Re: S-38B Tuning Shaft Query
If one does feel a shock, reversing the AC line plug should eliminate the problem, shouldn't it?? In the S-38B this current is below 5mA which is the threshold of the GFCI outlet.
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On mine, the set screws are almost flush with the surface of the knob
flutes when tightened. Since those set screws are connected to the
chassis, meaning a metal shaft, it might be possible to receive a shock
by pressing your finger tightly on the set screw hole.
I don't plan to test that and I have no idea whether or not the screws
are the originals or some longer ones that someone used sometime in the
past.
73,
Maynard
W6PAP
On 7/30/24 16:07, don Root wrote: Re /_It does have aluminum shafts_/. But, a well insulated knob; at
least on day one?
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Richard Knoppow
*Sent:* Tuesday, July 30, 2024 6:54 PM
*To:* [email protected]; ma.wright@...
*Subject:* Re: [HallicraftersRadios] S-38B Tuning Shaft Query
I have an S-38 awaiting rebuild. It does have aluminum shafts.
--
Richard Knoppow
--
don??? va3drl
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Re: S-38B Tuning Shaft Query
Tell me about it! A very long time ago I began to have trouble
remembering names. Never forgot anything but was sometimes very slow on
remembering. Has gotten worse. I asked my doctor if I was getting
dementia, he just laughed. What I find fascinating is that its much more
likely when I am speaking than when I am writing. I have discovered that
when I write I have a much larger vocabulary than when I speak. Perhaps
it is an effect of my deafness. Now that I have a cochlear implant
perhaps it will improve. I am still learning how to use it. Some
recipients report being able to hear clearly as soon as theirs is
activated, some report having a long struggle; I seem to be one of the
latter. Nonetheless, it does seem to work and I will keep at it.
Being deaf is awful! Hearing people just don't get it! If you are
blind or have a missing leg or something people will make adjustments;
If you are deaf people say "No Problem" and keep going as though you
could hear the tiniest pin drop. I once had exceptionally good hearing
and never realized just how big a disability deafness is.
Well, I am babbling in public and will stop now.
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On 7/30/2024 7:05 PM, Justin Bowser - KI5GKD wrote: Yeah, the older I get the more often I'm afflicted with brain-farts... :-\
--
Justin B.
KI5GKD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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Re: S-38B Tuning Shaft Query
In general, I've had trouble finding original Hallicrafters knobs.
They are a unique design or rather several designs. On the S-38 and some
other receivers, like the S-40 series, there were tuning knobs that look
similar but have differences, for instance the metal rings that are on
some but not others. Another toughy to find is the BFO knob on the
original S-38, also used on the S-40/A and maybe others. This fits on a
1/8th inch threaded shaft and has a stop that fits a tab on the cabinet.
I have had to makeshift them from standard small H knobs. Also, H used
slotted set screws on some knobs and Bristol head on others. One learns
not to expect consistency in older H gear.
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On 7/30/2024 7:43 PM, Maynard Wright, P. E., W6PAP via groups.io wrote: On mine, the set screws are almost flush with the surface of the knob
flutes when tightened. Since those set screws are connected to the
chassis, meaning a metal shaft, it might be possible to receive a shock
by pressing your finger tightly on the set screw hole.
I don't plan to test that and I have no idea whether or not the screws
are the originals or some longer ones that someone used sometime in the
past.
73,
Maynard
W6PAP
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: S-38B Tuning Shaft Query
On mine, the set screws are almost flush with the surface of the knob
flutes when tightened. Since those set screws are connected to the
chassis, meaning a metal shaft, it might be possible to receive a shock
by pressing your finger tightly on the set screw hole.
I don't plan to test that and I have no idea whether or not the screws
are the originals or some longer ones that someone used sometime in the
past.
73,
Maynard
W6PAP
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On 7/30/24 16:07, don Root wrote: Re /_It does have aluminum shafts_/. But, a well insulated knob; at
least on day one?
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Richard Knoppow
*Sent:* Tuesday, July 30, 2024 6:54 PM
*To:* [email protected]; ma.wright@...
*Subject:* Re: [HallicraftersRadios] S-38B Tuning Shaft Query
I have an S-38 awaiting rebuild. It does have aluminum shafts.
--
Richard Knoppow
--
don??? va3drl
|
Re: S-38B Tuning Shaft Query
Yeah, the older I get the more often I'm afflicted with brain-farts... :-\
--
Justin B.
KI5GKD
|
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Halden, I hijacked your 3 pix and piled them up so voltages superimposed, now you can see them all together with a bit of imagination. A little more work, and I might get all the blue, but I was surprised to get it even this good. I had no problem realizing the 180 phase shift, just by looking at time zero. ? ? -- don??? va3drl
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Re: S-38B Tuning Shaft Query
Or fat fingers. I have to read stuff carefully before sending it to
avoid saying nonsense. Even so I don't always see it.
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On 7/30/2024 4:31 PM, Justin Bowser - KI5GKD wrote: D'oh!? Yeah, aluminum shaft and plastic knob.? Had another brain-fart...
--
Justin B.
KI5GKD _._,_._,_
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: S-38B Tuning Shaft Query
The knob is insulated but its still possible to contact the set
screws although they are pretty deeply buried. The shaft can still
contact the cabinet if they are not centered in the holes. I think
Hallicrafters was just being extra careful to prevent shock hazards.
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On 7/30/2024 4:07 PM, don Root wrote: Re /_It does have aluminum shafts_/. But, a well insulated knob; at
least on day one?
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: S-38B Tuning Shaft Query
D'oh!? Yeah, aluminum shaft and plastic knob.? Had another brain-fart...
