rtaylor Posted September 1, 2003 Share Posted September 1, 2003 Have an old dynaco st-70 (that needs work) with a compliment of 4 el-34's plus 1. I know 2 are Mullards and believe the other 3 are also but can't be sure because the paint is gone. One tests out over 100% on the tester I've borrowed from a friend and the others are 95, 95, 94 and 86. The 86 and the 100 are the ones with paint still on them. What would be the line between a good tube and a bad tube here? Are these tubes still viable? Also have a mullard box with a gz-34 tube that tests new but again no paint left on it. Also a Sylvania gz-34 made in Great Britain that looks and tests new. 1)Would the two gz-34's be compatable? 2)Are the top four el-34's ok to use together in an amp? I'd like to try them in the modified MKII's that are currently biased for and using 6550's to compare sound. 3)On an unrelated note,Paul CBC,please contact me, I need to talk to you. Thanks and a hat tip to all, hope you've all had a great weekend, Randy Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted September 1, 2003 Share Posted September 1, 2003 Randy, This tube appear to be the large base XF1, which is the most desirble type (and the metal base too). Check if they all have a hole in the guide pin (all mullards do) and there should be a production code on the glass near the base. You can use the top 4 in the amp with no problem. Guy Quote Link to comment Share on other sites More sharing options...
rtaylor Posted September 1, 2003 Author Share Posted September 1, 2003 Hey Guy, thanks for the reply. Three out of five are the larger and a little lighter colored base and only two have the hole in the center guide, funny thing is the only one marked mullard is the one without the hole. The other two with the smaller and darker base have holes in the guide and holes in the base where the number 6 pin should be. One of these has the mullard name still visable. Is this a crazy world or what? Randy Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted September 1, 2003 Share Posted September 1, 2003 Randy, there was only one exception of the large base Mullard with very large round getter (and all metal base mullards) that didn't have the hole in the guide pin. If your tube has got the big round getter with double support than it's the reall mccoy. If the writing on the tube says "Mullard British made" and not "Made in Great Britain" and have double round getters and no xf1 marking near the base, it's a fake made by Tesla but still a nice sounding tube. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 1, 2003 Share Posted September 1, 2003 Those EL34's should all be good if that tester is Calibrated although I'm not sure that is a transconductance tester. Its most likely just a emision tester so matching really isn't accurate with it. The 5AR4's you have are both Mullards ones just branded Sylvania pretty common thing both are great tubes ! Craig Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted September 1, 2003 Share Posted September 1, 2003 Photo of the Mullard production code. Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted September 1, 2003 Share Posted September 1, 2003 Photo of real type 1 Mullard with large round getter and no hole in guide pin. Quote Link to comment Share on other sites More sharing options...
rtaylor Posted September 1, 2003 Author Share Posted September 1, 2003 Guy, It seems like the tube that tested new might be the one large base you are talking about. It does have a single large getter at the top and two supports. The lettering is not good enough to tell if it says British or Britain. There is no xf1 marking near the base that I can see but there is a marking on the glass (B7E) near the base on the glass. Does this seem appropriate to you Guy? Craig, The tester is a Century Model # FC-2. I don't doubt that it is a cheap tester but it is the best I can come up with now. I'm running .50 volts now with the #10 resistors in the bias loop with 6550's, do you remember what the bias is with the EL-34's?? Thanks, Randy Quote Link to comment Share on other sites More sharing options...
NOSValves Posted September 1, 2003 Share Posted September 1, 2003 Randy, The important thing here is what is the Plate voltage ?? If the amp is setup for 6550/KT88's you have to be carefull putting those EL34's in there ! Should I call you ? If so shoot me your number in a email and I will I have some time right now. Craig Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted September 2, 2003 Share Posted September 2, 2003 Randy, The tube is a real Mullars made in the Blackburn factory on may 1957. Quote Link to comment Share on other sites More sharing options...
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