Scott,
Just be careful in tube circuits.
I prefer using an isolated screwdriver as the probe and several fingers curled around the isolated shaft to give the capacitance. The dielectric is usually only good to 500V or so, so be careful on Ham Transmitters running at 3KV anode voltage...
I once managed to touch the anode on a EL34 based guitar amp at a very uncool 700V DC by accident. It took a lot to repair the damage to the amp out of my pocket, lucky I got thrown free and did not get any current through vital organs.
I still occasional show the burn mark scars to young and eager DIY'ers who want to play with high voltages and tell them - that was death right here, avoided by an inch because the hand also touched the chassis and completed the loop rather than something that was important (that was probably when I lost one of my nine lives).
They usually then get fascinated with the very obvious scars I got on the same hand (left - I'm right-handed so I use left for dangerous missions) from taking someone's knife away by the blade (don't ask, but that was another of my nine lifes), which kinda of spoils the lesson...
Ciao T
Just be careful in tube circuits.
I prefer using an isolated screwdriver as the probe and several fingers curled around the isolated shaft to give the capacitance. The dielectric is usually only good to 500V or so, so be careful on Ham Transmitters running at 3KV anode voltage...
I once managed to touch the anode on a EL34 based guitar amp at a very uncool 700V DC by accident. It took a lot to repair the damage to the amp out of my pocket, lucky I got thrown free and did not get any current through vital organs.
I still occasional show the burn mark scars to young and eager DIY'ers who want to play with high voltages and tell them - that was death right here, avoided by an inch because the hand also touched the chassis and completed the loop rather than something that was important (that was probably when I lost one of my nine lives).
They usually then get fascinated with the very obvious scars I got on the same hand (left - I'm right-handed so I use left for dangerous missions) from taking someone's knife away by the blade (don't ask, but that was another of my nine lifes), which kinda of spoils the lesson...
Ciao T
Of course we would always joke that the tech/engineer had to be shipped with the product, or at least the engineering sample.
I loved power supplies in my early knowing-next-to-nothing days. One requirement was for a constant current supply for hollow-cathode discharge lamps for spectroscopic calibration. So I decided if some regulation was good, more was better. Being a bit hazy on loop stability analysis I was accustomed to determining compensation by the cut-and-try method.
But in addition to having far too many stages to make compensation straightforward, I also had the system running directly off the unisolated mains with a cap-diode voltage tripler
Three hefty 450V computer-grade electrolytics. And worse still, the control electronics floated at the high voltage, around 500V.So I'm probing the circuitboard with little capacitors. At least I had learned the one hand in the pocket rule, so most of the damage was when things were jerked off the bench and thrown to the floor.
It did eventually work, although required substantial series resistance with the tubes to make the load line a bit more tractable.
Isolated 'lectricians screwdriver mate, take me word.
Capacitor leads can be wrapped to the blade.
Did I ever tell the story of the one time I got shocked and was lucky not to be thrown free?
It was above a sludge channel in a steel work, not only was the sludge very acidic but it was quite poisonous, not recommended to take an adult swim there by a long stretch.
I got stuck with my hand on a relay when I grabbed the back of the wiring in an open, live wiring closet (all against health and safety regs of course, it should have been shut down to work on - at around 500K USD loss per hour downtime - fat chance) and my hand and arm like cramped for almost 5 minutes. Until the relay mercifully closed with a massive clunk and I had the presence of mind to grab the frame (not the wiring) with my other hand. My arm hurt bad for days.
That was the worst I think. I escaped being turned into the statue of the heroic worker ('tis woz commie thymes) by having liquid steel poured on me and me mates by a few seconds, otherwise that would have been the worst, but I'd not be around to brag 'bout it, which would sux.
Ciao T
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Troubleshooting of tube gear in the field can be dangerous as well.
I once grabbed chassis by both hands and pulled the amp that was standing on a stage to turn over and see under the chassis where the smoke is coming from. It was hot day during that rehersal so I was half-naked, and one cap in a voltage doubler (about 300V on it's case) touched my naked belly. Ouch!
Speaking of oscillations and capacitances, I routinely used to add 1-10K resistor to the tip of oscilloscope working on SS designs.
I once grabbed chassis by both hands and pulled the amp that was standing on a stage to turn over and see under the chassis where the smoke is coming from. It was hot day during that rehersal so I was half-naked, and one cap in a voltage doubler (about 300V on it's case) touched my naked belly. Ouch!
Speaking of oscillations and capacitances, I routinely used to add 1-10K resistor to the tip of oscilloscope working on SS designs.
Ooooohh, you guys are so high tech ...
