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DIY For Audio
Radford STA25 HT current?
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<blockquote data-quote="Family_Dog" data-source="post: 981498" data-attributes="member: 82"><p>Something is terribly wrong if a 20w resistor pops. What value is it? Do you make use of a valve rectifier or diodes - I'm guessing diodes if the resistor is a modification.</p><p></p><p>I do not have a schematic of this amplifier but the specs should probably be much the same as for the Mullard 5-20, no doubt the unit upon which this unit is based. The Mullard 5-20 draws something like 70mA per EL34 valve, so 140mA in total per channel. HT voltage at the Anode of each EL34 is 430v, make sure you are not going higher than this is ufins diodes, which have a far lower voltage drop than the GZ34.</p><p></p><p>Also check the coupling caps (0.47uF?) for DC leakage, throw them out in any case if they have not been changed. Replace with same value capaccitance but I would suggest 600v DC. Replace the cathode electrolytic caps as well.</p><p></p><p>The EL30 anodes should NOT glow cherry red when switched on, but a purple glow within the valve is healthy.</p><p></p><p></p><p>-F_D</p></blockquote><p></p>
[QUOTE="Family_Dog, post: 981498, member: 82"] Something is terribly wrong if a 20w resistor pops. What value is it? Do you make use of a valve rectifier or diodes - I'm guessing diodes if the resistor is a modification. I do not have a schematic of this amplifier but the specs should probably be much the same as for the Mullard 5-20, no doubt the unit upon which this unit is based. The Mullard 5-20 draws something like 70mA per EL34 valve, so 140mA in total per channel. HT voltage at the Anode of each EL34 is 430v, make sure you are not going higher than this is ufins diodes, which have a far lower voltage drop than the GZ34. Also check the coupling caps (0.47uF?) for DC leakage, throw them out in any case if they have not been changed. Replace with same value capaccitance but I would suggest 600v DC. Replace the cathode electrolytic caps as well. The EL30 anodes should NOT glow cherry red when switched on, but a purple glow within the valve is healthy. -F_D [/QUOTE]
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Radford STA25 HT current?
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