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Re: Question about Ameritron AL-1200 Amp (Uses one 3CX1200Z7 tube)
开云体育Being curious, what exactly is arcing?Andy? K9ATX On 1/27/2020 6:05 PM, Cliff Fox (KU4GW)
wrote:
I have a Ameritron AL-1200 brought to me by the KN4UNA, P.J., who received the amp from his uncle's estate (W4WWF Dale Mash SK) and it has a problem with giving a arc when the power switch is first turned on. The amp runs fine after that initial arc. Can anyone offer any advice on what I should check that may be the cause? I own a AL-80B and I know it has a inrush current step-start circuit in it to prevent a surge, but know nothing about the AL-1200. Does it have inrush current protection or a step-start circuit? I had a issue with my AL-80B a while back arcing from the tube parasitic resistors to the shaft going to the band switch. I wrapped the shaft in heat shrink tubing and that solved that problem. What should I check first in the AL-1200, perhaps a current limiting resistor? The amp is as clean as a pin and looks like brand new! Thanks in advance and very 73!? -- "Where the Old Soo crossed the New Soo" Duplainville, Wisconsin Web page at: |
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Re: Question about Ameritron AL-1200 Amp (Uses one 3CX1200Z7 tube)
Cliff Fox (KU4GW)
No, not yet Alek, I'm planning on taking the cover off it tomorrow afternoon. One guy in Idaho told me the step-start relay may be the culprit or it could need the electrolytic caps replaced. If I could see the arc it would be very helpful, but I'm reluctant to turn it on without the cover on it, it may kill me! Maybe I can hear it, P.J. told me what it was doing when he brought it here, but I haven't hooked it up yet. The guy in Idaho told me the step-start relay in on the left side at the back so if I can hear it arc back in that area then maybe P.J. should order a new relay from Ameritron. Hopefuly I'll find a sign of the arc like a burnt or discolored resistor or a leaky capacitor, something I can see.?Thanks for your reply! Very /73 de Cliff On Mon, Jan 27, 2020 at 8:56 PM Alek Petkovic <vk6apk@...> wrote:
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Re: Question about Ameritron AL-1200 Amp (Uses one 3CX1200Z7 tube)
开云体育Have you determined where the arc might be? Bandswitch, RF deck, power supply, power switch, transformer, filter caps, etc? 73, Alek. VK6APK On 28/01/2020 8:05 am, Cliff Fox
(KU4GW) wrote:
I have a Ameritron AL-1200 brought to me by the KN4UNA, P.J., who received the amp from his uncle's estate (W4WWF Dale Mash SK) and it has a problem with giving a arc when the power switch is first turned on. The amp runs fine after that initial arc. Can anyone offer any advice on what I should check that may be the cause? I own a AL-80B and I know it has a inrush current step-start circuit in it to prevent a surge, but know nothing about the AL-1200. Does it have inrush current protection or a step-start circuit? I had a issue with my AL-80B a while back arcing from the tube parasitic resistors to the shaft going to the band switch. I wrapped the shaft in heat shrink tubing and that solved that problem. What should I check first in the AL-1200, perhaps a current limiting resistor? The amp is as clean as a pin and looks like brand new! Thanks in advance and very 73!? |
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Question about Ameritron AL-1200 Amp (Uses one 3CX1200Z7 tube)
Cliff Fox (KU4GW)
I have a Ameritron AL-1200 brought to me by the KN4UNA, P.J., who received the amp from his uncle's estate (W4WWF Dale Mash SK) and it has a problem with giving a arc when the power switch is first turned on. The amp runs fine after that initial arc. Can anyone offer any advice on what I should check that may be the cause? I own a AL-80B and I know it has a inrush current step-start circuit in it to prevent a surge, but know nothing about the AL-1200. Does it have inrush current protection or a step-start circuit? I had a issue with my AL-80B a while back arcing from the tube parasitic resistors to the shaft going to the band switch. I wrapped the shaft in heat shrink tubing and that solved that problem. What should I check first in the AL-1200, perhaps a current limiting resistor? The amp is as clean as a pin and looks like brand new! Thanks in advance and very 73!?
