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Re: 10A07-T vs 6A10 diode
<Alek Petkovic Nov 24 2:43 PM <I have not heard of 10A07s at all but Ebay is full of suppliers selling 10A10 diodes, which coincide with the <specs you quoted. <73, Alek. <VK6APK ##? 10A10's? are sold by? Mouser et all, in the USA.? made by Rectron.? Rated at 1 kv piv? @ 10A. But they only have a 400 A surge rating.? They also require a 1 square inch heat sink on the PC board they are soldered to.? ? Strung in series, you need? 2 square inches, like a 1" tall? x 2"? wide foil on board, with? wire from each? diode terminating dead center in the center of each 1"? square .? ?$48.30? per? 100.? ? ##? The 10A07? spec is here.? ? ? Rated? at? 1 kv? piv? @ 10 A.. BUT this? version has a 600 A? surge.? Made by? ?Diodes incorporated.? ? ? ? ? $42.00? per 100 ##? 6A10's? are still the cheapest... and still have a 400A? surge rating.? ?$15.50? per 100.?? ##? Prices are all over the map, depending on maker etc.? ?Mouser list abt a doz different versions of each type.? ##? all 3 diodes,? 6A10 /? 10A10 / 10A07? ? are the same diam / length / wire gauge out each end.? The 10A versions need the heatsink on a? board, and that's? going quite a bit horizontal 1st, out each end, b4 u do a 90 deg down into the board? / 1 " square heat sink.? ##? IMO,? In practical terms,? if a 6A10? isn't big enough for the job,? 2 x 6A10's in parallel? ?will do the job, and are still a big bang for the $. ... and no heat sink required.? ? 2 x 6A10's would be good for 12 A..and a 800A? surge...and still be cheaper? ?than a single? 10A10 / 10A07.? ##? In my case,? I used? 2 x separate? FWB? assy's.... in parallel .? ?24 x 6A10's per? each of the 4 x legs to make up one assy....? 96 x 6A10's in total.? ? ?And? 96 more for 2nd FWB assy.? ?Both assy's? in parallel.? ##? If I had to do this again,? ?I'd? use 2 x 6A10's? ?in parallel? to make up..."1 big diode".? ? 192? diodes still used either way.? ?Just leave the leads of the? 6A10 long, cuz that; is the heatsink on em.? ##? I use? 4-6 of em in parallel, to make up? one big? ?'safety diode'? that goes between B-..and chassis.? And? 2 more in parallel,? but rvs connected, also wired? B- to chassis.? Then the B-? is never more than? +/-? .7 V? ?from chassis? potential.? ? In the case of a? B+? ?to? chassis? arc, or? anode to grid arc, the? ?1600-2400? A? surge rating of the? paralleled 4-6 x diodes is ample.? The fault current? with? 7700 +? 50 ohm glitch is only? 154 A..and the? HV fuse opens up? in well <? 2 msecs.? Cro-bar the B+? all u want, those paralleled 6A10's never short out.? I usually buy em? by the 100, or? 250 qty.? ?And just use em on everything.? ?They work really good for bias for a GG amp, when loads of em are used in series.? ?My bias board uses? ?49 of em in series, then? tapped? ?with a rotary switch.? Then a big? 43,000 uf? @ 50 vdc? lytic across all? 40 of, then the bias? doesn't budge.? So far, so good.? Jim? ?VE7RF |
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Re: C-L-C, bad news
¿ªÔÆÌåÓýOr, would you have to parallel them? I'm thinking that's the right answer. Randy On 11/24/2018 6:02 PM, Randy
randy@... [ham_amplifiers] wrote:
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Re: C-L-C, bad news
¿ªÔÆÌåÓýJim: I wonder... "what if" somebody with way too much money needed 4H, and called one of the xfmr winders and ordered 2x 2H chokes, identical, *but* wound in opposite directions from each other....and ran them in series...? Wouldn't Kirchoff's Law, or some such crap apply. i.e., the back-EMFs would cancel when the DC flow stops? It might or might not be possible to make a winding machine run
in 2 different directions, I dunno. Or maybe Joe Junkbox could dig around in the parts pile and maybe
find 2 assorted chokes by different mfrs that happened to be wound
differently, maybe not identical, but close enough to somewhat
cancel the back-EMFs of each other. Just spitballing ideas. 73 Randy KZ4RV
On 11/19/2018 2:19 PM,
jim.thom@... [ham_amplifiers] wrote:
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Re: 10A07-T vs 6A10 diode