I was almost electrocuted by my dishwashing machine. It had a ribbon cable from the stand to the door, where the controls were located, so every time the door was opened, those cables were twisted front and back. Eventually, one of them gave up the ghost, and it was probably the power conductor, because when I touched the door, I rememebr being very surprised at what was I doing across the kitchen.
Compunded mistakes - my wife didn't turn it off (controls are all plastic) and I didn't unplug it from the wall socket, as I should have done.
But unlike you, I didn't have to go to exotic places to touch weird relays, nor did I need a test bench full of tube gear, a simple dishwasher was enough for me, I'm a humble kinda guy.
My advice to you is never buy an Italian Candy dishwasher machine, and thank your lucky stars, as I did, for having the good sense to cover the terazzo cement floor of the kitchen with a plastic covering.
I was almost electrocuted by my dishwashing machine. It had a ribbon cable from the stand to the door, where the controls were located, so every time the door was opened, those cables were twisted front and back. Eventually, one of them gave up the ghost, and it was probably the power conductor, because when I touched the door, I rememebr being very surprised at what was I doing across the kitchen.
Compunded mistakes - my wife didn't turn it off (controls are all plastic) and I didn't unplug it from the wall socket, as I should have done.
But unlike you, I didn't have to go to exotic places to touch weird relays, nor did I need a test bench full of tube gear, a simple dishwasher was enough for me, I'm a humble kinda guy.
My advice to you is never buy an Italian Candy dishwasher machine, and thank your lucky stars, as I did, for having the good sense to cover the terazzo cement floor of the kitchen with a plastic covering.
John,
In many ways eastern europe was "behind" on tech. So despite being a few decades your junior (not as many as I wish though) I got more than fair exposure to that kind of stuff.
Also, in Eastern Europe we did not have the commercial pressure to replace everything with next new thing. Consumer production was very low. You had to get on a waiting list to buy a car. My parents put me down when I was 2 or so, being "next in line" for a car allowed me to make so much profit on the black market, I was able to buy an old Lada, rebuild it and still pay for most the first Band/DJ sound system, when I had just turned 18...
We just did not throw things away. In my first band in the early 80's we had (donated by state youth organisation) a real Fender-Rhodes Piano and a real Leslie Organ, needed a lot of work, but these two made a lot of our sound, especially the Fender-Rohdes had such a lovely tone on leading lines...
At the time my TV was a Russian Raduga Colour TV, hacked for receiving west german TV, the Raduga had tubes everywhere where things connected to the picture tube and you could really crank up the cathode currents and anode voltage on the picture tube (this gives a brighter and sharper picture for all those who only know newly fangled Sony Trinitrons and LCD screens), the unavoidable occasional flashovers would just cause a "white blink". The much more modern and high tech east german TV's (full of IC's and silicon) would react to the same kind of flashover on the picture tube with the need for a total rebuild and so had a crappy picture...
Well, friends of mine homebuild ESL Panels and drive them directly of tube anodes with around 1500V on the anodes. Now THAT is scary. REAL scary... 10KV supply to the panel and around 1000V RMS on each stator with around 160mA peak current available undistorted.
The stators are powder coated, but trust me, I do not step up close when the system is energised. We are talking Enterprise dilithium core grade stuff here - I prefer to not be sacrificed for the good of the many.
That sh..t is scary.
Ciao T
In many ways eastern europe was "behind" on tech. So despite being a few decades your junior (not as many as I wish though) I got more than fair exposure to that kind of stuff.
Also, in Eastern Europe we did not have the commercial pressure to replace everything with next new thing. Consumer production was very low. You had to get on a waiting list to buy a car. My parents put me down when I was 2 or so, being "next in line" for a car allowed me to make so much profit on the black market, I was able to buy an old Lada, rebuild it and still pay for most the first Band/DJ sound system, when I had just turned 18...
We just did not throw things away. In my first band in the early 80's we had (donated by state youth organisation) a real Fender-Rhodes Piano and a real Leslie Organ, needed a lot of work, but these two made a lot of our sound, especially the Fender-Rohdes had such a lovely tone on leading lines...
At the time my TV was a Russian Raduga Colour TV, hacked for receiving west german TV, the Raduga had tubes everywhere where things connected to the picture tube and you could really crank up the cathode currents and anode voltage on the picture tube (this gives a brighter and sharper picture for all those who only know newly fangled Sony Trinitrons and LCD screens), the unavoidable occasional flashovers would just cause a "white blink". The much more modern and high tech east german TV's (full of IC's and silicon) would react to the same kind of flashover on the picture tube with the need for a total rebuild and so had a crappy picture...
