UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - OK need assistance or clarification of output transformer values

AdrianH · 31st Mar 2020, 9:24 pm

I know this will be a ripple on the pond to many, but to me resurrecting old and forgotten concepts (to me) is a milestone.

I have started to build my little amp and it is taking absolutely ages, working with the charts for the valves, plotting the load lines, then seeing what value resistors I need and then seeing what is the closest I have, checking wattage levels etc, then trying to build it up on strip board getting the lens out to check for shorts, etc.

The diagram I showed prior uses a supply transformer which is 250-0-250 Volts and I will be running this little amp at 150 Volts from a buck style filament and HT PSU.

Have a problem with caps, do not have any with suitable voltage ratings, all the ones I stripped out of the old cold war receiver leaked, I thought I had one which when tested was 3M4 Ohm might have been OK, but it caused an excessive anode current, which as I sit here typing this, should have seen it as it was connected to a 470K grid resistor, from 100 Volts off the first anode.

But still I am progressing slowly, the single double triode glows, the cathode and anode volts are within a few volts of calculated, so the project has started well.

Does anyone know anyone who sells kits of say 250 Volt rating capacitors from 0.022uF to 22uF, or will it be a case of individual part numbers.

Adrian

31st Mar 2020, 9:24 pm	#10
AdrianH Octode Join Date: Mar 2020 Location: Blackburn with Darwen, Lancashire, UK. Posts: 1,573	Re: OK need assistance or clarification of output transformer values I know this will be a ripple on the pond to many, but to me resurrecting old and forgotten concepts (to me) is a milestone. I have started to build my little amp and it is taking absolutely ages, working with the charts for the valves, plotting the load lines, then seeing what value resistors I need and then seeing what is the closest I have, checking wattage levels etc, then trying to build it up on strip board getting the lens out to check for shorts, etc. The diagram I showed prior uses a supply transformer which is 250-0-250 Volts and I will be running this little amp at 150 Volts from a buck style filament and HT PSU. Have a problem with caps, do not have any with suitable voltage ratings, all the ones I stripped out of the old cold war receiver leaked, I thought I had one which when tested was 3M4 Ohm might have been OK, but it caused an excessive anode current, which as I sit here typing this, should have seen it as it was connected to a 470K grid resistor, from 100 Volts off the first anode. But still I am progressing slowly, the single double triode glows, the cathode and anode volts are within a few volts of calculated, so the project has started well. Does anyone know anyone who sells kits of say 250 Volt rating capacitors from 0.022uF to 22uF, or will it be a case of individual part numbers. Adrian Attached Thumbnails