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Re: Re-membered (new to me) HT-37
Here is the tube specification:? Anecdotal?comment but I seem to remember rumors about those who modified?HV power to solid state shortened the life of the power transformer significantly... I've had three HT-37 all unmodified. Never had any issues. Still don't have any issues with the HT-37 I purchased in 1964. Not sure why amateur operators think they know more than the factory engineers who designed and tested our radios! Hope you get the HT-37 working to your?satisfaction. 73 dave wa3gin |
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Re: Re-membered (new to me) HT-37
¿ªÔÆÌåÓýHalden, Russ too Re ???¡°just a tad above 1000 V in STBY mode.¡± ?I think I made a question comment on Hilden¡¯s? topic, saying that I could find no information at all for the conditions under which the voltages in the chart or elsewhere were taken; so I am guessing? / we ?are guessing? ?, and as I recall there is no AC voltage anywhere for transformer HHv or the 5R4 plate voltages. ?? Without knowing enough about the operation, if one guesses or knows that STBY draws very little current from B++ , the power supply may well have been designed to unload into the higher voltage region typical of capacitor input filters.? and I should not say it here , but dumping a small current from the 8 Henry ?is not at all the same as dumping the energy of its rated 150 mA somewhere when turning the rig off with no pause in STBY. ? From: [email protected] [mailto:[email protected]] On Behalf Of HF via groups.io
Sent: Wednesday, August 14, 2024 2:15 PM To: [email protected] Subject: Re: [HallicraftersRadios] Re-membered (new to me) HT-37 ? Hi Russ, The 750V marked on the schematic might represent the voltage during key-down.? The HV in my HT-37 with the original tube rectifiers is just a tad above 1000 V in STBY mode. What kind of inrush current limiters (part #?) did you install and where? Cheers Halden VE7UTS _._,_._,_ -- don??? va3drl |
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Re: Re-membered (new to me) HT-37
Don.
The bleeders are the likely culprit, and the replacement capacitors may also have an effect.? Three 68uf 450V capacitors replaced the two 20uf at 600 V capacitors; about 22uf versus 10uf in the original circuit.? All I had on hand were 330K resistors to bridge each of the (3) new capacitors.? I have three 100K 2 watt resistors on order which should get it closer.? For testing the other circuits in the meantime, I've pulled the "5R4" module and the 6146's until the HV voltage is within spec.
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Thanks.
?
73, Russ
KW6T
The cheap item is rarely the least expensive. |
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Re: Re-membered (new to me) HT-37
¿ªÔÆÌåÓýOh, after looking, the bleeder is rather too small to make that difference. ? From: [email protected] [mailto:[email protected]] On Behalf Of don Root
Sent: Tuesday, August 13, 2024 12:31 PM To: [email protected] Subject: Re: [HallicraftersRadios] Re-membered (new to me) HT-37 ? Re 1000 volts: How is the bleeder? -- don??? va3drl -- don??? va3drl |
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Re: Re-membered (new to me) HT-37
¿ªÔÆÌåÓý
You can find a few technical discussions on the HT-37 at:
Walt Cates, WD0GOF
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From:[email protected] <[email protected]> on behalf of Russ Williams <rt998cc@...>
Sent:?Tuesday, August 13, 2024 10:56 AM To:[email protected] <[email protected]> Subject:?[HallicraftersRadios] Re-membered (new to me) HT-37 ?
Hello all.
Somehow, this group disappeared from my groups.io list, so I re-applied.?
?
Back in the 1970's I ran an HT-37 with good results--a fine transmitter.? I sold it to a friend, and after about 6 months, the power transformer died.?
(Not to merge into the other HT-37 transformer thread)?
?
Recently, I found another HT-37 that was said to be in good operating condition.?
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Re-membered (new to me) HT-37
Hello all.
Somehow, this group disappeared from my groups.io list, so I re-applied.?
?
Back in the 1970's I ran an HT-37 with good results--a fine transmitter.? I sold it to a friend, and after about 6 months, the power transformer died.? (Not to merge into the other HT-37 transformer thread)?
?
