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Nice finding! I worked on an SX-9 a couple years back for a friend. I was surprised at how well it performed.
Enjoy!
Tom W3TA
I did it again..... Went to an estate sale and 2 more Hallicrafters radios follow me home!?? Got an SX-9, and an SX-42.? the 9 plays quite nicely as found (newer power cord, and it was found plugged in at the salein such a manner that I gathered the previous owner had listened to it "recently"). The 42 needed a new cord. Did that and replaced the line bypass caps. It was brought up with a dim bulb a variac, and an ammeter.?? It too Plays!
?
Nest is a bit of cleaning, but it was a good day for boatanchors (geez that 42 is HEAVY).
?
BTW, the cost for both was under $50.00
?
Gotta love American technology and workmanship!!!
?
?
Howard
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I did it again..... Went to an estate sale and 2 more Hallicrafters radios follow me home!?? Got an SX-9, and an SX-42.? the 9 plays quite nicely as found (newer power cord, and it was found plugged in at the salein such a manner that I gathered the previous owner had listened to it "recently"). The 42 needed a new cord. Did that and replaced the line bypass caps. It was brought up with a dim bulb a variac, and an ammeter.?? It too Plays!
?
Nest is a bit of cleaning, but it was a good day for boatanchors (geez that 42 is HEAVY).
?
BTW, the cost for both was under $50.00
?
Gotta love American technology and workmanship!!!
?
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Howard
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Re: Gold Halli logos wanted for S-14 and 5-T
One of them , the 5T or the S14, had a faded gold emblem.? Must have been the more recently restored S14 if I began this pursuit when wrapping that one up.? Now that you mention it, the other was white faded to almost nonexistent light grey.? I can produce a white emblem but that gold one does look sharp, matches the dial and pointer nicely too.?
Thanks for the input.
--
Dan
K1DTS
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Halden, I have been wondering about the HV winding wire size{S}. From your ¡°stuff¡±? I would say ¡°the turns near the Center Tap need to feed B+ current and B++ current so must be thicker,?? while those far from the CT feed only ?B++ current so the outer turns can be thinner ?, all neglecting the little B+ tap. ?¡° ?¡° µþ+¡± = 300 VDC ?and ¡° B++¡± = 750 VDC ?from the drawing for whatever operating condition ?
toggle quoted message
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From: [email protected] [mailto:[email protected]] On Behalf Of HF via groups.io
Sent: Saturday, September 14, 2024 6:22 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY? A clarification to my post 30946: By "inner" and "outer" I meant from the perspective of the winding's schematic.? The wire between the HV taps and "B+" taps has higher resistance per volt developed than that between the B+ taps.? So the winding probably starts with the thinner wire and then switches to thicker wire at the first B+ tap and back to thin at the next B+ tap.? By "B+ tap" I mean the taps that go to the "L.V. RECT." anodes.? It's hard for me to call this "low voltage". The resistance measurements do show the increase in wire length as the layers accumulate. -- don??? va3drl
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
A clarification to my post 30946:
By "inner" and "outer" I meant from the perspective of the winding's schematic.? The wire between the HV taps and "B+" taps has higher resistance per volt developed than that between the B+ taps.? So the winding probably starts with the thinner wire and then switches to thicker wire at the first B+ tap and back to thin at the next B+ tap.? By "B+ tap" I mean the taps that go to the "L.V. RECT." anodes.? It's hard for me to call this "low voltage".
The resistance measurements do show the increase in wire length as the layers accumulate.
Halden VE7UTS
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Thanks for the comments, everyone!
I don't think the dielectric constant of material in the gap matters much here, but dielectric strength does.? At 2000V, I get a spark across the gap.? If the somewhat-humid air during that test has dielectric strength of 3kV/mm, then this means the gap is less than 2/3 mm.? I'll guess that it's about half of a mm.? It looks that way.
My RTV dielectric strength is probably in the 7-10 kV/mm range; much better than air and on par with "fish paper".? So after I put some varnish in there to prevent future shorts, I plan to put some RTV in the hole.? But as some have cautioned, the region certainly has some carbon or other oxidized materials around.? This means that if an arc were to try to form again, it might not matter what the hole filler is.? Therefore, I plan to insert some other material over the hole.? I looked up polyimide film (aka Kapton) properties and found that a single layer is good for at least 7.7 kV.? So I'll put in 1 or 2 sheets of that and hold it in place with PVC electrical tape (10 kV/mm).? Then I'll re-install the filament winding over the bulge.
I'll update on the outcome here!