Well, friends of mine homebuild ESL Panels and drive them directly of tube anodes with around 1500V on the anodes. Now THAT is scary. REAL scary... 10KV supply to the panel and around 1000V RMS on each stator with around 160mA peak current available undistorted.
The stators are powder coated, but trust me, I do not step up close when the system is energised. We are talking Enterprise dilithium core grade stuff here - I prefer to not be sacrificed for the good of the many.
That sh..t is scary.
Ciao T
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Hi,
Now in London (that would have been around '97), one time I was bothered by shocks I got from the cable TV box. I was living in a Nurses home at the time -working for the NHS - some of those nurses where quite cute and saucy - we eventually found out the house earth was somehow at around 180V RMS...
Good thing we had no dishwashers, washing machines etc. (washing was done central, the kitchen was gas and did not have single electrical appliance!)...
Ciao T
Now in London (that would have been around '97), one time I was bothered by shocks I got from the cable TV box. I was living in a Nurses home at the time -working for the NHS - some of those nurses where quite cute and saucy - we eventually found out the house earth was somehow at around 180V RMS...
Good thing we had no dishwashers, washing machines etc. (washing was done central, the kitchen was gas and did not have single electrical appliance!)...
Ciao T
Hell, man, there you say something!
I have some scars of that type, too, and only survived for the same reason, closing the loop from pinkie to palm that rested on the chassis. The culprits were the B+ caps of an Orange 120 that don't have any bleeders so when the HT fuse is blown, they won't discharge. These caps don't have isolated top sides, only tubing along the side walls! I even wasn't near the inside of the amp, I just opened the back dust cover, and then bang!
Lesson learnt (Beware of the Orange) and now I live on happily with my numb pinkie.
BTW, 700V on EL34 plates, that is daring. Not many of todays EL34's will take that (my beloved RFT dimple top "Telefunkens" will).
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One must learn the "one in the pocket" method for working on HV. So as not to have a current path through your chest from one hand to the other, you put one hand in your pocket and hold on to something close, then use your other hand for the adjustment.
I always have the arm reaching in touching something. I used to repair computer monitors. 17K for monochrome, 27K for color. 17K will knock you across the room and maybe stop your breathing. 27K just stops you heart. Period. One thing you learn is that after you discharge the anode, you do it again, then strap it down.
You'll like this one. When I was first in tech school, I was in a tube lab. The instructor was holding one of those old RCA VTVM's in one hand. He reached across the shoulder of a student who was not probing the correct point. "No,no,no, that 's not the grid, that is" at which point the VTVW was flipped over the shoulder like a pitching machine.
I always have the arm reaching in touching something. I used to repair computer monitors. 17K for monochrome, 27K for color. 17K will knock you across the room and maybe stop your breathing. 27K just stops you heart. Period. One thing you learn is that after you discharge the anode, you do it again, then strap it down.
You'll like this one. When I was first in tech school, I was in a tube lab. The instructor was holding one of those old RCA VTVM's in one hand. He reached across the shoulder of a student who was not probing the correct point. "No,no,no, that 's not the grid, that is" at which point the VTVW was flipped over the shoulder like a pitching machine.
Hi,
Yeah, hell mon!
Funny thing, in the early 90's I worked in London, in Tin Pan Alley for "World of Music" which owned most of the shops there (Denmark Street was known as Tin Pan Alley) and as it so happened, I worked for the guy who originally had started Orange, later sold the company but retained sales rights for the UK.
As a result we where sponsoring some bands with Orange Gear, including one called Oasis. I remember the Gallagher Brothers as total C.... (expletive self-censored).
I kinda quit when they refused to bankroll my work on a full serious webshop (in 1996) to the tune of 50K for the first year (most for scanning photos and typing in the catalog).
The company eventually sold most shops and downsized majorly, having lost much business to Soho Soundhouse around the corner, who around the same time majorly embraced the web and have been doing well...
It was a "Kölleda" 100W Amp with a pair of EL34. It incidentally used those precise RFT EL34's you mention, RFT was the east german overall consumer/av electronics combine (but not industrial/military)...
The most extreme case of re-labelled commie RFT Tubes where some (very expensive) "Valvo" 6SL7 I was send when I was still reviewing. They sure where Berlin made east german, some time in the 50's... Still got them somewhere, they are not far off Ken Rad VT-229!
Ciao T
Yeah, hell mon!
Funny thing, in the early 90's I worked in London, in Tin Pan Alley for "World of Music" which owned most of the shops there (Denmark Street was known as Tin Pan Alley) and as it so happened, I worked for the guy who originally had started Orange, later sold the company but retained sales rights for the UK.
