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Author Topic: Multimeter Nightmare  (Read 9386 times)

sheerline

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Re: Multimeter Nightmare
« Reply #25 on: September 05, 2008, 10:47:55 PM »

PMK, I saw a picture like yours in an ad in yellow pages... it was the electricians logo!
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OMK

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Re: Multimeter Nightmare
« Reply #26 on: September 05, 2008, 11:43:18 PM »

Hi, Mr. Sheerline.

Well, that logo ain't I. All I done was googled "electric shock" images and found it right there on the first page.
Reason being is because I don't think anybody told Footski that he won't really get to know and love his DMM until he's had at least a couple hefty belts from two-forty a.c while he's dabbling with the thing.

Bas - if you're earwigging - I don't wish to add more confusion to the issue, but like they said already.... REAL men are using AVOs.
 ::)
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sheerline

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Re: Multimeter Nightmare
« Reply #27 on: September 06, 2008, 12:17:35 AM »

No No PMK, don't start him messing with the mains... not yet anyway! You've already got me laughing as I have mental images surging through my brain of past belts I have received whilst working as a tv engineer in the 70s and my reaction to them, two spring to mind:
First, 25kV from the final anode cap of a Philips 25inch colour tv ... the swine didn't wait till I touched it... it just leapt out and got me, threw me up against a wall and as I slid down to the floor, the lady of the house appeared with a cup of tea and said "oh, have you finished already".
Second, whilst making an adjustment to the HT on a very badly designed set which requied one to reach down behind the chassis where the valves (yes valves) faced inward towards the back of the tube. I received a super mains belt which caused my arm to fly out in an upward direction, dragging half the valves with it and showering them around the room.
No matter how self controlled and guarded about foul language in a clients home one is, the slang word for excrement will be heard echoing around the four walls in an instant.
Strangely, I found over the years that I became more tolerant of short sharp mains belts as time went on... you kinda got used to it in a way. Those old sets were badly laid out and difficult to work on without receiving ones weekly dose of mains.
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Bunkerbarge

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Re: Multimeter Nightmare
« Reply #28 on: September 06, 2008, 12:31:43 AM »

So don't all shout at once but who knows (without looking it up!!) where the name Avometer comes from?
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"Dirty British coaster with a salt-caked smoke stack, Butting through the Channel in the mad March days"

Reade Models

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Re: Multimeter Nightmare
« Reply #29 on: September 06, 2008, 12:32:40 AM »

I became more tolerant of short sharp mains belts as time went on

I used to work with an electrician who would work on 240V lighting circuits live.  If he split the neutrals at a lighting fitting he would get a belt if he touched both wires simultaneously, but he could tolerate it without any apparent ill effects.

The poor blighter died of a heart attack eventually... :(

Malc

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OMK

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Re: Multimeter Nightmare
« Reply #30 on: September 06, 2008, 01:14:25 AM »

Mercy sakes! What a neat tale YOU tell, Mr. S. Nice one!

TV engineer, eh? See?... I knew all along there was summat suspect about you. I mean, I knew you were an engineer of sorts, but I didn't know you were into servicing tellies.
Now this is really weird, because just 10 mins ago I was outside having a quick puff when the memory of our old TV engineer suddenly popped into my bonce.
And now there's you suddenly telling me that you're also an engineer.
Well in that case, take yourself another 'Respect!'.

I'm curious about that 25Kv leaping at you though. I wish I could sit and have a chin-wag with you. I wanna ask you LOADS of questions.
Are you anywhere near me?
Fancy a pint somewhere?
The most Vs I've ever seen in one day is 415 @ 3-phase.
Blimey, little I did I realise that you HT boys had to actually stick your HAND in there!

I'm in the chair. What you drinking?
(Bring your mate Sweeper along and all).
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OMK

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Re: Multimeter Nightmare
« Reply #31 on: September 06, 2008, 01:30:05 AM »

"If he split the neutrals at a lighting fitting he would get a belt if he touched both wires simultaneously, but he could tolerate it without any apparent ill effects."

