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Test #5
Doug Renwick
I have a GU-78B that has developed a grid short. I have determined the grid
short initiates about 2 minutes after power on and ends after about 5 minutes. I have tried unsuccessfully to 'burn' the short by hooking up a 560?f capacitor fed with 300vdc. What other methods that can be tried to 'burn' this short? Doug |
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Re: Test
¿ªÔÆÌåÓýSomebdy has forgotten to take their pills today.Bad boy Carl. :-) Alek. VK6APK On 26/05/2019 9:02 AM, 'Carl' km1h@... [ham_amplifiers] wrote:
-- From sunny Binningup Family Businesses: SP Electrical. The Velvet Fox. Smart Design Electrical. Perth Interiors. |
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Removing grid shorts
Doug Renwick
¿ªÔÆÌåÓýLet's try this post for the 3rd time and see if it comes through. ? I have a GU-78B that has developed a grid short. I have determined the grid short initiates about 2 minutes after power on and ends after about 5 minutes. I have tried unsuccessfully to 'burn' the short by hooking up a 560?f capacitor fed with 300vdc. What other methods that can be tried to 'burn' this short? Doug ? |
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Re: Test
Doug Renwick
¿ªÔÆÌåÓýOther than one of my test e-mails getting through, other posts have not. Something is screwed up! And nothing is coming through on the Amps reflector either. Doug ? "The difference between stupidity and genius is that genius has its limits." Albert Einstein From:
ham_amplifiers@... [mailto:ham_amplifiers@...] ? ? ? Indeed Joe, the forum has been quite slow since the sad demise of central protagonist Rich Measures and the Rich / Carl sideshow jousts¡.. ? There¡¯s more interesting activity on the Amps group nowadays. ? Leigh VK5KLT ? From: ham_amplifiers@...
[mailto:ham_amplifiers@...]
Sent: Sunday, 26 May 2019 10:03 AM To: ham_amplifiers@... Subject: RE: [ham_amplifiers] Test ? No, not dead, been a bit slow, but not slow enough to
worry. |
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Re: Test
¿ªÔÆÌåÓýYAWN
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At least Rich and I were friends since about 1996
and I miss him
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I cant say the same about you. Go back under your
GU-74B rock and behave
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Carl
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Re: Test
¿ªÔÆÌåÓý? Indeed Joe, the forum has been quite slow since the sad demise of central protagonist Rich Measures and the Rich / Carl sideshow jousts¡.. ? There¡¯s more interesting activity on the Amps group nowadays. ? Leigh VK5KLT ? From:
ham_amplifiers@...
[mailto:ham_amplifiers@...]
? No, not dead, been a bit slow, but not slow enough to
worry. -----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...] Subject: [ham_amplifiers] Test Canada; the ship of fools where corruption and politics are synonymous Ham Amplifiers reflector dead?
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Re: Test
No, not dead, been a bit slow, but not slow enough to worry.
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Joe - W7RKN -----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...] Subject: [ham_amplifiers] Test Canada; the ship of fools where corruption and politics are synonymous Ham Amplifiers reflector dead? |
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Re: Test
Beep...beep...beep...beep...beep... -----Original Message----- From: 'Doug Renwick' ve5ra@... [ham_amplifiers] To: ham_amplifiers Sent: Sat, May 25, 2019 1:12 pm Subject: [ham_amplifiers] Test
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Canada; the ship of fools where corruption and politics are synonymous Ham Amplifiers reflector dead? --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
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Test # 2 Removing grid shorts
Doug Renwick
¿ªÔÆÌåÓýI have a GU-78B that has developed a grid short. I have determined the grid short initiates about 2 minutes after power on and ends after about 5 minutes. I have tried unsuccessfully to 'burn' the short by hooking up a 560?f capacitor fed with 300vdc. What other methods that can be tried to 'burn' this short? Doug ? |
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Removing grid shorts
Doug Renwick
¿ªÔÆÌåÓýOK the reflector is working now. Before, my message disappeared. ? I have a GU-78B that has developed a grid short. I have determined the grid short initiates about 2 minutes after power on and ends after about 5 minutes. I have tried unsuccessfully to 'burn' the short by hooking up a 560?f capacitor fed with 300vdc. What other methods that can be tried to 'burn' this short? Doug ? |
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Re: C-L-C update
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Did you try tuning the choke about 30 Hz
higher?
