Thanks once again to the generosity of Forum member
David G4EBT I received an 12AT7WA which I have used to replace the "
faulty" 12AT7 - you may remember that FM was completely silent on this set.
The great news is that I now have FM - quite good reception with just a single wire connected to the A1 aerial socket. The volume is, however, quite low and I have to turn it fully round to get a decent audible signal - gave me a fright when I switched back to AM!
Here are some voltage readings for the replacement 12AT7WA with the set switched to FM and at a quiet spot on the dial (no signal): -
1. Firstly, the heater pins - across Pins 4&5 we have 0.05V AC, across Pins 4&9 and across Pins 5&9 we have 6.62V AC.
2. Secondly, we have - Pin 1:132V - Pin 6:130V - Pin 3:0.85V
I note from previous Posts/Threads on the KB-MR10 that
" ... they aren't the most sensitive of sets on VHF anyway" so I'll wait until I've rigged up a decent dipole (or Poundland dual telescopic aerial) before investigating whether or not I need to look at increasing the gain on FM somehow?
I'm only 16 miles from my local FM transmitter at Black Hill at an angle of 77 degrees from North in an Easterly direction. This transmitter is chucking out all the main BBC FM stations at 250kW and is horizontally polarised so I'm assuming that would be better for any picture rail dipole??
https://www.aerialsandtv.com/blackhilltx.html
All good news (I think?) but as usual comment and feedback welcomed.