1

CP4500 Stereo Bus Compressor / Re: CP4500 - No output and incorrect voltages

« on: June 10, 2025, 01:59:24 PM »

Hi JPK,

Thanks for your patience (I was on vacation).
And thank you so much for your help!!!

After checking R95 to R99 and not finding any errors, I focused on U21 (based on your suggestion). I had already swapped that one for one from the RIGHT PCB.
And, you won't believe it, BOTH OPA2134s were defective. I swapped one broken IC for another. That doesn't help, of course :-) :-)
Ordered two new ones... ZACK... everything works!
I would never have thought of it without you. Thank you so much!!!

Cheers...
Stephan

2

CP4500 Stereo Bus Compressor / Re: CP4500 - No output and incorrect voltages

« on: April 01, 2025, 11:25:56 AM »

Yes, it goes between -11.8 and +11.8 V.

3

CP4500 Stereo Bus Compressor / Re: CP4500 - No output and incorrect voltages

« on: March 29, 2025, 05:06:31 PM »

Hello JPK.

Thank you very much for your help!
And sorry for the delay... I had some personal work to do.

So I did, what you suggest.
- Re-soldered the connections on potentiometer P1 and on connections CN1a and CN1b.
- Checked whether the DC voltage from the threshold potentiometer reaches R95 (left pin): Yes, it is between +11.8 and -11.8 V.
- Re-soldered the connections on U9, U10 and R36...R40.

But unfortunately, it is still 14.9 VDC at TP4 and a constant -14.6 VDC at TP13 (as described above).

Do you have any other ideas? I would be very happy. Unfortunately, I'm not making much progress on my own.

Thank you very much!!!

Cheers...
Stephan

4

CP4500 Stereo Bus Compressor / CP4500 - No output and incorrect voltages

« on: March 06, 2025, 10:03:12 PM »

Hi everyone,

My name ist Stephan, i'm from Germany and i need your friendly help with a CP4500 problem.

I am not getting a signal at the output, obviously because I have incorrect measurements at the test points.

I did the voltages checks on Channel 1 PCB (A) first:
----------------------------------------
Step 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+ = +15.9 VDC,
V- = -15.9 VDC,
+12V = +11.8 VDC,
-12V = -11.8 VDC
Everything good.
------------------------------------------------------
Step 1.2
conditions plus:
Input signal = 0V
Threshold at +15
Makeup on 0

TP1 = 0VDC
TP2 = 0VDC
TP3 = 0VDC
TP4 = 14.9VDC !!!!
TP11 = 0VDC
TP12 = 0VDC
------------------------------------------------------
Step 1.3
conditions plus:
Input signal = 0V
Threshold at +15
Rotate Makeup from 0 to +20

TP12 goes from 0 to -2.3VDC - YES exactly!
------------------------------------------------------
1.4
Input signal = 0V
Makeup on 0
Rotate Threshold from -15 to +15

TP13: constant -14.6 VDC !!!
------------------------------------------------------

At this time I stopped measuring.
I replaced U9 and U10 but unfortunately there was no change :-(
The PCB is Revision 1.4

Can you help me with this information or do you need more information?

Many thanks in advance and best regards...
Stephan