UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Leon Crampin · 14th Jan 2021, 12:09 pm

The cathode of this valve when used in a short superhet will be well above chassis potential to give the high value of AGC delay needed in a low gain set. EBL31s are scarce in their genuine octal based versions, and re-based EBL1s won't fit some sets such as the A22.

I would make or obtain a 1:1 heater transformer to supply this valve and fit (say) a 100k resistor between heater and cathode. Zapping an otherwise good valve is too risky.

Leon.

14th Jan 2021, 12:09 pm	#2
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: EBL31 Cathode to Heater Short The cathode of this valve when used in a short superhet will be well above chassis potential to give the high value of AGC delay needed in a low gain set. EBL31s are scarce in their genuine octal based versions, and re-based EBL1s won't fit some sets such as the A22. I would make or obtain a 1:1 heater transformer to supply this valve and fit (say) a 100k resistor between heater and cathode. Zapping an otherwise good valve is too risky. Leon.