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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育Repeating my Feb 15 ?attempt to get image thru the new GIO ???I will delete ?this message if it fails but the an other very important thing is IN THE MANUAL? [ edited from the BAMA manual] …. don -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
I don't see where zero-crossing voltage is a problem since it only happens during application of AC power. There is no collapsing flux since it hasn't been established.
The SSR's during turn off, don't "disconnect" (if that's the right word) until at "zero" current. From the Opto22 spec sheet: And actually, there is a "chance" every time one turns any piece of gear off, of having the contacts open at the "right" (or wrong) time(or somewhere in between) . I have "pulled the plug" on many devices while they were powered and sometimes there's a spark and a "snap" and/or see a spark and sometimes there is not. Turning the radio off then right back on is of course another issue regardless of how the circuit is interrupted either by a switch, relay contact or Triac. I cannot think of any reason why one would do that intentionally. And in the case of the original question I am afraid I have diverged from it by even mentioning the use of SSR's to reduce switch failures (as is the mention of step-start systems etc) REF: HT-37 transformer failure due to rapid STBY-->OFF-->STBYCan someone please indicate the page in the HT-37 manual where it says NOT to this? While I still cannot think of a reason why anyone would do this, I only found the "CAUTION" text I excerpted and posted earlier. (that is, to pause in STBY before turning it off) After printing out a pretty good copy of the HT37 schematic and taping it all together so as to see what's going on, (OPERATION SW is in the OFF position) .... It appears that the transformer remains powered and all voltages are present until selecting OFF. There are 3 wafers that control bias switching, and other low level "stuff" The only thing I can see that could be a problem is if one was doing RTTY , transmitting at full power, and then went from MOX directly to OFF, there might a problem with MAX AC current in. But that's just a guess . Again, I don't see how it would be a problem if the transmitter wasn't transmitting (or keyed) Again, the original "question" concerned OFF-ON-OFF rapidly. No reason to do it, so don't! Sorry for the long answer! 73/Rick On Sat, Jul 13, 2024 at 11:37 PM, Jim Whartenby wrote:
? -- 73/Rick W4XA __________________________________ All posts are created using OpenSuSE Leap 15.5 x64 Linux |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
As more zero voltage crossing SSRs are installed to power ON these radios, it will be interesting to see if there is an increase in power transformer failures due to corona discharge (aka wire insulation failure) in the? high voltage winding of these hallicrafters radios.?? Zero voltage crossover is at the instant where current in the transformer winding is at a maximum.? Inductive circuits want to maintain a constant current flow through a winding so the collapsing magnet flux at turn OFF will generate as high a voltage as is possible so as to maintain this current flow.? This is the nature of inductive circuits.?? I do not know what the exact failure mechanism is when switching from ON to STANDBY to OFF to STANDBY to ON in rapid succession.? But evidently it is the worst possible condition which generates a voltage high enough to cause the wire insulation to fail.? Not understanding this failure mechanism means to me that any proposed solution is just a shot in the dark.? Perhaps this point was understood by the HT-37 design team and that a workable solution was either just too costly or perhaps not even available? Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Saturday, July 13, 2024 at 10:51:13 PM CDT, Rick W4XA <myr748@...> wrote:
On Sat, Jul 13, 2024 at 06:09 PM, =R= wrote: Randy, I have to apologize for taking the discussion away from this and I have to say I have the same question too! The "Caution " (page-6) is to momentarily pause in STBY before turning it off. Is there another caution to not immediately turn it back on? I looked at the HT37 schematic (and my HT32B) but because I don't have a full schematic, I was unable to determine what exactly would happen by turning the thing directly off without pausing in STBY. The HT32B doesn't appear to have have that caution. ? -- 73/Rick W4XA __________________________________ All posts are created using OpenSuSE Leap 15.5 x64 Linux |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
On Sat, Jul 13, 2024 at 06:09 PM, =R= wrote:
Randy, I have to apologize for taking the discussion away from this and I have to say I have the same question too! The "Caution " (page-6) is to momentarily pause in STBY before turning it off. Is there another caution to not immediately turn it back on? I looked at the HT37 schematic (and my HT32B) but because I don't have a full schematic, I was unable to determine what exactly would happen by turning the thing directly off without pausing in STBY. The HT32B doesn't appear to have have that caution. ? -- 73/Rick W4XA __________________________________ All posts are created using OpenSuSE Leap 15.5 x64 Linux |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
On Sat, Jul 13, 2024 at 05:36 PM, don Root wrote:
Don, it might be a "Dream"!! I looked back to see if I mentioned a sales price for them. Maybe you can point me to the message number? I did say they're pretty expensive and looking just now at Mouser and Digikey, I found 240V 45A OPTO22's (like I have) for close $100USD. To me that's expensive. If I said $300 someplace, I clearly pressed the "3" when I should have pressed "1" !! I don't think I said only switching ON "wrecks" the switch. I believe I said that a step-start system tries to protect the switch but only during turn-on. Step-start systems don't help much (or at all) when switching OFF . Now one would presume that when switching off, the actual current would be less than when switching on because there's (relatively ) large instantaneous currents required due to charging the filter caps etc.... This is where the "Zero-Crossing" type SSR actually prevents switch erosion by removing those currents from the switch altogether. And of course, an electro-mechanical relay does the same thing but only by transferring those "sparks & arcs" to the relay contacts. The SSR eliminates them altogether because the AC voltage is at zero when the device is ready to conduct and the current is zero when the device disconnects.. And I still think the actual (transformer primary) current by "ramping" up the voltage from zero at the sine-wave rate vs being switched on (instantaneously) at "peak" voltage (roughly 170Vor 340V) has to be at least somewhat "less" As far as contact bounce? I guess someone could hook up a scope & try to measure it. I don't dispute that it could be a problem. Contact bounce in switches and relays is pretty well known and well documented....and another good reason to use solid state switching for either AC or DC. (Pin diode switching come to mind for RF T/R switching and it works well too, but those systems are really complicated and messy!) My main concern is for the Drake L-4/L-7 AC power switch and other switches (Collins, Drake, Halli etc) that are no longer available unless you scrounge one from a "Parts" radio that may already be "arced & sparked"!! (The surplus SSR's you can find on eBay work well for that use) You'll have to decide if you want to pay retail price for them. In the case of OPTO22 (and maybe others) they actually offer a "lifetime" warranty when using them so maybe the $100 or so isn't all that bad. I have a couple of SSR's that came out of very old computers that controlled various systems 240AC @ 10A and 120AC at 10A that still work fine...... I am guessing they're from the 70's or 80's and they still do the job. I'm thinking you cannot wear them out unless you far exceed the ratings on them. Cheers! -- 73/Rick W4XA __________________________________ All posts are created using OpenSuSE Leap 15.5 x64 Linux |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育Well Rick, ?????back a little you mentioned 300+ bucks for one but maybe that is a dream? How did you determine that switching ON? is what wrecks the switch, not switching OFF ??, I worry about contact bouncing on the ON stroke and acring when it is turned off , especially under load.? I guess I’m still wondering if it is a real toggle switch, or what.?? don ? From: [email protected] [mailto:[email protected]] On Behalf Of Rick W4XA
Sent: Saturday, July 13, 2024 7:47 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? On Fri, Jul 12, 2024 at 03:48 PM, don Root wrote: Rick they have oodles of ?SRS. ??which exact one ??? maybe a link so we can see what you recommend??? … don ?? --
-- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
On Fri, Jul 12, 2024 at 03:48 PM, don Root wrote:
Don, Are you asking which solid state relay I am putting in my Valiant? I only suggest using them in place of a "step-start" circuit since the only thing a step-start protects is the ON/OFF switch and only then during "Turn-On" especially if it's switch that is essentially irreplaceable, (like certain Drake, Collins, or other unique ON/OFF switches. It seems prudent to try to protect them. In the Drake AC-4 supply, I used an OPTO22 120A25 (120V @ 25A) controlled by AC. I found them on eBay, "pre-owned"........ if you have to get them from Mouser or Digikey etc (new) , You'll likely not want them. They cost way too much. In the Johnson Valiant, to replace the PTT plate transformer relay, I'll probably try an old used CRYDOM D1210 (120VAC 10A, controlled by 3-32VDC) since I have DC available for it. The Valiant plate supply transformer doesn't draw much current when keyed, probably somewhere around 3A . All the SSR's I have, I found on eBay, or scrounged from old equipment. One only needs to mind the maximum possible current draw during turn on. ? -- 73/Rick W4XA __________________________________ All posts are created using OpenSuSE Leap 15.5 x64 Linux |
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Re: HT-44 VOX issue - Final Solution!
Finally got back to looking at this problem. In short, the problem is that when sending CW in what Hallicrafters called "break-in" mode (Operation switch in VOX position), the first dit or dah sent is severely truncated to the point that a dit might not even be heard at the other end. Looking at the timings observed by Halden, if we could just somehow lengthen the leading dit or dah by 30 ms. or so, we would mask the problem and all would be well. I read through a lot of posts on the K1EL group here on groups.io (Winkeyer info) and found that K1EL had already thought of that solution and built it into the Winkeyer USB.