¿ªÔÆÌåÓýI have not heard of 10A07s at all but Ebay is full of suppliers selling 10A10 diodes, which coincide with the specs you quoted.73, Alek. VK6APK On 25/11/2018 2:38 AM, jim.thom@... [ham_amplifiers] wrote:
-- From sunny Binningup Our new house. Family Businesses: SP Electrical. The Velvet Fox. Smart Design Electrical. 0417 602 032 Perth Interiors. |
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Re: 10A07-T vs 6A10 diode
It's not something I've seen.? With the 11M folks, I never pooh-pooh their discoveries or practices because sometimes they are right.? I will say that we've had excellent results historically with 6A10s, and they're readily available from Tier-1 disti. Would this new rectifier be as readily available and as inexpensive?? If yes, given that it's a drop-in replacement with better specs, then we'd be wise to add it to our bag-o-tricks.? So who wants to test whether 10A07=6A10, and do a few price / mfg comparisons?? I am thinking that there may be an issue with the voltage standoff where the two flavors are identical, but the 10A07 is merely rated at peak volts, where the 6A10 is rated at "runs 24/7/365" volts.? In which case, it'd just be a matter of selecting the less expensive device. And -- testing on this group indicates that all 6A10 devices are basically the same, no matter where they come from.? My preference -- select a Tier 1 manufacturer and buy from Tier-1 disti with ISO9000-compliant traceability on devices.? YMMV. 73 Jim N6OTQ
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10A07-T vs 6A10 diode
? Has anybody used or seen a 10A07? ?diode ?? ?( often listed as? a 10A07-T)? Rated at 1 kv? +? 10A,? 600 amp surge.? ? ?It looks identical, dimension wise,? diam and? length? to a 6A10 diode.... and also has the same gauge wire leads on each end.? Appears to be a beefed up? 6A10.? ?It also looks like the? ?eq of? ?3 x? 1N5408's.? Apparently? 11m ops? ?will use? 10A07's,? but in pairs,? on FWB? B+? supplies.? ?IE:? 2 x 10A07's in parallel to make one big diode.? I sorta did the same thing, but paralleled? 2 x? ?FWB's .... and each? FWB uses? ?4 x strings of? 6A10's.? The 6A10 uses the same .051"? diam ( think that's? 16 gauge) wire leads as the bigger? 6A10..... which appears to be the same as the 10A07...so all 3 use the same gauge wire.? ? 6A10 is the same length as a 1N5408...so a 6A10? will always drop right in,,,where a 1N5408 once stood.? ? It appears that a 10A07? will also? drop right in where a? 1N5408 /? 6A10 once stood.? Prices are cheap, if you shop around.? Typ? bought in 100? or? 250? qty's.? Buddy is? gonna? hi pot test some? 1N5408 /? 6A10/? 10A07? diodes for me, in rvs.? ?Typ? 6A10? will high pot test? 1300-1400, with just a few ua? leakage.? ?Dahl rated his 6A10? FWB? assy's? at? 1250 PIV.... which is what they typ are anyway.? The? 10A07 is probably over kill for most applications, but the? 600A? surge? vs the? 400A? surge? of the? 6A10 ? ( vs the? 200A? surge of the 1N5408)? would make it a little more robust and forgiving, come glitch time, with ensuing fault current.? ?Usually a moot point IF? a HV fuse used b4 the? glitch R, since the hv fuse typ opens off in < 2 msecs.?? Jim? ?VE7RF? |
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Re: Plate Transformer
<Agreed. Do as Jim says. Put the 2 trannies in parallel . That halves the secondary resistance. If you put the secondaries in series and then use a full wave, you'll not gain much in regulation because the secondary resistance is now double. If you are concerned about the switch. Put in a 3 x 10A contact relay and use the main power switch to activate it. Cheers, Alek. VK6APK ##? agreed.? The heath xfmr sec is I believe? 11 ohms.? ? That's? ?22 ohms if in series..... but only 5.5 ohms, if in parallel.? ##? To really do it right, and since both xfmrs? will end up in an external box of their own,? use bigger caps, and a proper step start, like a 20 ohm HD resistor in one leg of the pri.? ?DPST-30 A relay to? apply the 240 vac.? A? SPST-30 A relay to do the step start.? ?Separate toggle switch for each relay coil.? ?Then you can also step start the fil xfmr too if you want.? ? ? ?I put my external step start, + HD? resistor and? ?both 30 relays in an electrical box,? 