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Author Topic: Line fuse opens after 40 minutes  (Read 19073 times)
N4ATS
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Posts: 800




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« Reply #75 on: July 18, 2013, 04:18:02 PM »

Amen brother

I am sticking to my guns the panel wires moved as well...
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AA4HA
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Posts: 1378




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« Reply #76 on: July 18, 2013, 04:30:46 PM »

What I found interesting about this thread was "both fuses opening up at the same time".

Maybe we are looking at it all wrong. We know that a 240 volt circuit is really the different legs on two separate 120 volt sources. The pole transformer is just a center tapped 240 volt winding that gives 120 volts per leg.

What if the problem is not with the 240 volt circuit (thinking of two wires) per sec, but a problem with the GROUND to or in the amplifier or the panel where something is happening like a ground fault and the result is that both fuses on both legs blow out at the same time?

Sometimes the world is not ideal and the ground wire and neutral wire are not tied together at the panel. You can end up with something floating and then if there is an intermittent connection (or an open) you can cause a fault that appears on both legs.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KC4MOP
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Posts: 729




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« Reply #77 on: July 18, 2013, 05:43:43 PM »

What I found interesting about this thread was "both fuses opening up at the same time".

Maybe we are looking at it all wrong. We know that a 240 volt circuit is really the different legs on two separate 120 volt sources. The pole transformer is just a center tapped 240 volt winding that gives 120 volts per leg.

What if the problem is not with the 240 volt circuit (thinking of two wires) per sec, but a problem with the GROUND to or in the amplifier or the panel where something is happening like a ground fault and the result is that both fuses on both legs blow out at the same time?

Sometimes the world is not ideal and the ground wire and neutral wire are not tied together at the panel. You can end up with something floating and then if there is an intermittent connection (or an open) you can cause a fault that appears on both legs.

No ground needed to operate a 220vac device. It works on the opposite phase    Shocked coming out of the distribution transformer on the pole. The bare ground wire is for safety. You have two HOT leads in a 220vac circuit. When one lead is positive the other is negative.
We'll be reading in few days if the loose wire in the receptacle was the culprit.
Fred
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N4RSS
Member

Posts: 258




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« Reply #78 on: July 18, 2013, 06:05:40 PM »

What I found interesting about this thread was "both fuses opening up at the same time".

Maybe we are looking at it all wrong. We know that a 240 volt circuit is really the different legs on two separate 120 volt sources. The pole transformer is just a center tapped 240 volt winding that gives 120 volts per leg.

What if the problem is not with the 240 volt circuit (thinking of two wires) per sec, but a problem with the GROUND to or in the amplifier or the panel where something is happening like a ground fault and the result is that both fuses on both legs blow out at the same time?

Sometimes the world is not ideal and the ground wire and neutral wire are not tied together at the panel. You can end up with something floating and then if there is an intermittent connection (or an open) you can cause a fault that appears on both legs.

No ground needed to operate a 220vac device. It works on the opposite phase    Shocked coming out of the distribution transformer on the pole. The bare ground wire is for safety. You have two HOT leads in a 220vac circuit. When one lead is positive the other is negative.
We'll be reading in few days if the loose wire in the receptacle was the culprit.
Fred

yeah i'm guessing she knows this, but you should have a neutral
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N4ATS
Member

Posts: 800




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« Reply #79 on: July 19, 2013, 06:50:54 AM »

BTW , For NN2X , we share a lot in common , Reading your Bio, I was in Bahrain many times as well as Saudi doing ATE setups for the F-15 / 18, Would like to chat with you but you have no email listed , email me if you would at grassa@earthlink.net when and if you get time. Love the "remove before flight" tag on your wifes jacket , at least it appears that is what it is.

Cheers
« Last Edit: July 19, 2013, 06:53:40 AM by N4ATS » Logged
K8AXW
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Posts: 3675




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« Reply #80 on: July 19, 2013, 08:48:42 AM »

I've been wondering how the amp acted (voltages/currents) when loaded and keyed? 

The only significant load an amplifer pulls in the idle mode is the blower current and filament current.  The total is much less than the current drawn by the amp under load.

I agree with the one poster who indicated that any heat generated by a loose connection at the outlet would be dissipated by the 6 to 8 feet of wire going to the amplifier.  I don't believe there would be enough residual heat to melt two fuses simultaneously.

As for the line being pulled loose clear back to the panel.... unless the line is 10ft or less, that ain't gonna happen!  I've cut wires just a tad short for receptacles and have tried pulling in a little slack to compensate.  Uh-huh.... you can forget that!

 I also think the high-fives are premature.
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WX7G
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Posts: 5920




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« Reply #81 on: July 19, 2013, 09:18:04 AM »

This thread, like many eham problem solving threads, illustrates critical thinking skills from weak to strong.

Many here could benefit from a course or two in critical thinking, or in lieu of taking a course, self study can be used to improve critical thinking skills. There are many books on this subject and one that I recommend for Kindle users is How to Think Clearly: A Guide to Critical Thinking by Doug Erlandson ($3.99).
« Last Edit: July 19, 2013, 09:47:39 AM by WX7G » Logged
N4ATS
Member

Posts: 800




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« Reply #82 on: July 19, 2013, 09:41:43 AM »

I think people over think , thats the issue, Some folks should take a course in simple basics instead of jumping ahead to rocket science... Some things you flat out can't put on paper. After you see something over and over , it becomes clear. Been there done it for years and years...

"I also think the high-fives are premature."

High Fives are not needed , no one gets one until he comes back with some answers. To many variables.

My number two post was not even answered yet...