Recently, I found another HT-37 that was said to be in good operating condition.? It showed a few problems on testing, but I picked it up anyway.?? The plate tune capacitor was arcing--that has been resolved.? A hum in the transmitted signal led to re-capping the rig.? No more hum in the signal. I replaced the 5R4 and 5V4 rectifiers with plug-in diode/resistor modules to take the HV off of the transformer filament windings; inrush current limiters are installed ahead of the primary winding.? Three tubes were weak, including a 6146.? The 6AB4 (heterodyne oscillator) was very weak and one of the 12AT7's in the SSB generator had been replaced with a 12AU7A.? All have been replaced with good or new tubes. ? In SSB mode, the carrier balance works and properly nulls the carrier.
?
My questions:
#1.? All bands function except 40 meters--it is dead. Thoughts?
#2.? The audio section produces a strong signal relative to the amplitude of the voice audio input in the SSB modes, but the audio is not heard in a local receiver.? Just a muffled hint that there may be audio there.?? I didn't have a 10uf 350VDC capacitor to replace the electrolytic in the audio section, so I temporarily installed a 33uf 450 in its place.? It appears to be a DC filter ahead of the 12AX7 plates and not in the audio stream.? Thoughts?
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The HV is running high at about 1000 volts.? It's higher than the 750 VDC in the schematic, but I have a plan for that.
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Regards and 73.
Russ
KW6T
"The cheap item is rarely the least expensive." |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
¿ªÔÆÌåÓýHalden, this is rather late too Re ?your comments in [quoted text] and ?pics? in ???/g/HallicraftersRadios/message/30775 ? I Halden, I see it much the way you describe, but ?we don¡¯t know the core¡¯s B-H curve, and would suggest that it is not saturating badly[it is not hard saturation], but ¡°saturation¡± is such a loose thing. ??The current peak ?is well behind the voltage, so there is still quite a bit of permeability left in the core, but it must be into the saturating region[my term] If it had really saturated [only resistance left] the current would be in phase with the voltage. That current lag seems to continue down to? current zero, then the negative current peak is very close to the voltage. I don¡¯t think you will find many power transformer cores saturating badly, but there will be gentle saturation, but those switching cores[hard cores] are another matter. When I say power transformer, I mean, any transformer intended to efficiently transfer power at 50/60Hz, wheather it is down near say 30 VA or up above 300 MVA. Please excuse all these ¡±I¡±s, but I don¡¯t want to imply that I have access to the bible. But Halden, I keep wondering about the 49 Amps you said, you mentioned a 1 ohm resistor, I thought, so I get 24 amps peak. Maybe you changed it to a half?? ?? ? From: [email protected] [mailto:[email protected]] On Behalf Of HF via groups.io
Sent: Thursday, August 8, 2024 12:38 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Here's an interpretation of the surge according to the theory that it represents the transformer core reaching saturation. In image #49, which shows the strong surge, one can see that the current waveform started normally, using image #58 as a reference.? The core had not reached a non-linear point as the current started to flow.? At about 45 degrees into the cycle, it reached a slightly non-linear region and increased at a higher rate until almost 90 degrees into the cycle.? At that point, the core reached saturation, but the applied voltage was still positive.? Then, there was no additional magnetizing that the current forced by the voltage could do.? Lacking such impedance to its flow, the current surged until there was no more voltage available to drive it.? At that point, the inductive nature of the primary winding maintained the current flow as the voltage reversed polarity.? This current took another cycle or two to fall back to zero.? Meanwhile, the negative applied voltage drove the core back out of saturation and partly towards the opposite magnetization polarity.? The next cycle began with the core less magnetized than the first, so the core didn't go as far into the saturation zone that time.? Did I get this right? Cheers, Halden _._,_._,_ -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io ? Don I am not posting here to argue, ?????if you are referring to ?my¡°for the sake of argument¡±, In my world that means?? ?¡°to propose something so we can discuss it¡± [or argue politely about THAT TOPIC]. ??I¡¯m sorry if I was too unclear. Perhaps that is colloquial? From the web: What does for the sake of the argument mean? It means that you don't believe that the thing you are about to say is necessarily true, but you are saying it to explore a hypothetical situation. For example, you might say: "Let's assume, for the sake of argument, that you start the building work in June.Oct 1, 2018 ? ????????? I am trying to understand what the posted data means and how it adds to the understanding of the HT-37 power transformer failure.??Me too So far, there was almost no information given on how the power transformer was tested, what type of loads were placed on the windings during tests, and so on.??? I am reluctant to comment on now much needs to be written; what is too much and what is too little? ? Without this information, I don't see how any of the o'scope images are of any use.? I have managed to fill in the gaps, but I have spent a few years looking at real CRT¡¯s starting with an EICO 460 kit when I was in grade 11, but any readers that don¡¯t have much scope time, would be at a disadvantage. ?When I have asked, what I thought were legitimate questions, I get replies full of rebuttals and wild guesses on what might be causing what was presented.? This has led to