In the Winkeyer USB settings, there's a parameter called "1stExt". If you put a value in there in milliseconds, Winkeyer will automatically lengthen the first dit or dah sent by that amount of time and all other dits and dahs are unaffected. I used the Winkey utility called "WinKey2 Standalone Editor" to play with the value and at 30 ms. it sounds pretty good. Later I'll hook up the scope and make a final adjustment of the value. This solution makes the HT-44 a very decent CW rig where before it was useless to me. 73, Floyd - K8AC |
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Re: Circuit breaker ratings
开云体育Jim, ??going back some years, MOST situations outside of equipment had thermo-magnetic trips to protect from overloads as well as short circuits. But yes? Some large breakers were magnetic, with a “dashpot” to try to replicate thermal I^2*t ? Things have changed over the years , probably a chip would do a good job.. if we could only trust them, but your trusty 1960 washing machine? might tire out slowly? but the new ones just say error 888 .. buy a new board for only 1000 bucks , and it does that the night before the wedding or some long vacation. ???Sorry for the diversion to a rant. Oh yes back to a 35 mA or 55mA into a transformer radio being left ?at the mercy of a nominal 15A breaker ..? if the filter cap shorts, everything in the line of fire fries too until something burns open or all burns down.. maybe right to the foundation?? ..more ranting , I got up too early. and found me on the wrong side of the bed! ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Saturday, July 13, 2024 1:45 PM To: [email protected] Subject: Re: [HallicraftersRadios] Circuit breaker ratings ? Don There are typical specs for a particular class of circuit breaker and then there are worst case general specs for all circuit breakers.?? ? AFAIK, there are two types of circuit breaker, thermal and magnetic.? The thermal types take some time for the heated sensor to trip the circuit breaker mechanism.? This is desirable to reduce nuisance tripping.? Not so with the magnetic circuit breaker.? There is no thermal delay but a time delay is still possible.?? ? Heinemann circuit breakers, for example, are magnetic but the pole piece is a iron slug sealed in a brass tube with a spring and a viscus fluid.? As the current through the circuit breaker reaches the rated current, the iron slug will move against the spring in a time determined by the fluid.? ?The breaker will not trip at 100% of the rated current.? At 120% of rated current or above, the breaker will trip.? Any current through the circuit breaker that is well above the rated current will cause the circuit breaker to trip immediately even though the iron pole piece is not in the desired position. ? You will have to check the timing curves for a particular circuit breaker to determine how fast a breaker will trip at a certain percentage of overload.? I would think that at 4X rated current, any good circuit breaker would trip immediately. ? As for fused plugs in the U.S. they are available, see? Regards, Jim -- don??? va3drl |
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Re: Circuit breaker ratings
Don There are typical specs for a particular class of circuit breaker and then there are worst case general specs for all circuit breakers.?? AFAIK, there are two types of circuit breaker, thermal and magnetic.? The thermal types take some time for the heated sensor to trip the circuit breaker mechanism.? This is desirable to reduce nuisance tripping.? Not so with the magnetic circuit breaker.? There is no thermal delay but a time delay is still possible.?? Heinemann circuit breakers, for example, are magnetic but the pole piece is a iron slug sealed in a brass tube with a spring and a viscus fluid.? As the current through the circuit breaker reaches the rated current, the iron slug will move against the spring in a time determined by the fluid.? ?The breaker will not trip at 100% of the rated current.? At 120% of rated current or above, the breaker will trip.? Any current through the circuit breaker that is well above the rated current will cause the circuit breaker to trip immediately even though the iron pole piece is not in the desired position. You will have to check the timing curves for a particular circuit breaker to determine how fast a breaker will trip at a certain percentage of overload.? I would think that at 4X rated current, any good circuit breaker would trip immediately. As for fused plugs in the U.S. they are available, see? Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Saturday, July 13, 2024 at 11:46:38 AM CDT, don Root <drootofallevil@...> wrote:
Jim, ?interesting, and I get the jist, ?but I wonder what the point is. Anyhow, as I read stuff, #18 copper will melt [1000 C nom] at 83 amps yes ,but that happens in 10s , not 2 minutes. ?That would be the same heat/temp [ I^2 *t ] ?= about ??25A for 2 min. I don’t know when insulation turns to carbon, but I’m getting worried now. Maybe I goofed-up? And I have lost my point now too.? My past understanding was that grounding conductors were based on fusing temps, but conductors with insulation were somehow based on the insulation. I have no Idea what it can take short term. ? ? RE????? According to the above link, a 20 amp circuit breaker must support a 20 amp current but must trip at 200% of rated current within two minutes.?? Ya ,that is a most common criteria, and seems rather High. It seems that this was instigated back in fuse only days, and fuses that got too hot would get tired [flip on a big string of tungsten lamps] and fail.? Thermal elements of breakers also heat up in normal current service so in that condition it wont take so much to trip them, so the 200% is a practical number ? ? Re ?code in Britton? ?…????????? ?fuses in plugs ? ? ? ? ? ? ? …….诲辞苍 ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Saturday, July 13, 2024 12:57 AM To: [email protected] Subject: [HallicraftersRadios] Circuit breaker ratings ? Don The fusing current for 18 AWG wire is 83 amps.? This is the point where the copper wire is hot enough to melt.? I found this info here:?? This is just over 2 times the must trip current rating of a 20 amp circuit breaker.?? ? For the skinny on circuit breakers, see:? According to the above link, a 20 amp circuit breaker must support a 20 amp current but must trip at 200% of rated current within two minutes.?? ? Since you brought up the electric code in Britton, just what is it that you like about it? Jim ? ?