Cheers
Halden VE7UTS
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Re: Gold Halli logos wanted for S-14 and 5-T
I have two 5-Ts , one with the later dial type, but the logo is not present (front panel has been repainted) and an unrestored 5-T Sky Buddy (Radio Boy dial) with the original Hallicrafters logo intact and it is the same white color as the lettering. It is definitely not gold colored. I can't really tell by any photos I have seen, but did the later (none boy) 5-Ts have a gold logo instead of white?
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Les
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
It is doubtful that the wire gauge for the high voltage secondary is different below the center tap then above it.? As the winding progresses from the lowest level to the highest, the length per turn increases which causes the winding resistance to also increase.??
All that really matters is the volt-per-turn which appears to be about 0.56 so the 1860 volt secondary has a total of 3382 turns, half below the center tap and half above.? Although the voltages are similar with respect to the center tap, the winding resistance is not.
It will be difficult to remove all of the imbedded carbon at the site of the breakdown so a successful repair is in doubt.? Without rewinding the transformer, the next best thing is to disconnect the 5 volt windings and solid state the power supply, as mentioned months ago.??
Soaking the transformer in a suitable varnish for days may help to minimize any damage caused by moving the top layer of the HV winding.? Vacuum impregnation of the varnish would be preferred. Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
Some more information about this transformer's arc-through injury:
I used resistance measurement between the arc site and the HV winding terminals to estimate where on the HV winding the arc-through occurred. ?It¡¯s about 125 turns from the end.?
Probably not relevant to the puzzle but possibly of interest:? Scaling up from the 9-turns on the 5V secondary, I calculated that the HV winding has about 3000 turns!? Based on resistance and winding length, I concluded that the outer part is probably 30 gauge and the inner about 27 gauge. ?At 30 gauge, probably 200 turns fit per layer; fewer at 27 gauge. ?So the HV winding probably has about 20 layers.
The maximum voltage at the arc site would have reached about 92% of what it would have reached at the end of the winding.? During normal operation, the filament winding was at most +950 to +1000 volts and the HV winding under it was reaching a similar, but negative potential.? For the arc to occur, one of these had to have even higher magnitude for a very brief time.?
Halden
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Some more information about this transformer's arc-through injury:
I used resistance measurement between the arc site and the HV winding terminals to estimate where on the HV winding the arc-through occurred. ?It¡¯s about 125 turns from the end.?
Probably not relevant to the puzzle but possibly of interest:? Scaling up from the 9-turns on the 5V secondary, I calculated that the HV winding has about 3000 turns!? Based on resistance and winding length, I concluded that the outer part is probably 30 gauge and the inner about 27 gauge. ?At 30 gauge, probably 200 turns fit per layer; fewer at 27 gauge. ?So the HV winding probably has about 20 layers.
The maximum voltage at the arc site would have reached about 92% of what it would have reached at the end of the winding.? During normal operation, the filament winding was at most +950 to +1000 volts and the HV winding under it was reaching a similar, but negative potential.? For the arc to occur, one of these had to have even higher magnitude for a very brief time.?
Halden
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
As a suggestion, try contacting Heyboer Transformers in Grand Haven
Mich to see if they
can rewind the transformer?
73
Mike W5RKL
On 9/13/24 11:56 PM, robert meadows via
groups.io wrote:
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Show quoted text
Jim,
I thought this had died.?
Seems that the fellow would be better off rewinding the
transformer with new and better insulation wire, I doubt that
the RTV will do what he intends.
Still real dampish and not
raining at? present.
R
On Saturday, September 14, 2024 at 12:23:13 AM EDT, Jim
Whartenby via groups.io <old_radio@...>
wrote:
Halden
What is the dielectric strength of
the RTV that you plan to use???
Dow 3120 has a rating of 457kV per
inch so this may not be good enough to prevent
another punch through in the same area.??
See:?
This means that a 0.01 inch thickness
may survive 4.6kV which is perhaps twice of what
it would see in a perfect world assuming uniform
coverage of the RTV over the defect area.
Jim
Logic: Method
used to arrive at the wrong conclusion,
with confidence.? Murphy
I
further opened up the transformer that
Randy donated for the cause, in
preparation for removing the ¡°YEL¡± 5V
winding to look for the arc path between
it and the HV winding.? Once
I got tape off the winding on the back
side (the side that does not have
winding terminations), I could see a
hole in the tape underneath.? Application
of 2000 V confirmed that this is the arc
site.? See first photo.
?
I
decided to remove 2 or 3 windings to
fully expose the hole so I could fill it
with RTV, apply kapton tape, and
re-install the removed windings.?