There is a lot of truth in what you're saying. Maybe the human body gets acclimatised to it or something. Or maybe some folk have a natural hiigher  body/skin resistance than others.
When I were a nipper I removed the insulation from a couple bits of wire with my teeth. The other end of the wire was connected to a 13A plugtop... plugged in and switched on. Stripping the neautral was fine, but as soon as I shoved the live in my mouth..... Boooom! SInce then, loads more shocks. I think you just kinda get used to it after a while. I mean, it still stings, but sometime it's just so much easier to work on a circuit when it's live.

I think it's good that at least your mate died of a heart attack, rather than electrocution.
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barryfoote

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Re: Multimeter Nightmare
« Reply #32 on: September 06, 2008, 08:03:38 AM »

<Footski> "Wife, wife! Come quick! Look... I finally got the hang of this multi-met....................."




Brilliant....

Only went out for an evening and missed all this fun...... O0 O0

Having read it all I have packaged up the meter and put it away for a while........My brother is coming out here for a week on Monday so will be busy anyway.....Then with a clear head I am going to start reading the replies through and trying all the Advise given.......I have to learn somehow.

Now....What on earth is an AVO????

Barry
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Reade Models

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Re: Multimeter Nightmare
« Reply #33 on: September 06, 2008, 08:56:44 AM »

but sometime it's just so much easier to work on a circuit when it's live.

Then I wish you a long and happy life - and a shedload of extremely good luck!

(Please guys, DON'T try this at home).

Malc
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Welsh_Druid

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Re: Multimeter Nightmare
« Reply #34 on: September 06, 2008, 09:27:52 AM »

I'm curious about that 25Kv leaping at you though.

Its happened to me as well mate.  Back in my "National Service" days I was a Radar Mechanic in the RAF. Instructing a new Mech. one day with the back of the Radar Cabinet open, I said, pointing at a 25Kv power pack,  "never touch that". Next thing I knew I was flat on my back two yards away with the rest of the crew laughing their heads off. You dont forget something like that  :o

Don B.
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wombat

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Re: Multimeter Nightmare
« Reply #35 on: September 06, 2008, 09:50:25 AM »

25KV, hardly worth getting out of bed for!

Now if you want high voltage power supplies try these

http://www.technosinfin.com/hv.html

Live-line working is essential at some points, however when said line has 1600KV on it, then a certain amount of caution is in order. As Welsh_Druid and Sheerline found out, high voltage jumps - at 1600kV it jumps a long way (measure it in meters not inches). Standard first aid kit for an HV lab is a dustpan and brush.

Wombat's 3 rules for high voltage areas

1/. You can't assume that just because it is switched off, it is safe - always go into the test area second
2/. Lightning follows the shortest path - always make sure the person who goes in first is taller than you
3/. Always carry spare underpants

AVO - Amps-Volts-Ohms, became a brand name for multimeters. They are still out there trading as AVO-Megger (another trade name - this time for insulation testers) The classic meters were the AVO 7 and AVO 8
http://www.richardsradios.co.uk/avo7.html

Wom








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FullLeatherJacket

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Re: Multimeter Nightmare
« Reply #36 on: September 06, 2008, 10:08:09 AM »

A lovely toy, but the latest list price of the AVO8 is an eye-watering 935!! Who cares if that includes VAT...........Mrs J would simply NOT countenance my purchasing such a luxury.
Mind, if I keep banging on about an AVOmeter then she might  cave in later to something else which I really do  want and which costs a lot less..............one needs low cunning with a wife as smart as mine!
FLJ
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Tug-Kenny

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Re: Multimeter Nightmare
« Reply #37 on: September 06, 2008, 10:15:53 AM »


AVO - Amps-Volts-Ohms, became a brand name for multimeters. They are still out there trading as AVO-Megger (another trade name - this time for insulation testers) The classic meters were the AVO 7 and AVO 8
http://www.richardsradios.co.uk/avo7.html


  I have both the AVO 7 & AVO 8, which I tried to sell on Ebay. Unfortunately there were no bids at all. I can see now, with a value of 2 & 10, according to that website, Wombat.  The postage alone would have exceeded their costs.

