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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育Jim ?yes mostly ?? I guess you are responding to? ?Same sort of goes for radios of old. ?I blame the NEC++ ?for allowing a? 0.35 amp radio to be *protected* by the 15 amp house fuse ? ? Quibbling ?…. “to the outlet厂” I support the good practice to ??“add a fuse to a consumer radio” but going back to NEC code you need to fuse every time you reduce wire size/rating unless upstream protects it too. ?But plug-in stuff has been immune from the NEC ideas, but they still get ULs blessing somehow .? A wired in transformer must be fused, but a plug transformer ..your handy powerstat doesn’t . I say it is all in the business politics of who sits on the board/ committee etc. but I should not start that here.? Seems to me fusing in Britain is more sensible.. in that way ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Friday, July 12, 2024 3:30 AM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Don Whatever is used as a circuit protection device, it is there to protect the hidden wiring from the distribution panel where the fuse or circuit breaker is located to the outlet, it is not used to protect the load.? It is good practice to add a fuse to a consumer radio when it is in for repair but few appliances have such protection.?? ? I believe that our vacuum cleaner has a thermal circuit breaker.? Not sure about the microwave oven or the fridge but they are both close to the 15 amp rating of outlets protected by 15 amp circuit breakers.? I live in Hot Springs, Arkansas.? The local electric code does not allow for anything smaller then 12 AWG wire so the smallest circuit breaker allowed is 20 amps. Regards. Jim ?? -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育Rick they have oodles of ?SRS. ??which exact one ??? maybe a link so we can see what you recommend??? … don ? From: [email protected] [mailto:[email protected]] On Behalf Of Rick W4XA
Sent: Friday, July 12, 2024 12:11 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? You have a pretty good point Jim, ?? -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
You have a pretty good point Jim,
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It appears that this could be a pretty simple solution to a problem,? but only if it is actually "the problem" but I'm not seeing where "soft" start solves it. An example might be the EF Johnson Viking Valiant where they actually "PTT" the plate supply via a relay in the plate transformer primary circuit.? No one has ever suggested that "soft-starting" the plate supply would protect the transformer.? (don't know how many Valiant transformers have failed though) Now, having said all that I still plan to put an SSR in place of that old electro-mechanical relay just to make it? quieter when pressing the mic button! (it's a pretty loud "clank" ) Also,? I looked through my HT32B manual, and although the HT32's are not identical or even closely similar to the HT37, I couldn't find any mention of hesitating in STBY when turning it off. (and I don't.? I just turn it off) My HT32B also has the FIL --> HV (winding) short that happened long ago so there's no tube-type rectifiers in it......but everything still works fine. Just checked Digikey and the price is still $319 (plus shipping/tax)
? --
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
Don Whatever is used as a circuit protection device, it is there to protect the hidden wiring from the distribution panel where the fuse or circuit breaker is located to the outlet, it is not used to protect the load.? It is good practice to add a fuse to a consumer radio when it is in for repair but few appliances have such protection.?? I believe that our vacuum cleaner has a thermal circuit breaker.? Not sure about the microwave oven or the fridge but they are both close to the 15 amp rating of outlets protected by 15 amp circuit breakers.? I live in Hot Springs, Arkansas.? The local electric code does not allow for anything smaller then 12 AWG wire so the smallest circuit breaker allowed is 20 amps. Regards. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Thursday, July 11, 2024 at 05:55:50 PM CDT, don Root <drootofallevil@...> wrote:
First,? sorry for?? the email that flew of my bit machine,? I went on line and deleted it. Ed I guess we are OT a fair bit, but you and Jim raised? stuff related to “turn-on” situations. As I recall in NA motors were typically required to draw less than 600% [locked-rotor] current? depending somewhat on the HP. It was known that these sacrificed efficiency for nicer starting as seen by lights on the same line, which is especially a problem for farmers and other rural people. ?European motor standards? allow higher startup / locked rotor current ?and their fusing standards expect this but put one of them on our wiring and you might have a problem. The standards NA vs Europe [perhaps old now] are/were not compatible.? Your problem is just like the farmers, as well as mine, since I am right at the end of the local line, so real dips come from the neighbors’ A/C unit too. ? RE: Same sort of goes for radios of old. ?I blame the NEC++ ?for allowing a? 0.35 amp radio to be *protected* by the 15 amp house fuse ?…… don ? From: [email protected] [mailto:[email protected]] On Behalf Of edward schumacher
