I found a Telefunken EMM801 tube for a reasonable price and decided to get it for my FM3. It was advertised as NOS/NIB and it does appear to me to be unused and it does have the Telefunken diamond on the bottom of the tube. My question deals with the degree of closure for the lower tuning portion of the tube. My old EMM801 would close fully when first turned on and tuned but then would open a little as the tuner warmed up. With the new EMM801, maximum closure for both moderate and strong signals leaves the space between the two innermost vertical lines open, about 1/16th of an inch. The "stereo" indicator on top closes fully with a stereo signal. So, how should a brand-new EMM801 operate? I guess with the new tube, optimal tuning is a little easier to see when there isn't full closure. So, how is this thing supposed to work?
Bill
Bill