As a result we where sponsoring some bands with Orange Gear, including one called Oasis. I remember the Gallagher Brothers as total C.... (expletive self-censored).
I kinda quit when they refused to bankroll my work on a full serious webshop (in 1996) to the tune of 50K for the first year (most for scanning photos and typing in the catalog).
The company eventually sold most shops and downsized majorly, having lost much business to Soho Soundhouse around the corner, who around the same time majorly embraced the web and have been doing well...
It was a "Kölleda" 100W Amp with a pair of EL34. It incidentally used those precise RFT EL34's you mention, RFT was the east german overall consumer/av electronics combine (but not industrial/military)...
The most extreme case of re-labelled commie RFT Tubes where some (very expensive) "Valvo" 6SL7 I was send when I was still reviewing. They sure where Berlin made east german, some time in the 50's... Still got them somewhere, they are not far off Ken Rad VT-229!
Ciao T
I found out the hard way that the brown spiral running along the outside of the o'scope's crt was a resistor supplying 5kV.
Hi,
And wear rubber sole shoes, preferably THICK rubber soles.
Ideally (I prefer that nowadays) have some eager beaver junior deal with the probing and remind him in stern tones about heath and safety and where to keep his other hand.
At my age, drinking, wenching and other habits I have no idea how yeah old ticker will hold up if I pull some of stunts I did when I was a lot younger...
And I'd really hate to die young.
Ciao T
And wear rubber sole shoes, preferably THICK rubber soles.
Ideally (I prefer that nowadays) have some eager beaver junior deal with the probing and remind him in stern tones about heath and safety and where to keep his other hand.
At my age, drinking, wenching and other habits I have no idea how yeah old ticker will hold up if I pull some of stunts I did when I was a lot younger...
And I'd really hate to die young.
Ciao T
Annals of Failures of Safety Interlocks: One night at UCLA there was a knock on the door, and I opened it to find my friend Chris looking for all the world like Wile E. Coyote in a Roadrunner 'toon episode, after one of his Acme novelty items went south very badly in his attempt to assassinate the bird.
It seemed that Chris was working with his constant-current supply for the CO2 laser, pursuant to his infrared photomixing heterodyne radiometry project, part of his doctoral work. The supply failed. He had designed it, and had used various surplus parts including some very large SCRs, large luminous sign transformers, and some large HV film caps from Plastic Capacitor Corp., the ones in the long red tubes. He opened the cabinet and was about to probe, confident that redundant safety features had engaged and there were no residual charged capacitors. The supply, by the way, provided 100mA with a compliance of 20kV.
At the last second he thought Wait this is dangerous --- I'd better make certain that the big caps are discharged. He did a quick order-of-magnitude calculation of the energy that might be present on an undischarged cap, fashioned a stick with a taped-on 2W Allen-Bradley hotmolded resistor of a convenient value, with lugs on the leads at the proper spacing for some terminals inside. He slowly reached in with the stick...
BANG! Abruptly he had hearing loss and the radio playing in the background became inaudible. He had some cuts about his hands, arms, and face that began to bleed a bit. After a while he could see a janitor standing in the doorway who had heard the explosion, talking to him (but he was still temporarily deaf).
He realized that, if anything, the supply had even an overvoltage, and that of course his quick calculation was, in any case, wildly off. He also thought that perhaps it was a bad idea to work on these things alone.
It seemed that Chris was working with his constant-current supply for the CO2 laser, pursuant to his infrared photomixing heterodyne radiometry project, part of his doctoral work. The supply failed. He had designed it, and had used various surplus parts including some very large SCRs, large luminous sign transformers, and some large HV film caps from Plastic Capacitor Corp., the ones in the long red tubes. He opened the cabinet and was about to probe, confident that redundant safety features had engaged and there were no residual charged capacitors. The supply, by the way, provided 100mA with a compliance of 20kV.
At the last second he thought Wait this is dangerous --- I'd better make certain that the big caps are discharged. He did a quick order-of-magnitude calculation of the energy that might be present on an undischarged cap, fashioned a stick with a taped-on 2W Allen-Bradley hotmolded resistor of a convenient value, with lugs on the leads at the proper spacing for some terminals inside. He slowly reached in with the stick...
BANG! Abruptly he had hearing loss and the radio playing in the background became inaudible. He had some cuts about his hands, arms, and face that began to bleed a bit. After a while he could see a janitor standing in the doorway who had heard the explosion, talking to him (but he was still temporarily deaf).
He realized that, if anything, the supply had even an overvoltage, and that of course his quick calculation was, in any case, wildly off. He also thought that perhaps it was a bad idea to work on these things alone.
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