Sent: Thursday, July 11, 2024 5:47 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Your last paragraph brings to mind all the issues we encountered at the railroad when we began to try to improve on the original systems in our older equipment. We were doing in house overhauls and switching to more modern technology in the various subsystems. New improved AC units using high efficiency motors was one of the bigger changes. It opened a whole can of worms. ? We had no ready replacement for the main motor--alternator that provided all the working voltages for all the auxiliary equipment in the cars so nothing was changed in that system. Imagine the surprise when the AC switching on caused the MA system to shut down. The much higher, though shorter, starting current of the AC caused enough voltage sag to the MA system to trip a field failure fault in the protective circuits and shut down the MA. ? Various soft start units were installed as well as having to change a number of system circuit breakers with proper curves to work with the upgraded devices. Took quite a while for our starry eyed "new efficiency" engineers to finally get everything playing nice again. The old technology worked because it was capable of handling what it was fed. ? Same sort of goes for radios of old. They were not really that sensitive to some things unless a design got too close to a limit somewhere and then smoke. My Signal One CX-7 was known for burning the ON-Off switch along with the Surgistor on it. Don't think anyone ever got into a close analysis of what the culprit was. It did have an early application of the hypersil transformer at over 1kv for the output tube. ? Bottom line is applying new tech to old tech may not be as easy as one would like. ? 73 ... Ed, WA9GQK -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育First,? sorry for?? the email that flew of my bit machine,? I went on line and deleted it. Ed I guess we are OT a fair bit, but you and Jim raised? stuff related to “turn-on” situations. As I recall in NA motors were typically required to draw less than 600% [locked-rotor] current? depending somewhat on the HP. It was known that these sacrificed efficiency for nicer starting as seen by lights on the same line, which is especially a problem for farmers and other rural people. ?European motor standards? allow higher startup / locked rotor current ?and their fusing standards expect this but put one of them on our wiring and you might have a problem. The standards NA vs Europe [perhaps old now] are/were not compatible.? Your problem is just like the farmers, as well as mine, since I am right at the end of the local line, so real dips come from the neighbors’ A/C unit too. ? RE: Same sort of goes for radios of old. ?I blame the NEC++ ?for allowing a? 0.35 amp radio to be *protected* by the 15 amp house fuse ?…… don ? From: [email protected] [mailto:[email protected]] On Behalf Of edward schumacher
Sent: Thursday, July 11, 2024 5:47 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Your last paragraph brings to mind all the issues we encountered at the railroad when we began to try to improve on the original systems in our older equipment. We were doing in house overhauls and switching to more modern technology in the various subsystems. New improved AC units using high efficiency motors was one of the bigger changes. It opened a whole can of worms. ? We had no ready replacement for the main motor--alternator that provided all the working voltages for all the auxiliary equipment in the cars so nothing was changed in that system. Imagine the surprise when the AC switching on caused the MA system to shut down. The much higher, though shorter, starting current of the AC caused enough voltage sag to the MA system to trip a field failure fault in the protective circuits and shut down the MA. ? Various soft start units were installed as well as having to change a number of system circuit breakers with proper curves to work with the upgraded devices. Took quite a while for our starry eyed "new efficiency" engineers to finally get everything playing nice again. The old technology worked because it was capable of handling what it was fed. ? Same sort of goes for radios of old. They were not really that sensitive to some things unless a design got too close to a limit somewhere and then smoke. My Signal One CX-7 was known for burning the ON-Off switch along with the Surgistor on it. Don't think anyone ever got into a close analysis of what the culprit was. It did have an early application of the hypersil transformer at over 1kv for the output tube. ? Bottom line is applying new tech to old tech may not be as easy as one would like. ? 73 ... Ed, WA9GQK -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
I am not sure what the problem is that is causing this need to limit this mysterious charging current.? What is causing it and why didn't the original designers notice it back then and come up with a workable solution, some 60 years ago? The charging current from the instant the power transformer sees the line voltage along with the initial charging current for the filter capacitors are random one time events with respect to the line voltage sinewave.? The current spike can be quite high but narrow in duration when the timing of the power switch closure is at it's worst.? Anything done to reduce the amplitude of this current spike will widen the pulse.? The area under the curve will remain a relative constant.? What detrimental effect will this limit to the current spike have on the power transformer and associated components???Using a zero crossing SSR will remove the random nature of this current spike.? Will this cause other problems down the line?? Are there any, yet to be discovered, unintended consequences?? Will it cause more stress on the power switch??? As an aside, in my home, the only time I ever notice that the house lights flicker is when the whole house air conditioner starts.? Now this is truly a very high current surge that causes this flicker.? I wonder why there is no current limit function designed into the compressor and fan motors?? What effect does this current spike have on the 240 volt, 40 amp circuit breaker that powers this system? Just wondering, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Thursday, July 11, 2024 at 02:52:16 PM CDT, Lou VK3ALB <vk3alb@...> wrote:
Hi Don, I've used a soft start module for a heavy duty power supply but not for my HT37 which is one of my retirement projects. I've bought these modules off ebay but they are designed for 220VAC to suit conditions in Australia and are probably not directly?suitable for use?with 110 VAC. They are pitched towards the Hi-Fi market but the concept is still valid. There's no point giving you the item number as they seem to differ in various parts of the world but the image might help you find one suitable for your?region. Here's some notes from the advertisement which I've edited to remove Hi Fi references ; The soft starter function is to reduce the inrush current at the moment of startup. This board uses a high current relay and 4 large thermistor NTC, and prevents excessive starting current.?This board does not require an auxiliary power supply. It has only 2 terminals, one is connected to the power input (before a switch control), and one output is connected to the load, which is very convenient to use. At the initial stage of power-on, the load is supplied through a thermistor with a negative temperature coefficient. As the temperature of the thermistor rises, the resistance decreases and the voltage rises slowly, thereby effectively suppressing the impact of the surge current on the line and other electrical appliances. After about 2 seconds, the relay pulls in (adjustable pull-in time, see the picture for details), short-circuit the thermistor, the module will directly supply power to the load through the relay contact, and the load enters the normal working state. Regards Lou VK3ALB On Fri, Jul 12, 2024 at 3:44?AM don Root via <drootofallevil=[email protected]> wrote:
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育Lou, ?how much$. ?you have some in operation? ? From: [email protected] [mailto:[email protected]] On Behalf Of Lou VK3ALB
Sent: Tuesday, July 9, 2024 4:44 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Hi all, ? What about combining a zero crossing switch with a soft start circuit giving a lower input voltage to the transformer for a handful of cycles before switching to fill voltage? -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育Jim I agree , but I know one ??absentminded driver that often does not know to “slow down” before turning. Maybe if they had put a HEFTY detent between STANDBY ?and OFF it would not happen so easily. ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Tuesday, July 9, 2024 5:19 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Why not just turn the switch, per the caution in the?HT-37?instruction manual, and avoid the problem?? If soft start and inrush were indeed a problem either one would have been addressed eons ago.? I love engineering as much as the next guy but I see no value in making anything fool proof.? For one thing, the item will never leave engineering and go into production. ? The equipment operator has to exercise some responsibility at some point.? Just saying, before operating, read the instruction manual, page 6, top left column. Jim ? Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy ? ? On Tuesday, July 9, 2024 at 03:44:26 PM CDT, Lou VK3ALB <vk3alb@...> wrote: ? ? Hi all, ? What about combining a zero crossing switch with a soft start circuit giving a lower input voltage to the transformer for a handful of cycles before switching to fill voltage? Regards ? Lou VK3ALB ? ? On Wed, Jul 10, 2024 at 6:28?AM don Root via <drootofallevil=[email protected]> wrote:
_._,_._,_ ? -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Why not just turn the switch, per the caution in the?HT-37?instruction manual, and avoid the problem?? If soft start and inrush were indeed a problem either one would have been addressed eons ago.? I love engineering as much as the next guy but I see no value in making anything fool proof.? For one thing, the item will never leave engineering and go into production. The equipment operator has to exercise some responsibility at some point.? Just saying, before operating, read the instruction manual, page 6, top left column. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Tuesday, July 9, 2024 at 03:44:26 PM CDT, Lou VK3ALB <vk3alb@...> wrote:
Hi all, What about combining a zero crossing switch with a soft start circuit giving a lower input voltage to the transformer for a handful of cycles before switching to fill voltage? Regards Lou VK3ALB On Wed, Jul 10, 2024 at 6:28?AM don Root via <drootofallevil=[email protected]> wrote:
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
开云体育Halden, now that everybody has been silent, ??? I looked around and can’t find just how much magnetism is normally left in good transformer steel. Sketches in tutorials are not to scale and deceiving IMO. ?I recall real hysteresis curves from years ago, and ?there was a only a small amount of magnetization left.? Restoring it to zero is a tall order. ??The idea of removing magnetism is best displayed in tape head demagnetizers and such where the AC magnetizing force is gradually reduced. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Friday, July 5, 2024 2:54 AM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Halden? I can't answer your question.? I don't know all of the pitfalls of using an SSR in place of a mechanical switch.? I don't know if there are any unintended consequences.? The SSR will turn ON and OFF at approximately the same part of the AC cycle every time so there may be an accumulative effect.? The random nature of a mechanical switch that has contact bounce would be very hard to repeat exactly and would be spread over a greater portion of the AC cycle.? ? Regards, Jim ? Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy ? ? On Thursday, July 4, 2024 at 03:48:33 PM CDT, HF via groups.io <incorridge@...> wrote: ? ? Hi Jim, -- don??? va3drl |
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Just completed a rewrite of the SR-400 series repair manual. This update fills some holes in the transmitter fault analysis which includes a transmitter troubleshooting flow chart. Go to wd0gof.com for no cost download.??
