Linear Amplifier, Part 1, Almost Electrocuted, Drake L4B Linear Amplifier, Jim W6LG YouTube Elmer

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Jim W6LG

Күн бұрын

Пікірлер: 34

@davidwilcox9110 2 ай бұрын

Just GOOD teaching from one who has been there, done that! Thank you Jim.

@robincross4625 3 ай бұрын

Jim is exactly correct!!!!!!!! I am a retired broadcast engineer. Inside every transmitter is an insulated rod that has a metal hook on the end. That hook [2 inch radius] has a wire about 1/4 inch diameter going from the hook to ground. First thing after the transmitter door opens is to ground all the known high voltage places. Second is to hang the hook where it will short high voltage to ground. Third is to put one hand behind you. Only work with one hand inside a transmitter. With one hand there is not a path that goes through your heart. OH, I forgot to say remove ALL jewelry. Follow the same procedure every time a transmitter is open.

@ham-radio 2 ай бұрын

Thanks. I now remember seeing that in a broadcast transmitter. It might have been the VOA near Fresno. That was decades ago. 73, Jim W6LG

@mewrongwayKOCXF 2 ай бұрын

I remember as a kid in the 70's a friends Dad got across a charged cap the voltage went in his hand and out his nose, taking the tip of his nose off. Great video Jim! 👍👍👍

@KO4VNX 2 ай бұрын

These days there are not nearly as many people making their own amplifiers... this is a great reminder of the creativity and work ethic, and just plain refusal to sit still and not learn more and create more... this is what our country was built on! Good stuff! I'm also surprised once again at how much of our radio theory has some cross-over application to the guitar world. Now I want to build my own HAM radio amplifier, and I also want to build my own guitar amplifier!

@KO4VNX 2 ай бұрын

And.... so glad you survived that incident!!!

@robertmeyer4744 3 ай бұрын

Great so far Jim ! HV safety is a MUST !!! . I trust nothing. I have HV probe and check everything . I go right to each cap and test. Then I grab my HV stick that is grounded and use the tip to discharge every cap . Then after that i use clip leads to short out caps. Leave them shorted as I work. HV caps can build up a charge on their own. In fact when extra on hand leave them shorted at all time . Only remove short on cap after installed just before power up. I always test caps first. that a outher step I do. If I find HV in a AMP I STOP . Discharge and look for why HV was their. Like a open bleeder resistor or safety interlock that failed. I fix that first ! Then I go forward to tubes and stull. Plate choke can open. A glitch resistor can open. Trust nothing. Test and verify before touching . I even test my ground leads first before I put them on. 73

@ham-radio 2 ай бұрын

Lots of good advice. Thanks for writing out what you do. It is so easy to make a mistake. There is no such thing as overkill with HV. 73, Jim

@highlander4413 2 ай бұрын

I heard you on the air having a rag chew on 14.225....been watching your videos for a few years..I always enjoy the subject matter and learn something Everytime... thanks for all you contribute! Kk7kll 73...

@ka0clg431 2 ай бұрын

Holy crap Jim! Be careful we need you around! 👍

@johnwest7993 3 ай бұрын

That's why I stick with 28 Volt FET amps these days. BTW, when I was about 14 or 15 I was working part-time at a TV repair shop. I'd installed a new transformer for a CRT, about a 26 inch screen console, and had my head in back of the wooden console cabinet adjusting the anode voltage, and the next thing I knew I was sitting on the floor against the wall with a lump on the back of my head, and there was no longer a top on the console TV. My boss came running back to the workshop and yelled, "Are you OK?" A couple of seconds later I was able to mumble, "No." I go out of my way to avoid HV these days. I turn things off, discharge caps, discharge them again, short the caps with jumpers if I'll be replacing components, etc. I even wear a rubber glove and a long-sleeve shirt when I'm tweaking HV with a long plastic diddle-stick. I figure that first shot of 30 kV back when I was a kid taught me enough of a lesson that that's why I've survived into my 70's. I still remember it all to this day, except what I did wrong, and taking the top off the console TV.

@Kilroy_Was_Here_1897 3 ай бұрын

I got a 90 KV hit once, off a hipot tester. It was at extremely low amperage, that saved me, but even though I wasn't launched across the room I didn't feel right for a month. I will never buy a piece of tube equipment for this reason; I figure you only get one chance regarding high voltage accidents and I already used mine up.

