Vacuum tube ! And Warnings


To all out there who have Vacuum tube Amplifiers .
my friend just bought his first tube amp , it came with EL34 power tubes he wanted to get a bit more punch . He ordered on EBay  6550s I told him I would assist in fine tuning the bias.
he plugged them in we turned it on and a huge transient goes through one of the speakers and a surge through one tube . I shut it down waited 5 minutes then turn it on bias has a built in meter ,I checked they were over 90 +milliamperes maxed the meter. should be around 50. I removed them , he is sending back.the story here is many Ebay sellers don’t even test them they just get them from Russia and state as a match quad ,and runin for 24 hours . Never buy from anyone that doesnot  personally check them .
viva tubes, and upscale Audio are good , Jim mc Shane is good.
for vintage tubes, Brent Jesse recording, and Vintage tube services   I recommend. 
audioman58
I am baffled here you put tubes in an amp that can't use 6550s? You said EL34-KT150 does that include 6550s? If not its not the fault of the tubes wherever they came from it's user error.
Some Quicksilver amps can use a number of tubes.... the bias pot has enough range but like rodman said turn the bias completely counter clockwise first then slowly up to bias spec.   My QS can use EL34, 6L6, 6550, Kt66, KT77, KT88, and some others.   
+1 Big_Greg. Very well said.

I've made a few tube purchases on eBay, with 100% perfect results as verified both sonically and on my Hickok tube tester. Of course the purchases were made after thoroughly checking out the seller's feedback/feedback left for others/other items for sale, etc., to get an idea of what kind of person I would be dealing with.

On the other hand, I've had issues with tubes purchased from both of the well known sources Big_Greg mentioned. Which ultimately were resolved reasonably well, although I'm not sure that would have happened if I didn't have a tube tester to help diagnose the problems.

Regards,
-- Al
 
I had problems with two NOS Mullard CV4003 tubes.  One went microphonic after a week and the other after six weeks.  I paid almost $100.00 each at the time.  Lucky for me Kevin Deal backs up his tubes and I got replacements that lasted a long time.  The ones I bought were Upscales highest grade.  I guess any 40+ year old tube can have problems.