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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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New tubes made in China maybe?
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
E-Mail: Steve@...
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----- 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
|
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
>
>
>
>
>
>
|
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
|
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
|
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
|
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
>
>
>
>
>
>
|
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
|
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
|
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
|
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.?
|
Thanks Jim, I agree with your assessment. I replaced the feed through with a rubber grommet?and soldered the HV wire directly to the glitch resistor. That seems to work fine business.
Thanks,
Robin Midgett K4IDC
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.?
|
Thanks for the kind offer, Tom. A trusted friend and amp builder suggested?a simpler fix..toss the feed through & replace it with a rubber grommet, solder the wire directly to the glitch resistor. That's what I did & it seems to be a good solution so far.
Thanks,
Robin Midgett K4IDC
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
|
If you have any teflon sleeving, put an inch length over the wire
where it goes through the grommet. If you only have teflon sheet,
cut an inch square and wrap it around the wire through the
grommet. If you don't have any teflon, use plastic bag but I'd be
wary of plastic. I've never used it in this manner but some
plastics break down really easily in the presence of high voltage.
0.01"-thick teflon withstands 1900 VDC, so a double or triple-wrap
of sheet would easily work. I've used 0.019" teflon sheet to build
HV bypass capacitors for the old AM-6154/6155 amplifiers before.
Steve, K0XP
On 11/9/2024 9:26 AM, Robin Midgett via
groups.io wrote:
Thanks
Jim, I agree with your assessment. I replaced the feed
through with a rubber grommet?and soldered the HV wire
directly to the glitch resistor. That seems to work fine
business.
Thanks,
Robin Midgett K4IDC
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.?
--
See my QRZ.com page at
|
Robin Midgett
Technotronic Dimensions
Bob