¡°From that point out, the NEUTRAL and the GROUND conductors, are always separate conductors. They are NEVER (or shouldn't be) tied together anywhere else in the system¡±. I think I said that¡..thanks, Alan. John VK6JX
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On 5 Nov 2024, at 1:44?AM, Alan - W5ARM via groups.io <W5ARM.mail@...> wrote:
From that point out, the NEUTRAL and the GROUND conductors, are always separate conductors. They are NEVER (or shouldn't be) tied together anywhere else in the system.
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Re: TenTec Centurion HV arc to ground
That's caused by....'surface creep'..... which will also depend on any dust/gunk / fluff sitting on the insulator.? ?The insulator can be cleaned up. The easy fix is to put a small piece of plastic sheet (with a hole in it). ..before the arced insulator is installed.? That will increase the leakage path by a bunch. ( plastic goes between the insulator and metal side wall)...so the hole in the plastic is just big enough....then the lip of the insulator sits on the plastic sheeting.? ? ?That or replace with a longer feedthrough HV connector, or use a feedthrough insulator ( 2 x piece type)...that is of the serrated type....which will also increase the leakage path by a bunch.?
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Re: TenTec Centurion HV arc to ground
That pointy end of the wire probably doesn't help. The ceramic feedthru from a Heathkit SB220 would probably work. Never seen one arc.
This reminds me of my automotive days. Anything, I mean anything not right with the ceramic insulator on a spark plug will cause a misfire. Same thing is possible here. Bob W4JFA
Robin- I may have a longer ceramic insulator that would fit your needs. Tell me how long it should be and I will check the junk box.
Tom K0SN?
On Thu, Nov 7, 2024 at 6:58?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote: Yes, these are the notions I've had about the remedy; maybe make an insulator from a solid rod of fiberglass or Teflon with a recess in one end to surround the bolt/nut/solder lug. Thanks Eric!
Thanks,
Robin Midgett K4IDC
I can't tell if the break-down happened because of a defect in the insulator, or if corona from a sharp edge degraded the insulator.? Either way, the insulator should be replaced as it will be impossible to get rid of the carbon track on the insulator.?
There is quite a lot of bolt sticking out of the top of the insulator.? If one can be found, a taller insulator, using the same length bolt, would be a good idea.
Eric WB6TIX
On Thu, Nov 7, 2024 at 6:10?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote:
I'd like to know if any of?you have suggestions as to what caused this HV arc to chassis and hopefully, what to do to prevent it in the?future. Amp is a TenTec Centurion. It was at idle when the arc happened; no RF applied. The glitch resistor took the brunt of the discharge, thank goodness. I've replaced it,?even though the original still?measured the?correct?resistance, it was visually damaged. The event spooked me...new pair of 3-500Z tubes was in the amp; no apparent?damage. The insulator appears to be made of fiberglass. The glitch resistor is on the opposite side of this aluminum panel. The HV feeds through from the resistor via the machine screw. Any thoughts?
Thanks,
Robin Midgett K4IDC
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Re: TenTec Centurion HV arc to ground
This reminds me of my automotive days. Anything, I mean anything not right with the ceramic insulator on a spark plug will cause a misfire. Same thing is possible here. Bob W4JFA
Robin- I may have a longer ceramic insulator that would fit your needs. Tell me how long it should be and I will check the junk box.
Tom K0SN?
On Thu, Nov 7, 2024 at 6:58?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote: Yes, these are the notions I've had about the remedy; maybe make an insulator from a solid rod of fiberglass or Teflon with a recess in one end to surround the bolt/nut/solder lug. Thanks Eric!
Thanks,
Robin Midgett K4IDC
I can't tell if the break-down happened because of a defect in the insulator, or if corona from a sharp edge degraded the insulator.? Either way, the insulator should be replaced as it will be impossible to get rid of the carbon track on the insulator.?
There is quite a lot of bolt sticking out of the top of the insulator.? If one can be found, a taller insulator, using the same length bolt, would be a good idea.
