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#26 pre amp
#26 pre amp
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Old 21st March 2013, 04:54 PM   #2781
merlin el mago is offline merlin el mago
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Channel right plate 174V
Channel left plate 160V
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Old 21st March 2013, 05:01 PM   #2782
stajo is offline stajo  Sweden
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#26 pre amp
Go for 20 k. Where we were yesterday. We'll get into the channel differences later

Last edited by stajo; 21st March 2013 at 05:03 PM.
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Old 21st March 2013, 05:15 PM   #2783
merlin el mago is offline merlin el mago
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Last filter R 20K channel right plate 156,6V
Last filter R 15K channel left plate 150,9V
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Old 21st March 2013, 05:25 PM   #2784
stajo is offline stajo  Sweden
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#26 pre amp
Ok. Seems both channels circuits are ok. Now we found the problem, the grid was floating. Always a learning.

Now, the difference might be tube differences, lets measure your current again. Measure B+, over OPTs, 100 R if you want and over 20/15k resistors.

After that, you can plug in scope and measure ripple before and after 20/15k resistors. That can give guidance on how to best drop that voltage without rising the impedance.

Try also what you started with. Some squarewaves thru the circuit.

Another lession learned: Dont ask whats wrong when your circuit doesnt follow posted schematic. We could have found that much quicker. Right?
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Old 21st March 2013, 05:27 PM   #2785
merlin el mago is offline merlin el mago
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The grid floating, the cathode resistor don't grounded, etc I'm a complet disaster, thank you so much for your kind support and patient with me.
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Old 21st March 2013, 05:28 PM   #2786
stajo is offline stajo  Sweden
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#26 pre amp
My pleasure
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Old 21st March 2013, 05:32 PM   #2787
massimo is offline massimo  Italy
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Quote:
Originally Posted by merlin el mago View Post
The grid floating, the cathode resistor don't grounded, etc I'm a complet disaster, thank you so much for your kind support and patient with me.

Sursum corda Pope Francis would say....
(Lift up your hearts)
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Old 21st March 2013, 05:37 PM   #2788
merlin el mago is offline merlin el mago
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Both tubes measurements
Attached Images
File Type: jpg felipe 26 measurement left channel.jpg (141.3 KB, 254 views)
File Type: jpg felipe 26 measurement right channel.jpg (141.6 KB, 241 views)
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Old 21st March 2013, 05:40 PM   #2789
merlin el mago is offline merlin el mago
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Now is time to do some scope measurements with calm.
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Old 21st March 2013, 05:41 PM   #2790
iko is offline iko  Canada
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#26 pre amp
Your right channel idle current is 1.8mA? Either something is wrong with the circuit, or the tube is old. Exchange tubes between and measure again. Also, show the measured voltage between grid and ground.
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