several off topic replies from this end.? Sorry about that chief. ???The old school said re-read/write 3 times and I say with breaks between before sending. After getting it ¡°off your chest¡±? one might decide to tame it down or clarify something, etc etc ?and fix the Auto-mutilate hits ?before sending. AI will soon complete your hole sentence after 3 words. ? I have learned a lot while debunking these guesses and I now realize that I have made some wrong assumptions on how a transformer actually works.? Apparently I got lost wading through the weeds. ? Rather than make a new posting about the half turn stuff, I hope you read it first. It is sneaky stuff , that is made more clear in another article, that thing called a ¡°half-turn¡±? is physically a whole turn around half the main core of a shell type transformer, if you split the core into 10 cores you could make ¡°tenths of a turn¡± on a secondary only.. a good school project. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io ? Don I am not posting here to argue, I am trying to understand what the posted data means and how it adds to the understanding of the HT-37 power transformer failure.??So far, there was almost no information given on how the power transformer was tested, what type of loads were placed on the windings during tests, and so on.?? ? Without this information, I don't see how any of the o'scope images are of any use.? When I have asked, what I thought were legitimate questions, I get replies full of rebuttals and wild guesses on what might be causing what was presented.? This has led to several off topic replies from this end.? Sorry about that chief. ? I have learned a lot while debunking these guesses and I now realize that I have made some wrong assumptions on how a transformer actually works.? Apparently I got lost wading through the weeds. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy ? ? On Sunday, August 11, 2024 at 08:41:34 PM CDT, don Root <drootofallevil@...> wrote: ? ? Jim they are both right, but for the sake of argument the in-phase is right, and it is right for a long time, but when the switch closes there is a good chance that the combination of left over flux, and switch closing angle will try to drive the flux past the normal peak and when things go to one extreme the core saturates extremely. In which case the inrush is so big that it swamps the load current, but likely when it is real high the transformer is no longer a ¡°transformer¡±. I¡¯m not sure it I the same image, but on one you could see the small load current partially ?going to the right, but at the left you see the load current rise then the ?inrush swamps the waveform., so it was not the worst case. If the transformer was really left saturated, the current would shoot up with no delay with the voltage. I recorded a 30X inrush on a Honeywell visicorder. That core was being driven very hard. Too many volts per turn. That was a early class H potted transformer, maybe 25 or 50 kVA. Fusing as a real problem for it. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io ? OK, back to the beginning. Some of Halden's scope images show the transformer's primary current in phase with the voltage across the primary, a few show a 90 degree phase difference with voltage leading current by 90 degrees.? Which is right? Jim
_._,_._,_ -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Don I am not posting here to argue, I am trying to understand what the posted data means and how it adds to the understanding of the HT-37 power transformer failure.??So far, there was almost no information given on how the power transformer was tested, what type of loads were placed on the windings during tests, and so on.?? Without this information, I don't see how any of the o'scope images are of any use.? When I have asked, what I thought were legitimate questions, I get replies full of rebuttals and wild guesses on what might be causing what was presented.? This has led to several off topic replies from this end.? Sorry about that chief. I have learned a lot while debunking these guesses and I now realize that I have made some wrong assumptions on how a transformer actually works.? Apparently I got lost wading through the weeds. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, August 11, 2024 at 08:41:34 PM CDT, don Root <drootofallevil@...> wrote:
Jim they are both right, but for the sake of argument the in-phase is right, and it is right for a long time, but when the switch closes there is a good chance that the combination of left over flux, and switch closing angle will try to drive the flux past the normal peak and when things go to one extreme the core saturates extremely. In which case the inrush is so big that it swamps the load current, but likely when it is real high the transformer is no longer a ¡°transformer¡±. I¡¯m not sure it I the same image, but on one you could see the small load current partially ?going to the right, but at the left you see the load current rise then the ?inrush swamps the waveform., so it was not the worst case. If the transformer was really left saturated, the current would shoot up with no delay with the voltage. I recorded a 30X inrush on a Honeywell visicorder. That core was being driven very hard. Too many volts per turn. That was a early class H potted transformer, maybe 25 or 50 kVA. Fusing as a real problem for it. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Sunday, August 11, 2024 8:13 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? OK, back to the beginning. Some of Halden's scope images show the transformer's primary current in phase with the voltage across the primary, a few show a 90 degree phase difference with voltage leading current by 90 degrees.? Which is right? Jim ? -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Don "Abstract¡ªThe half-turn effect is present in transformers if the
winding leads are taken out from the different sides of the core.
