Somehow......I managed to arc a 3kw rated amp with ~700 watts. ETA: problem found!

[ARCHIVED THREAD] - Somehow......I managed to arc a 3kw rated amp with ~700 watts. ETA: problem found!

Posted: 3/16/2012 10:14:50 AM EDT

Noticed my SWR wasn't behaving anymore. When trying to tune, it would jump around a bit, and at times, pulse the wattmeter. Swapped out coax jumpers, process of elimination, popped open the tuner. Never noticed this before, so it must be new. At about 50 watts, no problems. 50-100....intermittant jumps. Key up the amp, constant jumps and/or very high SWR.

How the heck? And how to fix? just file down the "blob" and hope for the best? This has me puzzled.

Posted: 3/16/2012 10:55:23 AM EDT

[#1]

SWR a little high perhaps?

Posted: 3/16/2012 12:11:44 PM EDT

[#2]

I think I have a bad connector and/or jumper somewhere. Not sure which one or where, so I ordered some LMR-240 patch cables. Right now i'm using some older RG-8x of unknown mfg/quality. I know it's at least 15 years old. Even when connecting to a 10 meter A-99 that's tuned, it still gives me goofy SWR readings.

Posted: 3/16/2012 3:56:42 PM EDT

[#3]

I guess those vaunted manual tuners aren't so tough after all!

Posted: 3/16/2012 4:05:42 PM EDT

[#4]

Quoted:
I guess those vaunted manual tuners aren't so tough after all!

How vaunted is it? We don't know the tuner brand or model number. 73, Rob

Posted: 3/16/2012 4:17:33 PM EDT

[#5]

Quoted:

Quoted:
I guess those vaunted manual tuners aren't so tough after all!

How vaunted is it? We don't know the tuner brand or model number. 73, Rob

I'd guess it's a Doubly Super Tuner, I can't quite read the text...

Stolen image from another thread:

I'll also add, maybe it had arced before NAM got it, and the flaw just made it arc easier this time for NAM? See that you never noticed it before, but who knows.

Posted: 3/16/2012 5:16:55 PM EDT

[#6]

Quoted:
I'll also add, maybe it had arced before NAM got it, and the flaw just made it arc easier this time for NAM? See that you never noticed it before, but who knows.

Entirely possible.

I have no reason not to trust the ham i purchased it from, so it could have been me, could have been something he didn't notice. Who knows.

I have had a few.....quirky....issues in the shack since the amp. I think I had a bad or loose connection, and all the moving around exacerbated it. few issues in the begging, then they cleared up. For a week or so, no problems at all. Today, can't tune anytihng over 50 watts without it going nuts.

AFM mentioned that it could be a combination of bad jumpers, and my coax. Antenna is a G5RV, fed with 75 ohm LMR-400. Why 75 ohm? Because I got it for around 10 cents a foot, and have most of a spool left. I figured it wouldn't matter so much with HF. But it seems it might be a bad length, causing issues.

I ordered 3 LMR-240 jumpers. Will add some length to the 75 ohm coax tomorrow, to see if it helps. If not, and the jumpers don't solve the issue, guess i'm gonna have to pick up some coax. Probably pick up some LMR-400 for the 2m/440, and use the wireman 8X from that antenna for the HF antenna.

Posted: 3/16/2012 5:23:51 PM EDT

[#7]

Quoted:
I think I have a bad connector and/or jumper somewhere. Not sure which one or where, so I ordered some LMR-240 patch cables. Right now i'm using some older RG-8x of unknown mfg/quality. I know it's at least 15 years old. Even when connecting to a 10 meter A-99 that's tuned, it still gives me goofy SWR readings.

Where did you order the 240 jumpers? Btw I like wireman cq118, it's very well made and easy to work with.

Posted Via AR15.Com Mobile

Posted: 3/16/2012 5:24:53 PM EDT

[#8]

The tuner is a Dentron Super Super Tuner, and whether Super2 or just Super, they are very tough, effective tuners.

What usually causes arcs is misadjustment for the conditions encountered.

Or the conditions change for the adjustment. He's got a problem somewhere in his coax or connections.

Mcooper... I've bought excellent jumpers and coax from www.hamcity.com (Jun's Electronics). Top quality coax, top quality PL-259s, and I could solder them better myself. Prices are very good, too.

