Author Topic: Output Issues On CP4500

April 10, 2022, 06:02:34 AM
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forcemusicgroup

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Ive gotten great readings all the way up to step 4 on PCB Board 1 - TP13 does not fluctuate from -1.8v to +2.8v it remains constant while adjusting the make up gain.

The value remains constant at 2.87v

Please advise.

April 11, 2022, 11:56:21 AM
Reply #1

JPK

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it remains constant while adjusting the make up gain.
Normal. TP13 should vary with the threshold knob, not the makeup.
JPK

April 12, 2022, 04:26:25 PM
Reply #2

forcemusicgroup

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my mistake... the threshold. remains constant. ive emailed close detailed pictures in your email for further review

April 12, 2022, 04:27:28 PM
Reply #3

forcemusicgroup

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April 13, 2022, 01:27:48 AM
Reply #4

forcemusicgroup

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Stopping at Step 5 these are the results 

tp4 - 0.0058 to 0.217
tp5 - 0.0 @-15   2.51@+15

tp11 - 0.0@-15
         0.0 @+15

tp12   0.0@ -15
          0.0@+15

April 13, 2022, 10:01:38 AM
Reply #5

JPK

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Conditions of step 4.
Check that you get the THRESHOLD command voltage on R95-left pin. It should go from -12 to +12V when moving THRESHOLD.
If OK, please report the DC volts on all the pins of U21.
JPK

April 13, 2022, 11:17:58 AM
Reply #6

JPK

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From your photos, I can see that you have misplaced a THAT 1246 in U7. It should be a THAT1646 here.
You probably also have an issue in U11 (I cannot see the ref on the picture).
This may have destroyed the IC's. Check if they are getting hot.
JPK

April 14, 2022, 01:37:25 AM
Reply #7

forcemusicgroup

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Yes they are getting Hot. You can smell heat if that makes sense...

April 14, 2022, 09:22:59 AM
Reply #8

JPK

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You will need to replace them.
JPK

April 26, 2022, 03:39:41 AM
Reply #9

forcemusicgroup

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Conditions of step 4.
Check that you get the THRESHOLD command voltage on R95-left pin. It should go from -12 to +12V when moving THRESHOLD.
If OK, please report the DC volts on all the pins of U21.
r95 pin isnt reading -12 to +12..... more like 4VAC going CCW and CW

April 26, 2022, 09:59:14 PM
Reply #10

forcemusicgroup

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That chips have been replaced as well please advise @JDK

April 27, 2022, 08:16:39 AM
Reply #11

JPK

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r95 pin isnt reading -12 to +12..... more like 4VAC going CCW and CW
We are looking for DC volts here. You must set your DMM to DC.
JPK

April 27, 2022, 02:33:56 PM
Reply #12

forcemusicgroup

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ok I have it +15 gives me -11.86 vdc
@ -15 gives me +12.03vdc


April 27, 2022, 02:39:05 PM
Reply #13

forcemusicgroup

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U21 pins from top left side down
pin 1 -.007
pin 2 -.007
pin 3 -.007
pin 4 - -16.27
pin 5 - +15.36
pin 6 - +2.884
pin 7 - 0.0
pin 8 - 0.00


April 28, 2022, 04:54:31 PM
Reply #14

forcemusicgroup

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Please advise @jpk

April 30, 2022, 09:12:35 AM
Reply #15

JPK

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Check the value and reflow the solder joints of R95 to R99 and U21.
If nothing works, try swapping U21 with another OPA2134 from channel 2.
JPK

April 30, 2022, 05:15:10 PM
Reply #16

forcemusicgroup

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Checked the of the resistors. all seem to be what is required. Swapped the OPA chip and got the same result and numbers. Please advise....

May 02, 2022, 04:59:41 PM
Reply #17

JPK

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Do do still confirm TP13 doesn't change FROM 2.9V when turning THRESHOLD ?
Check the continuity between R95-right and R96-right.
If OK, you will need to send us your unit for fixing.
JPK

May 02, 2022, 05:12:14 PM
Reply #18

forcemusicgroup

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Tp13 does change with threshold is turn... from 1.8vdc to 2.8vdc

May 02, 2022, 05:13:44 PM
Reply #19

forcemusicgroup

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Correction -1.8vdc to 2.8vdc

May 02, 2022, 05:34:06 PM
Reply #20

JPK

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Valeurs normales.
Quel est le problème maintenant?
JPK

May 02, 2022, 05:43:12 PM
Reply #21

forcemusicgroup

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May 02, 2022, 05:56:17 PM
Reply #22

forcemusicgroup

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I can't get the levels on the channels to balance... the meter does jump. 

May 02, 2022, 06:24:35 PM
Reply #23

JPK

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English?? Plz
Sorry!

You need too go again through the voltage tests here.
JPK

May 02, 2022, 08:01:49 PM
Reply #24

forcemusicgroup

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All voltage checks are fine at this point. Channel 2 is .5 - 1.5 db off. I've moved the trims and nothing changes.