Eric WB6TIX
On Thu, Nov 7, 2024 at 6:10?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote:
I'd like to know if any of?you have suggestions as to what caused this HV arc to chassis and hopefully, what to do to prevent it in the?future. Amp is a TenTec Centurion. It was at idle when the arc happened; no RF applied. The glitch resistor took the brunt of the discharge, thank goodness. I've replaced it,?even though the original still?measured the?correct?resistance, it was visually damaged. The event spooked me...new pair of 3-500Z tubes was in the amp; no apparent?damage. The insulator appears to be made of fiberglass. The glitch resistor is on the opposite side of this aluminum panel. The HV feeds through from the resistor via the machine screw. Any thoughts?
Thanks,
Robin Midgett K4IDC
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Re: TenTec Centurion HV arc to ground
Robin- I may have a longer ceramic insulator that would fit your needs. Tell me how long it should be and I will check the junk box.
Tom K0SN?
On Thu, Nov 7, 2024 at 6:58?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote: Yes, these are the notions I've had about the remedy; maybe make an insulator from a solid rod of fiberglass or Teflon with a recess in one end to surround the bolt/nut/solder lug. Thanks Eric!
Thanks,
Robin Midgett K4IDC
I can't tell if the break-down happened because of a defect in the insulator, or if corona from a sharp edge degraded the insulator.? Either way, the insulator should be replaced as it will be impossible to get rid of the carbon track on the insulator.?
There is quite a lot of bolt sticking out of the top of the insulator.? If one can be found, a taller insulator, using the same length bolt, would be a good idea.
Eric WB6TIX
On Thu, Nov 7, 2024 at 6:10?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote:
I'd like to know if any of?you have suggestions as to what caused this HV arc to chassis and hopefully, what to do to prevent it in the?future. Amp is a TenTec Centurion. It was at idle when the arc happened; no RF applied. The glitch resistor took the brunt of the discharge, thank goodness. I've replaced it,?even though the original still?measured the?correct?resistance, it was visually damaged. The event spooked me...new pair of 3-500Z tubes was in the amp; no apparent?damage. The insulator appears to be made of fiberglass. The glitch resistor is on the opposite side of this aluminum panel. The HV feeds through from the resistor via the machine screw. Any thoughts?
Thanks,
Robin Midgett K4IDC
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Re: the WORST ham built amplifier?
Seymour probably? used the amp also on 20m where I met him most on the long path.
We were talking about using the same tube in our amps.
?
73
Peter, DJ7WW
?
?
?
?
-----Original-Nachricht-----
Betreff: Re: [ham-amplifiers] the WORST ham built amplifier?
Datum: 2024-11-07T20:13:07+0100
Von: "Brandon DX via groups.io" <rfburnz@...>
An: "[email protected]" <[email protected]>
?
?
?
?
Jim, I snapped a pic of the bandswitched input network.
You can see the 40M toroid has been overheated, I recall that was the band W6CCP used it on.?
Note the red paint applied to the mica cap tuning screws.?
?
? ?
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Re: TenTec Centurion HV arc to ground
Nothing to do with tubes. ?Remove ceramic and inspect it. ?
On Thursday, November 7, 2024, 8:51 PM, Robin Midgett <RobinK4IDC@...> wrote: Not sure about country of?origin, but the tubes were acquired from Command Technologies.? I don't know what the tubes would have to do with it...the arc is prior to the tubes in the circuit.
Thanks,
Robin Midgett K4IDC On Thu, Nov 7, 2024 at 7:30?PM Technotronic Dimensions via <steve= [email protected]> wrote: New tubes made in China maybe?
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
E-Mail: Steve@...
----- Original Message -----
From: "Robin Midgett" <RobinK4IDC@...>
To: <[email protected]>
Sent: Thursday, November 07, 2024 8:10 PM
Subject: [ham-amplifiers] TenTec Centurion HV arc to ground
> I'd like to know if any of you have suggestions as to what caused this HV
> arc to chassis and hopefully, what to do to prevent it in the future.
> Amp is a TenTec Centurion. It was at idle when the arc happened; no RF
> applied. The glitch resistor took the brunt of the discharge, thank
> goodness. I've replaced it, even though the original still measured
> the correct resistance, it was visually damaged. The event spooked
> me...new
> pair of 3-500Z tubes was in the amp; no apparent damage.
