Seeking Valves

[Nowhere-Man]

There was some confusion about the valve line up.
I have looked at the data sheet for the N78.
http://www.r-type.org/exhib/aaa0341.htm
I have worked out the value for the resistor and come up with a figure of 150 to 180 ohms. the voltage here should be between 5 and 6 volts.
This resistor should be connected to p1n 2.
Pin 1 is G1 and should be close to 0 volts and no more than 0.5 volts.
The capacitor on pin 1 must be replaced if the voltage is more than 0.5 volts as this will make the anode volts low and cause the valve to get too hot.
The old resistor has indeed been hot.

The resistor I changed specifically is R13. You can see it if you go to Radio Workshop and click on the GEC BC5432 schematic. It was the only resistor that visually looked a bit off. On removal it had blisters and gunge. It measured 160 Ohms. That may have been the original value and may have been used in cases where the N78 replaced the KT61?

I think I can check some of the voltages you outline and make sure the rest of the resistors are rated correctly. I seem to recall I did check the grid stopper and that was fine. I should check R10 again which should be 330 K.

The capacitors ought to be find as they're all brand new. I tend to use the red Wima radials but I extend the short leads with sleeved, thin, copper wire.

Another problem I keep finding is dates. Last night I found the date was 1950 for this radio but originally I thought it was forties.

Anyway, I'll follow up on your suggestions and try to let you know what the voltages are relating to the grid. I'm also now thinking I ought to consider dramatically reducing the series resistance I put in the HT line. I was going to remove the 1 K and insert a 500 Ohm but now I think maybe I'll just parallel the 500 Ohm across the 1 K. That will give around the 300 and something range.As I said, I uprated my capacitors and the Wimas are all at 1200 volts max. Plus I have more high voltage caps across the silicon diodes.

Today my soldering iron packed in. It simply wouldn't heat. I just bought a new 30 Watt unit. I need to tidy up my soldering around the rectifier as at this experimental stage I have HT wire just 2 inches from chassis!!

P.S. Last night I was reading other people have had issues with the HT smoothing cans on this set. They are often replaced or bypassed with a new one. Mine seems a bit suspect to me as it doesn't seem to hold any charge once switched off.