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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 25th May 2006, 10:13 am   #1
DON THOMSON
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Default The art of coarse engineering

Good morning all,

Looking at a pic of some carbon rod resistors(used in the 30s and 40s) I was reminded when in the RAF in Egypt and we needed and didn't have a particular value of resistor we would select one of lower value and with an Avometer and grindstone would proceed to increase its value to the required amount. We had, of course to remember that we were reducing its wattage rating.

Wanting to check the HT on a T1509 which should have been 1600v and with no meter that went above 1000v I connected 2 identical meters in series and doubled the reading. HT checked Ok.

The Egyptian electricians method of detecting blown cartridge fuses on a main bus distribution board was to run finger and thumb down the strip of exposed terminals and when they got a belt they knew they had the blown fuse. To ensure good contact they used to lick their fingers first.

In a way I suppose that substituting capacitors for proper dropper resistors might be considered "coarse engineering"?

There must be stacks of other examples out there - dig into your memories. Any one reading these must remember the magic words DON'T TRY THIS AT HOME unless you really, truly know what you are doing and then don't.


Don
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Old 25th May 2006, 1:11 pm   #2
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Default Re: The art of coarse engineering

Quote:
Originally Posted by DON THOMSON
The Egyptian electricians method of detecting blown cartridge fuses on a main bus distribution board was to run finger and thumb down the strip of exposed terminals and when they got a belt they knew they had the blown fuse. To ensure good contact they used to lick their fingers first.
Many operating practices used in third world countries would give the HSE a fit of the vapours. I was staying in Luxor (Egypt) a few years ago when the air conditioning in the hotel room developed a fault. I reported this to reception who said they would send an engineer up. A short time later a bloke turned up, opened the (7th floor) window and climbed out He then proceeded to fiddle with the air conditioner with a screwdriver in his right hand, while holding on to the window with his left and standing on the windowsill. By this stage I couldn't watch any more so left him to get on with it

Best regards, Paul
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Old 26th May 2006, 8:57 am   #3
DON THOMSON
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Default Re: The art of coarse engineering

Had he only one eye and walked wih a crutch? I remember him!

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Old 26th May 2006, 10:17 am   #4
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Default Re: The art of coarse engineering

Not quite in the same league as the above, but my father used to check for dead batteries (single cells) by applying the top cap and case, which in days of old was uninsulated and adjacent to it, to his tounge. A sort of voltmetering by taste.

Checking that there is antifreeze in a car can also by done by taste. It is poisonous if taken in quantity but all you need is to taste the sweetness then wipe it off your tounge before it kills you.

Peter.
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Old 26th May 2006, 12:20 pm   #5
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Default Re: The art of coarse engineering

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Checking that there is antifreeze in a car can also by done by taste. It is poisonous if taken in quantity but all you need is to taste the sweetness then wipe it off your tounge before it kills you.

Peter.
I did this only last night to ascertain what was leaking from my wife's car!

Old habits die hard 'twould appear.

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Old 26th May 2006, 12:21 pm   #6
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Many, many years ago when I was an apprentice I was privilidged to visit a BBC World Service transmitting station. Whilst there one of the engineers demonstrated a quick test to see how well one of the HF Transmitters was doing. This was a kind of output and modulation check...

He contacted the feeder and drew a huge arc off of it. The length of the arc gave an indication of the power and the modulation could be heard audibly on the arc, thus giving an indication of modulation...

There began my love of very high power HF stuff and Napier Deltic diesel engines (as used in the Deltic Railway Locomotive) which were used for standby power generation
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Old 26th May 2006, 3:25 pm   #7
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Default Re: The art of coarse engineering

I once visited the radio station at Rugby many years ago (a works outing while doing my apprenticeship) and was told by one of the engineers there that if you went into the room where the PA tank was apparently you could sense the modulated RF by the hairs on the back of your neck moving! Seems to knock concerns of radiation from mobile phones into touch. I wonder if he's still alive?

