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Re: Re-membered (new to me) HT-37
OK then, Install an inexpensive delay relay and never worry again about the mythical pause delay off training.? Just ram that switch to the OFF position and let the trusted delay board keep the rig in standby mode for as many seconds or minutes as you want! 73 dave wa3gin |
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Re: Re-membered (new to me) HT-37
开云体育Hi Paul, my emails inbox is quiet today.. so.. ? RE “Jim also mentioned the mechanics of the HT-37’s Operation switch. ?I’m glad someone finally mentioned it as a possible root (or contributing) cause of the transformer failure problem. ? I can’t count the number of times I’ve mistakenly relied only on a schematics and have ignored physical attributes like cable routing and effects caused by wafer switch movement - the kind of things not easily recognized on a schematic diagram.?” ? ? Some time back on another “topic” I was asking about that switch because I wondered about having the AC ON/OFF run thru a wafer. Finally from the schematic, it appeared that it must be a toggle switch buried within the wafer part, and driven by the same shaft somehow.?? The AC ON/OFF? part? if hard to find? using the Bama manuals? schematics, and the parts list is no help. Somebody must have looked at it? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Paul Christensen
Sent: Thursday, August 15, 2024 3:54 PM To: [email protected] Subject: Re: [HallicraftersRadios] Re-membered (new to me) HT-37 ? “Other manufacturers, like Collins,? did use them in this same era since cost was a secondary or even lower concern to performance and reliability for Collins equipment.” ? The Collins 516F-2 power supply was fitted with tube rectifiers through the late 1970s. ?However, on 08/1976, Collins issued a Service Information Letter (SIL) that addresses solid-state diode replacement. ?For several reasons, I’ve kept vacuum tube rectifiers in my Collins supplies. ? Jim also mentioned the mechanics of the HT-37’s Operation switch. ?I’m glad someone finally mentioned it as a possible root (or contributing) cause of the transformer failure problem. ? ? I can’t count the number of times I’ve mistakenly relied only on a schematics and have ignored physical attributes like cable routing and effects caused by wafer switch movement - the kind of things not easily recognized on a schematic diagram.? ? Paul, W9AC _._,_._,_ -- don??? va3drl |
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Re: Re-membered (new to me) HT-37
开云体育Jim, Re your “I would think that one would have to see what the OPERATIONS switch is doing in those first three positions. Based on the manual this seem a most obvious ?place to begin.? Thanks to recent info posted, it seems that the finals are significantly, unloaded ?when in standby ?? ? Dave Mentioned part of this . here is the whole bit. So perhaps on some units the bias is not minus 49 and leaves the current draw ?too low allowing the B++ volts to reach 1000. As has been reported. Back to the pause; Their statement confirms that in standby the finals unload ?and we guess the B++ current slowly decreases in the choke, 5V4 and transformer,? which then allows a reasonable turn-off.? Reverse logic says the pause in standby is to allow the current/energy in the choke to subside.? ?As a reminder, when the transformer is powered by 117/60Hz, it controls the transformer voltages on all windings, but once the source is open, the choke has yet to discharge energy and will put out a lot of volts to do so, ?and the 5V4 connects it to the transformer HHV, so I wonder what takes place over the next little bit? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Thursday, August 15, 2024 3:27 PM To: [email protected] Subject: Re: [HallicraftersRadios] Re-membered (new to me) HT-37 ? To put this all in perspective: both cost and most-bang-for-the-buck were the driving forces in hallicrafters designs.? To address the question about the HT-37 design, hallicrafters engineers would have used solid state rectifiers?IF it wasn't cost prohibitive.? Other manufacturers, like Collins,? did use them in this same era since cost was a secondary or even lower concern to performance and reliability for Collins equipment. ? Solid state rectifiers were not readily availably when the HT-32 or 37 were made since they are both pre 1959 designs.? From the 1958 Allied Catalog, the 1N1095 was available but it's cost was $7.50 each.? The 5R4 was $1.90 each.? That is a 24:1 price difference when comparing solid state to tube rectifiers, back in 1958.? You would need at least 6 each 1N1095 diodes to replace a single 5R4.? Not to mention resistors and capacitors used to protect the more primitive silicon rectifier that are no longer needed with modern "controlled avalanche" silicon rectifier diodes. ? Since the transformer failure has to do with the rapid switch movement through the STANDBY position, I would think that one would have to see what the OPERATIONS switch is doing in those first three positions.? Are the switch contacts effectively make-before-break?? Something is going on that the engineers knew about but it was evidently too costly to correct the design and eliminate this problem. ? Perhaps a survey is in order.? How many HT-37 in use have solid state rectifiers?? How many of these have had a power transformer failure?? Same question for the stock tube rectifier HT-37s.? How many have had a power transformer failure? Regards, Jim