Funny how the value is in the eye of the beholder. ;)

ken

 

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malcolmfrary

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Re: Multimeter Nightmare
« Reply #38 on: September 06, 2008, 11:43:00 AM »

AVO's were a rare sight in telephone engineering circles.  Just too big and cumbersome.  In clockwork, the weapon of choice was a test lamp pluged into a handy battery jack.  Getting a bit more technical with yer actural elertonicery, a meter, multi-range 12a, technicians for the use of, was favourite.  As sensitive as the AVO, about a tenth the weight and it came in a nice solid pigskin case, essential armour when reading something with it balanced on the top of a rack.  Almost all our work was on live gear, as it was either solidly wired in, could only be faulted when in a live working condition, and you couldn't just switch an exchange off.  Complaints would arise.
Lethally high voltages were rare outside of the power units, even then they would'nt chase you round the room, but potentially lethal currents were readily available.  DC busbars just dont let go until either the battery goes flat or something vaporises.
Being a lineman in a rural area with wartime issue metal poles, reaching through a bed of wires and finding somebody ringing with your ear'ole had its moments.
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sheerline

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Re: Multimeter Nightmare
« Reply #39 on: September 06, 2008, 11:54:02 AM »

Hi PMK, I'm up here in Norfolk, miles away from you unfortunately. I reckon if we ever had a get together we would probably end up laughing our heads off all night....great!
One of the nastier aspects of e.h.t (extra high voltage) as found in televisions is that it is used to feed the tube (screen) and the lead which carries it is the thick cable with a silicone rubber flat insulator which fits onto the glass at the back. The tube itself is actually like a giant capacitor and even if you disconnect the lead, the tube will hold the charge for a very long time so if you ever had call to disconnect the lead you had to ensure you discharged the tube thoroughly before handling it otherwise.... BLAM!
In my particular case the set was running but the rubber silicone seal obviously had a tiny pihole somewhere and the last thing I saw was a 3inch blue spark which shot out of it and got me. It wasn't the first or the last time this happened but on the other occasions it was only 10kV from the old black and white sets. A hazard which went with the job I'm afraid so we were always aware and very careful but it's the old story, 'familiarity breeds contempt' and sad to say, in some professions where high voltage and high currents are experienced it could prove fatal. I was younger, had a strong heart and like all young men was fearless and contemptable.... oh, and I always wore thick rubber soled shoes in case I got between mains live and earth!

It's probably my fault but  you know we have deviated from the digi meter thread here and its probably scaring the life out of Barry if he's reading this lot but perhaps he will stay away from the mains and stick to 12Volts for the time being.
Stay safe chaps........ Chris

 
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barryfoote

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Re: Multimeter Nightmare
« Reply #40 on: September 06, 2008, 11:57:15 AM »

12 volts.........After reading all this that is a tad too high :o :o :o :o

I have put the thing away for a while till I pluck up the courage to try all your ideas...........maybe next year!!!!

Or........next week O0 O0
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sheerline

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Re: Multimeter Nightmare
« Reply #41 on: September 06, 2008, 12:01:52 PM »

Perhaps this forum section should be renamed: ' Electrics and all things black out!'
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OMK

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Re: Multimeter Nightmare
« Reply #42 on: September 07, 2008, 03:05:01 AM »

"It's probably my fault but  you know we have deviated from the digi meter thread here..."

At the risk of sounding like a brown nose, the way you pen your words is dead easy on the eye anyway. It all makes for damn interesting reading, so I don't think Bas will mind the slight deviation. Besides, his bro' is arriving on Monday - he's gonna be too busy with the sangria to even *think* about DMMs for a while.
Norfolk, eh? Nice part of the world. It's not exactly local to my neck of the woods, but who knows?.... maybe Ma Nature might intervene. Twould be good to share a puff, a pint and swap a few lies together. For instance, if ever we did get to rendezvous, the first thing I would ask you is why 6MHz? Why did they stick a 6MHz I.F. in there? It's fascinating. I mean, why that particular number? You know already, radio hams, etc, use their standard 10MHz / 455KHz, etc, itermediate frequencies, right? But why did they decide upon 6MHz for TV?
Naff question?
Yeah, sorry dude. But it's one of those Qs that nobody has ever explained - no reference books have been able to explain, neither.
So once you get past 6MHz, do you then drop down to the more usual 455KHz?... or am I confusing the audio I.F. with that of the visual I.F? (if you see what I'm struggling to ask).
I'll get a couple crates of apple juice sent your way if you don't mind taking time out to teach me something here.

