Completed the build, reflowed all boards, did the isopropyl alcohol bath & scrub. Channel 1 worked OK, got the in/bypass level matching trim, sidechain/distortion trim, meter readout all working OK. Onwards to channel 2, there weren't enough turns in the trim pot to get the in/bypass level matching to work, so I did a quick measurement and TP7 with 0V input signal showed 10.something V. That's well over 0, so I took off the channel 2 board and started the checklist. My rack is a Capi VPR511 and the PSU seems a hair hot on the 16V lines, but it hasn't been an issue with anything so far (which explains step 1.1 slightly high/low +/- 16V values).
Readouts are with a Fluke 87.
The checklist:
Voltages ChecksChannel 1Step..... | Conditions | Result |
1.1 | Mix = 100% Ratio = 10 Attack = 0.1 Release =1.2 IN button pressed HF lift, 100Hz, 50Hz buttons released Negative meter probe on 0V | - V+ =+15 to +16VDC, 16.23V
- V- =-15 to -16VDC), -16.39V
- +12V = +11.1 to +12.9VDC, 11.93V
- -12V = -11.1 to -12.9VDC -12.25V
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1.2 | Step 1 conditions plus: Input signal = 0V Threshold on +15 Makeup on 0 | TP1, TP2, TP3, TP4, TP11, TP12 = 0VDC TP1: -0.000V <- meter indicated minus, but still all zeroes TP2: 0.000V TP3: 0.000V TP4: 0.000V TP11: 0.006V <- Small deviation from zero! TP12: -0.005V <- Small deviation from zero! |
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1.3 | Step 1 conditions plus: Input signal = 0V Threshold on +15 Rotate Makeup from 0 to +20 | TP12 goes from 0 to -2.3VDC
TP12 went from the aforementioned -0.005V to -2.347V DC |
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1.4 | Input signal = 0V Makeup on 0 Rotate Threshold from -15 to +15 | TP13 goes from -1.8V to +2.8VDC
TP13 went from -1.801V to +2.978V DC |
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1.5 | Input signal = 3VAC (measured between output XLR pins 2&3 with compressor bypassed) Makeup on 0 Threshold goes from +15 to -15 | - TP4 goes from 0.060VAC to 0.190VAC
- TP5 goes from +0.35VDC to a negative value
- TP11 goes from 0VDC to -3.5VDC
- TP12 goes from 0VDC to +3.5VDC
3.019VAC was closest I could get on input TP4: 0.0528VAC (52.8mVAC) to 0.1902VAC (190.2mVAC) TP5: 0.348VDC to -1.203VDC TP11: 0.006VDC to -3.477DC TP12: -0x004VDC to +3.482VDC |
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1.6 | input signal = 3VAC Threshold on +15 Makeup on 0 | Signal level (VAC) on
- TP1=1.5VAC,
- TP2=1.5VAC,
- TP3=1.5VAC,
- TP4=0.06VAC
DC voltage (VDC) on
- pin 1 of U6 (white dot) = 0V.
Same input voltage (3.019VAC) TP1: 1.513VAC TP2: 1.530VAC TP3: 1.516VAC TP4: 52.7mVAC <-- OFF by quite a bit! Looking at the schematic, I hope U9 and U10 are OK. U6 pin 1: -0.000VDC
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1.7 | input signal = 3VAC Threshold on -15 Makeup on +20 | Signal level (VAC) on
- TP1=1.5VAC,
- TP2=0.4VAC,
- TP3=1.5VAC,
- TP4=0.2VAC
DC voltage (VDC) on
- TP11=-3.5VDC,
- TP12=+1.2VDC,
- TP13=+1.7VDC
TP1: 1.512VAC TP2: 0.443VAC TP3: 1.516VAC TP4: 0.1902VAC (190.2mVAC) TP11: -3.477VDC TP12: 1.143VDC TP13: 1.697VDC |
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Didn't do channel 2 measurements, as there are some issues in channel 1 already. Biggest issue in step 1.6, minor deviations in 1.2. What's your take on the rack power (+/- 16V lines)?
Any guidance is VERY welcome!