Improving old TV sets.

[Geordie McBoyne]

Here's another TV set that needs attention, the circuit design is fine but just look at that mains dropper!  Now there's some real dodgy repair work.                It goes without saying that the mains dropper resistor in this GEC BT311 needs replacement.   We know there is absolutely no chance of finding an exact replacement. However, I believe I've found a dropper resistor that might well serve as a replacement.   It is slightly longer than the original component so hopefully no metal bashing is needed to fit it in position.    The original values were: from left to right, 77, 38, 66, 66 ohms for the valve heaters and the HT sections are 17 and 32 ohms.    The replacement dropper resistor values are not too far away from the original, being 60, 33, 70 and 63 ohms for the heaters and 20, 19 and 15 ohms for the HT supply.    Last two HT sections will add up to 34ohms, so that's near enough for the last HT section of the original component.  Also, the heaters section are not too far out either.  The BT311 has and extra common IF amplifier stage so the slightly lower total heater dropper resistance will compensate for the additional valve in the heater chain.
The set is blowing the mains input fuse after the valves warm up so that's something else that will need looking at.

Geordie McBoyne.