All Rx'ed on what you said about wearing rubber shoes and all. I think we all get the point now. It's just, as Malcolmfrary said, working on a live circuit is sometimes the only option - exceptionally so in your case. My trade is the same as Malc Reade's late mate, so I can understand why he would have been working with live cables sometimes. Besides, the apprentice would normally take an hour just to go isolate the ciircuit, by which time it was quicker to work with it live anyway. It can still give you a tickle, but nowhere near as ropey as the sort of Vs you're playing around with.
Come to think of it, our old TV engineer, he gave me his copy of the Newnes transistor data book when I was around ten, maybe eleven.  Funny how this memory should suddenly come home, but his words were along the lines of, "Keep one hand in yer pocket."... even though he never followed his own advice. I mean, he didn't have to, did he? He was the TV man, right? So he obvioulsy KNEW what he was doing. As far as I was concerned he was a God, so he could do whatever he wanted. Not only that - he was the dude that inspired me to buy one of those screwdrivers with a neon in the handle. My old momma went nuts when she the saw me jabbing the thing in the back of our TV. "Get outta there or you'll get yourself all kilt and frazzled!", blah. "Nah, I'll be okay. Watch THIS!....".
That warm glowey neon glow attracted me like a moth to a naked chick's bedside lamp.

When you stop to think about it, that little gun inside the tube, bombarding the screen with all those tiny electrons, scanning the entire screen at the rate of................. HOW many times per second??! Wow!... Now that IS clever.
Same deal with oscilloscopes if you think about it. Compare how they are now to back when the radar boys were first dabbling with those squigly traces on their CRTs.
Which is why I'm wondering why Don B hasn't mentioned sooner that he was a radar operator!
Jeezus Kriced! Where have you blokes been all these years??!

I need to lie down and smoke some medicine now.
I'll be moving to my new house enn-neee day now. Been busy scrubbing, painting, blah, and right now I'm cream-crackered. Not only that, since FLJ said: "she might cave in later to something else which I really do want....", I can't keep meself from wondering what the dude is up to now.
Let's us continue this conversation as soon as I'm in and back online.

Until then, keep your high tensions off her suspensions......................................
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Welsh_Druid

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Re: Multimeter Nightmare
« Reply #43 on: September 07, 2008, 08:35:56 AM »

"Which is why I'm wondering why Don B hasn't mentioned sooner that he was a radar operator!

Hey PMK are you trying to insult me ? {-) A radar OPERATOR ? naw - I wa a radar mechanic complete with lightning flashes on my sleeve. All the operators had to do was watch those green wriggly lines on the screen. WE had to fix things when they went wrong. >>:-(

Mind you they were good blokes. On the night shift, as long as I cooked the supper for all of us, I could go to sleep secure in the knowledge that they would wake me up if anything went wrong, and even start the standby generator before I could get there if the mains failed, and that meant I could have the next day off instead of sleeping and my girl friend could pick me up in the family Rolls-Royce for a day out. Oh - happy days  {-)

Why have I never mentioned it before ? - simply because I have forgotten almost everything I learned about radar.

Sorry Folks this is really way off topic !!!

Don B.
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Rex Hunt

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Re: Multimeter Nightmare
« Reply #44 on: September 07, 2008, 09:48:07 PM »

"Which is why I'm wondering why Don B hasn't mentioned sooner that he was a radar operator!

Hey PMK are you trying to insult me ? {-) A radar OPERATOR ? naw - I wa a radar mechanic complete with lightning flashes on my sleeve. All the operators had to do was watch those green wriggly lines on the screen. WE had to fix things when they went wrong. >>:-(

Mind you they were good blokes. On the night shift, as long as I cooked the supper for all of us, I could go to sleep secure in the knowledge that they would wake me up if anything went wrong, and even start the standby generator before I could get there if the mains failed, and that meant I could have the next day off instead of sleeping and my girl friend could pick me up in the family Rolls-Royce for a day out. Oh - happy days  {-)

Why have I never mentioned it before ? - simply because I have forgotten almost everything I learned about radar.