Cliff, KU4GW |
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Re: Plate Blocking Capacitors again
开云体育The Marconi ?transmitter at BBC Wooferton used a water cooled vacuum capacitor 1nF 44kV as a coupling capacitor. ?
? Described in the video from about minute 6 ? That Marconi B6124 transmitter operates 3.95-16.1MHz ?
? ? There is a 1nF glass vacuum capacitor as a coupling capacitor in the 40kW driver stage of an older tansmitter visible at 13:40 ?
? 73 Peter ? From:
[email protected] [mailto:[email protected]] On Behalf Of Jim VE7RF ? shoulda? read...... with the? application? of? DC. |
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Re: Plate Blocking Capacitors again
Yes? I? realize? 95%? of? MW? these? days? are? SS......? I? was? referring? to the? older? tube? pa.
Fixed / variable? ?vac caps? have? to? be? severely de-rated? for plate block? use...per? jennings....and? that's? in? addition to? the? existing? de-ratings for? RF. IE:? ?15? kv? rated? vac? cap? is? good? for .6 x? 15 kv =? ?9? kv? ?max? for? RF? tank? circuit......? which? the? drops down to? 6? kv? for plate? block? use...(or? applications where? B+? is? on? the tune /load / bandswitch /coil),? Jennings sez? the? plates...'will? grow? whiskers'? ?with? the? application? of? RF.? Did? u? look? at? the? current? ratings of? those various CDE? mica's ?? ? A? lot? of? em? were very? high? >? 30? mhz? on? the? graphs.......? but? the? short? form? box for? each? cap? only? depicts ratings from? 100? khz? -? 3? mhz. Funny? how? zero? mention? of? applying B+? to a mica? in? their tech? notes.? ?Roy is? probably? correct? about? ?dielectric? migration.?? Jim? ?VE7RF |
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Re: Plate Blocking Capacitors again
W2XJ
a linear fo AM is just a bad idea. They are 25% efficient at best. AM broadcasters largely gave them up 80-90 years ago. The Doherty version is a much more efficient option but still less efficient than other techniques such as variations on plate mod. Ham radio is a bit different in that many of us don’t care that much about efficiency. If I were heavily into AM, I would build a plate mod transmitter and not a linear amp.
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On Jan 21, 2020, at 4:55 PM, Jim VE7RF <jim.thom@...> wrote: |
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Re: Plate Blocking Capacitors again
W2XJ
sw broadcast TXs use vacuum caps. MW transmitters are all solid state except for the very old ones. SW TXs 50KW and under are also mostly solid state these days as well.
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On Jan 21, 2020, at 4:55 PM, Jim VE7RF <jim.thom@...> wrote: |
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Re: Plate Blocking Capacitors again
He's? got? it? mounted? on a piece? of? fiberglass.? ?He? shoulda? used? nylon? screws? to? mount the? fiberglass to the? rear? wall....and? also? another? pair? of
nylon? screws? to? mount the? millen..to? the? fiberglass.? ?He? also? managed to? somehow? mount a female? blade? type? ?Sta-kon? male? to? the? back? end? of the millen.... then? connect to? it? with a mating? male sta-kon.....? presumably? for a fast? internal disconnect.? Millens? are? dangerous enough? at? the? best? of? times.? RL? Drake? used? large? diam? ?red? heatshrink? on? the? back? end of the? millen? male? connector.. not? quite? shrunk? down? onto the cable? (? 213? with? vynal? ?and? braid? removed).? That way? the? millen? male? can? still? be? rotated /twisted.? ?Toll? free? got? blasted? with? 6? kv....? just? from? 1 fine? strand? sticking? out? sideways.? Jim? ?VE7RF |
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Re: Plate Blocking Capacitors again
I? went? through the? entire? pdf.? ?They? state the? mica? caps? are? designed? for? 100? khz? to? 3? mhz..that's? it.??