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Re: Halicrafters SX17 transformer
John Download the Stancor transformer catalog from? Check top of page 12 for a formula to calculate the turns ratio for the interstage transformer. The values I used were: P = 0.15 watts to drive P-P 6V6s??bottom graph page 3 ????????????? ? 15 volts @ 0.01 amps Z sub L = 10k ohms,? E sub S = 38 volts I get 2.91:1 so it seems that a 3:1 voltage ratio is what is needed.? A-4723 seems to fit the bill.? YMMV! The center wire on the secondary winding is indeed a center tap and not a shield. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Monday, July 8, 2024 at 03:13:25 PM CDT, John via groups.io <siloam@...> wrote:
[Edited Message Follows] A little more detain on this transformer. I found the code A-4931* on its side. I found some Standcor catalogs online with A-47xx numbers, but not A-49xx.* corrected. original post erroneously stated A-4932 I can also add that the DC resistance of the secondary is around 3.9k. Unfortunately with the primary being open and having no center tap, it is not possible to ascertain the turns ratio. There is a center wire, but since it connects to the chassis and there is no indication of a center ground on the circuit diagram, I am assuming that this connects to a shield. |
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Re: Halicrafters SX17 transformer
开云体育John, if the existing one has been declared “grabage” you might assume that the failure is very near ?the coil end[s] and see if you can find the break and measure the ohms. And maybe be lucky and fix the connection. If nothing else, it is education. ? From: [email protected] [mailto:[email protected]] On Behalf Of John via groups.io
Sent: Monday, July 8, 2024 4:13 PM To: [email protected] Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer ? [Edited Message Follows] A little more detain on this transformer. I found the code A-4931* on its side. I found some Standcor catalogs online with A-47xx numbers, but not A-49xx. _._,_._,_ -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
As far as I know, the inrush current problem was due to the limitations of vacuum tube rectifiers then in use.? Filter capacitors just do not care about the initial charging current.? At the instant of turn ON, the uncharged capacitor is modeled as a short circuit.? The only thing that limits this initial current flow is the copper resistance of the primary and secondary transformer windings and any intentional series resistance in the rectifier circuit.?? There is also the inductive reactance of the power transformer and of any filter inductors that want to keep the present current flow constant.? At turn ON, there is no current so the magnetic field rapidly builds up and creates a counter EMF to oppose the current change.? At turn OFF, that magnetic field then collapses and generates as high a voltage as is needed to keep the current flow constant.? This results in the high voltage arcing that one notices when a mechanical switch opens. Those that are really curious about what is happening in power supplies would benefit from the Radiotron Designers Handbook, 4th Edition.? It contains a wealth of information on this and other topics and will demystify the process.? A searchable PDF document can be found at the World Radio History site. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Thursday, July 4, 2024 at 03:16:04 PM CDT, Scott Petersen <s-petersen@...> wrote:
I wonder if a MOV could be somehow used to soften the inrush, if not one perhaps 2 in some kind of toggle arrangement.
From: [email protected] <[email protected]> on behalf of don Root <drootofallevil@...>
Sent: Thursday, July 4, 2024 2:56 PM To: [email protected] <[email protected]> Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ?
Halden, your investigation is interesting and detailed. IMO, the DC [resistance only case, ignoring all inductances] is the extreme limit which won’t be reached. Inductance does not go away, especially in the wiring; and it is still there in the transformer, albeit quite reduced IF it reaches saturation. ?Core steel used in 60 Hz “power ” transformers is chosen to have soft magnetic steel, a low magnetic remnance, and a B-H curve with low hysteresis, so a fair bit of inductance remains, even IF the transformer is driven into saturation; like it most likely is when energizing at zero voltage crossovers. ?But there are some more recent high temperature cheapie transformers that have less steel, drive the flux into saturation, get hot with no load and tend to blow normal fuses when turns on, so old “typical” maximum inrush currents are not cast in stone any more. ? I don’t see how the stuff about “already be in positive saturation” that has be floating around ?has anything to do with any realistic enegization or re enegization of? a realistic power transformer, as the steel has little remnance. ? Yes it seems that the?? ?“STBY-->OFF-->STBY” failure mode has been overtaken by the SSR stuff, yet what caused circuit condition causes the failure has not been refined. Is ihr failure triggered when closing the power switch contacts, or opening them. Seems to me the old Halli warning was related to opening the switch, not closing! How much voltage spiking and or arcing takes place in the switch when it is opened under load as opposed to under standby? In the event that this is the problem, the solution might be to open the switch only near zero current--- so …….. ?don ? From: [email protected] [mailto:[email protected]]
On Behalf Of HF via groups.io ? Thanks, all, for the comments and lessons!?
-- don??? va3drl |
don Root
Rick W7IMM
Jim Whartenby
waltcates