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Need a new multimeter that goes past 1KV

Discussion in 'Home Brew' started by ElectronTubesRule, Sep 28, 2011.

  1. Shockwave

    Shockwave Sr. Member

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    The horror stories you tell of deal with people who did not have the background to safely work on this equipment. When a commercial TX goes off the air, I don't want someone who is unable to dive in and find the problem to spend the afternoon trying to figure out the problem because they won't take the internal measurements or a live visual inspection to confirm it. Ever try and find one of those internal arcs that does not leave an obvious carbon trail? Without question, sometimes the best way is to defeat those interlocks, shut the lights off and watch for the arc. Not a job for the faint of heart or the experience to do it in a risk free manner. But then again, you won't find anyone like that employed in this position. I mean no disrespect here either. This is a job you cannot be afraid of. Fear must be converted into knowledgeable respect to be successful here.

     

  2. jazzsinger

    jazzsinger Bullshit Buster

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    technical term for that is "operation save ass", its a natural reaction when your shit deep in danger.:D

    i remember it kicking in one time when i was young and found myself in the celtic end at a rangers v celtic game, not good when wearing a rangers top,;)
     
  3. Kamikaze

    Kamikaze Active Member

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    How would you guess these 2 people as not having the proper background? That's kind of a stretch. Incorrect guess also. Pop over to AMFONE and ask about W2WME. The electrician was trained for high voltage work too.

    The correct way to look for arcs is as mentioned before. Use a hi-pot tester. Suspecting an arc and firing up the transmitter's non current limited power supply is a great way to blow up even more stuff. A hi-pot tester used properly will find the arc with much less risk to the repair person and the DUT.
     
  4. Shockwave

    Shockwave Sr. Member

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    Your Hi-Pot tester is good for some applications. However, high voltage DC does not behave anything like high voltage RF and many situations cannot be duplicated with this device as the source. Most won't even develop enough current to charge the filter caps with the bleeder resistors loading it down. With respect to peoples experience, it goes both ways with this one too. People with lots of experience often develop a lackadaisical outlook because they have done it a thousand times before. That is dangerous because this is when careless mistakes are made.
     
  5. Kamikaze

    Kamikaze Active Member

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    True we don't want to charge caps during hi-pot testing and we disconnect them along with the bleeders. Testing the caps themselves is a PIA. A stack of old meter multiplier resistors is nice to have for that.

    Breakdowns in the rf areas are pretty easy to find without running the transmitter. Burns, missing hunks of dielectric and carbon traces make up 99% of problems found.

    Hard to qualify just who does what based on experience. There's no exit interview for electrocution victims. Bottom line is most professional folks working around high voltage equipment are charged (pun intended) with doing it cold whenever possible. Hot work is a last resort these days. A guy on the WWRF who says he wants to make a few thousand volts by series connecting some 800 volt transformers is not someone to encourage in the matter of live high voltage experiments.

    I predict some horror stories on the horizon.
     
  6. Shockwave

    Shockwave Sr. Member

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    I think you'll find the situation is different with large broadcast transmitters. Trying to search every square centimeter inside one of these cabinets for a carbon trail is not always practical. Many faults that develop internal RF arcs will trip the protection overload circuits in the transmitter before they leave nice carbon trails behind. Sure it's nice to open the back door and find shattered ceramic from a doorknob cap or holes punched through Teflon. Many of these transmitters are over 40 years old now and will likely have arc marks from previous failures. Not to mention most are not shiny and clean inside to the point where these things stand out.

    From a broadcast service standpoint, I would want to employ the Tech who's not going to waste hours searching by eye when he knows how to power it up safely with the back door open to spot the blue flash. I absolutely agree there are risks involved but they are completely predictable and avoidable. I don't think I could consider hiring someone for this position that did not have either the confidence or skills to do this task in a safe manner. I also don't encourage those unfamiliar with these risks to do any live testing and is why I suggested applying 10% of the rated primary voltage for his test.
     
  7. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    It can be pretty hard to find a blue flash in a tube using a Hi-Pot tester. The other thing I would like to mention is that in many cases there are no tell tale signs of carbon tracking or anything because sometimes it is a large mica capacitor that shorts. If and I mean IF you are really lucky it will have a crack in the ceramic case. Another mistake Kamikaze made is assuming there is no current limiting in a b'cast TX. There is but admittedly it is fairly high and is in the form of an overload detector and relay. Even the 40-50 year old stuff had relay operated overload circuits. They would prevent a disaster from happening.

    Basically there are three kinds of HV service people.

    1). The one that does not know his ass from a hole in the ground and should never be allowed near anything more than a 9 volt battery.

    2). The kind that has worked on so much HV stuff he has become overconfident and whimsical in nature and enjoys showing the uninformed the long arcs he can draw of the RF output of a transmitter using a big screwdriver. Note that this person is nearly as dangerous as number 1 above. He has become complacent and that itself can be dangerous.