? -- don??? va3drl |
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Re: Halicrafters SX17 transformer
John Yes, the Hammond 124A looks fine, don't know about the mounting hole spacing so perhaps a new hole is needed?? Strange that the shield terminal is between the two secondary leads.?? You might still be able to use that first replacement transformer.? Try using two resistors to make a phantom center tap.? You might try 3k from each 6V6 control grid to ground to see if it will work.? Or, if you have a small power or audio transformer, with a high voltage winding with a center tap.? Connect each winding end to each 6V6 control grid and ground the center tap.? Leave open any other transformer windings. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Saturday, July 13, 2024 at 08:36:16 AM CDT, John via groups.io <siloam@...> wrote:
Jim, Thanks for the detail. Taught me something about looking at the datasheets! Looks like there is an A-4723 available on eBay in the USA. However, someone elsewhere also pointed out this product from Hammond: https://www.hammfg.com/electronics/transformers/audio/124?referer=968 The 124A appears to fit the bill and is available in the UK. Would you concur that the specs are adequate? The reason I asked about the center wire in the secondary is because it was connected to the chassis, but does not connect to either end, although the ends do connect to each other. Thanks. On Tue, Jul 9, 2024 at 07:50 AM, Jim Whartenby wrote:
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Re: Circuit breaker ratings
开云体育Jim, ?interesting, and I get the jist, ?but I wonder what the point is. Anyhow, as I read stuff, #18 copper will melt [1000 C nom] at 83 amps yes ,but that happens in 10s , not 2 minutes. ?That would be the same heat/temp [ I^2 *t ] ?= about ??25A for 2 min. I don’t know when insulation turns to carbon, but I’m getting worried now. Maybe I goofed-up? And I have lost my point now too.? My past understanding was that grounding conductors were based on fusing temps, but conductors with insulation were somehow based on the insulation. I have no Idea what it can take short term. ? ? RE????? According to the above link, a 20 amp circuit breaker must support a 20 amp current but must trip at 200% of rated current within two minutes.?? Ya ,that is a most common criteria, and seems rather High. It seems that this was instigated back in fuse only days, and fuses that got too hot would get tired [flip on a big string of tungsten lamps] and fail.? Thermal elements of breakers also heat up in normal current service so in that condition it wont take so much to trip them, so the 200% is a practical number ? ? Re ?code in Britton? ?…????????? ?fuses in plugs ? ? ? ? ? ? ? …….诲辞苍 ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Saturday, July 13, 2024 12:57 AM To: [email protected] Subject: [HallicraftersRadios] Circuit breaker ratings ? Don The fusing current for 18 AWG wire is 83 amps.? This is the point where the copper wire is hot enough to melt.? I found this info here:?? This is just over 2 times the must trip current rating of a 20 amp circuit breaker.?? ? For the skinny on circuit breakers, see:? According to the above link, a 20 amp circuit breaker must support a 20 amp current but must trip at 200% of rated current within two minutes.?? ? Since you brought up the electric code in Britton, just what is it that you like about it? Jim ? ?
? -- don??? va3drl |
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Re: Halicrafters SX17 transformer
开云体育John ?if you really expect it is going to a shield, perhaps try measuring the capacitance to various winding leads. Just a thought out of the blue.? don ? From: [email protected] [mailto:[email protected]] On Behalf Of John via groups.io
Sent: Saturday, July 13, 2024 9:36 AM To: [email protected] Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer ? Jim, -- don??? va3drl |
don Root
Rick W7IMM
Jim Whartenby
Floyd - K8AC