Author Topic: Unable to level match on Channel 2, voltage issues on channel 1

May 19, 2022, 06:01:19 am
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Hillie

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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 Checks
Channel 1
Step.....ConditionsResult
1.1Mix = 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



1.2Step 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!



1.3Step 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



1.4Input 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



1.5Input 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



1.6input 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



1.7input 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





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!

May 19, 2022, 05:18:03 pm
Reply #1

JPK

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Your values for channel 1 are all good.
The variations from our values are caused by supply voltages differences and are irrelevant.

TP7 with 0V input signal showed 10
If this is DC you probably have a bad solder joint around U16.
JPK

May 19, 2022, 07:00:56 pm
Reply #2

Hillie

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Oh crapola, I interpreted 1.6 TP4 at a much lower value. Yes, ch1 does indeed look OK.

I'll go over the solder joints again, thanks! If I have an update, I'll update the topic.

May 19, 2022, 07:44:37 pm
Reply #3

Hillie

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Reflowed joints at and around U16, no luck with level matching yet. So I went to Channel 2 for the voltage checks:


Channel 2

Step.....ConditionsResult
2.1Mix = 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,
  • V-  =-15 to -16VDC),
  • +12V = +11.1 to +12.9VDC,
  • -12V  = -11.1 to -12.9VDC

On channel 2 board:
V+: 16.26V
V-: -16.42V

On channel 1 board:
+12V: 11.93V
-12V: -12.24V



2.2Step 1 conditions plus:
Input signal = 0V
Threshold on +15
Makeup on 0
TP6, TP7, TP8, TP9 = 0VDC

TP6: -0.000V
TP7: 11.06V       <-- Still problematic
TP8: 0.000V
TP9: 0.000V



2.3input signal = 3VAC
Threshold on +15
Makeup on 0
Signal level (VAC) on
  • TP6=1.5VAC,
  • TP7=1.5VAC,
  • TP8=1.5VAC,
  • TP9=0.06VAC
DC voltage (VDC) on
  • pin 1 of U16 (white dot) = 0V.

TP6: 1.514VAC
TP7: 1.090VAC   <-- Off here as well
TP8: 1.518VAC
TP9: 0.0525VAC (52.5mVAC) (seems to slowly move back and forth between 52.1mVAC and 52.5 to 52.7mVAC over the course of seconds)
U16 pin 1: -0.001VDC



2.4input signal = 3VAC
Threshold on -15
Makeup on +20
Signal level (VAC) on
  • TP6=1.5VAC,
  • TP7=0.4VAC,
  • TP8=1.5VAC,
  • TP9=0.2VAC
DC voltage (VDC) on
  • pin 1 of U16 (white dot) = +0.2V

TP6: 1.515VAC
TP7: 0.1798VAC (179.8mVAC)   <-- Off again
TP8: 1.518VAC
TP9: 0.1903VAC (190.3mVAC)
U16 pin 1: 0.064VDC    <-- Off as well


I can reflow once more, although I expect limited effect. A new U16/OPA2134?


May 20, 2022, 08:41:11 pm
Reply #4

Hillie

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Redid all the solder joints again, cleaned up, no changes.

May 22, 2022, 09:16:14 pm
Reply #5

forcemusicgroup

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May 23, 2022, 08:28:42 am
Reply #6

JPK

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Please report the DC voltages on all the pins of U16, against 0V with conditions 2.2.

JPK

May 23, 2022, 08:29:17 pm
Reply #7

Hillie

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Inputs disconnected.

U16
pin 1: 0.000V
pin 2: 0.000V
pin 3: 0.000V
pin 4: -16.42V
pin 5: 0.000V
pin 6: 0.000V
pin 7: 9.3V (varies slightly from 9.25 to 9.33)
pin 8: 16.26V

TP7 shows the same as pin 7, obviously.

Thanks in advance!
« Last Edit: May 23, 2022, 09:44:03 pm by Hillie »

May 24, 2022, 12:14:40 pm
Reply #8

JPK

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U16 looks OK.
The issue must be coming from before:
Look for bad solder joints or solder bridges on R75 to R82.
Have you go the pre-soldered SMD VCA's or the SIP VCA's?
Check that the VCA's are all in the right direction.
If SIP, check the the VCA's are properly inserted in the sockets.
Check the DC voltage on the VCA's:
pin2, pin3, pin6 : 0V
pin4 : near 0V
pin7 : +16V
Can you report the DC voltage on the 4 pin1 and pin5 of the 4 VCA's?
JPK

May 25, 2022, 06:52:06 am
Reply #9

Hillie

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R75 through R82 all look good, no bridges. Resoldered them just in case, plus the isopropyl bath & scrub.

VCAs are SMD, orientation the same on all 4 and mirrors channel 1, so that seems to check out ok.

2.2 conditions, IN button engaged.

TP7 11.20V (does the resoldering and cleaning do something here?)

Checked U12, U13, U14 and U15:
pin 2, 3, 6: 0V on all devices
pin 4: 0V on all devices.
pin 7: 16.26V on all devices

U12:
pin 1: -0.004V
pin 5: -2.821V

U13:
pin 1: -0.002V
pin 5: -2.812V

U14:
pin 1: -0.005V
pin 5: -2.827V

U15:
pin 1: -0.728V
pin 5: -2.896V

U15 seems to differ from the others, especially pin 1.

May 25, 2022, 06:26:58 pm
Reply #10

Hillie

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Measurements above are of course after inspection, resolder, IPA soak and scrub bath and re-inspection.

May 26, 2022, 08:09:57 am
Reply #11

JPK

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There may be an issue with U15.
Check that all the pin are correctly soldered.
Do you feel confident trying to replace it or would you rather send us the card?
In both cases please contact us here.
JPK

May 26, 2022, 07:08:18 pm
Reply #12

Hillie

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Just reflowed all soldering connections on U15, no change in behaviour. (My mistake: I never reflowed any of the existing SMD joints earlier)

I'm comfortable replacing it myself. If you want I can order through Mouser or Digikey, if that makes it easier. Can one mix & match the SIP with SMD, or is it better to get an SMD replacement?

I'll reach out through the site!


@everybody else: I'll update this topic once it's all resolved, so it might help folks in case they have similar issues.

May 27, 2022, 11:28:34 am
Reply #13

JPK

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We will send you a new part, hoping that was the problem.
JPK

June 16, 2022, 02:55:02 am
Reply #14

Hillie

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Just got the part in the mail. Desoldered the old one, installed the new one and at first glance things seem much better: with 2.2 conditions TP7 shows 0.004V. I'll clean up everything and do a proper evaluation and setup later.

June 19, 2022, 08:48:05 pm
Reply #15

Hillie

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Part mounted, voltages seemed OK and I was able to level match everything and complete the setup. Thanks JP for the support!

June 20, 2022, 03:32:19 pm
Reply #16

JPK

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