Trade ya War Stories, Fossil

A case of PEBKAC (Problem Exists Between Keyboard and Chair)? Tell us about your war stories!
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RFWarrior
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Re: Trade ya War Stories, Fossil

Post by RFWarrior » Thu Jan 15, 2009 8:23 pm

NECRAT wrote:Would a High School boom story suffice?
Any electrical, electronic BOOM is cool - once you've been there and done it once or twice, you can picture the poor soul in the story (in this case you :D). First one is the pants-wetting one, the second one is the "wonder if it will do it again" with the sort of excited feeling that you get on a roller coaster, where you're pretty sure it's gonna scare the crap outta you, but not 100% certain. By the third time it becomes routine, so it gets boring :lol:

The second time is the best, because of the aura of breathless anticipation you get when you know what's coming - even better if you can suck somebody else into walking by the device about to go boom just as you throw the switch :) :) :D :D :lol:

Cool story - I probably would have saved the burned piece until I got married and the wife made me chuck it :) That's what happened to the soldering iron I was using the day I learned it had a grounded tip and the TV probably should have been unplugged AND discharged, not just switched off :) I can still see the afterimage of that flash :shock:

Best,

Jeff

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RGORJANCE
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Re: Trade ya War Stories, Fossil

Post by RGORJANCE » Fri Jan 16, 2009 1:10 pm

Back about maybe 8 years ago, I get a call from an AM client. "We're off the air and the backup won't turn on." 45 minutes later I'm standing in front of the AM xmttr. I reset the breakers, hit filaments and wait the appropriate time delay relay time and hit the plates. KABOOM, FLASH, and wow, what bad dead body odor!!! Man does that stink!

I knew immediately we had been hit with biological warfare. Opened up the back and found the biggest, fattest, longest grass snake I had ever seen. He was big enough to eat! I kinda grew up in Oklahoma, and had crossed fangs with some really "big ones back in the day", so I understood snake stuff.

I extricated said "biological agent" from the high voltage stud he had "given his "all on", and proceeded to genetically alter the interlocks. Went around to the front, turned everything back on and hit the big switch. Goodie, nothin broke, we're back on. Found cockpit problem on the backup.

I contacted the owner, and he made it known that I "must put the snake in a bag and hang it on the door to his office".
OH KAY, you're the guy that signs the checks, you got it.

Fossil

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Chris from Milwaukee
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Re: Trade ya War Stories, Fossil

Post by Chris from Milwaukee » Fri Jan 16, 2009 1:44 pm

I don't know if this qualifies for the thread because it happened with a receiver instead of a transmitter but it's a good BOOM story.

One year for Christmas I bought my mother a big, shiny 27" console color TV because her old one had pickled out and she was watching TV on a 12" B & W.

I had the TV for about a week before in her basement and never bothered to check it before I wrapped it up. Heck, I didn't need to check it out... it was new. I should have plugged it in first. When she unwrapped it she lit up like a little kid on Christmas morning. However, when we connected her cable box the picture was fuzzy as well as the audio. Since I was in school for electronics and currently taking classes in IC technology AND it sure looked like a bad shield connection in the RF stage, I was HIGHLY confident that with a little of my tender loving care I could rectify the situation and Mom could enjoy her new TV. I grabbed my soldering stuff and some tools and promptly took the back off the TV, and sure enough, the shield connection to the board was bad. I soldered that puppy right up, plugged the cable in and there were cheers in the room as the TV came to life in all its vivid glory. The only thing left to do was put the back on it and I was the HERO!

I pulled the cable off the back and placed on top of the set to facilitate replacing the back. The TV was still powered up. Somehow, I knocked the cable off the set and it swung down inside the set where my head also was. There was this tremendous white flash and a deafening POP along with varying degrees of smoke coming from the back of the set. I had carbon poof all over my face and I instantly went from hero to goat... in front of the entire family. The TV didn't work anymore. You should have seen the look on Mom's face. :oops:

I had 12 service calls on that set in four months and it took an act of God to get a replacement TV from Thompson Electronics and their ONE (and always busy) phone line in Indiana. No, I made no mention of the operator error that occurred on my behalf. (Bad Chris, Bad Chris)

Moral of the story: " DON'T TOUCH THE CONTROLS"

P. S. Love the stories... keep em comin'!
Chris from Milwaukee
Feeding Broadcast Engineers Worldwide
(And transmitter salesmen too!)

captbob92
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Re: Trade ya War Stories, Fossil

Post by captbob92 » Sun Feb 26, 2012 9:24 am

Years ago I became the defacto go to guy for AEL transmitters in Ohio as I was the one who had his head in those boxes for the longest time. They were a death trap waiting to happen with push on push off plate switches, deadly interlock defeat mechanisums that people would forget to return to normal when reaching into the tank etc.