    3). The guy that has serviced HV equipment for many years and while he is not afraid of HV he does respect what it is and what it can do. He may from time to time defeat interlocks but doe so only when his safety is assured and when it becomes necessary in order to restore operation in a timely manner. While interlocks are defeated he is always extra cautious and maintain a high level of alertness and always thinks twice before acting once.

    As for never working on live HV gear I suggest the next time the power goes out in the neighborhood Kamikaze should inform his local utility company he will not accept power from them until they assure him that NOBODY anywhere will be working on live wires. I hope it doesn't happen this winter. He could get pretty cold waiting for HIS power to be returned. :D

    Nobody was encouraging anyone here to work on HV when they don't know what they are doing. Advice was given on what to do IF they were to go ahead and the OP has stated he already had some electronic knowledge and experience. I would never encourage anyone to work on live HV gear if they didn't know their ass from a hole in the ground however IF someone is asking for advice I will offer it. If someone is going to go ahead and work on it anyway I would feel compelled to inform them of the right way to do it. Unfortunately Kamikaze's right way and the universally accepted right way seem to be different. I am done with this thread. I DO KNOW WHAT THE HELL I AM DOING INSIDE A TX WITH HV AND I SURE DON'T NEED SOMEONE WHINING ABOUT WHAT I AM DOING WRONG.
     
  8. ElectronTubesRule

    ElectronTubesRule Active Member

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    I am not an electronics major or a broadcast engineer. I apprenticed for two years in a shop that did mostly commercial repair for broadcast and for aviation radar gear and also did warranty work for amateurs and other odds and ends that walked through the door that was in H.S. I am not a radio expert or RF expert at all! I worked for Consumer Power and Edison Electric as an Electrician and later int he Telcom Industry as an electrician but that was mostly fiber optic work but their was still a lot of electrical work to be done. Between working on huge transmission lines powering cities and General Motor's plants and the like I have been around insanely high voltage much higher then anything in a broadcast setting or in the amplifier I am building. I am more then able to follow a schematic and anyone that can follow one can build just about anything that someone else ahs designed. Just like I cannot design a transmission or an engine but I can rebuild one, replace parts on one. I do not need to be an engineer to work on a piece of machinery. Like wise I do not need to be an electronics major to build a RF amplifier. If I was wanting to design one it sure would help but really a house wife that can read the schematic and that can solder can put an amp together I am pretty sure Heathkit and Eico proved that point long ago!

    The other day I had to call an appliance repair man out to look at my refrigerator. See how time was short for all the food I did not want to parish in the coolers I had I called a pro so it could get fixed ASAP. He came out and the first thing he did was plug it in and take some reading with his clamp current Multimeter while he probed for voltages as well. It took him all of 10 minutes to figure out and repair it. A relay went bad. Short of him getting out a crystal ball or a Ouija Board how is it he would have figured that out with out testing for current draw and voltages?

    As to me.....I think it is no offense intended "Mind numbingly Stupid" to think a person that is building an amp for the first time and maybe never again to go through all the hoops you mention just to find out the output voltage of his transformer. It is not like I am going to hold the wires with my hands. Common sense tells you not to have the power hot when you are hooking up the test probes. I will hook them up with the transformer not plugged in. I am not going to be holding the multimeter either but will have it sitting on the bench top angled so I can read it with out holding. I will also have a piece of plexiglass between it and me and I will be about 2 foot away from the meter and and 4 feet from the transformer. I will have nitril gloves on as well. I will unplug it before I attempt to un-hook anything. The only way to be any safer would be to build a Faraday cage around it....LOL

    Their is more risk getting into your car and driving to work each day. I guarantee more people die every day in America from driving accidents then have died from High Voltage Hobby related accidents!Life is full of risk......I have held people hands while they died on the side of the road. I have had to wash their blood off my steering wheel. I have had to call their families. I have yet to have to contact anyone's family due to high voltage accident. Heck kids end up with closed head trauma from bike accidents or playing football in High School.....Their is no way to live life with out some risk. If you do then you are not living at all because most of the fun things in life carry some element of risk!

    Not everyone starts off in this hobby with an ociliscope, spectrum analyzer, highpot test gear, variac, PHd in Electronic Circuit Design and deep pockets to just buy what they want or what they need!

    Heck some people would tell everyone to pay an "Expert" to change your tubes because it is too dangerous for the average person to do! That is total garbage talk! In fact if everyone listened to people like you then Edison would never have invented anything since he was not educated in electronics or engineering and not in advanced mathematics either. I dare say that Tesla made it up as he went along and after he discovered something then he set out to figure out the nuts and bolts of the process he had just discovered. He would not have done anything either he would have just kept on digging ditch's. Did you know he did labor work???In fact thinking like yours is the reason why almost no innovation happens at the corporate level itis usually some guy in his basement that set's the world on fire then after he has done the heavy lifting then large corporations take the idea refine it and make it practical to mass produce!