Then? the? graphs? depict current? ratings? from? ?100? khz...up? to? 200? mhz .? What? do? the? dotted? lines? depict ??? Unlike HEC? ceramic? caps.....? which? revolve? around? 25? deg C..and? all having? a NEG temp? coef? >? 25? degC....? and? a positive? coef? <? 25? deg? C......... the? mica? caps? specs? don't? state where? the? ?baseline? temp? is.? ZERO? mention? of? applying DC? to? the? mica? caps,? ?none.? All? their? V? ratings? are? AC? ratings..at? some? unknown? freq.? HEC? sez? the? AC? vdrop? across? the? cap +? any? dc bias (B+)? can't? exceed? the? stamped rating? on? the? cap.? Doing? the? maths,? the AC? vdrop? across a plate blocker is? very? little,? 100-300? vac. It? will? be? interesting to see? what? ?CDE? sez? about? using? their caps? for a? plate? blocker.? I'm? betting? they? will? not? endorse? it.? Forget the? HB? amps? with? mica? blockers? for a moment,? what do the? SW? AM? broadcast? folks? use? for? plate? blockers ????? ?What's? used? for? plate blockers? in? MW? (550-1700? khz)? ?AM? broadcast? tube? tx's? ??? ? W8JI? uses? a single,? large? Mica? for the? plate blocker? on? his ..'shortwave? broadcast'? AM? linear? amps...which? use? a single? 3CX-15,000A7.? 25? kw? pep? out..., 6.25? kw? cxr...swings? to 9.375? kw with? 100%? modulation.... =? 3125? watts? of? TOTAL? sideband? power....? =? just? a measly 1562? watts? of SSB power? ..per? sideband.? ?Heck,? a 8877? can? do? 1562? watts? pep into? one? sideband. A? linear? for? AM? is? abt? as? inefficient as? it? gets.? ?The? 2 x side bands? never? combine in? phase? on? HF.... just? a few? degrees? outa? phase..and? poof,? there? goes? the? 3db.? Go? just? a few? more? degrees? outa? phase..and? poof,? they? just lost? a? bunch? more? db's...esp with the? higher? audio? freqs.? ?IE:? the? 6 khz portion? is? now? 12? khz? apart,? good? luck? with trying? to? get the? USB? +LSB? in? phase.? Then? toss? in...'selective? fading'..and? u? have a real? mess.? ? ?One? SW? AM? broadcaster? ?ran tests? between? 100? kw? cxr? AM...and? 10 kw? USB. The hundreds? of? sw? listeners? all? responded? that? the? 10 kw? USB? signal? won? that? battle ..hands? down.? ? ?They? would? be? better? off? running CXR? +? one? sideband...sri? for the? ? sw am OT? rant.? ? Jim? ?VE7RF? |
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Re: Plate Blocking Capacitors again
开云体育Interesting that he uses one of the ‘Millen HV connectors’ that are supposedly only rated at 2500VDC to bring his 6500VDC in! ? Mod-U-Lator, Mike(y)/W3SLK ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Peter Voelpel
Sent: Monday, January 20, 2020 6:58 PM To: [email protected] Subject: Re: [ham-amplifiers] Plate Blocking Capacitors again ? Seems to work ? ? 73 Peter ? From: [email protected] [mailto:[email protected]] On Behalf Of Sharalyn Koeppe ? I have understood that mica is not suitable for plate blocking due to dielectric migration from the DC applied. 73,?? Roy??? K6XK ? On 1/19/2020 7:36 AM, Tracey Gardner via Groups.Io wrote:
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Re: Plate Blocking Capacitors again
开云体育Not always: ?
? 73 Peter ? From:
[email protected] [mailto:[email protected]] On Behalf Of Jim VE7RF Current? rating? on? mica's? decreases as?
freq? increases.? |
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Re: Plate Blocking Capacitors again
I'd be? more? worried? about? the? current? rating..vs? V? rating.? ?What? bands are? you? planning? to? use..and? what? tube(s) ?? ?If? u? are? using? tubes? with? typ stray? C? between? anode? and? grid (assuming a GG? triode...or? ?tetrode..strapped? like a? high? ?mu? triode)....? the? current? through the? plate blocker? can? get? pretty? high? on? the? upper? bands? like? 10m.....? it's? easy? to? calculate? plate? block? current.? ?Alpha? just? uses? a pair? of? 6? kv? disc? ceramics? in? parallel? for the? plate blocker.?