> The insulator appears to be made of fiberglass. The glitch resistor is on
> the opposite side of this aluminum panel. The HV feeds through from the
> resistor via the machine screw. Any thoughts?
>
> [image: IMG_20241107_184817794.jpg]
>
>
> Thanks,
> Robin Midgett K4IDC
>
>
>
>
>
>
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Re: TenTec Centurion HV arc to ground
There could be a hairline crack in the ceramic. ?Needs to be take apart and checked to see if the arc was internal to the feed thru.
On Thursday, November 7, 2024, 8:58 PM, Robin Midgett <RobinK4IDC@...> wrote: Yes, these are the notions I've had about the remedy; maybe make an insulator from a solid rod of fiberglass or Teflon with a recess in one end to surround the bolt/nut/solder lug. Thanks Eric!
Thanks,
Robin Midgett K4IDC I can't tell if the break-down happened because of a defect in the insulator, or if corona from a sharp edge degraded the insulator.? Either way, the insulator should be replaced as it will be impossible to get rid of the carbon track on the insulator.?
There is quite a lot of bolt sticking out of the top of the insulator.? If one can be found, a taller insulator, using the same length bolt, would be a good idea.
Eric WB6TIX
On Thu, Nov 7, 2024 at 6:10?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote:
I'd like to know if any of?you have suggestions as to what caused this HV arc to chassis and hopefully, what to do to prevent it in the?future. Amp is a TenTec Centurion. It was at idle when the arc happened; no RF applied. The glitch resistor took the brunt of the discharge, thank goodness. I've replaced it,?even though the original still?measured the?correct?resistance, it was visually damaged. The event spooked me...new pair of 3-500Z tubes was in the amp; no apparent?damage. The insulator appears to be made of fiberglass. The glitch resistor is on the opposite side of this aluminum panel. The HV feeds through from the resistor via the machine screw. Any thoughts?
Thanks,
Robin Midgett K4IDC
|
Re: TenTec Centurion HV arc to ground
Yes, these are the notions I've had about the remedy; maybe make an insulator from a solid rod of fiberglass or Teflon with a recess in one end to surround the bolt/nut/solder lug. Thanks Eric!
Thanks,
Robin Midgett K4IDC
I can't tell if the break-down happened because of a defect in the insulator, or if corona from a sharp edge degraded the insulator.? Either way, the insulator should be replaced as it will be impossible to get rid of the carbon track on the insulator.?
There is quite a lot of bolt sticking out of the top of the insulator.? If one can be found, a taller insulator, using the same length bolt, would be a good idea.
Eric WB6TIX
On Thu, Nov 7, 2024 at 6:10?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote:
I'd like to know if any of?you have suggestions as to what caused this HV arc to chassis and hopefully, what to do to prevent it in the?future. Amp is a TenTec Centurion. It was at idle when the arc happened; no RF applied. The glitch resistor took the brunt of the discharge, thank goodness. I've replaced it,?even though the original still?measured the?correct?resistance, it was visually damaged. The event spooked me...new pair of 3-500Z tubes was in the amp; no apparent?damage. The insulator appears to be made of fiberglass. The glitch resistor is on the opposite side of this aluminum panel. The HV feeds through from the resistor via the machine screw. Any thoughts?
Thanks,
Robin Midgett K4IDC
|
Re: TenTec Centurion HV arc to ground
I can't tell if the break-down happened because of a defect in the insulator, or if corona from a sharp edge degraded the insulator.? Either way, the insulator should be replaced as it will be impossible to get rid of the carbon track on the insulator.?
There is quite a lot of bolt sticking out of the top of the insulator.? If one can be found, a taller insulator, using the same length bolt, would be a good idea.
Eric WB6TIX
On Thu, Nov 7, 2024 at 6:10?PM Robin Midgett via <RobinK4IDC= [email protected]> wrote:
I'd like to know if any of?you have suggestions as to what caused this HV arc to chassis and hopefully, what to do to prevent it in the?future. Amp is a TenTec Centurion. It was at idle when the arc happened; no RF applied. The glitch resistor took the brunt of the discharge, thank goodness. I've replaced it,?even though the original still?measured the?correct?resistance, it was visually damaged. The event spooked me...new pair of 3-500Z tubes was in the amp; no apparent?damage. The insulator appears to be made of fiberglass. The glitch resistor is on the opposite side of this aluminum panel. The HV feeds through from the resistor via the machine screw. Any thoughts?
