.
>
> Why would the caps check as okay, but be absolutely worthless
> in the
> circuit? IF it is the series cap (270pf at 1kv) that fails,
> then why
> doesn't it ever seem to take the .05 @ 200v series cap right
> at the antenna
> port? If not the series cap, how does a 100 watt radio
> generate enough
> voltage to cause a 2kv cap to fail? There are resonate
> auto-switched
> antenna on each band, so it "shouldn't" see high SWR.
>
> Thanks,
> Mark
>
>
> ...
> >What usually happens when the filter fails is that one or both
> >of
> >the capacitors on the radio side of the Pi changes value.
> >
> >Mouser has a good selection of heavier-duty replacement caps.
> >For example, Mouser part number 5983-19-1KV330 for 15 meters.
> >Even with those, the filter can still fail.
> >
> >Dave Hachadorian, K6LL
> >Big Bear Lake, CA
> >
> >
> >-----Original Message-----
> >From: James C. Hall, MD
> >Sent: Monday, July 18, 2011 2:28 PM
> >To: towertalk@contesting.com
> >Cc: tcg1@googlegroups.com
> >Subject: [TowerTalk] ICE 419B schematic
> >
> >Hello:
> >
> >I sent an email to ICE inquiring about their ability to repair
> >my
> >ICE 419B's
> >which have a couple blown filters. I got a response that since
> >Mike died,
> >they can't repair anything right now.
> >
> >I asked about a schematic of these 2-stage filters and they
> >came
> >back with
> >'they don't have them either', which I found rather strange.
> >At
> >any rate,
> >does anyone have a schematic or parts list of the 419B so that
> >I
> >may attempt
> >to fix them myself ?
> >
> >This may or may not be the correct forum to send this, so if
> >not,
> >please
> >advise and I'll redirect this.
> >
> >Thanks.
> >
> >73, Jamie
> >
> >WB4YDL
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
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