Posted: 3/16/2012 5:37:07 PM EDT

[#9]

I'll throw a couple more ideas out there NAM, they may or may not apply to your situation.

When I got my amp going last Fall everything was fine. Then the rains came and I saw my amp's current meters spike occasionally while tuning, but only when using the 40/80 inverted-V and only when it was raining. I figured something was arcing in the balun on it or something. Never heard arcing in the shack but not sure since the amp makes noise when getting a bad load like that. Then the same thing started happening when using my vertical on 20M too. All only when running my amp when things were wet outside, and it never happened with 200W barefoot. Never found evidence of arcing in my gear and it stopped when the rains stopped. I wonder what will happen here if it ever rains again. Have you been having any rain?

All has been fine so far here this dry Winter...

I'll also add that I think the tuner will be fine if you carefully file the cap plates smooth and make sure everything else is in order. What AFM says is true too.

Posted: 3/17/2012 5:09:53 AM EDT

[#10]

Quoted:
Where did you order the 240 jumpers? Btw I like wireman cq118, it's very well made and easy to work with.

Posted Via AR15.Com Mobile

Ham City, per AFM's recommendation. I ordered Friday afternoon, and they shipped that same afternoon

Posted: 3/17/2012 6:10:22 AM EDT

[#11]

My apologies, that Dentron should have been GTG. It's seeing too high of an impedance from the antenna system. The higher the impedance, the higher the voltage, especially on the output capacitor. If you're an ARRL member there is an article on tuning the "T" configuration tuners. It's "Getting the Most Out of Your T Network Tuner" GL HTH 73, Rob

Posted: 3/17/2012 7:09:35 AM EDT

[#12]

Quoted:
My apologies, that Dentron should have been GTG. It's seeing too high of an impedance from the antenna system. The higher the impedance, the higher the voltage, especially on the output capacitor. If you're an ARRL member there is an article on tuning the "T" configuration tuners. It's "Getting the Most Out of Your T Network Tuner" GL HTH 73, Rob

The arc was on the tX matching side, not the antenna matching side if that makes any difference.

As to Wireman CQ118....That's what I'm using on the 2m/70cm j-pole and the A-99. Definitly good stuff, and rated at 1300w IIRC.

Posted: 3/17/2012 10:11:34 AM EDT

[#13]

Hi NAM,
Yes, an intermittent could have caused an initial arc. Once there is a sharp point on one of the plates the break down voltage becomes less. Hope it can be fixed. 73,
Rob

Posted: 3/22/2012 3:25:41 PM EDT

[#14]

Well...i think I have found something.

Received the LMR-240 jumpers (well... LMR-240 x2 and Belden 8X). Did some testing.

Things seem to tune fine on pretty much every freq EXCEPT 20M. Tuning around 14.3, it gets jumpy. Tune as low as 5 watts, and it'll be fine one minute, bad the next. 1.7:1 one minute, 4:1 next. No lose connections, nothing.

The only things I can figure at this point are

A: the 75 Ohm coax is at a bad length for 20M
B: Something on the G5RV no likey 20M.

FWIW, I tried tunning on my 10M A-99, which is fed with

Tandy RG-58. No such problems. Mind you, it is very touchy, and the amp no likey, but I can tune it at lower power with no problems.

Posted: 3/22/2012 3:33:00 PM EDT

[#15]

14.0675. 42 watts. CW carrier, not touching anything on my end, other than the key (no tuning, etc)

http://tinypic.com/r/14bj6ol/5

Posted: 3/22/2012 4:38:40 PM EDT

[#16]

And you have the burnt spot on the cap cleaned up?

Posted: 3/22/2012 4:42:30 PM EDT

[#17]

What happens if you leave the SWR meter in place, but bypass the tuner, hooking the amp directly to the antenna?

What does the SWR do with low power input?

Posted: 3/22/2012 5:10:42 PM EDT

[#18]

From the video, it looks like something with the antenna. The swaying reading looks like it might be a bad connection "swaying" in the wind.

Posted: 3/22/2012 5:13:48 PM EDT

[#19]

Quoted:
And you have the burnt spot on the cap cleaned up?

