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Blues Junior sounds muffled
Blues Junior sounds muffled
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Old 2nd February 2018, 12:49 PM   #1
opauly is offline opauly
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Default Blues Junior sounds muffled

Hello! My Blues Junior (green board) sounds muffled/distorted even with low gain. Tubes are OK (tested with a tube tester and swapped with good ones). Bias seems to be fine. Checked resistors, caps, speaker, and seems to be everything fine. I am getting crazy! Any ideas?
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Old 2nd February 2018, 01:32 PM   #2
turk 182 is online now turk 182  Canada
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these amps have input jacks that are directly soldered to the pc board, if there has been any mechanical stress from a jack cord pull or it's been knocked over on it's face with a cord plugged in it's quite likely it's developed cracked solder joints.
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Old 2nd February 2018, 02:19 PM   #3
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Check the Anode load resistors on the ECC83s. R3 (100k), R10 (100k), R17 (91k) and R19 (100k).
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Old 2nd February 2018, 02:28 PM   #4
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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They are off pins 1 & 6 of the ECC83s. The new model uses different indent numbers but the values are the same.
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Old 21st February 2018, 02:05 PM   #5
opauly is offline opauly
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I already tested R3 (100k), R10 (100k), R17 (91k) and R19 (100k) but they seem to be OK. Also tried replacing input and output 1/4 jacks, but the same result.
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Old 21st February 2018, 02:59 PM   #6
Malcolm Irving is offline Malcolm Irving  United Kingdom
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I wonder if the speaker could be rubbing or something like that. Can you try into a different speaker?
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Old 21st February 2018, 05:39 PM   #7
opauly is offline opauly
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Yes, already tested a different speaker and the ugly distortion is still there.
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Old 22nd February 2018, 10:28 AM   #8
dotneck335 is offline dotneck335  United States
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Try this:
Billm Audio >> Why mod your Blues Junior?
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Old 22nd February 2018, 03:49 PM   #9
alkuz1961 is offline alkuz1961
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Recently I fixed a similar issue. Just check the resistors of the second grids of the output tubes. They have very little power and often fail.
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Old 26th February 2018, 01:19 PM   #10
opauly is offline opauly
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Thanks for the hint. How do you check them? I measure continuity between each resistor terminals to check if the resistor has blown, but I am not sure if it would be better to unsolder them and measure ohms as single components. What do you think?
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