Why JJ tubes are not Tesla tubes
There is a common misunderstanding in the internet called TESLA-JJ tubes. I don't know which duck invented this word, but such tubes don't exist. There are TESLA tubes, and there are JJ tubes, both made in different factories, by different people, with different technologies. Only the machines are the same, and in the Tesla days they were new, and now they are old. The used materials definitely are not the same. TESLA has used the cathodes from the former TESLA Rosnov factory, but this factory is closed now. Also wires, and nickel technology came from Tesla plants that are all closed now. Cathodes are elementary for tube performance.
May be you know that Yugoslavian "EI" ECC-series tubes are made on old Philips machines. This is EXACTLY the same situation, but I hear nobody talk about EI-Philips tubes. They are regarded something different, which is correct.
Until 1997, the world market prices of tubes like ECC83 were relatively low. There was enough NOS around. Many people thought this situation would always stay that way, and the TESLA management thought so too. (Later they understood the mistake, but were not successful with re-constructing the KT88 tools)
The Russians sold NOS EL84 for 200$ per 1000, and from China you could buy good EL34 and ECC83 for incredible low prices, if you knew the way. It was by that time that TESLA decided to sell off their line of Audio tubes to JJ. In the last years, the TESLA ECC83 was sold for only 2 € in OEM quantities, by company in Austria, who claimed to be their exclusive distributor. From this you can see that the factory price must have been very low. After selling off the audio line, TESLA went on making transmitter tubes, and other devices like vacuum capacitors, and military devices, which they considered more profitable.
So the TESLA tubes like ECC83, EL34, and KT88 were out of production now. The machines were moved out of the building and reinstalled at a factory of a man called Jan Jorgo, better known as JJ.
Unfortunately for TESLA, this was a big mistake. In the years after that, Ebay made the NOS prices soar, and as we write the year 2004 now, NOS prices they still rise 20..30% per year. NOS KT88, or ECC83 is practically unavailable in quantities. Russians and Chinese tube factories raise their prices twice a year due to higher energy costs and higher cost of all kinds. It appears that JJ made a perfect buy!
Since most JJ tubes are made with old TESLA tools, differences are small. They do use a different cathode, because the TESLA cathode factory in Rosnov is closed now. Both TESLA and JJ used to get their cathodes there. So NOS TESLA tubes have cathodes from Rosnov, and where JJ has their cathodes from today, I don't know. This is one difference.
Another difference is in the part numbering. E88CC originally is a long life version with gold plated leads, but the TESLA version has only normal leads. In the below picture you can see this difference clearly.
The next difference I noted, are some costs savings on the shielding. With this tube there is a shielding plate between the two triodes. With the TESLA tube, they did something nice. The shielding plate was coated black, and is used to transport the heat out of the tube center. So is is used a cooling fin. This is great, because the center anode plate is already hotter than the outside anode plate.
Gray coated shield by TESLA
With the JJ tubes, exactly the same shielding plate is used as with the TESLA tube. Only JJ uses lower cost, untreated white nickel, so the cooling fin function is not present any more. This will give the old TESLA tubes a better lifetime expectation. In vacuum, only black material will radiate heat very good.
Here you see a close up of the gold plated grid bars coming out of the mica. So obviously they did not use just gold plated grid wire, they gold plated the complete grid after it was made. What a quality this is!
TEST RESULTS JJ vs. TESLA NOS
I bought a lot of 20 pcs new JJ E88CC (one of those I have pictured above). On my tube tester (Metrix U61B) initially they tested very nice. Then I let one tube warm up, and apparently it started to reduce plate current slowly. This was curious, because with NOS, I never had this. Well ok, JJ is new production, so I thought this was the explanation. I though they need some more burn-in perhaps. So I let the tube run on the tester, and the next day it was testing weak. Oh well, I thought one bad tube out of 20 can happen. Then I tested another, and another and they all went down 5% per hour. I sold this lot where it belongs: on Ebay. I wrote in the Auction why I sold them, and they were with the option to return if not satisfied. Bidders were fighting for them. How typical for Ebay. I got a higher price than expected, and the buyer was satisfied he wrote me. Well, then everybody is happy.
When testing TESLA gold pin E88CC, the experience was so much better. First of all, the needle of the tube tester goes up faster as with the JJ's, and that gave me a good feeling. Same as with all NOS when I see that. Then after the initial heat-up, the Tesla's change their readings only very little, and give a totally stabile reading after just minutes. Wow! Then they keep just this value no matter how long (hours or days) I let the tester run.