Cleaned up, but not polished. I.e. filed by hand, but still noticable a wee bit. I did pick up a dremel bit that will fit between the plates, just haven't gotten to it yet.

As for bypassing the tuner.....SWRs are high across the board. even at 5 watts, the reflect meter pegs.

Right now I'm using a coax switch. I tested from the switch, to the tuner/wattmeter. No short.

Tested common port on switch, set to empty port. Nothing
Tested common, switched to A-99. Shorted (this is normal, as it's a loaded vertical).
Tested common to G5RV. I get a split second shorted tone, then nothing.

http://tinypic.com/r/2itoies/5

When testing the coax from the antenna only, I get the same problem. So it's something in the feedline outward. I'll try pulling the PL-259 in the shack, and connecting a different one a little back. That should tell me if it's the connector in the shack, possibly shorted. If that's not it, I can test the external connection to the ugly balun. If that's good, I can check the other end.

Being a G5RV, it's fed with ladder line. at the base of the ladder line is a PVC tube with the SO-239. No balun is inside. From there, coax (RG-11) is coiled around a 5" piece of PVC, as an ugly balun. As it exits, it connects to the LMR-400-75. All external connections are waterproofed.

Maybe the good deal I got on the 75 ohm coax was a curse in disguise.

Posted: 3/23/2012 5:09:47 AM EDT

[#20]

Pulled the plug in the shack. Bare coax has the exact climbing reading on the VOM. Gotta be something in the coax, or outside the shack. It's raining, and I'm working from home. Hopefully, if it stops by my lunch break, I can pop out the ladder and check external connections.

Posted: 3/23/2012 5:36:48 AM EDT

[#21]

Also popped the case on the tuner. No new arcs, no new damage. Same as I left it before.

Posted: 3/23/2012 8:11:49 AM EDT

[#22]

My hand smells like burning.

I found the problem: Moisture. Partially.

So, here's the story:

The PVC piece that converts the ladder line to an SO-239 was mounted vertically, with the ladder line up. Apparently, the ladder line was not sealed or glued shut (i did not notice this). Water and moisture slowly built up in the PVC section. Eventually got into the SO-239. Over time, got waterlogged. Add AL-811H, and watery shorted mix cooks the dielectric, which now covers my hands and smells like....burning.

it's hard to tell in the shitty pic, but the dielectric is gone. Stuck my knife in there, and there's nothing left. Feedline now reads no short at all, no little beep or blip, nothing, nada.

Looks like i need to pick up an SO-239, some PVC, and some caulk to re-build this mofo.

Red = where water leaked in by windowed ladder line
Green = SO-239 that is fornicated in above pics.

high res:

Posted: 3/23/2012 11:04:00 AM EDT

[#23]

Glad you found the problem, add a weep hole in the bottom of the PVC tube too for added drainage. 73, Rob

Posted: 3/23/2012 11:35:18 AM EDT

[#24]

Quoted:
Glad you found the problem, add a weep hole in the bottom of the PVC tube too for added drainage. 73, Rob

As soon as I get an SO-239, I'm going to build a new end piece. Gonna probably mount it horizontally, as well as better waterproofing.
I also rewound the ugly balun with 75 ohm LMR-400. Just don't trust that RG-11. Works fine for ground straps though.

Posted: 3/23/2012 3:03:59 PM EDT

[#25]

I would mount it vertically, seal the top and add weep holes on the bottom. If you need some good sealer use automotive RTV Ultra Black. It is high temperature anaerobic sealer and works very well. I used that on my pelican case for my SGC-239. I tested it in the bath tub held underwater for about 12-15 hours, not one leak. I use the stuff nearly everyday and it works well.

Posted: 3/23/2012 6:41:50 PM EDT

[#26]

I'll give it a 1.

Overcooked.
No beverage.
No gun.
No tactical utensils.

Posted: 3/24/2012 2:14:33 PM EDT

[#27]

Personally, I would toss that balun, and buy another. If it's toasted like that on the plug, imagine what it's like inside.

All baluns I've used have a 1/8" or so "weep hole" on the bottom, with the admonition to keep it weep hole down.

Posted: 3/24/2012 2:57:57 PM EDT

[#28]

Quoted:
Personally, I would toss that balun, and buy another. If it's toasted like that on the plug, imagine what it's like inside.

