AL-811 Problem

[W1MSG]

I have a realatively new AL-811 3 tube. Last night I turned it on and it blew the fuses ?? Checked everything and really dont know what I am looking at but everything looked Ok, changed the fuses and pop again ?? I didconnected it from everything and tried one more time and again it blew the fuses.

Any ideas before I send it back to ameritron ??

Craig

 

[wavrider]

If it is still under warranty send it back, of course you may end up eating the shipping charges.

If it is not under warranty and you are not familiar with working with high voltage I would recommend not to try to repair it unless you have an elmer who knows about high voltage helping you.

I think 1700vdc is on that HV B+ supply.

As far as what may be causing it? Bad rectifier diodes, shorted filter caps, many different things.

 

[W4KVW]

811?

Pull the cover & take out ALL of the tubes & see if it still blows a fuse when you turn it on.If NOT then plug in ONE tube ONLY & turn it back on.Continue until when you turn it on & it again blows a fuse & the last tube you added will be SHORTED! This is just ONE possible fix but worth a try.When turning the amp back on just set the cover on it do NOT put all of the screws back in just for testing purposes.The amp can operate if you NEED to or have to with as few as ONE tube but output of course will be only what one tube can produce.This is also a way of testing your tubes to see how they compare against others in a set ONE AT A TIME! If this fails call AMERITRON & ask for ROB HOOD.He will tell you what else you can try before sending it back & tell him Clayton said HELLO from Florida! }:>)

SIX-SHOOTER

 

[W1MSG]

Thanks Six, I am kind of leaning tword a bad tube as I did see a bright flash through the vent side when I turned it on and the fuses blew.

Now is it safe to remove tubes, I have no idea on working with high voltage and have no idea how to ensure all the capacitance is discharged.

I havent really been pushing the amp very hard so I am really surprized a tube blew, its only 2 months old. Should I just put the 572b tubes in it ?

Working on an amp is the one thing that scares the crap out of me.

Thanks for all the helpful hints..

Craig

 

[airplane1]

Just be very careful, let it sit for a long while before opening it and wear rubber gloves too. What brand tubes are in your amp?

 

[W1MSG]

Just be very careful, let it sit for a long while before opening it and wear rubber gloves too. What brand tubes are in your amp?

It is in fact a shorted tube, it was the number one tube, or the one farthest to the left looking from the front of the amp.

No evidence of a diode blowing out, so I ordered 4 matched 811A's from E-Bay and will have them on Wednesday. I will replace all 3 tubes and that will leave me with 3 extra's as needed.

I have the factory installed Tubes from Ameritron, no idea who the manufacturer is but they are probably the cheap Chinese Tubes.

I'll post up when I get the Amp back working..

Craig

 

[TonyV225]

I was laughing when you spoke of that dreaded flash!! Kind of startles you a bit dont it!!! Im glad you got it all figured out and your on the road to getting it all straightened out a broken HF amp is a sad sad thing

 

[W1MSG]

I was laughing when you spoke of that dreaded flash!! Kind of startles you a bit dont it!!! Im glad you got it all figured out and your on the road to getting it all straightened out a broken HF amp is a sad sad thing

Well there wasnt a pop with the flash, and some of the great info I have received has lead me to believe that the diodes are gonna be Ok. So thats one good thing. I could hook it up and run it on two tubes but the new tubes will be here on Wednesday and the amp is off the bench right now because it is easier to work on that way, so I'll just wait on the new tubes. I ordered a matched set of 4 811A tubes so at least now I will have some spares if I ever have a problem again ..

 

[Toll_Free]

Well there wasnt a pop with the flash, and some of the great info I have received has lead me to believe that the diodes are gonna be Ok. So thats one good thing. I could hook it up and run it on two tubes but the new tubes will be here on Wednesday and the amp is off the bench right now because it is easier to work on that way, so I'll just wait on the new tubes. I ordered a matched set of 4 811A tubes so at least now I will have some spares if I ever have a problem again ..

Shoulda grabbed some 572s. Although WAY too much for that amp, woulda been the last tubes you'da bought unless a MAJOR catastrophe happened.

--Toll_Free

 

[W1MSG]

I did consider the 572B's but 3 tubes were more than twice the price of 4 811A's and buying the 4 811A's I now have a spare set of tubes. I dont push the amp to max performance and I am betting I just had a weak tube to begin with. You dont gain anything with the 572's other than they are a bit more durable so I just figured I would stick with the factory recommended tubes.

 

[Toll_Free]

I did consider the 572B's but 3 tubes were more than twice the price of 4 811A's and buying the 4 811A's I now have a spare set of tubes. I dont push the amp to max performance and I am betting I just had a weak tube to begin with. You dont gain anything with the 572's other than they are a bit more durable so I just figured I would stick with the factory recommended tubes.

You don't gain anything with the 57s, although they are a more durable tube.


Cheapest = !not_the_best

To each his own. The guy who buys 5 sets of 811As (at HALF the price) is better off than the guy who purchases a single set of 572s how?


--Toll_Free

I'm just a dumb CBer who runs a pair of ceramic tetrode 15,000s, though.

 

[Toll_Free]

I did consider the 572B's but 3 tubes were more than twice the price of 4 811A's and buying the 4 811A's I now have a spare set of tubes. I dont push the amp to max performance and I am betting I just had a weak tube to begin with. You dont gain anything with the 572's other than they are a bit more durable so I just figured I would stick with the factory recommended tubes.

The factory recommended tubes for an AL811 or AL811H are the 572s... Just read Ameritrons BULLSHIT "spec and sales" sheet.


AL811s are > 60 years old. 572s > 40 yrs old. Which one is "solid state"?

--Toll_Free

 

[W1MSG]

Your right to each his own, so why are you bashing me for buying 811A's.

It came with 811A's and thats what I am putting back in it, and buying 4 tubes gives me an extra set. Its better than buying 3 tubes and having 2 others I cant even use if I had to.

 

[Toll_Free]

I couldn't tell you, Craig.

When I put a tube in an amp, it lasts > 20 years.

trying to tell me you made a "good decision" by purchasing some "spares" that are > 20 years older than the originals is........

BUT, to each his own. To tell someone that actually works on this stuff for a living that you "replaced it with the original OEM parts" is a laughable offense. Anyone that can actually read realizes that Ameritron supplies their 811 amps with American and Offshore tubes, BOTH 811 and 572.

It's OK. When someone smarter than me speaks up, I argue with them. That's the BEST way to get better help. Keeping 811As in your amplifier is like keeping sweep tubes in my SB220. I COULD keep them in it, but why? It might be cheaper THIS time, but over time, it would RAPE my wallet.

You know better though.... Keep correcting others.

Then again, I've NEVER replaced tubes or worked on an 811 or 811H Ameritron with 572s in it. I've probably REBUILT more 811 ampliifers than you've ever RUN, though that has 811A's in it.

--Toll_Free

 

[Toll_Free]

Your right to each his own, so why are you bashing me for buying 811A's.

It came with 811A's and thats what I am putting back in it, and buying 4 tubes gives me an extra set. Its better than buying 3 tubes and having 2 others I cant even use if I had to.

And OBVIOUSLY you can't differentiate between tongue in cheek and actual facts.....

Sorry to confuse you. ALL my posts where made to point you to actually buying real tubes, rather than almost 80 year old technology. 40-60 years > 60 - 80 years.

--Toll_Free