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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
almarg's avatar
almarg
9,670 posts
 
+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
 
stereo5's avatar
stereo5
6,548 posts
 
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. 
ozzy62's avatar
ozzy62
3,329 posts
 

03-08-2020 6:14pm
hello Jond the amp can take anything from El-34, KT-88-6550 kt120,kt150s

Is this the same amp you are selling here?
mickeyb
590 posts
 
It’s hit or miss. Recently bought a nos Siemens 6922 off eBay. Got it and checked it out on my Hickok. Tested at 1500 which is really bad. It doesn’t sound bad after I compared it to a newer gold lion but I was disappointed. That tube was 100$. Tube selling is big money and many of these sellers don’t test them properly. 
vegasears
1,173 posts
 
Every few months there is a thread titled "Where Do Buy Tubes" or "Good Tube Vendors".  Good Reading.
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