8x8x4.? Box sits on floor, behind desk, next to my drake L4PS? power supply.? ? ?Then one small? diam cable to a? mini box on desk, which contains the pair of toggle switches.? ?Hit toggle? #1.. watch? B+ come up most of the way, like 95%...and also? both? 3-500Z's? ?are at 3/4? brilliance. Hit 2nd toggle switch,? ? 20 ohm resistor shunted,? B+? jumps to the top...and tube brilliance increases? ?to max.? ##? OK,? for the above case, the on /off? switch on the SB-220? stays in the ON position..( or is bypassed).... since the on/off? function is now done via an outboard toggle.? ? ? SSB /? CW? function is still done from front panel of amp.? ?IF? you are in? CW position, and now want to go to? SSB position,? the 2nd toggle switch can be thrown to? off..... then CW /? SSB switch? moved to SSB position, then? 2nd toggle thrown to on position. ##? That allows you to step start between? ?cw? and? ssb positions.? ?With normal or bigger caps,? you will get a? surge / thump, when going from low to high B+ .? That's the problem? with typ? automatic? step start setups.? Ok,? when going from? SSB... back down to? CW position,? non issue,? just throw? rocker? from ssb..to cw.? ##? On the? 3400/6800 vdc? ?HB? pole pig B+? supply? I built.... used on the YC-156? pix page,? I used an adjustable? 0-15 sec timer..which plugs into a flush mount? octal? base.... the kind u can bolt to a chassis with 2 x screws.? ? A? DPDT-? 10 A relay is inside those timers,? made by? P+B / agastat etc.? ?On the? high / low? B+? switch, we? used a? DPDT-CENTER OFF? type toggle switch.? ?When switching from 3400? to? 6800, the toggle has to pass through the center? 'off' position.? ?In the? center 'off' position, the? timer? drops out,,? including the? dpdt-10A internal timer module? relay.? Those? 10A relay contacts? drop the 120 vac? to the step start relay? coil,? step start relay drops out...and the? 25 ohm step start resistor is back in the pri of plate xfmr.? ? ##? Once? switch up to the 6800 position, the step start timer has to go through its timer sequence? all over again.? ?The 2nd set of contacts on pole? #2 of the timer relay were used to open off the key line.... so no way? you can key the amp... UNLESS? timer has completed it's? sequence.? ?And IF a commercial? AC power? failure occurs,? all the relays drop out.? ? ? When power comes back on, the timer goes through it's sequence again. ##? Simple,? sounds more complex than it really is.? ## The simpler approach I used on one of my drake? L4PS? outboard? supplies,? ?with the? 8x8x4? electrical box, and mini box on desk with 2 x toggles is dead nuts? simple.? ?Used since the? ssb / cw? rocker on front of drake amp, doesn't have a center off position.? Jim? ?VE7RF |
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Re: Plate Transformer
¿ªÔÆÌåÓýAgreed. Do as Jim says. Put the 2 trannies in parallel . That halves the secondary resistance.If you put the secondaries in series and then use a full wave, you'll not gain much in regulation because the secondary resistance is now double. If you are concerned about the switch. Put in a 3 x 10A contact relay and use the main power switch to activate it. Cheers, Alek. VK6APK On 24/11/2018 3:00 PM, jim.thom@... [ham_amplifiers] wrote:
-- From sunny Binningup Our new house. Family Businesses: SP Electrical. The Velvet Fox. Smart Design Electrical. 0417 602 032 Perth Interiors. |
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Re: Plate Transformer
<wa4npl Today at 6:14 AM <I have a couple of questions about plate transformers. I've never considered voltage doubler transformers as the "optimum"? way to achieve a good plate regulation. That said, I have a working SB-220 with a pair of good 3-500zs and a? donor SB-220 in parts. Just thinking about how I could use the second plate transformer. Two possibilities ¡ I could wire them as two separate full wave supplies and put the HV in series or I could connect the two secondaries of both transformers in series? ahead of the diodes. Probably no differences, but just wanted to see what the brain-trust thinks. I would mount both transformers on a separate chassis , properly? grounded and shielded with relays to eliminate the primary plate? circuit from being fed through the fragile front panel switches. Don W4DNR ###? The