All baluns I've used have a 1/8" or so "weep hole" on the bottom, with the admonition to keep it weep hole down.

While it technically converts balanced to unbalanced line, there are no chokes, coils, or anything inside, other than some wire nuts, and the SO-239 wired to the balanced line. I rebuilt the whole thing, and am testing it out now. Also cut down a tree branch, and moved one side of the G5RV higher.

Posted: 3/25/2012 9:28:40 AM EDT

[#29]

Nothing like going QRO to fly some bacon, eh?

Glad you found it before you shocked something expensive.

As a suggestion, an item to put on your "should have list" for your shack - an Antenna Analyzer.

You're definitely technically adept enough and interested in things radio enough to make good use of one.

If your could score a decent TDR that would be another big plus.

The VK5JST substitutes "sweat equity" for $$$ http://www.users.on.net/~endsodds/analsr.htm and is very highly rated.

Tomi Engdahl designed a TDR add-on for an Oscilloscope (if you already have one or can borrow one) that is pretty cost effective if you can't score a RiserBond yellow box http://www.epanorama.net/circuits/tdr.html for $10 for the board whole kit at http://www.farcircuits.net/test1.htm

73

Steve
K9ZW

Posted: 3/25/2012 3:19:41 PM EDT

[#30]

Quoted:

Quoted:
Personally, I would toss that balun, and buy another. If it's toasted like that on the plug, imagine what it's like inside.

All baluns I've used have a 1/8" or so "weep hole" on the bottom, with the admonition to keep it weep hole down.

While it technically converts balanced to unbalanced line, there are no chokes, coils, or anything inside, other than some wire nuts, and the SO-239 wired to the balanced line. I rebuilt the whole thing, and am testing it out now. Also cut down a tree branch, and moved one side of the G5RV higher.

Then it's not a balun, just a connection device. Well, get it fixed, waterproofed.

Posted: 3/25/2012 3:50:05 PM EDT

[#31]

Quoted:
Then it's not a balun, just a connection device. Well, get it fixed, waterproofed.

Done and done. New one is assembled. For all intents and purposes, identical to the original. Added additional waterproofing, and oriented coax up/ladder line down. This seemed the most logical, as the ladder line holes have some wiggle room, and can double as weap holes. The coax end...well... there's no good way to get that end to drain. The endcap concave, water is going to want to always seep to the middle....which caused the problem in the first place.

Antenna works much better. I still have a few odd spots that it doesn't want to seem to tune all that great. But naturally, since the change, I've had to map new tuning spots. I've also added an Alphe Delta coax switch, replacing my older Pace. First problem I had with that.... I overtightened the screw. Missed the part about "finger tight". Doh...my bad. Switch still works fine, but the arg plug likely need a replacement (mfg in 2000, so probably time regardless.

Will hopefully be able to test things out some more this week. Also have some more work planned for the other end of the antenna....tree cutting, and raising the height a bit, also a bit further from the metal roof. Should help a bit.

Posted: 3/25/2012 6:10:53 PM EDT

[#32]

Quoted:

Quoted:
Then it's not a balun, just a connection device. Well, get it fixed, waterproofed.

Done and done. New one is assembled. For all intents and purposes, identical to the original. Added additional waterproofing, and oriented coax up/ladder line down. This seemed the most logical, as the ladder line holes have some wiggle room, and can double as weap holes. The coax end...well... there's no good way to get that end to drain. The endcap concave, water is going to want to always seep to the middle....which caused the problem in the first place.

Antenna works much better. I still have a few odd spots that it doesn't want to seem to tune all that great. But naturally, since the change, I've had to map new tuning spots. I've also added an Alphe Delta coax switch, replacing my older Pace. First problem I had with that.... I overtightened the screw. Missed the part about "finger tight". Doh...my bad. Switch still works fine, but the arg plug likely need a replacement (mfg in 2000, so probably time regardless.

Will hopefully be able to test things out some more this week. Also have some more work planned for the other end of the antenna....tree cutting, and raising the height a bit, also a bit further from the metal roof. Should help a bit.

Your SWR is now stable? Watching for arcing in the tuner? All looks good?

Posted: 3/26/2012 4:48:03 AM EDT

[#33]

Quoted:

Your SWR is now stable? Watching for arcing in the tuner? All looks good?

