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Help with Tube Amplifier

TonyV225

TonyV225

W9WDX Amateur Radio Club Member
Apr 18, 2005
5,824
323
143
Wisconsin
Well there I was an hour ago talking to my usual 80 meters group when they were all signing out I put the Yaesu FL- 2100B on stand by and and walked into the kitchen to get something to eat when BAM a loud gunshot nois errupted from the livingroom I came in and asked my wife and youngest daughter what the hell they did.

They looked at me puzzled and insisted it was something I did in the kitchen I assured them I did nothing I started looking around thinking ohhh ohhhhhh Ilooked at the amp which was still running as it was I looked at it some more then switched to operate keyed gave my callsign and all was good 7oo out wher it was before I left. I put the amp on standby and within a few seconds BAM!!! once again.

I said what the hell so now my wife said it was indeed coming form over by my bench I started looking into the top of the amplifier once again when BAM!@!! sure enough there by the tubes was a loud gunshot bang and blue flaming spaking flash my wife said she seen it from across the room it scared the $h!+ out of me all was still lit up but I imediately turned off and unplugged the amplifier pulled it out of line and packed it away until its journey to wherever for the repair if need be.

What the hell would do this Like I said power was still there and its coming fro where the tubs are in the back right corner. First though I had was did a bug crawl in there or what the hell would do this or cause it?? Anyone ever seen this or heard it before?
 

Im thinking maybe resisitors went if it were capps Ide have seen other things happen or a dead amplifier but this still keyed and had full pep
 
no smells thats what got me....It popped loud like a firecracker 4 seperate times while idoling not even under a load or keyed up. The 4th time we seen the blue flash and off and out of line it went
 
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When the amp is in standby with no load the high voltage is at it's maximum.

Pop it open, short out the power supply caps and give it a good spring cleaning. Look around for damaged stuff. If there is no damage to be seen and there was enough dust/dirt buildup it could have been nothing more than a flashover.

Stuff that runs on high voltage requires cleaning from time to time.

It didn't blow the fuse (check to make sure the fuse is properly sized) and still made power. That's a good thing.

Take a good look at the resistor/coil combo leading to the tOOb plate caps. Those are the parasitic suppressors. If they look or smell funky your amp my have an issue with oscillating. That's a problem with the FL-2100 especially with certain replacement tOObs.
 
Ok Ill have to look into this. Ive had this amp for 4-5 years nota a problem ever until lastnight. I also just cleaned this amp out about a month ago I actually try and do all my powersupplies amplifiers ETC 2 times a year as I do my DJ equipment as we know dust is a major cause of death in electronincs.

This just freaked me out even with the flash/ bang there wee no burning smells thats why I was thinking maybe something got inside like little asian beatle spinder fly etc. What is the best way to short these caps out and know there shorted ifg I remember right theye make a popping noise kinda like they did lastnioght when there being shorted.

Anyways I have a youth Gun Deer Hunt this morning with my son so were out smacking bambi and will be in later I really need to get this amp fixed I feeel lost already and its only been 7 hours or so LMAO !
 
Maybe one of the parasitic chokes was just a little to close to ground? Check the distance and if you can reposition them further away. I'll try to look at my 2100 and see if I can see anything else that might be suspect.
 
keep in mind that this just started doing this lastnight Ive had the amp for 4 or more and it operated without a problem
 
All it takes is one speck of dust thickness to cause an arc. Possibly the parasitic choke on one tube is cracked? It is strange however it does not do it while keyed. But like someone said in a previous post the HV is at it's highest point while not keyed.
 
Im leaning towards the dirt aor dust in a touchy spot reguardless of the fact I just blew it out a month or so ago I had also called Q5 Communications here in Madison Wisconsin and he also said it sounds like theres dirt or dust aswell. I also brought up the fact of the lady bug asian beatle fly spider or some other bug getting in and he said that also would do that so we shall see when I open it up Monday.


What is the best way to ground out these caps or tubes?? I watched a buddy do it years ago and if I remember right he just took a rubber or plastic handle screwdriver and toughed the cap of the tube and shorted it to the inside of the case but I need to make sure I do this right and I remember also when he did this it made a pop or loud click to show it was shorted out.
 
That's it. Use a screwdriver with a well insulated handle. Odds are if the amp has been off for a while (as a result of the POP) the capacitors are discharged. But don't take any chances. The best way is to ground the tube caps out through a resistor, somewhere around 100K or more to slowly let them discharge. To be extra safe place a clip lead on the parasitic chokes after discharging the caps. Sometimes a cap will recharge itself to a certain extent. Then you are good to go.

Just remember to remove the clip lead before you fire it back up.........BANG!!!
 
Always work your way back to the capacitor bank itself when confirming discharge.

An open plate choke or wiring could make shorting the plate caps quite useless.

The zorch condition you hear could ALSO be a bad connection somewhere in the B+ supply line. That's relatively rare but should be considered from a safety perspective.
 
I need to get this going I am lost with out it I have my solidstate ameritron but that on the secondary setup in another room this tube amp is on my main setup. I at several times was looking at a purchasing spare amplifier and never did and just told my wife I was now paying for it.

I will deffianetly get another amplifier this spring or if this Texas Star 1600 should sell or I trade it for another amplifier.I will however get my Yawsu 2100B fixed its a great amp in excellent condition other than its current problem and the best part is boy this thing is easy to tune and fast to tune aswell.
 

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