Thanks,
Robin Midgett K4IDC
|
Re: TenTec Centurion HV arc to ground
Not sure about country of?origin, but the tubes were acquired from Command Technologies.? I don't know what the tubes would have to do with it...the arc is prior to the tubes in the circuit.
Thanks,
Robin Midgett K4IDC On Thu, Nov 7, 2024 at 7:30?PM Technotronic Dimensions via <steve= [email protected]> wrote:
New tubes made in China maybe?
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
E-Mail: Steve@...
----- Original Message -----
From: "Robin Midgett" <RobinK4IDC@...>
To: <[email protected]>
Sent: Thursday, November 07, 2024 8:10 PM
Subject: [ham-amplifiers] TenTec Centurion HV arc to ground
> I'd like to know if any of you have suggestions as to what caused this HV
> arc to chassis and hopefully, what to do to prevent it in the future.
> Amp is a TenTec Centurion. It was at idle when the arc happened; no RF
> applied. The glitch resistor took the brunt of the discharge, thank
> goodness. I've replaced it, even though the original still measured
> the correct resistance, it was visually damaged. The event spooked
> me...new
> pair of 3-500Z tubes was in the amp; no apparent damage.
> The insulator appears to be made of fiberglass. The glitch resistor is on
> the opposite side of this aluminum panel. The HV feeds through from the
> resistor via the machine screw. Any thoughts?
>
> [image: IMG_20241107_184817794.jpg]
>
>
> Thanks,
> Robin Midgett K4IDC
>
>
>
>
>
>
|
Re: TenTec Centurion HV arc to ground
New tubes made in China maybe?
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
E-Mail: Steve@...
toggle quoted message
Show quoted text
----- Original Message ----- From: "Robin Midgett" <RobinK4IDC@...> To: < [email protected]> Sent: Thursday, November 07, 2024 8:10 PM Subject: [ham-amplifiers] TenTec Centurion HV arc to ground I'd like to know if any of you have suggestions as to what caused this HV
arc to chassis and hopefully, what to do to prevent it in the future.
Amp is a TenTec Centurion. It was at idle when the arc happened; no RF
applied. The glitch resistor took the brunt of the discharge, thank
goodness. I've replaced it, even though the original still measured
the correct resistance, it was visually damaged. The event spooked me...new
pair of 3-500Z tubes was in the amp; no apparent damage.
The insulator appears to be made of fiberglass. The glitch resistor is on
the opposite side of this aluminum panel. The HV feeds through from the
resistor via the machine screw. Any thoughts?
[image: IMG_20241107_184817794.jpg]
Thanks,
Robin Midgett K4IDC
|
TenTec Centurion HV arc to ground
I'd like to know if any of?you have suggestions as to what caused this HV arc to chassis and hopefully, what to do to prevent it in the?future. Amp is a TenTec Centurion. It was at idle when the arc happened; no RF applied. The glitch resistor took the brunt of the discharge, thank goodness. I've replaced it,?even though the original still?measured the?correct?resistance, it was visually damaged. The event spooked me...new pair of 3-500Z tubes was in the amp; no apparent?damage. The insulator appears to be made of fiberglass. The glitch resistor is on the opposite side of this aluminum panel. The HV feeds through from the resistor via the machine screw. Any thoughts?
Thanks,
Robin Midgett K4IDC
|
Re: the WORST ham built amplifier?
Jim, I snapped a pic of the bandswitched input network.
You can see the 40M toroid has been overheated, I recall that was the band W6CCP used it on.?
Note the red paint applied to the mica cap tuning screws.?
?
I wasn't in So Cal when W6BWG completely redesigned it so I don't have any pics of the new version but I'm certain it looked 100% professional.
I believe he used relays instead of the long leads going to the wafer switch as shown.?