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Old 26th May 2006, 4:20 pm   #8
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you could sense the modulated RF by the hairs on the back of your neck moving! Seems to knock concerns of radiation from mobile phones into touch. I wonder if he's still alive?

Biggles.
RF would not have killed him. I spent a good 10 or so years of my working life at HF transmitting stations in a veritable sea of RF that would light flourescent tubes. I remain in the best of health as do all those who worked with me, no one I know has suffered any ill effects that could be remotely attributed to the RF. I have four children who are exceedinly healthy so as far as HF goes there is no risk.

We always thought that RF was actually good for you. The only time the hairs on the back of my neck stood up were during thunder storms when it was not unusual for ball lightning to roll into the TX hall on the open-wire feeders
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Old 26th May 2006, 5:30 pm   #9
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O, I've been there Jim ! The other scary was when the resident bull ("maximum utilisation of resources" required us to have livestock grazing the fields beneath the antennae) decided to scratch himself on one of the feeder posts: with the feeder connected to our lead-throughs, the whole hut shook as if we were suffering an earthquake.
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Old 26th May 2006, 7:21 pm   #10
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Default Re: The art of coarse engineering

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Originally Posted by G4MEZ
I have four children who are exceedinly healthy so as far as HF goes there is no risk.
All girls by any chance? We noticed that the men who worked for long periods on our Radar stations almost always had daughters. Don't know if that was just chance, or high power RF - the number of people involved wasn't really high enough.

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Old 27th May 2006, 12:18 am   #11
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Default Re: The art of coarse engineering

Hi all.

Quote:
The Egyptian electricians method of detecting blown cartridge fuses on a main bus distribution board was to run finger and thumb down the strip of exposed terminals and when they got a belt they knew they had the blown fuse. To ensure good contact they used to lick their fingers first.
I wonder if the ground was probably be quite dry, giving a higher resistance back to the neutral connection at the sub station.

I only tend to bodge my own stuff, rather than other peoples repairs (your only as good as your last job......but you're welcome to check out some of my repairs on Pauls main site and decide for yourself!! ) but the stuff I did on my old Bedford HA van must have horrified the subsequent owners-and probably Kat!!
Fuel pipes joined by rubber hose, metric bolts shoved into BSF holes, silicone sealant for engine gaskets (and egg boxes for door handle gaskets), engine hoses joined with a box spanner and jubillee clips, and an SU carb from a Hilman Avenger in place of the original Solex. I even drilled holes in 1/2 p coins(they were cheaper than washers!!-and no longer legal tender at the time). I also remember fitting a peice of cable sheathing under a headlamp rim to correct the beam aim after a small front end collision, throttle linkages made from welding rod, and countless other no budget "modifications".
However VOU 587 T was never without an MOT, and my "coarse" engineering never let me down. If you think that's bad you wouldn't have wanted to see my Bedford CF 2.3 after 213,000 miles..........

I have seen some interesting examples of C.E in some wireless sets I have had in for repair!
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Old 27th May 2006, 7:13 am   #12
Jim - G4MEZ
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Default Re: The art of coarse engineering

Quote:
Originally Posted by jim_beacon
All girls by any chance? We noticed that the men who worked for long periods on our Radar stations almost always had daughters. Don't know if that was just chance, or high power RF - the number of people involved wasn't really high enough.

