Uploaded February 2014 | Updated September 2026, 4 days ago
See our non-profit green energy site here: lablancinventors.org
13.56 mhz EL84 vacuum tube power supply in the design phase.
The tube outputs 5.7 watts of audio per the spec. sheet but we have had it to 18 watts before. This caused the tube to fail after 20 minutes. The input was over 23 watts of DC. The output was over 300 VAC RF. We were feeding it 400 VDC at the time as we do now.
We have not been able to figure out why it drew so much power to output 18 watts RF.
The new tube and L. C. tanks output 9.6 watts RF and draw 13 watts DC. This is within the spec. of 19.5 watts DC input.
The spec. sheet calls out max of 300 VDC on the plate, but guitar amp. makers design some of their amps to push the EL84 to 400 VDC.
The Grid tank circuit (C1 and L1) 17 turns of # 20 AWG magnet wire on a 1/2 inch ID PVC water pipe. C1 is a Johnson M style 15 pf variable air capacitor. Use an APC 18pf if needed.
radiodaze.com/category/418.aspx
A plate L. C. tank replaced the L2 and R4 parasitic filter. L2 is now 11 turns of # 20 AWG magnet wire wrapped around a FT-125-67 ferrite toroid core. amidoncorp.com/67-material-ferrite-toroids
The tank capacitor is an APC-40L (40 pf variable air capacitor). fairradio.com/catalog.php?mode=viewitem&item=972
Long term testing is under way.
See our non-profit green energy site here: lablancinventors.org
13.56 mhz EL84 vacuum tube power supply in the design phase.
The tube outputs 5.7 watts of audio per the spec. sheet but we have had it to 18 watts before. This caused the tube to fail after 20 minutes. The input was over 23 watts of DC. The output was over 300 VAC RF. We were feeding it 400 VDC at the time as we do now.
We have not been able to figure out why it drew so much power to output 18 watts RF.
The new tube and L. C. tanks output 9.6 watts RF and draw 13 watts DC. This is within the spec. of 19.5 watts DC input.
The spec. sheet calls out max of 300 VDC on the plate, but guitar amp. makers design some of their amps to push the EL84 to 400 VDC.
The Grid tank circuit (C1 and L1) 17 turns of # 20 AWG magnet wire on a 1/2 inch ID PVC water pipe. C1 is a Johnson M style 15 pf variable air capacitor. Use an APC 18pf if needed.
radiodaze.com/category/418.aspx
A plate L. C. tank replaced the L2 and R4 parasitic filter. L2 is now 11 turns of # 20 AWG magnet wire wrapped around a FT-125-67 ferrite toroid core. amidoncorp.com/67-material-ferrite-toroids
The tank capacitor is an APC-40L (40 pf variable air capacitor). fairradio.com/catalog.php?mode=viewitem&item=972
Long term testing is under way.