    In fact large corporations and bean counter's and safety personal and most doctors are so into not taking any risk that it is almost impossible for any innovation to take place because of the aversion to risk!

    I am not going to be standing in a bucket of salt water, with 3000 volts going through a chassis, reaching around inside with metallic probes like Helen Keller trying to find her way around in a new unknown environment!

    Also just so you know.....If mechanics tried to work the way you suggest it would take 3 months to figure out what was wrong with a car if they even could! Sometimes their is no way around having a machine running or electricity going through the circuit in fact even on low voltage devices like VCR's, two way radio's, stereo amplifiers the company's give you schematics with voltages for major test sites inside the unit. When doing an alignment on a radio you have to have power running through the unit no amount of advanced diagnostic logic will allow you to align a radio with no power and no signals being sent through it.


    I thank you for your concern about everyone's welfare and safety but I think you are a fear monger and need to calm down a bit! No one is recommending that people reach into their amplifier with it hot and try to take voltages with it hot. Common sense tells you to un plug the unit, discharge the caps, hook up the probes then power it up. No one on this site is telling people to avoid driving their car at all cost because it is dangerous and might kill you! No one is telling anyone to not eat because food is killing us! More people die from heart disease, diabetes and cancer's that are linked to dietary intake but we all still eat!

    Balance between risk and out come is what is needed. My ex father inlaw is paralyzed from the chest down because he fell off his tractor and got ran over. Yet we are not telling people to stop farming are we? In his case he did something mind numbingly stupid! He stood up on the seat of a moving tractor to see how much fertilizer was left in the spreader. Common sense would tell most people not to stand on a metal seat that is springing on a moving tractor in a field full of ruts and furrows! He had done it most of his life and it only took one time for him to fall off and get ran over. So one has to know the risk, have some common sense, take precautions and not do do high risk things that have no real reward or pay off. It would have taken just a second to stop the tractor.

    :bdh: Listen up everyone do not go into to your bathroom, stop bathing at all cost's because the most dangerous part of your home is the bath room! More people get harmed or killed in their bathroom then any place else in the house!!Bathing and using the rest room is just too risky for the average Joe to do.....Go see an expert in bathing and let them bath you in a secure facility.

    You want to know what has killed most of my friends from birth to today? Heart conditions , cancer, car accidents, combat, and training accidents!
     
  9. Kamikaze

    Kamikaze Active Member

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    My kilowatt rig works.
     
  10. Once Bitten

    Once Bitten Member

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    Try this tech equipment
     
  11. ElectronTubesRule

    ElectronTubesRule Active Member

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    I am sorry but I just get all riled up when people start fear mongering and telling people the sky is falling or something to dangerous for them to try for themselves....... People jump off building, bridges, elevations etc.... and have to hand toss the droug chute the second they jump off so the chute has time to open before you hit the ground. But building your own HF RF amplifier and testing the voltage is too dangerous for anyone to do.......

    So I just get tired of fear mongering......
     
  12. ElectronTubesRule

    ElectronTubesRule Active Member

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    For the record I no longer jump out of functioning planes and no longer BASE jump either.I no longer climb with out a rope I out grew such things. LOL I still shower and bath though which makes me a real adrenaline junky!!!LOL


    Oh and for the record I meant everything in a way the same tone that one would use if having a debate with the boys at the bar over a pint of beer. Never with an angry tone just to be clear.
     
  13. straight razor

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    630PLK by TRIPLETT - Buy or Repair at PLCCenter - PLCCenter.com their goes the link and its cost $450.00
     
  14. 137

    137 Member

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    What does it smell like? You had nothing to offer the member as far as what he was looking for, yet you babble to folks who obviously have been in the field servicing units you will never even get close enought to "smell..."

    For once in my life I'll appologize for my remarks to whoever might find it offensive I guess, I suppose I was more in to this thread because I was looking for the very same type of meter, reading this jackholes comments struck a chord with me and it was very out of tune...
     
  15. W5LZ

    W5LZ Crotchety Old Bastard

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    Meters that read very high voltages are not common, mainly because of the expense of making them and the lack of demand. They are certainly not impossible to make your self. The 'catch' is that you have to understand exactly how a volt meter works, and that can get 'complicated' very quickly (not how you use them, but how it works). Very basically, it's a matter of how they are 'fed', and how much.
    The meters you find in a typical amplifier that read voltages are never directly 'fed', but always through a shunting circuit. Unless you do understand how they work, and realize that the deadly nature of what they are measuring, the best advice is don't even -think- about making your own.
    - 'Doc
     

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