The result is an additional half-turn in one of the core windows
in a single-phase transformer, which can create overfluxing of the
core leading to excessive losses and temperature rises. This paper
presents a methodology to analyze the half-turn effect in power
transformers....." The above found in:?? AFAIK, fractional transformer turns smaller then a half turn can only be implemented in certain styles of ferrite core high frequency transformers operating above 50kHz.? Not possible to do in iron core transformers. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Sunday, August 11, 2024 at 08:05:43 PM CDT, don Root <drootofallevil@...> wrote:
Ooops ?sorry that was a copy of Jims post enlarged so I could read it I will delete it on line later Jim if you are going to measure the volts or amps , you need a meter and two leads, and then the leads somehow go to the core, and perhaps it is a whole turn, then you cut it to a half turn, and ? ?and 1/8 th turn, and then a 0.00005 turn and finally no turn, I¡¯ll bet your meter reads the same. In the final test the leads go around the core and join and the meter leads become the whole turn. ??I don¡¯t think that was apparent when ?? did his first experiments but ?´¡³¾±è¨¨°ù±ð ??or Faraday spoke about the closed loops. ? You can make a super micro-mini- meter anf put it right at your half turn, but to get any volts they have to extend ?the two ? turn leads around the core to reach your half turn, and that makes one whole conductive turn. ?I have never been able to walk up half-a-step either.. frustrating stuff If you don¡¯t finish the turn the laws mean nothing, ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Sunday, August 11, 2024 7:34 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Don In a transformer, a half turn starts on one side of the laminated core and exits on the other.? Since the Weller has that plated copper tube entering the core on one side and exiting the core on the other, it is by definition, a half turn.? It does not matter if the tube wraps around the outside of the lamination, it is still a half turn through the core.? If a winding makes one full wrap around the core that holds the primary and exits on the same side that it entered, then it is a full turn.? If you measure the open circuit voltage of the Weller soldering gun tube, it should be approximately a quarter volt.? That tube allows about 100 VA to be transformed to about 400 amps @ 0.25 volt! ? As long as you can fit an insulated wire between the bobbin and the laminations and make a full turn as in above then you can determine the turns-per-volt of any power?transformer.? I prefer 10 turns, make the measurement and then divide it by 10 but you can do as you like.? You must have a transformer or two in your junk-box so it should be easy to verify this procedure. ? Typically one strips off only the secondary windings and keeps the primary intact.? Knowing the voltage produced by a high current heater winding and counting the turns will give the same result for the turns-per-volt of that particular transformer.? Then wind as many turns as needed to get the output voltage wanted in the secondary windings.? This was one of the first lab experiments in college for transformers in AC circuits. Regards, Jim -- don??? va3drl |
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
¿ªÔÆÌåÓýJim they are both right, but for the sake of argument the in-phase is right, and it is right for a long time, but when the switch closes there is a good chance that the combination of left over flux, and switch closing angle will try to drive the flux past the normal peak and when things go to one extreme the core saturates extremely. In which case the inrush is so big that it swamps the load current, but likely when it is real high the transformer is no longer a ¡°transformer¡±. I¡¯m not sure it I the same image, but on one you could see the small load current partially ?going to the right, but at the left you see the load current rise then the ?inrush swamps the waveform., so it was not the worst case. If the transformer was really left saturated, the current would shoot up with no delay with the voltage. I recorded a 30X inrush on a Honeywell visicorder. That core was being driven very hard. Too many volts per turn. That was a early class H potted transformer, maybe 25 or 50 kVA. Fusing as a real problem for it. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Sunday, August 11, 2024 8:13 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? OK, back to the beginning. Some of Halden's scope images show the transformer's primary current in phase with the voltage across the primary, a few show a 90 degree phase difference with voltage leading current by 90 degrees.? Which is right? Jim ? -- don??? va3drl |
Dave Jordan
don Root
Russ Williams
waltcates
Jim Whartenby