Problem? with? mica's? is.... they? rate? em? for? current at? 1? mhz? (and? in? ur? case,? 300? khz) .? U? might? be? able? to? test? by? feeding? RF? through? the? mica...then? into? a dummy? load.? ?200w? is? 2A? into? ? 50? ohms.? Then? try? all? bands.? Current? rating? on? mica's? decreases as? freq? increases.? Jim? ?VE7RF? |
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Re: Plate Blocking Capacitors again
开云体育?
Many thanks for that Peter.
At 10kV peak working that capacitor looks to have a much lower rating than mine.
?
73s Tracey G5VU
?
?
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Re: Plate Blocking Capacitors again
开云体育Seems to work ?
? 73 Peter ? From:
[email protected] [mailto:[email protected]] On Behalf Of Sharalyn Koeppe ? I have understood that mica is not suitable for plate blocking due to dielectric migration from the DC applied. 73,?? Roy??? K6XK ? On 1/19/2020 7:36 AM, Tracey Gardner via Groups.Io wrote:
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Re: Plate Blocking Capacitors again
开云体育I have understood that mica is not suitable for plate blocking due to dielectric migration from the DC applied. 73,?? Roy??? K6XK
On 1/19/2020 7:36 AM, Tracey Gardner
via Groups.Io wrote:
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Plate Blocking Capacitors again
开云体育?
I have an 1100pf large block shaped Dubilier?mica capacitor?dating from 1944.
It measures approx. 3.75w x 2.25d x 3.25h inches
It states on it that it was tested as follows
?
(a) 6 amps at 300kHz for 1 hour
(b) 28kV dc
?
It also states that the max working conditions should be approx. 80% of those ratings.
?
Considering its age has anybody got any thoughts on if it would be safe to use?
?
It still measures?1106pf
?
Thanks
?
Tracey G5VU |
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Re: Interesting High Voltage capacitors
OK, I? downloaded? the? entire? catalog on? that? series.? ?Most? are? rated? at? c 100 Amps? of? ripple? current....? but? at? lower? ambient? temps.? ?Per? cornell? dublier? ( who? bought? out? ?Mallory)....? for? applications? like? dc? drives etc,? where? high? currents? are involved,? caps? are? wired? in? parallel? to? increase? the? current? rating.? ?Per? CD,? the? 10-32? screw? terminals? are? rated for? 30A? CCS.? ?The? 1/4-28? terminals? are rated?for? 50A.? ?Caps? can? also? be? wired? series? parallel for? both? more B+? and more ripple current.
Using? PSUD-2? software.....? (and? also Hammond? xfmr? notes), the? ripple? current is? typ? 2.5 X? the DC? plate? current.? ? Similar? results? using? ?Spice? and? LT spice? software.? ?So? if? u? are? sucking? 1A? of? plate? current, ideally,? u? want at? least? 2.5A? ripple? current? rating.? Ripple? current? ratings will? increase? when? ambient? temp surrounding the outside? of? caps? is? less? than? the? typ 85? deg C? rating? (or? 105? deg? C).? ? CD? has? ripple current? multiplier? charts? on?their? site....? for reduced? ambient? temps....and? also? when ripple? current? freq? is? > 120? hz.? I? suspect? those? ?135mm? diam? x? 300mm? long? caps? ?will? be in? the? $200.00? to? $300.00? ?price? range.? Jim? VE7RF? |
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Re: Interesting High Voltage capacitors
开云体育?Friday, January 17, 2020 ?In an RF amp where might be appropriate to use Teflon capacitors? Best regards, ?Chris ? ?2E0ILY ? ? ??mailto:chris@...
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