--
Justin B.
KI5GKD
|
Re: S-38B Tuning Shaft Query
Re ?It does have aluminum shafts.?? ?But, a well insulated knob; at least on day one? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Tuesday, July 30, 2024 6:54 PM
To: [email protected]; ma.wright@...
Subject: Re: [HallicraftersRadios] S-38B Tuning Shaft Query? I have an S-38 awaiting rebuild. It does have aluminum shafts.
--
Richard Knoppow ? -- don??? va3drl
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Locked
Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Halden Good As an aside, I found that remanence or Br ?is the remanent flux density is most commonly derived from the flux after complete saturation, but it seems to be used as you intended too. It is not clear to me.? You likely recall that the best electrical way to demagnetize anything is to take it to full saturation with AC, and slowly take the voltage to zero., but that means high voltage first, which you are reluctant to try, so ?unless you have an old 25 cycle generator which will saturate the core with ?much lower voltage. From all I have read they have tried to remove ?the remanent flux on huge transformers before closing, but it is not easy to determine what it is. It might be reasonable to assume that the core is being tested at a common voltage so it will turn of using the SSR in the same way other than the polarity which you can watch; but don¡¯t hold me to that assumption. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of HF via groups.io
Sent: Tuesday, July 30, 2024 5:54 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY? That's exactly the kind of clue I was hoping for.? You're right, I did not control the polarity of the last cycle before turn-off.? So my statement about invariable remanence is not correct.? Remanance could have two quantities, A and B.? I can't control which one it is, but I should be able to record which one it is in a future experiment.? I'll try this again by noting the last cycle polarity and the off time before each measurement in a new session.? I might also try to set the remanence by applying some DC to the transformer prior to energizing. I haven't found anything about remanence decay time, but I imagine it's quite long because once you magnetize a piece of steel, it stays that way for a long time.? -- don??? va3drl
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Re: S-38B Tuning Shaft Query
I have an S-38 awaiting rebuild. It does have aluminum shafts.
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On 7/30/2024 12:16 PM, Maynard Wright, P. E., W6PAP via groups.io wrote: I was thinking about removing a tuning knob from the S-38 to check the
shaft, but I measured from a set screw to the chassis and there is
continuity.
73,
Maynard
W6PAP
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: S-38B Tuning Shaft Query
Do you mean the KNOB or the SHAFT? I don't think any metal knobs
were used on the S-38 series.
> The knob on my S-38 is solid aluminum.
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--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Thanks, Don!
That's exactly the kind of clue I was hoping for.? You're right, I did not control the polarity of the last cycle before turn-off.? So my statement about invariable remanence is not correct.? Remanance could have two quantities, A and B.? I can't control which one it is, but I should be able to record which one it is in a future experiment.? I'll try this again by noting the last cycle polarity and the off time before each measurement in a new session.? I might also try to set the remanence by applying some DC to the transformer prior to energizing.
I haven't found anything about remanence decay time, but I imagine it's quite long because once you magnetize a piece of steel, it stays that way for a long time.?
Cheers,
Halden VE7UTS
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Re: S-38B Tuning Shaft Query
Justin , do I read you correctly ??
one post:?? yes, the S-38 shaft is aluminum.
then next post The knob on my S-38 is solid aluminum.
it would seem that your fingers get connected to the hot? chassis
^something strange stuck in this post
--
don??? va3drl
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Locked
Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Haden, further to my last posting,? I now see? your? ¡°In all cases, the transformer was turned off in the same state- that of zero primary current - so the remanance should be invariant.¡± etc .? ?I am guessing that you can¡¯t ensure the same polarity of the last half cycle in terms of voltage or current, or flux, so the results of any test will depend on the last one.. perhaps that? is part of the answer. I think you had thoughts about this ?a while back. Is that any help? ? -- don??? va3drl
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Re: S-38B Tuning Shaft Query
The knobs on my S-38 appear to be black plastic. If they were aluminum,
then the full AC line voltage would appear on the knobs if the line cord
were plugged in one of the two possible directions.
73,
Maynard
W6PAP
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On 7/30/24 12:59, Justin Bowser - KI5GKD wrote: The knob on my S-38 is solid aluminum.
73,
--
Justin B.
KI5GKD
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Haden ?,in reply to the first shots ..for turn off , are you able to control, or does it control the polarity of turn off polarity [my term], or is it actually rather ?random? This of course relates to the ???polarity left in the core after turn off. If you are not sure about the turn off polarity you might want to run a series of tests to find out if the voltage jut before turn-off is random or fixed.? Then when you do turn-on tests, you might log the polarity of the previous turn off. Dunno if this makes sense. -- don??? va3drl
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Hi Jim
Actually, the 1-> and 2-> markers on the left portray the zero line for the 1st and 2nd channels, respectively.? The horizontal lines next to those markers show that the quantity being measured is zero up until the time the SSR connects the transformer to the AC power source.? The current starts to rise at the same time the voltage starts to rise (or fall if you consider going negative from zero to be "falling").
Both waveforms displayed are measured simultaneously.? This is a Tek TDS 2000 series dual-channel storage 'scope.
I deliberately do not include the previous message thread in my post because doing so fills the forum's limited disk space with redundant copies of prior messages.? It's very easy to see all the previous messages by just scrolling down in the groups.io window, which I presume is the way most members interact with the forum.? Those who interact with the forum solely in an email program don't experience that convenience (or many others) that groups.io offers.
Cheers
Halden VE7UTS
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Re: S-38B Tuning Shaft Query
The knob on my S-38 is solid aluminum.
?
73,
--
Justin B.
KI5GKD
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Jim Whartenby
don Root