heath sb-220? ?is only a 500 VA? CCS unit.? I would parallel both primaries? and also both secondarys... then? run it through the normal doubler set up.? Then use bigger caps,? like? 330u to 700uf? range.? ?Then it won't? droop.? ? I will barely flicker on ssb.? ##? The drake amp uses? a 850 VA xfmr and doubler.? ?2650 on RX,? down a bit? with normal idle current..and down to just? 2500 V with 800 ma cxr.? ?That's? with oem 200 uf caps.? ?That's only a 150 V drop from rx to tx.? ?Your real no load B+ is what you see, with normal idle current. ##? By paralleling the 2 x sb-220 xfmrs, the sec resistance drops in half...ditto with primary side.? ?Then u end up with essentially a 1 kva setup..vs? oem 500 va.? ##? I would not suggest wiring sec in series, then u have to worry about? V break down? to casing? etc.? ##? another option is just to build a real outboard supply, but since u have 2 x xfmrs, that will also work.? ##? I just a? test with psud software on the drake supply, using 8 x 330 uf caps? vs? 8 x 200 uf oem caps..and the loaded? B+? ?with 800ma? cxr? increases by 47 volts. Dynamic regulation on ssb is superb.? Below is the? 330 uf cap everybody uses? for retrofits.? Tiny thing,? 105 deg C rated, low esr, and high ripple current rated.? Jim? ?VE7RF ? ? |
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Re: Plate Transformer
I would sell the 2 transformers and purchase one good transformer. A lot simpler and probably more efficient. Just my 2 cents. Mike
-----Original Message----- From: donroden@... [ham_amplifiers] To: jim.thom@... [ham_amplifiers] Sent: Fri, Nov 23, 2018 9:21 am Subject: Re: [ham_amplifiers] Re: Plate Transformer
?
I have a couple of questions about plate transformers.
I've never considered voltage doubler transformers as the "optimum" way to achieve a good plate regulation. That said, I have a working SB-220 with a pair of good 3-500zs and a donor SB-220 in parts. Just thinking about how I could use the second plate transformer. Two possibilities ¡ I could wire them as two separate full wave supplies and put the HV in series or I could connect the two secondaries of both transformers in series ahead of the diodes. Probably no differences, but just wanted to see what the brain-trust thinks.. I would mount both transformers on a separate chassis , properly grounded and shielded with relays to eliminate the primary plate circuit from being fed through the fragile front panel switches. Don W4DNR Quoting "jim.thom@... [ham_amplifiers]" : > > Nov 21 12:30 PM > > > > best IMD3, 3-500Zs > > > > > > > > ## Where did u come up with the 'best imd' info ? Eimac states > best IMD is at 1500 V under load.... and degrades as B+ is > increased. Look up their spec sheets, they depict IMD at 1.5 > kv / 2.0 kv / 2.5 kv / 3,0 kv / 3.5 kv. > > > There is a quite a bit of difference between 1.5 kv and 3.5 kv > > > Having said that, I ran 5 kv no load on a HB single 3-400Z back > in the mid 70's..ran like a top. The real advantage of using > higher B+ levels is to minimize plate current required...and also > grid current. > > > IE: 4 kv under load @ 500 ma..... vs 2.5 kv under load @ 800 > ma. Tube requires way less emission at 500 ma vs 800ma. > With just 500ma, the fil V could be reduced a bit. Then the tubes > would last forever. When the fil is lit.... the clock is ticking. > Tube life IS number of hrs on the fil. > > > That 3CX-6000A7 u see on the pix page, the fil is rated at 7.0 > vac. It's being run at 6.1 volts for the last 10 years...with > full bore output. Tube rated for 3.5 A CCS plate current. It's > run at just 2.7 to 2.8 A plate current. Again, loads of excess > emission capability, so fil V is reduced... until PO just drops a > few watts, then fil V increased by .1 V ( 1/10th volt) > > > Emission on a new tube ( directly heated tube like a 3-500Z, or > 3CX-3000A7 / 10,000A7 etc)... will increase a bunch during the > 1st 200 hrs. Normal deal is to run the tube at rated fil V for the > 1st 200 hrs, then reduce the fil V until the PO just drops off a > few watts, ( knee effect)... then increase a tiny bit. Sola > constant voltage xfmr + variac used for this setup. Plus an > hr meter across the output of the sola..so we know exactly