I was called to a station whose main would overload each time you tried to put it on. First step, I removed the load from the power supply- Still overloaded, that was a good sign since the problem had to be in the power supply. next I removed the bleeders Wala! the power supply came up and held. It must be a shorted bleeder. This was to be an easy fix as I had spares on hand but first I had to discharge the filter caps which is what the removed bleeder was for.

Back home at my station I had an old Gates FM1B and got a slight POP if I had to short the caps in the power supply so I wasn't expecting anything spectacular when I shorted the AEL. Worse yet, I leaned my head into the AEL cabinit to look for the terminals on the caps this was akin to sticking your head in an oil drum and lighting an M80. The discharge was so deafening that I could not hear for the next 20 minutes and worse yet the preasure on my ears made me dizzy. After I checked my pants, I sat down and slowly got my breathing back to normal. The following week I added a pair of sound deadening eaphones to my regular tools.

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RGORJANCE
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Re: Trade ya War Stories, Fossil

Post by RGORJANCE » Sun Feb 26, 2012 10:40 am

OUCH!

Yea, those explosions can really be impressive.

I just remembered a high school radio class I was in back in 1955 - yes that was the 20th century for those of you that don't go back that far. I may have posted this several years ago, but I don't see it. Here goes.

We were given a project to build a 5 tube superhet from a bag of well used parts. As we got to completion of the radio, we plugged them in and turned them on. WOW! Mine worked right first time. A fellow one row in front of me plugs his in, turns it on and after things warm up, it starts growling. The kid sees the aluminum cased filter cap expanding and leans way back on his tall stool. There was a thunderous bang, flash and a rapidly ascending -flipping- torn piece of aluminum, which impacted the very high ceiling. This was followed by the sound of him landing on his butt on the floor and a mushroom shaped cloud rising into the ceiling.

The instructor, sitting quietly at his desk calmly looks up to see what happened, then slowly shakes his head and goes back to his paper work - while the rest of the class is dying laughing, rolling on the floor.

Fossil

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NECRAT
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Re: Trade ya War Stories, Fossil

Post by NECRAT » Mon Feb 27, 2012 8:20 pm

Boom.

Any TV guy will tell you about troubleshooting a 30,000 volt crowbar circuit on a UHF transmitter, and multiple , repeated "booms".

Especially if you work on the crowbar assembly, and the Thyratron gets "gassy".
Boom, click Boom, click, Boom.


Me and our transmitter's company field tech were trying to get a malfunctioning crow-bar circuit working in this transmitter. Hit the test button, nothing would happen. On this model of transmitter, there is a grounding mechanisim, operated by a handle , held up by a locked key. Release the key, the handle drops, shorting the HV to ground. After several attempts at troubleshooting it, we could not get the test circuit to fire. Finally, we shut down the HV, and as it was decaying (from 33,000 volts, it dropped to about 29,000 volts), we "turned the key".

POW! Ker-Chunk!. Crowbar fired correctly on that test. We later determined the problem to be a bad pin in a internal molex connector.

Ah I miss those days. VHF solid state just isn't as much FUN!
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Re: Trade ya War Stories, Fossil

Post by ChuckG » Tue Feb 28, 2012 1:19 am

RFWarrior wrote: even better if you can suck somebody else into walking by the device about to go boom just as you throw the switch :) :) :D :D :lol:
Jeff
Lord yes, lol. It got to the point where if the GM (an old RCA guy) and I had our heads stuck in the back of the transmitter the PD would just leave the building as a preemptive move. :lol:
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boiseengineer(old)

Re: Trade ya War Stories, Fossil

Post by boiseengineer(old) » Tue Feb 28, 2012 3:52 pm

Never had the pleasure of being anywhere near a UHF TV when it crowbared. The Channel 7 engineers hated that Harris IOT because of that(now gone that' they're back on 7 digital). Anyone need a 7200/480 120 KvA transformer?

After a long night the tower guy was trying to catch a nap in a big comfy recliner. Problem? It was in front of the BTF-20E1. Every time the light flickered it went BANG across the PS choke.

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Re: Trade ya War Stories, Fossil

Post by n9lhm » Wed Feb 29, 2012 3:57 pm

"Every time the light flickered it went BANG across the PS choke." Huh?

