9 Original Tung-Sol 6550 3-Hole Plate Triple Getter Vacuum Tubes
PLEASE MAKE SURE TO READ MY TERMS AND CONDITIONS (BELOW) CAREFULLY BEFORE PURCHASE.
This is for a group of 9 original Tung-Sol 6550 3-hole plate triple getter tubes in original boxes.
My strong preference is to sell these as a group, and this listing is for the group of 9, but I may split up for the right offer. I may also consider some trade value (see below).
Tubes #1-8 have a common date code of 3227134, while tube #9 has a slightly earlier date code of 3226952-3.
These tubes look very clean (it was actually difficult to get them out of the boxes). The pins are bright and shiny, and the center key on each shows little (if any wear), so it is clear that these tubes have seen very little use (if any use at all) outside of a tester. The boxes are for the most part in OK shape, but are somewhat on the brittle side (and I have taped up a couple of flaps to keep everything together).
Based on all the evidence (including test results), these are most likely NOS (“new” old stock).
Because these are premium tubes, and I am asking a fairly premium price, I have tested these tubes in a variety of ways.
I first tested these on my Weston 981 III (for transconductance), which I find to be very reliable for most tubes except higher current draw tubes as I have a very slight amount of transformer sag in the unit. As a result, these readings should come out slightly on the lower-than-actual side. The original Weston 981 settings for 6550 use a very low plate voltage, so I ended up using the settings from the Heathkit TT-1 (which is based on the same circuitry as the Weston). The reject point (65%) for these settings is 1430, and Gm is 5X the meter reading. All tubes were clean for shorts and leakage. The results are as follows:
Tube #1 2050
Tube #2 2125
Tube #3 2075
Tube #4 1950
Tube #5 2000
Tube #6 2000
Tube #7 2150
Tube #8 1800
Tube #9 2125
Next, I tested the tubes on a reasonably calibrated B&K 700, where 65+ is in the green ("good"), and I believe that 100 is supposed to be "average new" (but this can vary from tube to tube). The B&K meter does not have much definition, so the numbers are approximate. All tubes were clean for shorts and leakage, and easliy passed the "life" test. The results are as follows:
Tube #1 102
Tube #2 106
Tube #3 101
Tube #4 96
Tube #5 93
Tube #6 98
Tube #7 108
Tube #8 82
Tube #9 108
I then tested the tubes on a Precision 660 emissions tester, where 65+ is in the green ("good") and, according to the manual, 84 is supposed to be "average new" (but this can vary from tube to tube). All tubes were clean for shorts and leakage. The results are as follows:
Tube #1 96
Tube #2 97
Tube #3 97
Tube #4 96
Tube #5 96
Tube #6 96
Tube #7 98
Tube #8 96
Tube #9 98
Finally, I ran the tubes through a Transcendent Tube Analyzer which, unfortunately, also has some limitations with regards to the test conditions (limited as far as plate voltage and plate current draw conditions). As a result, I ran the tubes at a plate voltage of 300V and a bias voltage of -7.5V (to get a decent current draw). According to the manual, the screen voltage for testing as a pentode is held at 120V. I am not sure about 6550 specs under these conditions (Gm and plate current draw), but the information is useful in comparing the tubes to one another (and the results from the other testers). The results are as follows (Gm in ma/V, plate current in ma):
Tube #1 10.3 52.7
Tube #2 10.1 51.8
Tube #3 9.7 48.3
Tube #4 9.8 48.8
Tube #5 10.2 52.9
Tube #6 10.2 52.5
Tube #7 10.1 51.5
Tube #8 9.6 46.5
Tube #9 10.4 54.7
For using four very different testers, the test results are REMARKABLY consistent, and generally indicate that most can be paired up (or even a quad plus a couple of pairs), plus a spare (#8).
I can provide additional information or pictures upon request.
GENERAL TERMS AND CONDITIONS – PLEASE READ CAREFULLY
Please note that these tubes are being sold "AS IS", but I will guarantee against a DOA tube (does not work at all). In such event, I will refund purchase price less shipping upon return of the tubes in the same condition as sent.
I ONLY describe what I know about the tubes, and what I have tested for. Although my tube testers tend to be reliable, YOUR TUBE TESTER MAY GIVE A DIFFERENT RESULT THAN MINE, so please take that into account. If the information is not there, DO NOT ASSUME, and do not rely on any of YOUR assumptions. If you need more information than provided in the listing, ASK IN ADVANCE. If I happen to have the information, I will provide it. If I can get the information in a reasonable way, I will get it. If I do not call a tube NOS, consider that tube used. I do the best I can with very limited time and capabilities. I am an honest seller, but I am NOT a tube professional, and I am NOT in the tube business.
AS SUCH, PLEASE NOTE THAT I CANNOT GUARANTEE (OR EVEN REMOTELY PREDICT) HOW THESE TUBES WILL SOUND OR PERFORM IN YOUR EQUIPMENT. THE TEST RESULTS ARE ONLY PROVIDED AS AN INDICATION OF TUBE PERFORMANCE IN A VERY LIMITED (AND NON-IDEAL) ENVIRONMENT. OTHER THAN AS SET FORTH ABOVE, I EXPRESSLY DISCLAIM ANY LIABILITY WITH RESPECT TO THESE TUBES OR RESPONSIBILITY FOR YOUR USE OF THEM.
Shipping will be via US Postal Priority Mail unless otherwise requested. Insurance if desired will be extra. Please contact me for a shipping quote.
Money order/cashiers check/personal check preferred, but all (other than US Postal money orders) must clear my bank first.
I may also consider some trade value. My needs are few, but some possibilities include speaker cables (one or two pairs, 6-10 feet, but nothing too exotic), a pair of high-efficiency speakers, a PS Audio or other power regenerator (like a P300), an ESS Sabre 32-bit DAC (like the Eastern Electric Minimax DAC), certain vacuum tubes (45, 46, 12AZ7, 12AZ7A, certain 12AT7 types, KT90, certain 7DJ8/PCC88, certain 6922/7308 and possibly others), and possibly other items at the right value.
I also accept Paypal for convenience (but add 3% to the total for USA, and 4% to the total everywhere else). IF YOU PAY VIA PAYPAL, HOWEVER, A CONDITION OF YOUR PAYMENT IS THAT YOU EXPRESSLY WAIVE THE RIGHT TO FILE A PAYPAL CLAIM OR CHARGE BACK (but do retain the right to sue me in court should you so desire).
IF YOU ARE NOT WILLING TO ACCEPT EACH AND EVERY ONE OF THE ABOVE TERMS AND CONDITIONS, DO NOT CONTACT ME AND DO NOT PURCHASE THESE TUBES. NO EXCEPTIONS!
Please check my feedback on Audiogon, Videogon and Ebay (ID=baileyler) and buy with confidence.