how many > hrs on the tube > > > Nobody does that of course on a 3-500Z amp. Still, using more B+ > and less plate current will make the tubes last longer. One of my > L4B's that I bought back from a buddy...the tubes were soft. > Required more drive to get 800 ma..... at which point the grid > current was 400 ma. Installed new tubes...and way less drive > required to get the same 800 ma.... and grid current down to normal > 300 ma. > > > Be careful with increased B+ on the L4B / L7. Tune cap will > arc with 4 kv on it. 3 to 3.5 kv no load is ample. If you > need more power, build a bigger amp. The idea is to optimize it, > not blow stuff up. The squirel cage blower on the L4B is marginal > at best. Somebody posted a drop in Dayton blower that fits like a > glove.... but I will be damned if I can find the dayton model > number... lost the info. The oem 1550 rpm blower really needs to > be increased just a little bit, like 1750 rpm..and no more than > 1900-2000 rpm. > > > Jim VE7RF |
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Re: Plate Transformer
I have a couple of questions about plate transformers.
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I've never considered voltage doubler transformers as the "optimum" way to achieve a good plate regulation. That said, I have a working SB-220 with a pair of good 3-500zs and a donor SB-220 in parts. Just thinking about how I could use the second plate transformer. Two possibilities ¡ I could wire them as two separate full wave supplies and put the HV in series or I could connect the two secondaries of both transformers in series ahead of the diodes. Probably no differences, but just wanted to see what the brain-trust thinks. I would mount both transformers on a separate chassis , properly grounded and shielded with relays to eliminate the primary plate circuit from being fed through the fragile front panel switches. Don W4DNR Quoting "jim.thom@... [ham_amplifiers]" <ham_amplifiers@...>: <Bryan Swadener |
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Re: Plate Transformer
<Bryan Swadener Nov 21 12:30 PM ?<Re/winding a transformer can give you the output you want (for best IMD3, 3-500Zs <like 3000-3500V). <vy 73, <Bryan WA7PRC ##? Where did u come up with the 'best imd'? info ?? ? Eimac states best IMD is at? 1500 V? under load.... and degrades as? B+? is increased.? ?Look up their spec sheets, they? depict? IMD? at? 1.5 kv? /? 2.0 kv /? 2.5 kv? / 3,0 kv? / 3.5 kv.? There is a quite a bit of difference? between? 1.5 kv and? 3.5 kv Having said that,? I ran? 5 kv no load on a HB single? 3-400Z? back in the mid? 70's..ran like a top.? ?The real advantage of using higher B+ levels? is to minimize plate current required...and also grid current.? IE:? 4 kv under load? @? 500 ma..... vs? 2.5 kv under load @ 800 ma.? ?Tube requires way less? emission? ?at? 500 ma? vs? 800ma.? ? With just 500ma, the fil V could be reduced a bit.? ?Then the tubes? would last forever.? ?When the? fil is lit.... the clock is ticking.? Tube life? IS? number of hrs on the fil.? That? 3CX-6000A7? u see on the pix? page, the fil is rated at? 7.0? vac.? ?It's being run at? 6.1? volts for the last? 10 years...with full bore output.? ?Tube rated for? 3.5 A? CCS plate current.? ?It's? run at just 2.7? to 2.8 A? plate current.? Again, loads of excess emission capability, so? fil V is reduced... until? PO? just drops a few watts, then fil V increased by .1 V? ( 1/10th? volt)? Emission on a new tube? ( directly heated tube like a 3-500Z, or 3CX-3000A7 / 10,000A7? etc)... will? increase a bunch during the? 1st? 200 hrs.? Normal deal is to run the tube at rated fil V for the? 1st 200 hrs, then? reduce the fil V until the PO just drops off? a few watts, ( knee effect)... then? increase a tiny bit.? ?Sola constant? voltage xfmr? +? variac? ?used for this setup.? ?Plus an hr meter across the output of the sola..so we know exactly how many hrs on the tube? Nobody does that of course on a 3-500Z amp.? Still,? using more B+? and less plate current? will make the tubes last longer.? ?One of my L4B's that? I bought back from a buddy...the? tubes were soft.? ?Required? more drive to get 800 ma..... at which point the grid current was 400 