-- don??? va3drl |
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Re: Re-membered (new to me) HT-37
Paul I see your point about the 516F-2.? What I had in mind was the KWT-6 which is also a commercial designation and it's high voltage power supply of 2kv @ 500 mA.? AFAIK, this is also a 1958-9 design that is all solid state.? The related ARC-58 transmitter also has a solid state high voltage power supply which is even earlier, circa 1955-6. The Army and Navy authorized solid stating the power supply for the R-390A and the SRR-13 and FRR-23 and their lower frequency variants.? All in an effort to reduce heat and to increase reliability.? AFAIK, those mods were not rescinded but obviously not all R-390A have this mod but all of the SRR and FRR receivers that I have do. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Thursday, August 15, 2024 at 02:54:24 PM CDT, Paul Christensen <w9ac@...> wrote:
“Other manufacturers, like Collins,? did use them in this same era since cost was a secondary or even lower concern to performance and reliability for Collins equipment.”
?
The Collins 516F-2 power supply was fitted with tube rectifiers through the late 1970s. ?However, on 08/1976, Collins issued a Service Information Letter (SIL) that addresses solid-state diode replacement. ?For several reasons, I’ve kept vacuum tube rectifiers in my Collins supplies. ?
Jim also mentioned the mechanics of the HT-37’s Operation switch. ?I’m glad someone finally mentioned it as a possible root (or contributing) cause of the transformer failure problem. ?
?
I can’t count the number of times I’ve mistakenly relied only on a schematics and have ignored physical attributes like cable routing and effects caused by wafer switch movement - the kind of things not easily recognized on a schematic diagram.?
?
Paul, W9AC
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Re: Re-membered (new to me) HT-37
“Other manufacturers, like Collins,? did use them in this same era since cost was a secondary or even lower concern to performance and reliability for Collins equipment.”
?
The Collins 516F-2 power supply was fitted with tube rectifiers through the late 1970s. ?However, on 08/1976, Collins issued a Service Information Letter (SIL) that addresses solid-state diode replacement. ?For several reasons, I’ve kept vacuum tube rectifiers in my Collins supplies. ?
Jim also mentioned the mechanics of the HT-37’s Operation switch. ?I’m glad someone finally mentioned it as a possible root (or contributing) cause of the transformer failure problem. ?
?
I can’t count the number of times I’ve mistakenly relied only on a schematics and have ignored physical attributes like cable routing and effects caused by wafer switch movement - the kind of things not easily recognized on a schematic diagram.?
?
Paul, W9AC |
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Re: Re-membered (new to me) HT-37
To put this all in perspective: both cost and most-bang-for-the-buck were the driving forces in hallicrafters designs.? To address the question about the HT-37 design, hallicrafters engineers would have used solid state rectifiers?IF it wasn't cost prohibitive.? Other manufacturers, like Collins,? did use them in this same era since cost was a secondary or even lower concern to performance and reliability for Collins equipment. Solid state rectifiers were not readily availably when the HT-32 or 37 were made since they are both pre 1959 designs.? From the 1958 Allied Catalog, the 1N1095 was available but it's cost was $7.50 each.? The 5R4 was $1.90 each.? That is a 24:1 price difference when comparing solid state to tube rectifiers, back in 1958.? You would need at least 6 each 1N1095 diodes to replace a single 5R4.? Not to mention resistors and capacitors used to protect the more primitive silicon rectifier that are no longer needed with modern "controlled avalanche" silicon rectifier diodes. Since the transformer failure has to do with the rapid switch movement through the STANDBY position, I would think that one would have to see what the OPERATIONS switch is doing in those first three positions.? Are the switch contacts effectively make-before-break?? Something is going on that the engineers knew about but it was evidently too costly to correct the design and eliminate this problem. Perhaps a survey is in order.? How many HT-37 in use have solid state rectifiers?? How many of these have had a power transformer failure?? Same question for the stock tube rectifier HT-37s.? How many have had a power transformer failure? Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Wednesday, August 14, 2024 at 02:55:12 PM CDT, Dave Jordan <wa3gin@...> wrote:
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
开云体育Ed,?? re my “designed to unload into the higher voltage region typical of capacitor input filters”??? Yes ?the HHV ?has an input ?choke of 8 Henrys. What I said poorly I guess is that when it has little load it acts more like a capacitor Input filter and the voltages rise to almost peak of the sine wave, as cap input filters do ? From: [email protected] [mailto:[email protected]] On Behalf Of edward schumacher
Sent: Wednesday, August 14, 2024 7:37 PM To: [email protected] Subject: Re: [HallicraftersRadios] Re-membered (new to me) HT-37 ? The HT-37 as built did not have a capacitive input filter. There is a swinging choke at the input which was commonly used with tube rectifiers. ? Ed, WA9GQK ?