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Carl
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Re: C-L-C update
I? made a serious? error? when plugging numbers into the PSUD-2? ?power supply software.? Like an idiot,? I used the? wrong? plate xfmr? ?DC? primary? resistance.? I was plugging in? ".1 ohm"..... when it shoulda
been? ",01 ohm" .? ? ?Well that? makes a helluva? difference? to the calculated? ?source? Z? of the? plate? xfmr.?? I did have the? secondary? ?DC? resistance correct though? ( 4.5 ohms? across the 3900? tap....and? 6 ohms across the? 5200? tap).? On the 3900 tap, source? Z? is actually? just 7.411? ohms.....? and? NOT? ?33.61? ohms.? ?? On the? 5200? tap,? source Z? ?is actually just 11.61? ohms.... and NOT? ? 57.6? ohms.? B+? ?V drops? under a steady...or? varying load are of course? much improved.? ?Hardly any drop at all.? The resonant choke? setup is still? a dud? though.? ?It's? a glorified? 120 hz? notch? filter...and let's all the? harmonics? pass on through.? ?? Too? easy to make? errors.? Jim? VERF? |
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C-L-C update
Ok, here is why a....? C1 -? resonant choke -? C2? cap is? 1 step forward and? ?6 steps backwards.?? Ditto? with a? classic? ( henry radio style)? ?.. resonant choke -? Cap? config.? When you resonate the choke, at 120 hz,? ?you now have a glorified? 120 hz? notch filter.? ? You no longer have a? good? LP filter, with a low freq? cut off.? ? Reason is.... the small cap that's in parallel with the choke (used to resonate the choke)? will? simply pass all the? harmonics, like? 240/360/480/ 600? hz? ?etc, etc.?? Typ value parallel? resonating caps have low? XC? at? >240 hz.? ?The ONLY thing that is killing the harmonics is the cap on either side of the choke ( in the case of a C-? resonant choke - C filter).......? or the output cap ( in the case of a? ...Resonant choke -? C filter.? ?Ok, now you know why? FM broadcast? TX..that use the? classic? ?resonant choke +? cap setup.... also follow it up with a? 2nd choke? +? 2nd cap.? ?The? 2nd choke (NOT resonated)? ?+? 2nd cap is? there strictly to kill the harmonics.? ?Now in essence? they end up with a resonant choke notch filter..... followed by a? ?C-LC? filter.?? With a simple? ?C- choke - C? ?filter.... it forms a bonafide? real deal? LP? filter..with a real low freq? cut off.? ?In my case, the? cut off freq is real low, like 3.7 hz.? ? ?Attenuation at 120 hz? is? -131 db ... and lower still on the? harmonics? at? 240/360/480/600/ etc.? ? ? Max? gross overkill,? I like it.? ? So do the glass tube? audio geeks. I can see why the FM broadcast folks? want? loads of? 120..and also? 240/360/480? etc? ?harmonic redux? (this is on single phase? B+? supplies).? ? FM is about the only mode I can think of, that sucks max plate current.... with no modulation / audio / program? material /? music? applied to the TX.? ?IE:? 100 kw? ERP? and during pauses? etc, if there is any 120/240/360? etc products, they? will be heard on the RX end.? ?Esp if the? 100 kw erp station is fairly local,? full quieting, and? S meter? pegged.? A few folks? tried? 75M? ?FM late one night..that was an eye opener.? ?Locally,? FM is used on 11 M band !? later.... Jim? ?VE7RF |
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Re: 6 Meters Parasitic for 3-500Z
Hi Jim,?
Sorry about the late answer. I ending? 1300W with 70W amp and grid current on the limit.? I will keep it like this for now. Several coil have been tested and the last one was the best compromise, btw i not and tested the L to cancel the C of tube.. i have put so much time in this box.. i want it to go :)? ?This is for a friend,. The YC-156 is not a 6M amp, it is a HF low band.? I have a 4400 V 2A CCS Xformer, rectifier diode from a FM transmitter and 26 uF 7500V oil cap for HV. Pi Net will be like many, roller inductor + variable Vac Capacitor for both..nothing fancy but i can't wait to see? and what will be the output and IMD ( with and without Puresignal).? This amp will be used with a ANAN 8000 exciter the 200W out will help for sure. Guillaume |
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Re: RG-213 Hi pot ?
Excellent!? That is exactly what I have used for decades when trying to move extremely angry electrical pixies from one place to another.? Sometimes, I have run the 440 through Teflon? tubing before inserting the whole assembly into the braid.
Packard 440 is, by itself, usually sufficient; but, when routed through another layer of insulation, especially when protected by grounded braid from coaxial cable, it is safe for toddlers to play with while doing its job (Not a recommendation!).
Ed. KI6DCB
Although the author has received many significant electrical shocks and burns, among which were several from potentials greater than 30 kV and a few others from RF sources [much] greater than 1 kW PEP, some of which required medical attention, these events have not impaired his ability to have opinions about many things, especially the care and feeding of high-voltage/high-current electrical power sources.? Furthermore, no toddlers were injured in gaining the knowledge and experience required to have this opinion, although many smaller things -- most notably, various insects, bugs, small rodents, several screwdrivers, three or four voltmeters, and one oscilloscope -- have made the ultimate sacrifice in the furtherance of the author's knowledge and experience.? It must be noted that everyone's constellation of experiences is different from that of every other person, and that the author's experiences may not be applicable in any or every other situation.? Your experiences may be substantially different from those of the author of this post. -----Original Message-----
From: donroden@... [ham_amplifiers] To: jim.thom@... [ham_amplifiers] Sent: Fri, May 10, 2019 10:14 am Subject: Re: [ham_amplifiers] RG-213 Hi pot ?