@dennisyoung4631 2 ай бұрын

275 volts DC - tossed me downrange about 6 feet when I was 14 or so.

@michaelpolimer2128 3 ай бұрын

Hi Jim, you were a lucky kid.........I designed and worked on high voltage RADAR transmitters for 42+ years, many of them had signs that read "death on contact"........an exception I would take with your HV discharge procedure is to NOT use a screwdriver as the "crowbar".......we called it a "zott stick" or shorting wand.......instead I would recommend making up a stick using a 2 or 3' piece of fiberglass rod (good enough for 3 KV but not 54 KV as in the Patriot DTWT transmitter) with a big alligator clip ty wrapped to the business end connected with 3 or 4 feet of the braid out of some good coax (or real ground braid if you have it) connected to the clip with a solid "ring tongue" (not a fork) at the other end. Before you go near the HV you MUST solidly screw the ring tongue to the chassis and THEN touch the clip to the HV . (good crimps and solder) Once the cap bank has been discharged you then put in your solid shorting wire with the clip remaining on the HV. The problem with the screwdriver (IMO) is you might touch the HV but not the chassis and it is possible your fingers might touch the screwdriver shaft.......... plus you have no way of knowing what the dielectric strength of the screwdriver is and generally the metal runs right up into the handle..... I have an L4-B and an old RayTrack..hard to beat.........good old stuff.....like us!..........73 Mike K1FNX near Boston

@bendeleted9155 3 ай бұрын

So i take it those voltages CAN arc through the half-inch of plastic handle to you? I hadn't thought of it until you reminded me that the metal shaft is right there.

@ham-radio 2 ай бұрын

There is a couple of inches. 73, Jim

@michaelpolimer2128 2 ай бұрын

@@bendeleted9155 probably can't arc thru (at "X" volts per mil you can do the math) but the plastic handle can develop cracks over time, all my old Craftsman drivers have developed a white haze in the plastic.....who knows what that is.......... a known non conductive rod 2 or 3' long with the clip on the business end keeps your hands away from any lethal voltages. we used 4' long G-10 rods (or Micarta) with a 1/4 " brass "shepherds hook" at the business end, connected to ground with #6 motor brush wire. I have seen a capacitor bank vaporize the hook when a transmitters automatic electronic crowbar (or drop bar) discharge system failed and the tech/engineer discharged the bank before they went in...........joules are joules..........

@JBud1911 3 ай бұрын

Jim keep your hands off the goodies. We want to keep you around much longer. God Bless John KR6BJ

@ham-radio 2 ай бұрын

Blood tests yesterday for Leukemia showed a problem. I will have yet another transfusion today as an emergency because my HGB was just above 6. 73, Jim W6LG

@timothymaimone8611 3 ай бұрын

Jim, I learned in electronics vocational school, how to discharge CRTs (40kvac). Even when you disconnect the voltage source, there are other supplementary components that store lethal charges. Using a thick insulated screwdriver connected to a cable with an alligator clip you ground the potential circuit for your safety. Glad to hear your story! Experience can be deadly but you lived to tell about it. NO JOKE! 73 de KD6UYK (Tim).

@LeeMcc_KI5YPR 2 ай бұрын

I suggest caution with this method. Shorting out a capacitor will discharge it instantly with the possibility of it exploding. Also, there is something called capacitor soakage. Basically you can take the charge off the top, then soakage will charge it up again, putting the user at risk.

@kierinhortle1784 3 ай бұрын

thanks, Jim, thats a serious looking amp, i would love to see the schematic if possible? i was wondering how you determined that the tube was the problem? {i did see some scorch marks on the top tube} and what type of tube to replace them with? thank you Sir for all your knowledge

@amateurshooter6054 3 ай бұрын

Thanks Jim

@USA-GreedyMenOfNoIntegrity 2 ай бұрын

I was being electrocuted by a neon light transformer- 7000 VAC, at 12 yrs old. I couldn’t get away from it. Mom knocked me off of it. At least DC knocked you away.

@TonySummy 2 ай бұрын

Jim, does Eimac no longer produce tubes? I hear you talk about Penta Labs (hope I spelled that right), but never about Eimac's. -Tony, K7AKS

@thuff3207 2 ай бұрын

I started working on TVs and yes that is quote dangerous. I use a chicken stick its like your screwdriver but made of wood and use a clip to case to short out every cap twice. PS keep one hand in your pocket.