Back in the REALLY old days (RCA TTU-12) before OSHA, the factory recommended procedure to check the thyratrons was to wrap a piece of #30 wire around the end of the God Rod and, with the HV on, take it and touch the HV connector on the tube with the wire.

Well one of the old guys I know did that, the thyratrons didn't fire, he was temporarily blinded by the big flash, and was then waving the ground rod around blind inside of the cubicle with the 6KV still on. Fortunately the second guy told him to freeze and hold still until he could get the HV turned off.

It's a wonder some of us have any nerves left.

Brian

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Re: Trade ya War Stories, Fossil

Post by ChuckG » Wed Feb 29, 2012 8:56 pm

n9lhm wrote: wrap a piece of #30 wire around the end of the God Rod and, with the HV on, take it and touch the HV connector on the tube with the wire.
Brian
No. :lol: And you can't make me.
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Re: Trade ya War Stories, Fossil

Post by boiseengineer(old) » Wed Feb 29, 2012 10:52 pm

On the BTF there's an open spark gap on the choke's terminals. Gives any extra energy from power surges someplace to go other than the rectifiers or the PA .

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Shane
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Re: Trade ya War Stories, Fossil

Post by Shane » Thu Mar 01, 2012 9:18 am

Three quick stories - one I posted a few years ago here: viewtopic.php?f=19&t=488.

The other two involve BTF-20s. The above AEL story reminded me of a troubleshooting session where three of us had the rig opened up and had removed one or more of the bleeders. Can't remember why but there was a good reason. After cycling power once I dutifully went around to the back to discharge HV. I do distincly remember thinking, "I wonder if I can skip this. This rig NEVER gives me the slightest bit of spark when I use the shorting stick." It was overnight, probably one or two in the morning, when one is more likely to not think straight.

But I not only did my duty with the stick, but was also loudly reminded that we had the bleeders out, what they were for, and that they normally did their jobs very well. My first reaction was shock (fortunately the mental kind, not the physical kind). Second reaction was, "Hey, that was cool." Third reaction was, "I'm awake now!"

Next BTF story: This one a backup transmitter at a separate site. I came out to do a check and regular clean-out of the rig. When I opened the back, I saw that mice had taken air filter material and created a nice warm home on the floor of the rig. Of course, when I disturbed their home they scattered everywhere. So I cleaned up the mess, put new filters in, closed it up and prepared to fire it up.

At some point there was either an unusual noise when the blower came on, or I got as far as "plate on" and a zap - I can't recall which now - but something made me turn it back off and open the PA cabinet. There is a small opening with a grill over it at the bottom of the PA cabinet for air to enter. Peering into the opening I see a piece of mouse stuck to the grill and said to myself, "That's an ASS!" Which was accurate except it was only part of one. One of the fleeing mice earlier had crawled into the blower cage.

I don't remember what gave me this idea but the next thing I did was try to clear the mess by leaving the PA cabinet door open, standing back, and turning the filaments back on. While this did clear out a bunch of the mess, it did so by splattering even more guts on the underside of the grill. And smell!

This was at the end of the work day so I decided to open up the rig as much as possible and leave it with the building fan thermostat turned down to allow the place to vent and came back the next day with help to finish cleaning up the mess. I think that included removing the blower and cleaning all the blades in the cage.
Mike Shane, CBRE
---Omaha---

n9lhm
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Re: Trade ya War Stories, Fossil

Post by n9lhm » Thu Mar 01, 2012 10:39 am

"On the BTF there's an open spark gap on the choke's terminals. Gives any extra energy from power surges someplace to go other than the rectifiers or the PA ."

Yeah, well, I know that, but why does a "light flickering from a recliner" set it off? :)

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RGORJANCE
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Re:"light flickering from a recliner"

Post by RGORJANCE » Thu Mar 01, 2012 11:29 am

This is a real SWAG! As I have heard, the VSWR triggering on the BTF-20 used a light and photo cell to turn the rig off when it sensed high VSWR, Could you have been "flashing" the xmttr with a light that might have been seen by the photocell???

Fossil

n9lhm
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Re: Trade ya War Stories, Fossil

Post by n9lhm » Thu Mar 01, 2012 4:00 pm

Probably not, they were inside the API panel meter(s) on the front panel. I took care of several of those transmitters, both FM and TV, and never had an ambient light issue like that.

Now on Harris transmitters with arc detectors, I did :)

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