ma.? ? Installed new tubes...and? way less drive required to get the same 800 ma.... and grid current down to normal 300 ma.? Be careful with increased? B+? on the? L4B? / L7.? ?Tune cap will arc with 4 kv on it.? ?3? to? 3.5 kv? no load is ample.? ? If you need more power,? build a bigger amp.? The idea is to optimize it, not blow stuff up.? ?The squirel cage blower on the L4B is marginal at best.? ?Somebody posted a drop in Dayton blower that fits like a glove.... but I will be damned if I can find the dayton model number... lost the info.? ?The oem 1550? rpm blower really needs to be increased just a little bit, like? 1750 rpm..and no more than 1900-2000 rpm.? Jim? VE7RF |
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Re: Plate Transformer
Hi Bryan, Yes, that hydro project attracted my attention years back. As I indicated before I consider him to be an excellent engineer. I, by the way, am a retired RF and analog engineer. I lave an L7 and use an external PS with it. 4KV and the HV drops 60 volts under full load. It uses a large transformer that weighs 124 lbs. 60mF of oil capacitance is used along with step start. Complete PS weighs 204 lbs. Large PS is a direct plug in for the amp. Uses a transistor regulator to set bias on the tubes. RF bypass caps had voltage ratings increased to 7.5 KV. The amplifier uses external RF switching with a vacuum relay and reed relay using high voltage speed up. The vacuum relay is switched and becomes stable in 3.5 mS. The reed input relay is switched and stable in 0.8 mS. No hot switching issues with it. Enjoy the Thanksgiving holiday. 73, Russ, NM3DX |
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Re: C-L-C, bad news
<On the Harris 35KW FMs they use 1/4 acorn nuts on a couple of? <brackets to create the spark air gap. <Don W4DNR ##? Ingenious !? ? Never thought? of acorn nuts...perfect solution.? ? They have loads of em..in brass, in? 1/4" -20? sized thread..and mating? 1/4-20? brass? bolts? at local home depot? 1 mile away.? ?Dirt cheap..and the acorn nuts are easily replaceable... like if one / both have their? domes? blown, pitted / chunks out of them? etc.?? ##? The domed? shape of the acorn nut? is perfect for this job.? ?2 x acorn nuts, with? domed sides facing each other is the next best thing to? a pair of? metal balls..with embedded threads.? ##? Then just a pair of? ?'L'? brackets? and lock nuts on either side of each? bracket..to set the gap.? ? Or threaded, thick? bar stock, again, with locking nuts on either side.? Then the threaded brass rod would stay put, no wiggle? up /down.... b4 even locking the nuts on either side.? Tnx? ?for the invaluable tip? Don, much appreciated.? ?Now I'm? back on track.? ?They would also be ideal to protect a vac? tune + load cap..or any other? application..that needed an adjustable gap.?? Jim? ?VE7RF?? |
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Re: Plate Transformer
Hi Russ, Yes. Manfred's callsign: XQ6FOD I've included links to his practical re/winding info, as well as his general magnetic theory page:?. ?I first became aware of him after reading about his microhydro project.?It included winding two 8KVA transformers: . Manfred's info helped w/ rewinding a > 3KVA transformer (). Using a FWD rectifier, I provided taps from 3300-4050V. The Ameritron transformers suggested by another are rated 900V/500mA (450VA). A single 3-500Z can run on that but, the Drake L4/L7 mentioned by the OP uses a pair. The best off-the-shelf unit is the xfmr used in the?SB-220 (about 600VA), and it'll give a bit better HV that the tubes want to see. Re/winding a transformer can give you the output you want (for best IMD3, 3-500Zs like 3000-3500V). vy 73, Bryan WA7PRC Subject: Re: Plate Transformer From: Russ NM3DX Date: Tue Nov 20, 2018 11:54 am Hi All, A person by the name of? *Manfred Mornhinweg*? has written about transformer rewinding. Manfred is an excellent engineer. The information is located at: <> with design information at: <> Russ, NM3DX |
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Re: C-L-C, bad news
Seriously, I have used sparkplugs ... the racing ones without resistors on twin lead at a grounding block. Tapped the block to fit the sparkplug threads.