Needs more playing around, but it seems to be. Yes. I did notice when tuning on 160M, I get an occasional buzz in the amp. If I let off, and re-key, it goes away. I don't see any arcing or anything, tubes look fine. Not quite sure what that is, but may be related to that 8X jumper still in the chain. Should hear back from Ham City today...they replied right away on Friday to let me know that they'd be more than willing to make good on it. apparently 8X is in the bin right next to the LMR-240.

Posted: 3/26/2012 4:04:29 PM EDT

[#34]

Got home from work, and was tuning in to see if intercon was still receivable (14.300).

Anything more than 7 watts drive, and SWR goes through the roof. It's odd... I can key with 5 watts, increase to 20 or even 40 watts drive, and it's fine. But as soon as I let off the key, and key again, SWR goes through the roof. Removed the 8X cable, and used a stiff LMR-400 I found on the pile. Same thing. So I know it's not that jumper.

Hmm....Gonna have to pop the tuner cover again I think, and possibly the amp. See what's going on here.

ARC PLUG. Pulled the access hole, and the problem went away. I think (as I probably mentioned earlier) the plug is kaput. Increasing power keep the SWR low. But starting with high power is causing it to just arc. Makes sense...when the plug blows, it shorts center to ground (iirc).

Posted: 3/27/2012 6:10:45 PM EDT

[#35]

Quoted:

Quoted:
Then it's not a balun, just a connection device. Well, get it fixed, waterproofed.

Done and done. New one is assembled. For all intents and purposes, identical to the original. Added additional waterproofing, and oriented coax up/ladder line down. This seemed the most logical, as the ladder line holes have some wiggle room, and can double as weap holes. The coax end...well... there's no good way to get that end to drain. The endcap concave, water is going to want to always seep to the middle....which caused the problem in the first place.

Antenna works much better. I still have a few odd spots that it doesn't want to seem to tune all that great. But naturally, since the change, I've had to map new tuning spots. I've also added an Alphe Delta coax switch, replacing my older Pace. First problem I had with that.... I overtightened the screw. Missed the part about "finger tight". Doh...my bad. Switch still works fine, but the arg plug likely need a replacement (mfg in 2000, so probably time regardless.

Will hopefully be able to test things out some more this week. Also have some more work planned for the other end of the antenna....tree cutting, and raising the height a bit, also a bit further from the metal roof. Should help a bit.

Would filling the bottom of the PVC tube (over the cap) with a couple inches of dialectic (potting) compound seal the bottom, then drill weeps out the sides - say four 1/8 inch holes at 90 degress from each other? Thinking something like silicon or pourable sealer if you have access.

I didn't fully understand your last post - you found another fried part/connector?

73

Steve
K9ZW

Posted: 3/27/2012 6:15:03 PM EDT

[#36]

Quoted:
Got home from work, and was tuning in to see if intercon was still receivable (14.300).

Anything more than 7 watts drive, and SWR goes through the roof. It's odd... I can key with 5 watts, increase to 20 or even 40 watts drive, and it's fine. But as soon as I let off the key, and key again, SWR goes through the roof. Removed the 8X cable, and used a stiff LMR-400 I found on the pile. Same thing. So I know it's not that jumper.

Hmm....Gonna have to pop the tuner cover again I think, and possibly the amp. See what's going on here.

ARC PLUG. Pulled the access hole, and the problem went away. I think (as I probably mentioned earlier) the plug is kaput. Increasing power keep the SWR low. But starting with high power is causing it to just arc. Makes sense...when the plug blows, it shorts center to ground (iirc).

I had to remove some of my arc plugs after getting my amp, of course they were only rated at 200W!

Once they fire, like maybe due to your wet antenna parts, they're more likely to easily fire at lower levels after that due to the sharp points created inside from the first arc.

Posted: 3/27/2012 6:53:30 PM EDT

[#37]

Quoted:

Quoted:

Your SWR is now stable? Watching for arcing in the tuner? All looks good?

Needs more playing around, but it seems to be. Yes. I did notice when tuning on 160M, I get an occasional buzz in the amp. If I let off, and re-key, it goes away. I don't see any arcing or anything, tubes look fine. Not quite sure what that is, but may be related to that 8X jumper still in the chain. Should hear back from Ham City today...they replied right away on Friday to let me know that they'd be more than willing to make good on it. apparently 8X is in the bin right next to the LMR-240.

