Author Topic: Channel 2 has very low level after connecting in and out in the wrong way

May 27, 2022, 10:03:54 PM
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ajdewit

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Hello,

I have an issue with my CP4500. It worked perfectly after assembling it myself and I've used it successfully for a couple of months. Then after a recording session on location I re-connected the CP4500 to my audio interface (antelope orion studio), but I made a mistake by connecting the outputs of the CP4500 to outputs of my interface and inputs to inputs (all line level). That seemed to have triggered some kind of loop, (I remember a loud noise) so I assume it got quite a hot signal into the circuit. I cannot remember exactly what happened, because it was a combination of hardware and software routing that got messed up.
In any case, the 2nd channel has a much lower output now. I did some measurements and the results below are the steps that are different from what is expected. Channel 1 is working without issues, but I assume something is damaged on channel 2. Could you help out?

Step 2.3 // 3VAC input on channel 2, threshold +15, make-up gain 0:
TP6 = 322 mV
TP7 = 380 mV
TP8 = 322 mV
TP9 = 13.2 mV

VDC pin 1 U16 = 0V

Step 2.4 // 3VAC input on channel 2, threshold -15, make-up gain 20:
TP6 = 322 mV
TP7 = 105 mV
TP8 = 322 mV
TP9 = 39.7 mV

VDC pin 1 U16 = 67.4 mV


all the best,
Arjan

May 30, 2022, 08:28:17 AM
Reply #1

JPK

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Probably a damaged U17 (THAT1646).
Try putting the one from channel 1 (U7) in U17 and see if the level is back to normal.
JPK

June 01, 2022, 06:23:32 PM
Reply #2

ajdewit

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Hi JPK,

Sorry for my late response. I was away from my studio these last days.
I've tried swapping U17 for U7, but there is no difference. Can I try anything else?

kind regards,

Arjan

June 02, 2022, 04:55:32 PM
Reply #3

JPK

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JPK

June 03, 2022, 08:40:30 AM
Reply #4

ajdewit

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Hi JPK,

The CP4500 I have is a Rev. 1.3. There is no BR3 on it.

Arjan

June 03, 2022, 03:42:09 PM
Reply #5

JPK

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Try replacing, one at a time, U16, U17, U18, U20 with the IC's from channel 1 until the issue disappear.
Do the same with U19, U12 to U15.
JPK

June 04, 2022, 07:33:27 AM
Reply #6

ajdewit

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I've replaced each IC 1 by 1. Turned out to be U11 that seems to be damaged. Is there a place I can order that part?

Arjan


June 07, 2022, 10:03:03 AM
Reply #8

ajdewit

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