AS for:

"As for the line being pulled loose clear back to the panel.... unless the line is 10ft or less, that ain't gonna happen!  I've cut wires just a tad short for receptacles and have tried pulling in a little slack to compensate.  Uh-huh.... you can forget that!"

Wrong..If the wire was already loose and it "moved" (making contact) is what was stated , not pulled free , 'nother mis-worded answer....

Sorry
« Last Edit: July 19, 2013, 10:13:35 AM by N4ATS » Logged
W0BTU
Member

Posts: 1577


WWW

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« Reply #83 on: July 19, 2013, 01:52:35 PM »

My number two post was not even answered yet...

And neither was mine at:
http://www.eham.net/ehamforum/smf/index.php/topic,90996.msg686390.html#msg686390


 And again this is when it is idle (No key down)

Let me get this straight. You plug the amp in without anything connected to it, turn it on, and with no plate or grid current, both fuses blow 40 minutes later? That is very odd. How many times have you tried this?
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W1QJ
Member

Posts: 1443




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« Reply #84 on: July 20, 2013, 01:34:42 AM »

Yikes, doesn't look like he is coming back.  His last word was he checked the connection on the outlet, he made it tight as it did seem loose, said the problem went away, and so did he.  He is a happy camper now and is on his way.  Sure seems to me that it was the problem since I mentioned for him to check that, he did, he made the connection tight and problem gone.  I know many of you are looking for the explanation as to why it fixed the problem. Since we can only theorize as to why and some theories don't make sense to many of you.  As far as I am concerned I applied the truth table (which I call it) and it seemed to work.  Maybe truth table is not the right term.  I also use the term flow chart.  Maybe that is a better term?  Whatever you want to call it, that is the logic I used to arrive at the conclusion to ask the man to check those connections on the outlet.  I use the same logic when I attempt to fix any problem I am up against.  Often times I am surprised as to what the fix is on some problems and really can't explain it in the long run.  Don't have time to dwell because I have to move on to the next problem.  I make a mental note of all fixes I make and when the next amp or whatever comes in for repair I make checks on all the fixes for all the problems.  I lose a lot of money because most problems can be fixed by just knowing what the problems are with most amps.  Tell the owner what to fix if he can do it himself and I never see that amp for repair.  Read the thread below and the AL-80B.  The fellow gave partial information on the problem I asked him about the grid meter going negative, he never said that it did but went and looked when the problem popped up and saw that it did.  Problem...bad tube with G-F short.  seems to be intermittent.
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NN2X
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Posts: 159




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« Reply #85 on: November 21, 2013, 11:31:04 AM »

I would like to give an update....

I have never tried so hard to repair and amplifier, and I thought I had repaired this AMP..I sold this AMP, only to find that the problem came back to the Buyer, of course, I would not let the buyer take the hit, so I worked with him to repair the AMP..

I was very luck the person who bought this AMP did actually find the problem..But before I say what the problem was, let me spell out how many service providers where involved and how many times I send back to the factory only to have the amp not working...I sent to the factory at least three times, only to come back all OK...Now, I still had a problem, so I sent was told by other service providers that the HV transformer needed re wiring, so I went and sent to a supplier that rewinds the HV transformer, and he indicated yes indeed that is the problem..I had it rewound and once again same problem. I send the filament transformer as well, but he said this is good.

I had a Electrician check my Electrical outlet, all good...

So what was it? The darn Filament transformer, this was missed by manufacturer, the a separate company that specializes in rewinding transformers (He rewound the wrong one HV)..

There was someone who indicated this was the problem WW9W (Robert Evans), so once he told me I sent the filament transformer, to the folks repairs and these transformers, and of course the wrong transformer was rewound

The buyer, actually saw the problem, and had the transformer (Filament) rewound..I paid for 50% of the repair and the shipment

I counted the funds I paid for the repairs from Manufacturer, shipment, rewingding, well over 2,000 (USD) (This also includes Buyer repairs)....That really (Beeps)...I have been a Ham operator for 30 years, and check every one of my posts, you will never see a bad word to a manufacturer, or a supplier I am not built this way..It is not in my DNA...But I was really shafted.....

The point is, that if you have a QRO2500DX and if is inter mentent, check the Filament transformer..

I rather take the 2,000 and give this to someone without an AMP...73's Tom.,
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W0BTU
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Posts: 1577


WWW

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« Reply #86 on: November 21, 2013, 12:06:23 PM »

... so I sent was told by other service providers that the HV transformer needed re wiring, so I went and sent to a supplier that rewinds the HV transformer, and he indicated yes indeed that is the problem..I had it rewound and once again same problem. I send the filament transformer as well, but he said this is good. ...

Thank you for this interesting report.

If I were you, I would send a very detailed, tactful yet firm, letter to that supplier. They apparently told you that something definitely needed fixing, and his error cost you $_____ which they need to reimburse you for. It was their mistake.

Now, if they said something like they weren't 100% sure that was the problem, that might be different.

When that happens to me, I simply say that I am in business too, and I have never charged any of my customers for my mistakes. Put the old part (that was good) back on my car, I will not be paying for this.

My $0.02 worth.
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K8AXW
Member

Posts: 3675




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« Reply #87 on: November 22, 2013, 08:31:26 AM »

BTU:  Quite often I do as you suggested and many of those times I am reimbursed with a replacement unit or coupons....  Nothing is lost except a little time and with the Internet I don't even spring for a stamp! 

Now:  It's been determined that the filament transformer was bad.  It seems to me the transformer would have had shorted windings to create this problem.  Which in my experience should have at the very least created a very hot transformer and more often than not, smoke.

The filament voltage should have been lower.....but that's iffy.

What do you think?

Al - K8AXW
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