Pye VT4

[ppppenguin]

Having got some light on the screen of the first set, yesterday I thought I'd take a look at the other. First check showed an open circuit heater chain. Flurry of cold resistance checks showed what I should have found with Mk 1 eyeball in seconds. Somebody had nicked the ECL80 sound output valve. I've got plenty in the stores but I borrowed the one from the other set. Heater chain was fine. Next reform the main smoother can using bench supply. Leakage dropped to a very acceptable 0.5mA for both sections together. Disconnected leads and went to do something else. Came back to resolder connections to the cap. Assumed it had discharged itself by then. It hadn't I was clearly not having a good day.

Bring up HT on variac, sound appears immediately, line whistle audible and adjustable to something like correct frequency. No video on CRT cathode. No trace of light yet buit no signs of distress either. LOP can still on the set so can't check for sparks yet.

As a sideline, there's an interesting effect as to how different meters read AC current. I've got the variac supplying HT via a 1N4007. My true RMS Fluke 87 is in series to check current and reading around 300mA. The variac's moving iron ammeter is showing not far short of 1A. The 2 meters obviously take a very different view of the ripple current. I know I should really take the reading after the reservoir cap but it's less convenient.