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Audio and Video Talk
Valves / Vacuum Tubes
Quad II trouble
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<blockquote data-quote="Maestro" data-source="post: 398750" data-attributes="member: 1686"><p>Charles, initial testing revealed the voltages around L1 to be quite out of whack. My voltage input was set to 220V. I measured 235V at the mains last night, so I set the input to 240V.</p><p></p><p>What a good difference! I now get the following readings:</p><p></p><p>On the amp that is eating valves, I get the following:</p><p></p><p>L1 331.2V, 336.6V</p><p>C2 113.5V, 220mV</p><p>C3 130.3V, 205mV</p><p></p><p>On the amp that is giving no trouble right now (with rebuilt OPT):</p><p></p><p>L1 328.8V, 333.3V</p><p>C2 131.5V, 240mV</p><p>C3 105.7V, 250mV</p><p></p><p>Ampdog, thank you for that detailed reply. I will reply myself in more details later, but in short I have 10W resistors fitted at R21, mounted as high as possible from the choke. C5 is very old, but on order along with the other parts. I have ordered the parts to both do an original bias, or dual bias resistor mod. I will measure the voltage at the EF86's as suggested later.</p><p></p><p>Thank you so much to all of you for all the helpful answers so far.</p><p></p><p>Paul</p></blockquote><p></p>
[QUOTE="Maestro, post: 398750, member: 1686"] Charles, initial testing revealed the voltages around L1 to be quite out of whack. My voltage input was set to 220V. I measured 235V at the mains last night, so I set the input to 240V. What a good difference! I now get the following readings: On the amp that is eating valves, I get the following: L1 331.2V, 336.6V C2 113.5V, 220mV C3 130.3V, 205mV On the amp that is giving no trouble right now (with rebuilt OPT): L1 328.8V, 333.3V C2 131.5V, 240mV C3 105.7V, 250mV Ampdog, thank you for that detailed reply. I will reply myself in more details later, but in short I have 10W resistors fitted at R21, mounted as high as possible from the choke. C5 is very old, but on order along with the other parts. I have ordered the parts to both do an original bias, or dual bias resistor mod. I will measure the voltage at the EF86's as suggested later. Thank you so much to all of you for all the helpful answers so far. Paul [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Quad II trouble
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