It turned out that the wires to
the terminals of this winding are routed
under the other 5V winding.? I
couldn¡¯t access them without removing
that winding, too.? So I
cut the wire and pulled it through the
gap between it and the core.? This
exposed the insulation hole further.?
I could see the HV windings
underneath.? See second
photo.
?
It¡¯s
now apparent that the 6.3V winding is at
risk of arcing over to the HV winding,
too.? I was able to pry
its first turn away enough that I should
be able to insert some tape under it to
prevent such arcing.? See
third photo.
?
I
was barely able to push that first wire
back through the core, so I¡¯m not
confident that I¡¯d be able to restore
this winding if I were to remove 3 or 4
turns from it.? So, I¡¯m
considering loosening a few turns just
enough to get access under them to
restore the insulation.? I¡¯m
also considering removing this winding
in its entirety which would render the
transformer unsuitable for service in an
un-modified HT-37.? It
should work fine in one in which one of
the rectifiers has been replaced by
diodes.
Suggestions,
anyone?
Halden
VE7UTS
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
An update:
I'm going try to keep the filament winding.? I was able to loosen 3 filament winding turns.? Between the time I posted the message with the 3 photos and when it appeared here, I posted a question about insulating materials to Amateur-Repairs (I'm not moderated over there) and got responses that the RTV has to be non-acidic, I should use some insulating varnish, and I have to make sure there isn't a short between turns anywhere.?
This image shows the whole hole.
One aspect of the situation that belongs here, not at the more general forum, regards where the arc fault occurred.? It's at the edge of the HV rectifier filament winding.? I can't discern whether it's at the edge of the HV winding.? I suppose I could use an ohmmeter to approximate where along the HV winding it is.? I'd use a sewing needle to poke through what remains of the insulation on the HV winding.? This might provide a clue about what caused the failure.? I figure the failure should occur at either end of the HV winding where it's close to the filament winding OR where the HV winding is close to a flaw in the insulation.
Cheers
Halden VE7UTS
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Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Jim, I thought this had died.? Seems that the fellow would be better off rewinding the transformer with new and better insulation wire, I doubt that the RTV will do what he intends.
Still real dampish and not raining at? present. R
On Saturday, September 14, 2024 at 12:23:13 AM EDT, Jim Whartenby via groups.io <old_radio@...> wrote:
Halden What is the dielectric strength of the RTV that you plan to use???
Dow 3120 has a rating of 457kV per inch so this may not be good enough to prevent another punch through in the same area.?? See:?
This means that a 0.01 inch thickness may survive 4.6kV which is perhaps twice of what it would see in a perfect world assuming uniform coverage of the RTV over the defect area. Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
I further opened up the transformer that Randy donated for the cause, in preparation for removing the ¡°YEL¡± 5V winding to look for the arc path between it and the HV winding.? Once I got tape off the winding on the back side (the side that does not have winding terminations), I could see a hole in the tape underneath.? Application of 2000 V confirmed that this is the arc site.? See first photo.
?
I decided to remove 2 or 3 windings to fully expose the hole so I could fill it with RTV, apply kapton tape, and re-install the removed windings.? It turned out that the wires to the terminals of this winding are routed under the other 5V winding.? I couldn¡¯t access them without removing that winding, too.? So I cut the wire and pulled it through the gap between it and the core.? This exposed the insulation hole further.? I could see the HV windings underneath.? See second photo.
?
It¡¯s now apparent that the 6.3V winding is at risk of arcing over to the HV winding, too.? I was able to pry its first turn away enough that I should be able to insert some tape under it to prevent such arcing.? See third photo.
?
I was barely able to push that first wire back through the core, so I¡¯m not confident that I¡¯d be able to restore this winding if I were to remove 3 or 4 turns from it.? So, I¡¯m considering loosening a few turns just enough to get access under them to restore the insulation.? I¡¯m also considering removing this winding in its entirety which would render the transformer unsuitable for service in an un-modified HT-37.? It should work fine in one in which one of the rectifiers has been replaced by diodes.
Suggestions, anyone?
Halden VE7UTS
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Locked
Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
Halden What is the dielectric strength of the RTV that you plan to use???
Dow 3120 has a rating of 457kV per inch so this may not be good enough to prevent another punch through in the same area.?? See:?
This means that a 0.01 inch thickness may survive 4.6kV which is perhaps twice of what it would see in a perfect world assuming uniform coverage of the RTV over the defect area. Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
I further opened up the transformer that Randy donated for the cause, in preparation for removing the ¡°YEL¡± 5V winding to look for the arc path between it and the HV winding.? Once I got tape off the winding on the back side (the side that does not have winding terminations), I could see a hole in the tape underneath.? Application of 2000 V confirmed that this is the arc site.? See first photo.