? ? -- don??? va3drl |
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Re: Re-membered (new to me) HT-37
Good points Russ. But to tell you my subjective opinion of one... A plate supply?that swings 350 volt when keyed without drive is a garbage power supply. If that happened on a screen supply as well that transmitter would be a splatter master! Plenty to learn here and for me it happens almost every day.?? Enjoy, dave wa3gin On Wed, Aug 14, 2024 at 9:04?PM Russ Williams via <rt998cc=[email protected]> wrote:
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Re: Re-membered (new to me) HT-37
Dave, WA3GIN.
Thank you for your comments.?
?
First off, I am not an engineer and have never played on TV; however, I also believe the engineers in the day knew what they were doing.? I also believe in keeping the rig stock, if possible. ?However well a rig is engineered, I also believe that it had to sell for a competitive price, so the accountant may have influenced the quality of specified components specified by the engineer.? It is also possible that components available today will extend the lives of these marvelous machines.
??
Given that, I do know the power transformer in my old HT-37 (in the 1970's) suffered power transformer failure after I sold it to a friend.? It was a bone stock HT-37.? A year or so ago, I learned this was a common problem with the HT-37 and HT-32.? The collective thoughts from that group concluded the problem was with the high voltage DC appearing on the filament winding and that solid-stating the HV and isolating the filament winding was the best preventative measure.? That was the group that helped in my rebuild of a long-suffering Johnson Viking 500; without modern components to duplicate the previous delay action of one of original its relays, it would not be feasible to safely operate the 500 today.? When it comes to the HT-37 transformer, right or wrong, I respect their wisdom.? I do desire to keep that thread separate form this one.
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Regarding the 1KV on the 6146 plates, it may well be the 22uf filter I installed.? It does drop to 650 on key up.? My thought is solid-stating is possible without compromising the transformer, the tubes or other components.? If the 22uf filter is a factor in the high voltage, I will change to three 33uf in series with the original 300K (3X100K) bleeder.? That will essentially equal the original 10uf filter circuit.?? The voltage drop in the tube is approximated using a dropping resistor.? Is it perfect? In my opinion, it is a risk versus reward scenario.? I want my HT-37 to work as intended by the makers and to maintain this level of operation in the future.
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When all is said and done, I can buy a new Icom, Yaesu or whatever, and it will work perfectly as a plug-and-play.? That's great for emergency communication, but there is very little challenge in that.?
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I have a deep appreciation for my old gear and have hopes for bring them back to good, safe operating condition.
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Again, I appreciate your comments and concerns.? A mix of ideas usually results in a stronger group.
--
73, Russ
KW6T
The cheap item is rarely the least expensive. |
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Re: Re-membered (new to me) HT-37
Thanks Don,? I couldn't find the test in the file links provided. No matter. It's an interesting comment. I presume just another effort by the engineers to do best effort to increase longevity of the components. The engineers were pressing the? envelope with the available technology of the early 60s. I wonder whether an FT10 will still be operative in 60 years, hahaha.? 73 dave wa3gin On Wed, Aug 14, 2024 at 6:08?PM don Root via <drootofallevil=[email protected]> wrote:
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Re: Re-membered (new to me) HT-37
Dave and all,?