Jim.
Yes! Funny you should say that Jim as a lot of people I know who have worked around high RF at any time have more daughters. Again only a small sample but interesting. Apart from the health benefits of being in RF we always used to reckon it boosted fertility. The sheep that grazed the aerial fields always seemed very productive too!
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Old 27th May 2006, 8:01 am   #13
Mike Phelan
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Default Re: The art of coarse engineering

I suppose that drawing arcs off a PL or PY top cap with a screwdriver, as we all did/do is a bit like that. We always located an O/C heater chain with a neon screwdriver, as well!
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Old 28th May 2006, 12:10 am   #14
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Default Re: The art of coarse engineering

I can remember drawing arcs off the top caps of the PL and PY valves. The most livley though was off the metal top cap of the DY802 EHT rectifier on the Decca mono sets (MS1700,2001) if you were not careful the arc would jump to chassis or worse to the EHT overwind of the LOPTX. Could be quite an expensive conclusion to a normally straightforward line output stage test.
There was also a large majority of television engineers that ended up with all girls, again it was put down to the prolonged exposure to radiation from the back of tellies.
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Old 28th May 2006, 9:32 am   #15
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Default Re: The art of coarse engineering

One of the "Engineers" (I use the term loosely!) in our workshop used to draw an arc from the Pl top cap to light his fag, the bodges that went on were horrendous and included all sorts of ways of getting the last out of the tube, using glue to repair arcing LOPTS and Triplers, the old BRC open type triplers were taken apart and repaired! That said it kept sets going that would have otherwise been beyond economic repair , A term these days applied to most TV s etc on the first fault occuring! I think the days of C E are probably numbered ! ?
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Old 30th May 2006, 10:39 am   #16
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Default Re: The art of coarse engineering

In reply to the thing about daughters, I have heard this one too, but sorry, I have been exposed to RF pretty much all of my working life and I have three sons!
And yes, as a radio site engineer I have been chased by/have chased various forms of livestock over the years, much to the amusement of my colleagues. Hazard of the job.

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Old 31st May 2006, 7:45 am   #17
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Default Re: The art of coarse engineering

Working on high power RF amps used for EMC and Sat-Com, this business about daughters certainly carries some weight, it seems that a large percentage of children born the EMC type people are daughters, there was a study carried out in Germany which tended to confirm this...,
Yes and we still use valves in our big amplifiers!!!

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Old 31st May 2006, 8:05 am   #18
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Default Re: The art of coarse engineering

One of my erstwhile colleagues used to do that as well, and then found a better use for his dog-ends. We'll call him "A" to protect the innocent, as I don't know anyone called "A" with or without quotes.

"A", while on field service, had problems with dirty valve bases on Thorn 800/850 chassis, so he and others used to stuff a wad of paper betwixt the EF and a convenient IF can.

Sometimes these fell out, so A devised a MkII version, using an elastic band from the can to the pip on the valve.
After thinking about this, he realised that the heat from the valve would make the band break.

Then - a breakthrough! Mirabile dictu! "A" had cracked it! The MkIII version had a dog-end impaled on the pip, to protect the "laccy band."

Quote:
Originally Posted by slidertogrid
One of the "Engineers" (I use the term loosely!) in our workshop used to draw an arc from the Pl top cap to light his fag, the bodges that went on were horrendous and included all sorts of ways of getting the last out of the tube, using glue to repair arcing LOPTS and Triplers, the old BRC open type triplers were taken apart and repaired! That said it kept sets going that would have otherwise been beyond economic repair , A term these days applied to most TV s etc on the first fault occuring! I think the days of C E are probably numbered ! ?
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Old 31st May 2006, 6:15 pm   #19
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Quote:
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Then - a breakthrough! Mirabile dictu! "A" had cracked it! The MkIII version had a dog-end impaled on the pip, to protect the "laccy band."
This is scary Mike. I can clearly remember seeing the evidence of this in a few sets. I wonder if "A" published his "method" and thus it saw use far and wide..

I stopped testing by drawing arcs off the Line Output and Boost Diode top caps after once using a pencil.. It hurt.
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Old 31st May 2006, 8:18 pm   #20
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Default Re: The art of coarse engineering

A collegue tv engineer used to put his finger on the anode of the crt,this charged him up by his thick rubber boots,he would walk about the workshop with his charge of 10KV,everybody dissapeared,if you did not he would discharge himself to your ear,usually when you was not looking!
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