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On the Harris 35KW FMs they use 1/4 acorn nuts on a couple of brackets to create the spark air gap. Don W4DNR Quoting "jim.thom@... [ham_amplifiers]" <ham_amplifiers@...>: <W4DNR |
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Re: C-L-C, bad news
<W4DNR? Today at 7:15 AM <?Use an AC Delco spark plug across the terminals unless its a German? <Choke.. then use Bosch. <Don W4DNR ##? LOL.? ?And both of em have a resistor built into em, for??RFI suppression.? So don't know if a spark plug would handle any amount of energy.? ?It should work though.? Easy to gap.? ?Instead of the typ .060? just? reduce it to like .01? to .02? ##? with my luck, the plug tip will burn clean off.? ##? Brass machine screws, and locknuts will work, sorta like the various adjustments on a Vibroplex keyer paddle.? ?The 80-10m? ?YC-156 on the pix page uses a hb adjustable spark gap across the vac load cap, with? gap big enough, to?arc with a? 3? or? 4? to 1? swr...? but lower than the rated peak V rating of the cap. ? ?Normal swr protection is already provided? at some pre-set value, like? 2:1? ?or? 2.5:1? ? ? ?The spark gap is there as? a brick wall device, when? dumb stuff happens, like? switching to wrong ant, no ant etc.? ? Vac load caps are harder to procure these? days, so anything to protect them is welcomed.? ?The concept works too.? ##? 1/4 -? 20 or? 1/4-28? brass bolts..or bigger, will? do the job? for me.? ?I have a smoked plexiglass front ?door on the new? 24"? wide x 24" deep? x 6' tall rack.? ?Then I get to see whats?going on inside.? ?50 x lytics and choke reside in that rack.? Plate xfmr and contactor/? ?and paralleled? FWB? assy's, meters, breaker? etc, reside in a small? 19"? wide x 30"? deep? x 36" tall rack.?? Later... Jim? VE7RF |
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Re: C-L-C, bad news
Use an AC Delco spark plug across the terminals unless its a German Choke.. then use Bosch.
