The AM Forum

Well after a couple of weeks of not being on the air, I decided tonight to fire up the CCA AM1000D bcast TX and get on 160M. Went to transmit and all I got was a couple of bumps of power out, then a shut down.  I went out to the shop where the TX is and tried it on dummy load, to eliminate any antenna issues. I hit the B+ a few times and each time it went immediately to overload shutdown. 3rd time was the charm.  Hit the HV and WHAM! A God aweful bright explosion like a firecracker on Steroids, up in the tuning section....no smoke, no smell, no output, just ringing ears and no power out.

I powered it down and went had an 807 and watched a rerun of e.r.

Got to get at it this week...the only thing I can think of is a mouse got in there and disrupted the tuning and maybe exploded, or maybe one of the caps. That's what I'm hoping anyways. Or the neighbours' cat, who complains about the QRM in her phone, (the neighbour, not the cat). The transmitter is buried and up against a wall, and is a buggar to get at the back door. I'll post pics of the "demised".

73
Paul

Hmmmmm... I've never had a mouse expode  ;D   WAAAAAAAAAAAAAAAAAYYYYYY back in my early career as a broadcast chief engineer, the main transmitter went off line at WORC - 5KW in Worcester...

Went up to the transmitter site, opened up the back of the 21E, and there - across the mod transformer, from the secondary to ground - was a mouse.  This sort of thing was to be repeated several times in various parts of the transmitter.  None of the mice ever exploded or even burned up very much.  Just shorted things out and kicked out the overload protection.

Pesky little buggers, aren't they  ;)

Regards,

Steve

I withdrew one from a linear amp. The deceased was paper dry and had a hole burnt clean through him. If a varmint actually exploded in your radio, the pictures could be interesting.

Lotsa stuff pops .........

http://www.youtube.com/watch?v=vX9ktjqcMvM

and the classic.........

http://www.youtube.com/watch?v=fEX2-npA6vU&feature=related


klc

In 1977 I was renting a really cool mother in law behind a house in Santa Rosa, CA. It came with 1940's appliances, a Crosley shelve A door refrigerator and a huge GE electric stove/oven.

The oven had a problem and in the process of tracking down the fault I pried off the cover under the knobs.

I found an ancient mummified mouse that had found it's way into the stove and stepped across the 220V line.

I pulled him out and he stood up like a toy in one piece.  The problem with the oven was a broken heater element but finding that old mouse added to the entertainment of an otherwise nasty job.

Mike

Had a mouse get into the cabinet for my 2M repeater a couple of years ago. Started gnawing away on the cloth-insulated wires.

He stopped when he found the B+ lead for the 5894.  ;)

A squirrel got across the pole pig HV on the pole across the street from my house early one sunday morning.  I happened to be having a cuppa in the kitchen and got a ringside seat.  He came down off the pole in a couple of smoking peices.  the power reset but the carbon-squirrel residue caused another arc over and we lost power for good.  they replaced the pole pig later that morning...

So, if you can't get a mouse to explode, you need MORE POWER!!!

I was about 5 sitting on my G.M's front steps when the same thing happened....nothing bur fur and a loud bang.

Gee, reading these replies was interesting!

I used to be a field engineer for a food packaging equipment manufacturer and some of the repair calls I tended to were interesting!

One had an old scale in the vegetable department of some Toronto store flicking on and off by itself. Very odd since these old scales were built like tanks, there just wasn't much that could go wrong with them.

Turned out to be a mouse who got across the terminal block that led the 120 VAC in. His legs got across the hot and return and the juices led to corrosion which caused an intermittent connection. The mouse had become mummified since then and I used my needle-nose pliers to pick him off. Pretty awful.

Another time, one job at a burglar alarm company I worked at shortly after graduation.....odd smell permeated the work area for about a week. Then one day without warning there was a giant flash from the 30 kVA transformer on the wall and the lights went out. It turned out to be an expired rat whose body ended up falling across the Xformer's internal leads.

I'd removed the front panel to my home's load center once, to find the skeletal remains of a mouse that had gotten it's front paws across the load side of a dual breaker [220V]. It appeared as if one "shoulder" joint had been blown away, and bits of fur were around the breaker and wiring.

Strangely, there was never a smell that emanated from the panel, and it is in the kitchen [with people in and out all the time, naturally]. I'd only gone into the panel to check the make/model of the breakers, for a contemplated additional circuit. ???

They may not explode but they do loose all control of their bodily funtions!

Interesting thread after spending all day Friday in high voltage training.

bud, I think mice can still generate output while dancing....but that is just a guess.

They do, Frank. I had a mouse chew on an EMI bypass cap off a 400VDC bank in one of my supplies once. You could see his tiny little footprints in his "emissions" like looking at one of those "learn to dance" floor mats made popular in the 50's!

I had a picture of it somewhere around here...........

 ::) Well, since you guys brought it up, my xyl and I were cleaning up the debris left by house movers on property next door. She's on one end of the lot and I'm at the other. 

She yells out, "Look what I've found!" I look up to see her holding a completely mummified cat.  Heaven only knows how long it had been underneath the house.

Yup
They are a pain in the ass. My 330 watt 4CX250B amp on the repeater went off the air. When I got to the site there he was, spread eagle across the plate transformer. Justice. One of the favorite things to build this time of year is a high voltage mouse trap. One large piece of metal, two inch insulator in the center, a smaller piece of metal on the top. Use a 1960's TV transformer with a light bulb in series with the primary. Maybe you want to really punish the offenders? In that case just put a fuse in the primary. Costs more but causes more damage. One thing you need to watch out for is picking a high voltage transformer with too much snot! For some unknown reason they will not go for the bait on the top plate when it's got blue corona discharge all over it.
Mouser

i am ready to see what really happened. hope you find out soon and have battery's for your camera

When Mr. Squirrel got across the pole pig outside my house, he made it blow up. I don't know how that happened, since he was outside it. He had about a 1/2" hole through him. A few parents took their children and made them look at the deceased there at the curb, as a warning not to play with electricity.