I checked the crystals in circuit.? Taking the signal at the test point.? Both the 25 and 32 MHz crystals are oscillating; the 21.5 MHz crystal is not.? Just for grins, I plugged in a random 17.098 MHz crystal in place of the 21.500 (40 meter crystal), and voila!? We have liftoff, albeit at 17.098 MHz.?
?
For more grins, I tried the 21.5 (40 meter) crystal in the 15 meter socket--there is activity.
Replacing the 21.5 crystal in the 40 meter socket and tuning C66 brought 40 meters to life.?
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17.098MHz crystal in the 40 meter socket.
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40 meter crystal in the 40 meter socket.? Retest after tuning C66
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Thank you.
--
73, Russ
KW6T
The cheap item is rarely the least expensive. |
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Re: Re-membered (new to me) HT-37
开云体育Dave ? See ?? ???page PDf 8 ? I ?looked at?????? ?6-3-9 Power Supply.??? It mentions setting R61?? … perhaps? too much unloading of the finals allows the HV to skyrocket ??? but I’m shooting from the hip again.? I made the assumption that guys with now very old HT-37’s have gone thru the manual a few times before mucking with the old and new unknowns. ? ? From: [email protected] [mailto:[email protected]] On Behalf Of Dave Jordan
Sent: Wednesday, August 14, 2024 5:29 PM To: [email protected] Subject: Re: [HallicraftersRadios] Re-membered (new to me) HT-37 ? Oh Don, ? It's not always about you...;-) or L26 ? The final tubes along with C68 and C80 which I don't think are going to be very happy with a 35% over voltage. The margins are beyond best practice. I ask myself what is being fixed that is so broken that would allow for a half baked mode. I've never seen the write-up for the mod. Besides installing diodes to replace the tube(s) even if the mod included replacing C68 and C80? that? wouldn't make it any better as the finals are still in jeopardy at 1,000vdc.? ? I can't find the quote that was mentioned earlier about pause at stand-by before switching off the unit but I did find a decent statement of best practice on p13 section 6-3-9 Power Supply.? "...This reduces the stand-by current drain of the final amplifier tubes, resulting?in prolonged tube life". In this section the engineer explained the theory of operation and the wanted end result. Not sure that was the case with the standby statement. Maybe AI can answer our questions. ? 73 dave wa3gin -- don??? va3drl |
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Re: Re-membered (new to me) HT-37
Oh Don, It's not always about you...;-) or L26 The final tubes along with C68 and C80 which I don't think are going to be very happy with a 35% over voltage. The margins are beyond best practice. I ask myself what is being fixed that is so broken that would allow for a half baked mode. I've never seen the write-up for the mod. Besides installing diodes to replace the tube(s) even if the mod included replacing C68 and C80? that? wouldn't make it any better as the finals are still in jeopardy at 1,000vdc.? I can't find the quote that was mentioned earlier about pause at stand-by before switching off the unit but I did find a decent statement of best practice on p13 section 6-3-9 Power Supply.? "...This reduces the stand-by current drain of the final amplifier tubes, resulting?in prolonged tube life". In this section the engineer explained the theory of operation and the wanted end result. Not sure that was the case with the standby statement. Maybe AI can answer our questions. 73 dave wa3gin On Wed, Aug 14, 2024 at 4:37?PM don Root via <drootofallevil=[email protected]> wrote:
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Re: Re-membered (new to me) HT-37
开云体育Dave, Perhaps you are aiming that at me. I am just looking in, and mostly still wondering why that caution {pause in STBY }was in the manual. I have to believe there is a reason why it says what it says, and am suspicious that if it is not heeded ??L26 will “kick back” energy into the transformer. Of course I am a lone wolf, ?but nobody has said where that energy/ current will go any why it can’t hurt the transformer ? From: [email protected] [mailto:[email protected]] On Behalf Of Dave Jordan
Sent: Wednesday, August 14, 2024 3:55 PM To: [email protected] Subject: Re: [HallicraftersRadios] 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 -- don??? va3drl |
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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
开云体育Halden, 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 |
Dave Jordan
don Root
Jim Whartenby
Paul Christensen
Russ Williams