Hello Barry, R626 to 1.3K and just 180V on output ?? No good at all: the problem have to be elsewhere... I am just wondering that your 6BH6 (V607) can be leaky. If you have another one, please swap it ! R624 at 600K should not make any difference if there is no grid leakage current from the 6BH6, but it is exactly what I am thinking now... I already mentioned a possibility of a "higher than normal" 6BH6 transconductance, but internal leakage is also a definitive possibility.
I once encountered a 6DC6 that disturbed the ACG line in my 51S-1 completely. And this particular tube passed all the test on my AVO VCM163 ! But inserted as the RF amp in the 51S-1, it turns the whole set into a basket case... Tubes tester are good, but do not tell you all the truth, obviously. This does not means that a tube that test bad on the tester will perform correctly in the receiver, however. Like testing the 5651 on your Hickock 752A: this is not the real test to do, because all the testing currents and voltages within are AC. In the R-390 PS, the 5651s should run at 2.7mA and have 85 volts across each of them. The only valid way to test VR tubes is to test those using a DC supply, monitoring both the current thru and the voltage across. I took me few years to understand that, but... OK, let's change that 6BH6 and try again, please. Don't forget to re-adjust the hum balance with the new 6BH6. If you don't have any, just tell me: it's another tube type I have enough to dance on. 73, Jacques, VE2JFE in Montreal ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