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Don W4DNR Quoting "jim.thom@... [ham_amplifiers]" <ham_amplifiers@...>: ## I will have to put the spark gap well away from the choke terminals. Last thing I need is any molten debris |
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Re: C-L-C, bad news
<6M QRO Today at 4:50 PM <?I had an old either Navy or Air Force choke that had exactly that.? An adjustable spark gap across the choke.? ## Tnx Lou.? Looks like I re-invented the wheel.? ?I know what the normal? V drop across the choke is for normal operating conditions, like toggling between idle current and? full bore.? IE:? 150 ma and? 1.5 A? on a 3x3? tube... or say? 200 ma and 3A on a YC-243 tube.? Its not very much, like 60-70 v, swinging in polarity and amplitude.? ?So any? adjustable spark gap can be set real narrow, like 200-500 volts.? 1-3 sheets of paper would probably suffice as a spacer... or feeler gauges.? ?.030 is like? 1 kv.? I will look up the gap vs V stand off in my book.? ## I will have to put the spark gap well away from the choke terminals.? Last thing I need is any molten debris? ?falling down onto the? choke.? ?I'll use some al or flat? cu bar..sticking out side ways? from the? choke terminals..which are already wide spaced on the red micarta... each on it's own? oem dahl insulator.? ##? I will also wire the NC? contacts of the Kilovac? 25 kv / 65A? CCS? ceramic relay? across the pair of bars. I bought 3-4 of these Kilovac? SPST-NC? relays, with?12 vdc coils, years ago at a surplus place, nib.? Hi-pot tested to > 30 kv.? The ham fellow, who is the eng at? Hammond,? who handles the? Dahl amateur and commercial items, freaked out when I mentioned using the vac relay? across the choke terminals...to? do a instant? A/B testing. He said if I short the choke, with? normal current flowing, the initial back emf... being opposite polarity,? will spike into the C2 cap.? It's? additional Vdc..added to the? C2 cap..which also can fry the C2 cap...and also? your tube, etc. I then came up with a simple? DPDT-Center off? toggle? switch config..with key line on pole #1.... and? 12 vdc? for relay on pole #2.? When? de-energizing the 12 vdc coil... ( so NC relay? now closes), the key line will be opened off, so amp? will be temp offline, no idle current, no? normal plate current.? ?This is with? toggle in center off position.? ?With toggle all the way down, coil? still? de-energized,? but key line is closed via pole #2. Dead? simple? config,? engineer? at? Hammond / Dahl? approved the simple? config, problems? solved... or so I thought.? ?Then I modeled the? C1 - L- C2? ?config in PSUD, using the stepped load feature, but? using?the 100? /? 135 A?? peak fault current as the initial load, then? dropping down to just? 6ma? of? eq bleeder current...and instantly.? ?The resulting wave form oscillations? ?both for current..and also voltage? on the? FWB rectifiers,? C1? cap,? choke, C2 cap is crazy.? ?With the? choke V? swinging wildly? ?from? positive to negative, the? positive end at any given time, is in addition to the caps? voltage =? sky high voltages.? The V breakdown? on these Dahl chokes, between? winding and C cores /? or angle steel? frame at top and bottom is only limited by the insulation on the wires..and the single piece of external? fish tape? dahl used? across the top and bottom on both sides... plus the inner walls of both C cores.? ?Hence the reason I will float the entire choke on? 1"? thick? UHMW, with a couple of? 2x2 x 3/16? angle al pieces underneath the uhmw, to support the 127 lbs.? It? get even worse, if? no glitch R used !? ? ??? Real crazy if? no? HV fuse in the B+ line...and B+? arcs in RF deck / tube.? ?Mains breaker is one item that might open off vs??a non existent HV fuse.? ?That or the diodes in the FWB go open, or shorted.? ?Diodes? will blow in half with too much V.? Diodes short? with too much current.? ?Cap V? goes through the roof.? ?I'm using 25 x 450 vdc caps as is =? ?11,250? V rated....and? ?12,500 vdc..using the? 500 V surge rating.? ?Surge ratings on lytics is for a max of? 2 secs.? Adjustable spark gap is the only fix.? That or don't even install the choke.? Without the spark gap, it's a bomb ready to go off.? ?Placing the? choke in series with the B- lead won't work either, that's more? arrl? fubar / wifes myth.? ?I can see why chokes in Henry radio amps go open, the? L-C? config they used..along with the choke resonated, no glitch R, and no HV fuse is another disaster in the making.? ?If just any one bleeder in the henry amps? opens? up, the B+ skyrockets.? Now get a B+ to grid / chassis arc, etc.... and the back emf on the choke is insane, taking out the oil cap in the process, along with the resonating cap across the choke, the choke itself, and also the FWB? assy.? I already smoked the 0-?60 vdc? @? 5A? lab supply, from the? back emf of the dahl choke..with just opening off a mere 2 A of current flowing through the choke.? stay tuned Jim? ?VE7RF
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