Dave,
Hi !
Various tube type industrial RF generators use the #30/32 wire “fuse” with good
results. Those HV fuses and Ohmite resistors tend to be costly these days.
Also, the problem may have been some condensation.
de:W1SMS
Steve Simons
Manitou Systems Inc.
Tel.203.733.2110
ssimons@manitousys.com
Sent from my iPhone
> On Jun 17, 2021, at 4:37 PM, David Olean <k1whs@metrocast.net> wrote:
>
> Hi Pete,
>
> Well, I wasn't rolling on the floor laughing when it happened. I went looking
> for my hard hat and ducked as the shrapnel flew around behind the rack! The
> good news is that the amp is OK. I dragged it home to look it over. There are
> some protective diodes in the metering circuit and those usually short out
> when there is a tube arc. I checked those and both seemed fine. The 12 volt
> 50 watt zener bias diode also looked OK. I had to rebuild the fuse holder as
> part of it was missing after the bomb went off. I found a big fuse clip
> thingey in some old surplus stuff, and stole the two fuse clips to fix the
> amplifier. I got that done and then replaced the fuse with a new 1.5 amp HV
> fuse. I tried it out and the amp came up just fine down in the shop.I ran
> some 222 energy into the amp from my signal generator. I had a wideband amp
> that will make about 4 watts so I stuck that into the 8877 input connector
> and saw 100 watts coming out. That is over 13 dB gain so it all looks OK.
>
> So what happened? It could have been that the fuse just decided that it was
> time to give out. It would make a pretty good noise just letting go. It
> could have been a tube arc, but having good protection diodes afterward,
> makes me think that maybe there was not an arc at all. With all the news
> stories about politics lately, it also could have been caused by Donald
> Trump. I am going to stick with that explanation, or maybe it was cosmic rays
> from outer space. Everyone knows that cosmic rays are really bad too.
>
> All this leaves me wondering about my crazy idea to use electrolytic
> capacitors as HV caps in series for HV filtering I think I went overboard a
> bit. The end result is a huge capacitor bank value of 166 MFD. That is a
> good amount of stored up energy at 3500 volts. If anything in the HV line
> wants to consume current, 166 MFD will surely oblige that request. I think I
> might remove the electrolytic bank and substitute a modern non PCB 6 MFD 10
> KV cap instead. That way, if I get another arc, it will sound like a 30 cal
> handgun instead of turret B on the USS. Missouri!
>
> Maybe I should use #32 wire as Jay recommended. I went with smaller stuff,
> like #47. It will pull over an amp without burning out, so I figured it was
> OK. I tried running some current through some #32 wire and it will do 5 amps.
> If I push the current higher, it breaks open at 7 or 8 amps, which seems
> awfully high to me. That is 28 kilowatts.
>
> 73
>
> Dave K1WHS
>
>> On 6/16/2021 11:10 PM, Peter Motyl wrote:
>>
>> Yah, but reading about the explosion had me rolling on the floor with
>> laughter. Oh, I know from experience it isn’t funny when it happens but
>> reading about it is really funny.
>>
>> *From: *jrusgrove@comcast.net <mailto:jrusgrove@comcast.net>
>> *Sent: *Wednesday, June 16, 2021 6:22 AM
>> *To: *David Olean <mailto:k1whs@metrocast.net>; Fred Stefanik
>> <mailto:n1dpmfred@gmail.com>
>> *Cc: *222 >> 222Activity@groups.io <mailto:222Activity@groups.io>; VHF
>> Contesting <mailto:vhfcontesting@contesting.com>; NEWS Reflector
>> <mailto:newsvhf@mailman.qth.net>
>> *Subject: *Re: [NEWSVHF] 222 Activity Night
>>
>> Dave
>>
>> If you don't have it the circuit already, I'd suggest a 'glitch' resistor in
>> series with the HV output to limit current to a high, but manageable, level.
>> Also, for a high voltage fuse, try a small length of #30 - 32 wire (approx)
>> between two ceramic standoffs. Since these two items have been in place I've
>> experienced no fireworks or power supply damage when an amplifier 'incident'
>> occurs ... everything shuts down quietly. Previous to this I've experienced
>> a number of flash/bangs as you, and others, have.
>>
>> Jay W1VD
>>
>> ----- Original Message -----
>>
>> From: David Olean <k1whs@metrocast.net>
>>
>> To: Fred Stefanik <n1dpmfred@gmail.com>
>>
>> Cc: 222 >> 222Activity@groups.io <222Activity@groups.io>, VHF Contesting
>> <vhfcontesting@contesting.com>, NEWS Reflector <newsvhf@mailman.qth.net>
>>
>> Sent: 6/15/2021 11:43:15 PM
>>
>> Subject: Re: [NEWSVHF] 222 Activity Night
>>
>> ________________________________________________________________________________
>>
>> Well I was very happy that Fred N1DPM showed up for 222 activity night.
>>
>> We had a nice rag chew and signals were 59+ each way. Fred's signal was
>>
>> outstanding. I listened to Fred run with KO4YC near Richmond, VA.
>>
>> K04YC was peaking up really fine, hitting a good 559 on the S-meter.
