I am having trouble at step 6 of the setup.
Turning the output pot does not change the gain at all.
I am using the XT500 to power the MU524 for setup.
IN pot @ max
OUT pot @ min
REC pot @ max
All Push buttons @ UP
Jumper JMP1: removed
Tube side pins reading at 6.17V after startup. Tube glows.
+16 Pin reading at 15.44V.
-16 Pin reading at -15.43V.
B+ reading at 45.4V.
Meter lights up when bypass switch to IN
Turn bypass switch to center (off).
Sending 1VAC to Input to pins 8 and 10 on XT500.
Reading 0.97V at pins 2 and 4 on XT500.
Turn bypass switch to IN.
Output rises to 3.21VAC.
Turn up output potentiometer.
No change in output, remains at 3.21VAC.
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IN pot @ max
OUT pot @ min
REC pot @ max
Bypass toggle @IN
All Push buttons @UP
Input signal: Sinus 1kHz, 1VAC
Jumper JMP1: removed
Results:
TP1 = 29.9VDC, 1.18VAC
TP2 = 29.9VDC, 1.29VAC
TP3 = 1.58VAC
TP4 = 1.6VAC
Output (pins 2 and 4) = 3.2VAC
--
Changed conditions:
Jumper JMP1: on 1-2
Input signal: Sinus 1kHz, 0.3VAC
OUT pot @ max (note that there was no change in signal when turning output pot)
TP3: 0.26 VAC
TP4: 0.26 VAC <-- appears that the trouble is around U1.2
TP5: 2.65 VAC <-- a bit lower than expected 2.9 VAC
TP6: -2.22VDC <-- also off from target -3.5VDC.
Output: 0.5VAC <-- very low output
Meter: shows -3dB
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I have checked the components around U1.2 (R15, R16, R17, C10, C11).
Potentiometer values are correct. The input pot appears to work.
Since TP4 and TP6 are both near U1, I tried swapping two of the OPA2134s but got the same results.
