UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Regentone A133 HT smoothing capacitors, V4 cathode resistor

space_charged · 21st Sep 2019, 12:35 am

I'll look at the wiring on the EL41 base to see if any n/c pins are being used as tagstrip - good thought. I've seen that done before. Floating them might help but really the EL41 looks a mess! Its obviously been "hammered"! Nasty brown deposits on the inside of the glass and some silvery deposit on the glass at the base where the pins come out. Looking at photos of new ones, they don't have either of these "features". Only place I've seen worse hammered valves is TV line output valves. Some of them work fine, but then the function of a line output valve is ON or OFF and as little in between as possible!

I've already put a 100K across the existing (680K) grid leak resistor.It helps and the cathode current does decrease. I've got it down to 36mA so just within spec. The grid is now down to about 0.5V.

A new valve or two are on order and I'm fairly sure that will sort the problem out. I'll increase the cathode bias resistor value, as discussed here earlier, so prolong the life of the new valve.

Been spray varnishing the case this afternoon. It looks very nice indeed. Needs a rub down now and some more spraying tomorrow - oops, later today.

21st Sep 2019, 12:35 am	#23
space_charged Hexode Join Date: Dec 2014 Location: West Midlands, UK. Posts: 315	Re: Regentone A133 HT smoothing capacitors, V4 cathode resistor I'll look at the wiring on the EL41 base to see if any n/c pins are being used as tagstrip - good thought. I've seen that done before. Floating them might help but really the EL41 looks a mess! Its obviously been "hammered"! Nasty brown deposits on the inside of the glass and some silvery deposit on the glass at the base where the pins come out. Looking at photos of new ones, they don't have either of these "features". Only place I've seen worse hammered valves is TV line output valves. Some of them work fine, but then the function of a line output valve is ON or OFF and as little in between as possible! I've already put a 100K across the existing (680K) grid leak resistor.It helps and the cathode current does decrease. I've got it down to 36mA so just within spec. The grid is now down to about 0.5V. A new valve or two are on order and I'm fairly sure that will sort the problem out. I'll increase the cathode bias resistor value, as discussed here earlier, so prolong the life of the new valve. Been spray varnishing the case this afternoon. It looks very nice indeed. Needs a rub down now and some more spraying tomorrow - oops, later today.