?
I decided to remove 2 or 3 windings to fully expose the hole so I could fill it with RTV, apply kapton tape, and re-install the removed windings.? It turned out that the wires to the terminals of this winding are routed under the other 5V winding.? I couldn¡¯t access them without removing that winding, too.? So I cut the wire and pulled it through the gap between it and the core.? This exposed the insulation hole further.? I could see the HV windings underneath.? See second photo.
?
It¡¯s now apparent that the 6.3V winding is at risk of arcing over to the HV winding, too.? I was able to pry its first turn away enough that I should be able to insert some tape under it to prevent such arcing.? See third photo.
?
I was barely able to push that first wire back through the core, so I¡¯m not confident that I¡¯d be able to restore this winding if I were to remove 3 or 4 turns from it.? So, I¡¯m considering loosening a few turns just enough to get access under them to restore the insulation.? I¡¯m also considering removing this winding in its entirety which would render the transformer unsuitable for service in an un-modified HT-37.? It should work fine in one in which one of the rectifiers has been replaced by diodes.
Suggestions, anyone?
Halden VE7UTS
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Locked
Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
I further opened up the transformer that Randy donated for the cause, in preparation for removing the ¡°YEL¡± 5V winding to look for the arc path between it and the HV winding.? Once I got tape off the winding on the back side (the side that does not have winding terminations), I could see a hole in the tape underneath.? Application of 2000 V confirmed that this is the arc site.? See first photo.
?
I decided to remove 2 or 3 windings to fully expose the hole so I could fill it with RTV, apply kapton tape, and re-install the removed windings.? It turned out that the wires to the terminals of this winding are routed under the other 5V winding.? I couldn¡¯t access them without removing that winding, too.? So I cut the wire and pulled it through the gap between it and the core.? This exposed the insulation hole further.? I could see the HV windings underneath.? See second photo.
?
It¡¯s now apparent that the 6.3V winding is at risk of arcing over to the HV winding, too.? I was able to pry its first turn away enough that I should be able to insert some tape under it to prevent such arcing.? See third photo.
?
I was barely able to push that first wire back through the core, so I¡¯m not confident that I¡¯d be able to restore this winding if I were to remove 3 or 4 turns from it.? So, I¡¯m considering loosening a few turns just enough to get access under them to restore the insulation.? I¡¯m also considering removing this winding in its entirety which would render the transformer unsuitable for service in an un-modified HT-37.? It should work fine in one in which one of the rectifiers has been replaced by diodes.
Suggestions, anyone?
Halden VE7UTS
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Re: Gold Halli logos wanted for S-14 and 5-T
Looks good!? I am getting ready to dig out my ALPS printer and make some decals and I think I have some gold foil ribbons so I might try this.
?
73,
--
Justin B.
KI5GKD
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Re: Gold Halli logos wanted for S-14 and 5-T
Your printing on white took me back to old school method.? Pasted the logo into a black square in MS Paint and used the paintbrush & pencil to fill in the white.
Then printed onto plain white copy paper.? Coated front and back with two coats of clear acrylic.?
Then, when dried, cut it out close to the gold outline, traced the edge with a black sharpie to cover the thin white edge of the paper.
(After the sealer so as not to bleed thru to the gold on front.)?? Stuck it on with tacky adhesive.
The Chief makes #26. ? Its the earlier model with the "270 degree" dial and pointer, plays real nice too.? Got a kick tuning in the BFO to hear SSB airport weather reports and operators last night.??
Thanks for the tickler that had me go back to paper.? Next, there's an SX-16 due in tomorrow.
--
Dan
K1DTS
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Re: Gold Halli logos wanted for S-14 and 5-T
No, a standard inkjet from Cannon.? I also have white decal paper but it's not transparent, the white background showing in the circle and letter voids looks awful.
I only run into this issue with black chassis', the grey's and chrome and even wood cabs the decals on the clear film appear good.?
?
This is what I'm working with:
?
--
Dan
K1DTS
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Re: Gold Halli logos wanted for S-14 and 5-T
Dan - I remember buying white decal paper several years ago.? Are you using an Alps MD printer?
?
73,
--
Justin B.
KI5GKD
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Gold Halli logos wanted for S-14 and 5-T
Finished the S-14 restore this weekend, it'll join the 5-T in the collection.
I need to source the gold Hallicrafters logo each originally had in the upper right corner.?
My standard printer makes a decal too transparent and the black background washed out the yellow/gold.
RDaze does not have them listed.? Any referrals are appreciated. The gold logo would be the icing on the cake for each.
--
Dan
K1DTS
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don Root
Jim Whartenby