He said an ex-Henry Radio employee did the original Kluge for Seymour.? yeah, a 3K would be the chassis.? I had to move the counter dial drive out front on the panel an inch or more to get the roller coil into the chassis. Kintronics supplied the coil. By some stroke of luck it just worked at 1.8+/-MHz with the coil almost end-stopped (like a 1/4 turn left on the tuning dial).? ?
I was told that after CCP died the linear was bought by someone and moved to FL. I seem to remember a K5 call??
?
As for the plate voltage, 6500 is as high as I would go and mind you I am not doing tube calculating any longer but the drive requirements would be less and I don't have any IMD data on the 3000A7 but I did at one time have a binder full of everything you can imagine on tube calculations on this and lots of other tubes with some actual data taken when  I had access to the Advance Products Lab.? ? When CPI eliminated my position I was acting marketing manager of the ailing Eimac business and management wouldn't allow me to log onto my PC that fateful morning.? I went to HR and got my "walking papers" and they placed everything out of my file cabinet in a dumpster.??
73,? Reid? W6MTF
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Re: the WORST ham built amplifier?
I guess efficiency and IMD will improve with 6500V at the anode, but 10m will be difficult to tune and on 160m the Gates inductor might be too small in inductance.
Mine is run at 4800V, 10-160m on any frequency, no tuned input.
Second RF choke is shorted out from 40m down while another short across the roller inductor is taken out by deenergizing another relay.
Yes, W6CCPs rack was probably a Henry 3000D generator, perhaps the OEM version by Perkin Elmer.
I modified many of them, most to mono band amps, three out of 10 to all band.
?
73
Peter, DJ7WW
?
?
?
?
?
?
?
?
-----Original-Nachricht-----
Betreff: Re: [ham-amplifiers] the WORST ham built amplifier?
Datum: 2024-11-06T17:49:25+0100
Von: "Jim VE7RF" <jim.thom@...>
An: "[email protected]" <[email protected]>
?
?
?
Reid, can you safely put 6500 vdc (loaded) on a 3x3 tube ?? ?What about IMD with that voltage ?? ?Most folks are getting 68% eff on the lower bands (160-30m)....with 4800-5500 vdc loaded...and a little less on 20-17-15m.? ?Typ they are driven with a 200 watt xcvr in most cases, but not always.?
That RF deck appears to be a Henry RF generator, modified with a roller coil and 2 x vac caps.?
The 3x3 will typ hi-pot test to 20 kv (anode to grid).?
Do you remember what was used for the tuned input ?? ?Was it a mess of bandswitched PI networks, or direct driven ???
? ?
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Re: the WORST ham built amplifier?
Reid, can you safely put 6500 vdc (loaded) on a 3x3 tube ?? ?What about IMD with that voltage ?? ?Most folks are getting 68% eff on the lower bands (160-30m)....with 4800-5500 vdc loaded...and a little less on 20-17-15m.? ?Typ they are driven with a 200 watt xcvr in most cases, but not always.?
That RF deck appears to be a Henry RF generator, modified with a roller coil and 2 x vac caps.?
The 3x3 will typ hi-pot test to 20 kv (anode to grid).?
Do you remember what was used for the tuned input ?? ?Was it a mess of bandswitched PI networks, or direct driven ???
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In the case of the Hallicrafters S-38 and many many others, the chassis was on one side of the AC line, which could have been hot or neutral depending on how the (non) polarized plug was inserted into the (also non-polarized) outlet.? The chassis was insulated from the case.
Even the ARRL was guilty of this. ?
For example, The 5V power supply design for the original WB4VVF Accu-Keyer (mid-1970¡¯s, I believe) had the 117 VAC hot and neutral lines bypassed to ground through some rather-high-value capacitors, I always got mildly zapped by mine whenever I touched it and it wasn¡¯t connected to a transmitter.
I was so young and naive at the time, I thought getting zapped when touching stuff was normal. ?
Best regards
Mahlon - N4ZK
<We hams experience this leakage current often in ungrounded old tube equipment that have large capacitors bypassing the AC line. These capacitors are connected from each side of the incoming AC line to the chassis, which <effectively places an ungrounded chassis at half the AC potential! That's why you'll usually see a small spark when you brush a grounded conductor against the chassis of such equipment.