Sometimes you get "RF in the shack", especially on 80 and 160 m with an amp.

Add more beads to the coax.

Posted: 3/27/2012 11:59:32 PM EDT

[#38]

Quoted:

Quoted:
Got home from work, and was tuning in to see if intercon was still receivable (14.300).

Anything more than 7 watts drive, and SWR goes through the roof. It's odd... I can key with 5 watts, increase to 20 or even 40 watts drive, and it's fine. But as soon as I let off the key, and key again, SWR goes through the roof. Removed the 8X cable, and used a stiff LMR-400 I found on the pile. Same thing. So I know it's not that jumper.

Hmm....Gonna have to pop the tuner cover again I think, and possibly the amp. See what's going on here.

ARC PLUG. Pulled the access hole, and the problem went away. I think (as I probably mentioned earlier) the plug is kaput. Increasing power keep the SWR low. But starting with high power is causing it to just arc. Makes sense...when the plug blows, it shorts center to ground (iirc).

I had to remove some of my arc plugs after getting my amp, of course they were only rated at 200W!

Once they fire, like maybe due to your wet antenna parts, they're more likely to easily fire at lower levels after that due to the sharp points created inside from the first arc.

Ah - got it - lightening suppressor in the antenna switch? Or?

When you add an amp, things get interesting.

Anything underrated or dicey is likely to go.

You have to be more careful about staying above minimum bend radius specs on coax - I have a sample from where we violated that and when fired up QRO the center & shield arced. A one-time kink that does damage but works ok at 100 watts often fries at 1500 watts.

A fair bit of generic or "just like" mystery coax is not QRO capable.

Minor water in the jacket that doesn't act up when running PSK will fry when running QRO - have a sample of that too.

I went to all N-Connectors building my shack knowing I would go QRO, as loose UHF outer connector shells are a QRO problem.

You should never had significant RF in the shack. If you do, check it out and deal with it before it affects your gear, your health and creates RFI problems.

Dollar for dollar most stations benefit from upgrading antennas, feed lines and station basics more than they do from adding an amp.

I've worked QRP levels of power on very good antennas and it simply rocked. The "ears" were awesome and I could be heard.

73

Steve
K9ZW

Posted: 3/28/2012 4:42:59 AM EDT

[#39]

The Arc Plug was not liking QRO. Odd, as supposedly it's rated to legal limit. I do see that AD has separate non-switch static/lightning arrestors that are rated at 200W, so i have to wonder if maybe this one has a 200W plug instead of the QRO plug.

Coax from the switch to the windowed ladder line is all LMR-400-75 ohm. I had used RG-11 in the ugly balun, but removed the RG-11 and replaced with LMR-400 75 ohm. I have a whole spool, and I trust Times Microwave much more than generically labelled "RG-11" from an unknown MFG. I tihnk i'm going to keep that stuff to ground use only from now on.

Had a long day yesterday, and took a half day because of it (wife's dog is no longer). She decided to take a nap for a bit, and I headed to the shack. With no arc plug in the switch, I can tune on all bands, QRO, no problems. Even made it to the arfcom net last night with booming results. Which brings up another general thought....If you're in...say, Fond Du Lac Wisconsin.... and you're talking on....say..3.850.... to another guy in Fond Du Lac....Don't brag about using legal limit power. You bleed at least 5khz over... if not more. It makes it hard for others to talk on an already crowded band.

Posted: 3/28/2012 4:45:37 AM EDT

[#40]

Quoted:
Dollar for dollar most stations benefit from upgrading antennas, feed lines and station basics more than they do from adding an amp.

Fully agree. I just happened to catch a great deal (1/2 the price for a year old amp, delivered for free, with as long to test it out as I wanted) at a time when I had the cash on hand. Eventually, I would like to replace the 75 Ohm with some 50 ohm....maybe even try something with open feeder. Have already replaced all jumpers with LMR-240, except for one that i'm still....err....sorting out with Hamcity.com.

[ARCHIVED THREAD] - Somehow......I managed to arc a 3kw rated amp with ~700 watts. ETA: problem found!

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