Folks, Got a pair of WE205D tubes and without the amp or tube testing am unable to test them. I do have a knight 600b tube tester and it does have the 4 hole slot which is perfect, however I dont have any other settings to apply for testing. Any other means to test them? I also see that the silver coating inside is there for one tube but not the other. The sheet included does have a print from WE that not all were coated or something like that. I can get the exact wording later after I reach home. Any thoughts?
The 205D was not a 'normal' consumer tube so it is unlikely you'll find a settings for your Knight tube tester, I had a bunch of these a few years back and got good money for them on Ebay - from memory they are what I call a low to medium power triode good for around 30mA at 135V compared to a say a 2A3 which is good for up to 60mA at 300V.
One way to test is to rig up a test circuit -
You say to have the data sheet, if you decide to rig up a test circuit start off with the bias on the grid set to -60V DC - and the HT set to one of the WE recommended voltages, then slowly lower the grid negative supply and keep an eye on the HT mA meter - you may need to slight adjustments to the HT supply as you do this to keep the HT constant. If your tubes are good then you should be able to set the bias to the WE recommended settings and see the corresponding anode current as per WE data sheet, give or take a few percent, be careful not to go over current, extended over current will damage the tube. If the tubes check out ok don't be concerned about the silver coating.
One way to test is to rig up a test circuit -
You say to have the data sheet, if you decide to rig up a test circuit start off with the bias on the grid set to -60V DC - and the HT set to one of the WE recommended voltages, then slowly lower the grid negative supply and keep an eye on the HT mA meter - you may need to slight adjustments to the HT supply as you do this to keep the HT constant. If your tubes are good then you should be able to set the bias to the WE recommended settings and see the corresponding anode current as per WE data sheet, give or take a few percent, be careful not to go over current, extended over current will damage the tube. If the tubes check out ok don't be concerned about the silver coating.
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Thank you. The test rig seems simple but I don’t think I have this level of expertise to be confident. I am looking for a tv7 tester locally so that I can lend and test. Hate to put it on eBay with no testing.
Here's a link to a video of a guy testing the older tennis ball version of the 205D on a US made tube tester - not sure if you have the tennis ball type or the later ST shape, shouldn't make any difference they are both electrically the same - the video may help you once you locate a tube tester to use.
Update : I found a thread where someone mentioned that I could use 01A setting on Knight 600B. I set it up and both tubes glow. Line test go closer to 60. Now the knight has Green shade above 50 and red below 50. But WE205D per TV7 states 37 is the value for NOS. So 37 will be in Red. How do I interpret this.
what settings did you use to test? anode voltage, grid voltage?
if you know them you can go to the data sheet, look on the characteristics graph at the intersection of those values and see expected cathode current. if it is on or close to the line the tube is strong.
if the tube is weak, it can still perform ok in the right circuit, but it helps to trace curves.
if you know them you can go to the data sheet, look on the characteristics graph at the intersection of those values and see expected cathode current. if it is on or close to the line the tube is strong.
if the tube is weak, it can still perform ok in the right circuit, but it helps to trace curves.
Setting were from the tube tester manual which had 01A setting. I need to check anode voltage, grid voltage. The filament voltage was at 5.2v which is same in data sheet. I just read that the Red Green is just an indication for gas test but there is a note in the tester manual that if the tube data calls for lower number then just ignore the red green and use the numbers.
I take it that you are testing the 205D in a Knight 600B using 01A settings and using data from a TV7 as an indicator of the tube being good or bad, is this correct ? if so then I would advise against it, the 205D has a 4 volt filament and the 01A has a 5volt filament, it would be a shame to damage the 205D with over voltage on the filament - in addition the TV7 operates in a totally different way to the 600B so it's good/bad data has no relevance to the 205D.
You are correct. I agree on voltage. But even on TV7 the setting of 205f is being used in one of the video which has 5v. Ofcourse it’s a short amount of time. I do see the bulb glows and for sure it works. This weekend driving 3 hours one way to put them on TV7 and test it. Atleast that’s a better reference. Thank you for the feedback