(01-01-2017, 02:05 AM)Nowhere-Man Wrote: There are some points to note in the schematic I find interesting. As I gather C60 is the smoothing capacitor that supplies R12. Notice the HT line goes to the output transformer in series with R35. This 1K resistor was once off circuit so I can confirm the HT line directs across it. Further evidence is the huge shock I got from the cap (with the set unplugged months ago).
So this HT line heads to R12 which is 33 K. Now here's the punch line: If supply is 230 and the ECH81 anode 95 volts, R12 would drop 135 volts with the anode (triode) drawing 13 milliamps. So, oddly I get 0.013/135 = 10384 R. That's a fair way from 33 K. Or 34 K if you wish. My only explanation is the drop across the windings??
So far as I know the Mullard and Telefunken tubes are not different.
Given I'm hoping to learn as I go along I am trying to get a bit sharper with the schematic.
I like to ask myself these questions so I share my observations although I ought to be celebrating New Year. Anyway Happy New Year let's hope it's a good one.
Maybe there's something wrong with the maths, a 135 volt drop across a 33k resistor = 4mA approx., if the receiver was working to spec then current through R12 would be 3.7mA approx.....0.013/135...should be the other way round...academic anyway because I think your original current calculation is wrong.
Amongst other things, R35 is part of an impedance balancing network, one section of the output transformer being the other, those two will balance the impedance in the other leg which consists of the other section of the output transformer and the output valves anode resistance (ra).....I think, but stand to be corrected.
Lawrence.