Sorry Folks this is really way off topic !!!

Don B.


Neatishead, Boulmer, Staxton, Buchan, Bishopscourt or Saxaford?

T84, HF200, T85,
I is ...notta 'Scopie!'   either!

Rex
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sheerline

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Re: Multimeter Nightmare
« Reply #45 on: September 07, 2008, 11:41:56 PM »

Hi Rex this is still of topic but I guess were just chatting amongst ourelves till Barry gets back!
 Neatishead is just up the road from me and is now a radar museum, we visited it last year and it was very fascinating.
I have to say you are not alone in forgetting much of what you learnt about radar, what I can remember of tv servicing wouldn't fill the back of a fag packet now and given the modern technology in the present day sets, my retained knowledge is absolutely worthless.
Some of my experience does still come in handy from time to time as I did manage to restore the old Austin radio to full working condition a year or so ago and it sits proudly in its own large box under the bonnet of the car, complete with vibrator ht supply humming away. It has one MW band and six short wave bands... we reckon it was probably a bit of surplus wartime kit which was pressed into use for post war domestic vehicles. Lovely old bit of kit and smells great when it has been running for a while and gets heated up.
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OMK

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Re: Multimeter Nightmare
« Reply #46 on: September 08, 2008, 12:05:58 AM »

Mind if I ask another question?...

I'm guessing, T's 84 and 85 are probably transmitters, and the 200 is a HF receiver?
Right so far?
And Neatishead, Boulmer, Staxton, etc, are all the places where you were posted.
Am I still on the right track?
Sounds dead interesting.
What were you doing?

Hi, Mr. Druid.
Did I say radio operator? Mate, what's a few thousands volts between sparks. To my mind, part of the fun of reparing 'em is actually using 'em as well. Imagine how it must have been when your Op boys were ogling all them blips... all them tell-tale clues/proof that radio frequency signals actually does bounce off metal.
And imagine how it must have been when you mech' blokes were actually repairing them.
You paint a pretty neat picture, Mr. D.

Why did you have to cook supper?
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barryfoote

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Re: Multimeter Nightmare
« Reply #47 on: September 08, 2008, 07:26:39 AM »

Hi Rex this is still of topic but I guess were just chatting amongst ourelves till Barry gets back!

I will be keeping an eye on things, but will not have much time, so you guys enjoy yourselves....It is very interesting to read....

Right....Off to the airport now....Hasta Lluego,

Barry
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Welsh_Druid

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Re: Multimeter Nightmare
« Reply #48 on: September 08, 2008, 11:38:03 AM »

[

Neatishead, Boulmer, Staxton, Buchan, Bishopscourt or Saxaford?

T84, HF200, T85,
I is ...notta 'Scopie!'   either!

Rex


Nope - RAF Barkway - on the highest hill in Hertfordshire.   

The monitoring station for the GEE (AMES Type 7000)  chain of TXs which transmitted from Daventry (main signal), Stenigot ( nr Louth), Gibbet Hill  (Somerset ?), Clee Hill, (Shropshire) - all slave stations to Daventry.


PMK - Supper. As the GEE system was a navigation aid it had to be working round the clock. Our job was to monitor the accuracy of the phasing of the signals otherwise the aircraft got lost !!

So we worked three eight hour shilfts. At night there were four operators plus one mechanic.on duty. There was rarely any work for the Mech. (all the routine maintenance was done by the day shifts)  except that if the mains power failed he had to start the standy-by diesel generator (big powerful beasts that took a lot of swinging). We were issued with food ( egg, bacon etc) to cook for our supper and we came to an arrangement that the Mech. would cook for all the shift and then he could go to sleep on a camp bed in his little office, and the Ops. would wake him if needed. Only two Ops were actually working at any time and being good chaps if the mains failed they would try to start the Generator themselves as well as waking the Mech.

Don B.
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