>>
>> That is pretty impressive for over 500 miles away. I tail ended KO4YC
>>
>> and called Fred. I had worked Cornell earlier with my driver amp at 80
>>
>> watts. It was a squeaker, but while I was ragchewing with N1DPM, KO4YC
>>
>> heard me OK on ssb with my 80 watts, so there were definitely some good
>>
>> tropo peaks going on. You should not be able to work 525 miles with 80
>>
>> watts on 222 normally.
>>
>> A try with VE3DS was not successful with my 80 watts. Still it was a
>>
>> great evening on 222 with 13 stations worked including
>>
>> KA2LIM Ken in FN12
>>
>> W9KXI Al also in FN12 Ken and Al seem to be FN12!!
>>
>> WW1M Bruce in FN43 (just down the road a few miles)
>>
>> WA1LWC in FN42 5 watt power house!
>>
>> VE2XX Stu near Montreal in FN25. I could hear him working KA2LIM. 59
>>
>> when we aimed at each other!
>>
>> N1SV Les in FN42 One of the 222 night regulars
>>
>> WZ1V Good Buddy Ron. Always shows up for 222 night and stirs up the
>>
>> pot with lots of contacts.
>>
>> N3RG Ray way down at the bottom of FM29
>>
>> K3WHC Steve in FN10pa.
>>
>> K1PXE Pete in FN31. The voice of Milford! and a staunch supporter of
>>
>> activity night.
>>
>> WA2VNV in FN30 on Long Island with a booming signal up here in Maine.
>>
>> K2AEP Pete in FN33 Vermont. One of the few people who keeps a briefcase
>>
>> full of alphabetically organized jokes.
>>
>> KO4YC Cornell in FM17 near Richmond, who must have a fantastic takeoff
>>
>> angle. Just a phenomenal signal up here every week.
>>
>> I had some excitement here. Not too long after I got on the air, There
>>
>> was a very large explosion and a flash behind the rack as the 222 MHz
>>
>> 8877 amp decided to arc over. I hate it when that happens. The high
>>
>> voltage fuse is about 4 1/2" long and is a phenolic tube with brass end
>>
>> bells. When it went off. The two end bells were blown out of the tube
>>
>> ends and one of the brass end bells shattered into little pieces. It
>>
>> even blew up the beryllium copper fuse holders! This could be serious.
>>
>> At a minimum, I probably have shorted diodes in the metering circuit. At
>>
>> worst, the tube might be hosed. I dragged it back to the house and will
>>
>> look it over in the morning.
>>
>> I recall this happened another time many years ago with this same
>>
>> amplifier on Pack Monadnock Mountain in New Hampshire during a June
>>
>> Contest. The 220 rig was set up in a cargo van and I had built up an
>>
>> eight yagi array of NBS 4.2 wavelngth design for EME. The group was W1FC
>>
>> and there was an aurora on both Saturday and Sunday evening. We were
>>
>> cleaning up on 220 MHz and our section total was way ahead of the 144
>>
>> station. I remember working Iowa and Minnesota that weekend along with
>>
>> EME to California. Word got around that we were doing so well, and a
>>
>> crowd formed all poking their heads in the van door to see what we were
>>
>> doing. At that exact time, the 8877 amp decided to arc over and that
>>
>> same HV fuse exploded. It sounded like someone shot off a M1911 45cal
>>
>> pistol inside the van and to add some spice to the effort, the two end
>>
>> bells went ricocheting off the walls of the van. The crowd instantly
>>
>> thinned out and we replaced the fuse and got back to working DX.
>>
>> Thanks to all who came out to play, including Marshall, K5QE from Texas.
>>
>> He ran some MS schedules. Thanks Marshall!
>>
>> 73
>>
>> Dave K1WHS
>>
>> On 6/15/2021 9:59 PM, Fred Stefanik wrote:
>>
>> > I was able to get on 222 here tonight for about 30 minutes. I worked
>>
>> > VE3DS at 369 miles, KO4YC at 385 miles, and K1WHS at 125 miles.
>>
>> > Hopefully I can get on more often on Tuesday nights.
>>
>> > Thanks Dave for drumming up the activity!
>>
>> > 73
>>
>> > Fred
>>
>> > N1DPM
>>
>> > FN32qb
>>
>> >
>>
>> > On Tue, Jun 15, 2021, 5:18 PM David Olean <k1whs@metrocast.net
>>
>> > <mailto:k1whs@metrocast.net>> wrote:
>>
>> >
>>
>> > Just two days after the big June VHF Contest. I know everybody is
>>
>> > probably sick to death of working 50 MHz DX. You would most likely
>>
>> > rather do anything but more ham radio, but it is 222 Night! I will be
>>
>> > on starting around 7 or 7:30 PM local time or 2300 UT and will be
>>
>> > making
>>
>> > noise on 222.100 thereabouts. When we quit contesting Sunday
>>
>> > night, I
>>
>> > am sure that the diesel generator was running on fumes. I will
>>
>> > drag up a
>>
>> > 6 gallon can of diesel fuel to make sure I don't run out.
>>
>> >
>>
>> > I hope to see you on 222 MHz
>>
>> >
>>
>> > Dave K1WHS
>>
>> >
>>
>> > ______________________________________________________________
>>
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>>
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>>
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>>
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>>
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