1

CP4500 Stereo Bus Compressor / VU Meter Jumps to 5 when there is power to my lunchbox, weird board measurements

« on: November 20, 2021, 09:42:07 AM »

Hello,

I am having a bit of a weird issue, i was trying to re measure and troubleshoot my CP4500 when I noticed it started this weird behavior with the meter sticking to 5, until the power is taken out from the unit or case. 

I still took some measurements up until step 4 which were looking good right before the VU started sticking around the 5 position, now all of the measurements from TP1-12 are wrong 

Can you help guide me as to what i should look at here? 

Channel 1

Step.....	Conditions	Result
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, 0.73 VDC V-  =-15 to -16VDC) ,-15.97 VDC +12V = +11.1 to +12.9VDC,??? -12V  = -11.1 to -12.9VDC -11.78 VDC
2	Step 1 conditions plus: Input signal = 0V Threshold on +15 Makeup on 0	TP1, TP2, TP3, TP4, TP11, TP12 = 0VDC TP1: 2.27VDC  TP2: 1.28VDC Tp3 1.52 VDC TP4 1.39 VDC TP11 1.50 VDC TP12 1.50 VDC
3	Step 1 conditions plus: Input signal = 0V Threshold on +15 Rotate Makeup from 0 to +20	TP12 goes from 0 to -2.3VDC 1.50 - 1.50
4	Input signal = 0V Makeup on 0 Rotate Threshold from -15 to +15	TP13 goes from -1.8V to +2.8VDC 1.07 -1.50

Thank you for your help 

2

CP4500 Stereo Bus Compressor / Cant Level Match Channel 2 - Measured Channel 1 voltages and some were off

« on: August 06, 2021, 01:03:14 AM »

Hi, 

Having some issues with my CP4500, hopefully can get some assistance on where to check, its a bit over my head. 

I got to the channel 2 calibration and all was seeming to work fine, all throughout calibrating channel 1. The behavior of each knob was normal and functioning as expected. 


When i got to adjusting the trimmer on Channel 2 i had a difference of several dBs beyond the range of the trimmer. I measured all of the voltages from the guide for channel 1 and 2. Here are the results 

Any help would be greatly appreciated: 

Channel 1

Step.....	Conditions	Result
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,15.97 V-  =-15 to -16VDC),-15.94 +12V = +11.1 to +12.9VDC,11.93 -12V  = -11.1 to -12.9VDC -11.77
2	Step 1 conditions plus: Input signal = 0V Threshold on +15 Makeup on 0	TP1, TP2, TP3, TP4, TP11, TP12 = 0VDC  TP11: 0.01 VDC
3	Step 1 conditions plus: Input signal = 0V Threshold on +15 Rotate Makeup from 0 to +20	TP12 goes from 0 to -2.3VDC 0 to -2.3VDC
4	Input signal = 0V Makeup on 0 Rotate Threshold from -15 to +15	TP13 goes from -1.8V to +2.8VDC -1.76 to 2.84
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 0 VDC  TP5 goes from +0.35VDC to a negative value +0.34 to -1.10 VDC TP11 goes from 0VDC to -3.5VDC 0.01 to -3.46 VDC TP12 goes from 0VDC to +3.5VDC 0 to 3.5 VDC
6	input signal = 3VAC Threshold on +15 Makeup on 0	Signal level (VAC) on TP1=1.5VAC, 1.53 TP2=1.5VAC, 1.73 TP3=1.5VAC,1.535 TP4=0.06VAC0.57 DC voltage (VDC) on pin 1 of U6 (white dot) = 0V. 0.0
7	input signal = 3VAC Threshold on -15 Makeup on +20	Signal level (VAC) on TP1=1.5VAC,1.53 TP2=0.4VAC, .423 TP3=1.5VAC, 1.53 TP4=0.2VAC .184 DC voltage (VDC) on TP11=-3.5VDC, -3.48 TP12=+1.2VDC, 1.18 TP13=+1.7VDC  1.73

Thanks

-KJ