21-07-2015, 04:36 PM
(17-07-2015, 04:22 PM)AlanBeckett Wrote: I'm sorry, I don't understand you. Are you saying that they are the Valves that the Service Data specifies? If so it's an odd mixture, even for GEC.
X61M is ECH35, which is International Octal. There's plenty of those about, along with it's 'CV' equivalent. A 6K8 would probably work as well although the Electrodes are actually different.
http://www.r-type.org/exhib/abh0083.htm
DH77 is 6AT6. Again, there's plenty of those available along with EBC90, it other equivalent. However, it's a B7G.
http://www.r-type.org/exhib/aaq0240.htm
Alan
This set was either made with all Octals or all B7. However, the service manual clarifies it may be a mix of Octal and B7s. I found a couple of tube supply firms and am now pretty sure what my Detector and Mixer will be. The Mixer has a bigger can than the detector so it ought to be the X61M by my reckoning. The only possible doubt I may have is over the IF Amplifier tube as this gives 3 possibilities, not just two.
It seems a bit crazy to discover the valves under the cans were history but I've always been reluctant to force old valves out of the chassis so I tend to leave them be. They can break easily in the process. In this case, I began to suspect something was very wrong so I forced the cans off only to find them damaged or missing. Perhaps I'll now be forced to check any future can but, for now, I'll just have to press on and fit the tubes.
