01-08-2012, 02:15 PM
I did some more playing around with the set this afternoon. The 'noise' seems to be the result of bad valve socket connections. After some jiggling of the valves the noise goes away completely. I seem to have reception on all three bands which is nice.
So, there remains the issue of the dropper. I'm doubtful that a resistive solution will ever be good enough (from a heat dissipation perspective in so small a cab) so I'm going to have a go at the capacitive version. I've put the data into the (Paul Stenning) spreadsheet tool and come up with the following:
Input voltage - 110V
Freq - 50Hz
Heater voltage - 70V (actual value measured when set is warm)
Heater current - 0.3A (not measured but I suppose I should!)
Surge Limiter Drop - 10V
Result:
Dropper Cap - 10.68uF
Surge Limit Resistor - 33 Ohms / 3 Watt
I've found a source of motor run caps and a 10uF one is the largest value that just fits into the large (electrolytic) can.
I'll order up the cap but let me know if I've missed something crucial here.
Cheers, John
So, there remains the issue of the dropper. I'm doubtful that a resistive solution will ever be good enough (from a heat dissipation perspective in so small a cab) so I'm going to have a go at the capacitive version. I've put the data into the (Paul Stenning) spreadsheet tool and come up with the following:
Input voltage - 110V
Freq - 50Hz
Heater voltage - 70V (actual value measured when set is warm)
Heater current - 0.3A (not measured but I suppose I should!)
Surge Limiter Drop - 10V
Result:
Dropper Cap - 10.68uF
Surge Limit Resistor - 33 Ohms / 3 Watt
I've found a source of motor run caps and a 10uF one is the largest value that just fits into the large (electrolytic) can.
I'll order up the cap but let me know if I've missed something crucial here.
Cheers, John
Time flies like an arrow, fruitflies like a banana!