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I'm using neon sign HV wire on a 10,000 volt 30KW FM transmitter
( Inside a run of metallic conduit ) Packard 440 ignition cable is tinned / stranded from Auto Parts stores... you could run it inside a braid stripped from RG8 or RG 58. Don W4DNR Quoting "jim.thom@... [ham_amplifiers]" : > Does anybody know how much max V is on RG-213 ? Like what are the > results if a hi-pot tester used..and say cranked up to the point > where just a few microamps occurs . I have an application where > I need a HV cable, less than 10 ft, that will easily handle 5700 / > 7700 vdc. It will be hardwired at both ends, no HV connectors. > And with braid peeled way back from the center conductor, like 2-4 inches . > The plan was to also wrap some red electrical tape every few > inches along its entire length, to readily identify it as a HV > cable. > > > I have loads of RG-393, but don't want to waste it for this application. > > Tnx.... JIm VE7RF |
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Re: 6 Meters Parasitic for 3-500Z
If? you use? GM3SEK's? ?pi? spreadsheet,? ?you will have some wiggle room.? The trick is to insert a tiny bit
of uh... between plate block cap and C1 main tune cap.? ?The combined tube C? from both tubes? ( anode? to chassis).....? +? that extra? tiny? uh? between? plate block caps..and? C1? tune cap..... will then form a step down? L network.? ? IE:? it will step down the plate load Z..way down.... to a lower value.? ?Then? the PI net will? easily match the lower value.... down to? 50 ohms.? ?Then you won't end up with a sky high loaded? Q.? To pull this off,? you need to measure the pf? ?between either anode..and chassis..... with both tubes plugged into sockets..... and also with all 6 x grid pins? bonded to chassis.? ?Knowing that info..it's then? plugged into the spreadsheet? ?as? ? "stray pf? between anode and chassis".? ? Enter calculated plate load Z... and let it spit out results.? ?You may? well have to increase the loaded Q? on the spreadsheet? to get a C1? value? that your tune cap can handle.? ? ?Then start inserting a tiny bit of? uh,? like? .1 uh....? in the stray uh column for the spreadsheet.? ? It will then spit out the lowered plate load Z the PI net is now trying to match.? ?At that point,? you should also be able to also lower the Q? in the spreadsheet.? Then? try a tiny bit more? uh before the C1 cap.... like say .15 uh..or? even? .17 uh.? ? You want to insert just enough? uh? ?to do the job, and no more.? ?That extra uh? should be made of? strap material...and ditto with the main? 6m? coil? ( between? tune and load cap).?? Same trick is used on the YC-156? to get it to work on 6M....? dues to the c 50 pf? ?between? anode and chassis.? ?YC-156? is? 35 pf as is.... on a wooden bench..... but rises to 50 pf...when bolted to chassis.? The extra 15 pf comes from the proximity of the lower anode fins to the chassis below the fins.? later.... Jim? ?VE7RF? |
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Re: RG-213 Hi pot ?
I'm using neon sign HV wire on a 10,000 volt 30KW FM transmitter
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Show quoted text
( Inside a run of metallic conduit ) Packard 440 ignition cable is tinned / stranded from Auto Parts stores... you could run it inside a braid stripped from RG8 or RG 58. Don W4DNR Quoting "jim.thom@... [ham_amplifiers]" <ham_amplifiers@...>: Does anybody know how much max V is on RG-213 ? Like what are the results if a hi-pot tester used..and say cranked up to the point where just a few microamps occurs . I have an application where I need a HV cable, less than 10 ft, that will easily handle 5700 / 7700 vdc. It will be hardwired at both ends, no HV connectors. |
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RG-213 Hi pot ?
Does anybody know how much max V is on? RG-213 ??? Like what are the
results if a hi-pot tester used..and say cranked up to the point where? just a few microamps occurs .???? I have an
application where I need a? HV?cable, less than 10 ft, that will? easily handle 5700 /? 7700? vdc.?? It
will be hardwired at both ends, no HV connectors.
And with braid peeled way back from the center conductor, like? 2-4 inches
.?
The plan was to also wrap some red electrical tape? every few inches? along
its? entire? length, to readily identify it as a HV cable. I have loads of? RG-393, but don't? want to waste it for this application.? ?
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Tnx....? JIm?? VE7RF |
Leigh Turner