<Steve, K0XP
Back in 1979, at my 1st home, I had the drake C line setup on a small table in the kitchen.? ( C line bought new in 1977). Table was right next to the kitchen sink.? ?Got zapped one day, when plugging in coax.? I measured 60 vac... between chassis of drake gear...and cold water pipes.? Same deal as Steve mentioned.? Drake wired one bypass cap between hot and chassis....and a 2nd bypass cap between neutral and chassis.? What u end up with is 2 x caps in series...with the junction point being the chassis.? Then a 60 vac drop across each cap...which is why the chassis? ends up with 60 vac on it.? ?Hence the 60 vac? between? Un grounded chassis...and my cold water pipes.? And if some gear does have a grnded chassis? ( with a 3 prong? 120 vac cord).... like a scope etc, when the coax from that gear is plugged into the drake gear, then the drake chassis all get grnded.? ?That works.... until u unplug the coax going to the gear that is grnded.? ?Then u get zapped when plugging in the coax, with one hand on the shell....and other hand on the? gear, so it does not slide about.? WTF ?? ?you woulda thought drake et all, woulda figured this one out well before.? ?Heck, they didn't even use polarized 2 x prong plugs.?
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<We hams experience this leakage current often in ungrounded old tube equipment that have large capacitors bypassing the AC line. These capacitors are connected from each side of the incoming AC line to the chassis, which <effectively places an ungrounded chassis at half the AC potential! That's why you'll usually see a small spark when you brush a grounded conductor against the chassis of such equipment.
<Steve, K0XP
Back in 1979, at my 1st home, I had the drake C line setup on a small table in the kitchen.? ( C line bought new in 1977). Table was right next to the kitchen sink.? ?Got zapped one day, when plugging in coax.? I measured 60 vac... between chassis of drake gear...and cold water pipes.? Same deal as Steve mentioned.? Drake wired one bypass cap between hot and chassis....and a 2nd bypass cap between neutral and chassis.? What u end up with is 2 x caps in series...with the junction point being the chassis.? Then a 60 vac drop across each cap...which is why the chassis? ends up with 60 vac on it.? ?Hence the 60 vac? between? Un grounded chassis...and my cold water pipes.? And if some gear does have a grnded chassis? ( with a 3 prong? 120 vac cord).... like a scope etc, when the coax from that gear is plugged into the drake gear, then the drake chassis all get grnded.? ?That works.... until u unplug the coax going to the gear that is grnded.? ?Then u get zapped when plugging in the coax, with one hand on the shell....and other hand on the? gear, so it does not slide about.? WTF ?? ?you woulda thought drake et all, woulda figured this one out well before.? ?Heck, they didn't even use polarized 2 x prong plugs.?
|
Alan, Didn't matter. It got more written which is a good thing. Good story on the fridge.? Bob W4JFA
On Mon, Nov 4, 2024 at 9:43?PM Alan - W5ARM via <W5ARM.mail= [email protected]> wrote: On Mon, Nov 4, 2024 at 03:20 PM, Bob wrote:
Alan, It wasn't me. Someone wrote that it happened to them. Maybe it was another group?
Bob W4JFA
On Mon, Nov 4, 2024 at 06:41 PM, Eric wrote:
It was in the Electrical Improvements thread on this group.
Eric
?
Ooops... my bad! LOL
?
I didn't even know there was an "Electrical Improvements" thread here.? I can delete my post if desired...
?
--
73,
~Alan
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On Mon, Nov 4, 2024 at 03:20 PM, Bob wrote:
Alan, It wasn't me. Someone wrote that it happened to them. Maybe it was another group?
Bob W4JFA
On Mon, Nov 4, 2024 at 06:41 PM, Eric wrote:
It was in the Electrical Improvements thread on this group.
Eric
?
Ooops... my bad! LOL
I didn't even know there was an "Electrical Improvements" thread here.? I can delete my post if desired...
?
ON EDIT: Post deleted. Sorry 'bout that y'all... should've been paying better attention.
--
73,
~Alan
|
Bob
Robin Midgett
Technotronic Dimensions
Brandon DX
Alan - W5ARM