Hi Guys,

Wow! I had no idea there was much hatred for the little vermon...this is great. What a great response. thank you.

I have a 2 day road trip and when I return, I will be pulling the TX from the wall to find out what exploded in the cabinet...hopefully, "rodentus terminalus furgoness".  ;D

Cheers

Paul...still not on 160M due to the above rodentus problematus

Hopefully not the neighbor's nice kitty.

If it's the kitty just send it to Dipsy Dumpster land.
:)

Well this is just too weird.  ::)

I pulled out the TX, removed all the covers and looked and poked and proded and there is not a damn thing in the TX that shouldn't be there. No mice, cats, squirrels, bears et al. A few old fly parts and two pellets from the back end of a mouse but otherwise nadda.  What can cause such a horific bright explosion and leave no residue?

Anyway, while I had it apart, I gave it a good wash with brake clean and then a big blow job and made it all purrty and clean, fired it up and it works perfectly. WTF!   >:(

Oh well, played ABBA through it for over an hour into a dummy load then got on 160M for a nice QSO at the tube shoot in Tum Tum. Worked 100%.

Push it back against the wall and pretend nothing happened. And I was looking forward to mouse guts and great pics.

73

Paul
VE7 Kilohertz

Spiders... or other insectoid life possibly.

yessir Paul ...you have an interdimensional transporter ...live long and prosper  ..beefus

someone mentioned to me that spider webs can do this.

Well, it had been working fine for a few more QSO's but once in a while it would crap out after 10 minutes. It also explodicated again a few more times, scaring the crap out of me and causing great light flashes and bangs but 10 minutes later it would work again..except this time it was only putting out 600W instead of full power. One of the 4-400 current readings were way down, less than 50mA where it should be around 250mA. I swapped tubes around and the problem stayed at the socket so I looked underneath, very closely and found a destroyed 2W 100 ohm resistor, which turns out to be a suppresion R feeding the screens. Ah ha!

Changed that out and shazam...works 100% and has been now for a few weeks. Not sure why it went but it's fixed and I'm happy.

Best 73

Paul
VE7KHz

I bought a 1939 philco slant front tabletop years ago for 10 bucks opened it up inside was nothing but chewed wires, a  huge nest, and a little mousie skeleton. he died at home listening to the radio.

Well Schit (I'm German),

The damn CCA blew up again tonight...same bloody resistor that I replaced. I think maybe I have a bad tube.   ::) :P ???  It's the screen grid R well, suppresion R, there is a 100W 15K or ?? supplying the major current to the screens) of one of the 4-400's in the final stage.  The resistor is 100 ohm and is just cooked. I guess a bad tube could cause excessive current draw and pop the R.

Well at least I can soak in the tub now that the GFCI problem is fixed.   :D

Your thoughts?

Paul
The KHz guy

Wouldn't that be Scheiße?

Ja ficken

h

So I went thru the TX again yesterday and changed the resistor and the screen bypass cap that was 470pF but was a big ceramic job with terminals, sitting on the floor of the RF deck with wires attached. I put a proper disc cap with short leads in there, replaced the R and the 4-400 and ran it for a couple of hours into the dummy load. Worked FB 100%. Then I switched over to the antenna and it powered up fine for 2 secinds then the line voltage dropped 10VAC and the power dropped like it was drawing huge current. Shut it down...tried it again...same thing, starts for 2 seconds fine, then power drops off with line voltage drop. Buggar!

I thought why would it do this on antenna but not on dummy laod so I started looking at coax going to the house and found that the shields were not soldered to the PL-259, just screwed on. I hate it when people do that. Do I redid both ends and tried it again....same thing....oh man.

So I went back to the house and I noticed the hot tub was running...and it wasn`t a minute ago. Mmmm. Shut it down with the touch panel and went to the shop and rekeyed the TX and sure as Shiebe, the hot tub came back on. Bloody hell. RFI turns on the hot tub, heaters come on, takes two seconds, the line voltage drops and that is what I was seeing in the TX meters. Well that was an easy fix. It wasn`t the TX or coax after all.

So, now I need to find torroids that will take 8/3 wire.   ::)

Cheers

Paul

 "  So, now I need to find torroids that will take 8/3 wire.   ::)  "

A gambeling man would take some tori and wap 'em sharply, than get out the super glue....  not that I would try anything that stuped......... 

klc

cores from old flyback transformers.. they come apart in halves like the letter "C", you remove the windings, wrap the big AC wire around, then screw the bolts back on or put the clamps back on. Very lossy at RF.

Stack a few together if you like, need not be same size, and tape them up when done so they act like one big core.

In February there should be an ample supply of used flyback transformers inside all the TV sets out on the curbs. No need to ruin antique ones.

sombetch and I L B damed

Im west virginian

It may be a radiated problem with RF getting into the controller. Beads on the main may not help. Why not just turn the tub off when you are not using it.

For now I can just shut off the tub...but eventually I want to remote operate the station with an HT and be able to be `hot tub portable`on 160M.   ;D

I`ll try beading the small leads first, then the big wire.

Cheers

Paul

Then figure out a way to have excess transmitter heat warm up the tub....

I could be the first kid on the block to have a water cooled transmitter. Mmmm, something to think about.  ;)

Paul