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CP4500 Stereo Bus Compressor / Re: CP4500 second channel (PCB B) low gain

« on: June 21, 2021, 08:04:17 PM »

Thank you for your answers and your time. It is finally working. The issue was the connection between PCB A and one of the XT500 extenders which was not stable, don't know why. All seems better now.

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CP4500 Stereo Bus Compressor / Re: CP4500 second channel (PCB B) low gain

« on: June 21, 2021, 01:33:46 PM »

Thank you for your answer, I have a fixe value of 0.48 VDC (same as on R65) on CN3A pins 9-10 independently of  the thresold pot moving, with no signal in.

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CP4500 Stereo Bus Compressor / Re: CP4500 second channel (PCB B) low gain

« on: June 21, 2021, 11:15:23 AM »

The PCB is revision 1.4. I'll reflow all the solders in the area you described. All seems to be in order however ( solders, component values), i'll double check this evening.

I confirm the DC voltage on R65 (left for if REV1.4) doesn't change when thresold pot is moved. I measure a fixed -0.29 VDC with 3VAC, 1kHz signal in and thresold pot turning from -15 to +15, and a fixed 0.48 VDC with no signal in and the thresold pot turning from -15 to +15.

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CP4500 Stereo Bus Compressor / Re: CP4500 second channel (PCB B) low gain

« on: June 19, 2021, 11:45:13 AM »

Thank you for your answer. I did double check my first channel measurments, because they seemed illogical to me also. So finally, the first channel seems perfectly right ( I did the measurments too late in the evening, and they were not good at all).
However, I can confirm the measurments on the second channel : everything seems right, except the TP7, TP9 and pin 1 of U16 which all have fixed, wrong values that never change.

I also checked, the connexion on the second channel doesn't affect the TP 12 and Tp 13 voltage from the channel 1 test steps 3 and 4 after I connect the channel 2. They are still ok ( about 2 % change in value when PCB B connected).

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CP4500 Stereo Bus Compressor / Re: CP4500 second channel (PCB B) low gain

« on: June 17, 2021, 09:53:05 AM »

Hello again,

What do you thin could be the cause of the TP11 voltage not following the Threshold pot ? I am a bit confused here.

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CP4500 Stereo Bus Compressor / Re: CP4500 second channel (PCB B) low gain

« on: June 16, 2021, 12:14:58 AM »

Ok, I just checked the measurments you ask, and it seems the first channel doesn't work properly after all (see my measurments in red). I got these results without the PCB B connected.

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, +16 V V-  =-15 to -16VDC),  -16V +12V = +11.1 to +12.9VDC,  +11.9V -12V  = -11.1 to -12.9VDC  -11.9 V
2	Step 1 conditions plus: Input signal = 0V Threshold on +15 Makeup on 0	TP1, TP2, TP3, TP4, TP11, TP12 = 0VDC  OVDC for all
3	Step 1 conditions plus: Input signal = 0V Threshold on +15 Rotate Makeup from 0 to +20	TP12 goes from 0 to -2.3VDC  ok, -2,3VDC
4	Input signal = 0V Makeup on 0 Rotate Threshold from -15 to +15	TP13 goes from -1.8V to +2.8VDC ok
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  0.11 VAC to 0.24 VAC TP5 goes from +0.35VDC to a negative value ok TP11 goes from 0VDC to -3.5VDC  0V to 0V TP12 goes from 0VDC to +3.5VDC  0V to 4V
6	input signal = 3VAC Threshold on +15 Makeup on 0	Signal level (VAC) on TP1=1.5VAC,  3VAC TP2=1.5VAC,  3VAC TP3=1.5VAC,  3VAC TP4=0.06VAC 0.11 VAC DC voltage (VDC) on pin 1 of U6 (white dot) = 0V. 0V
7	input signal = 3VAC Threshold on -15 Makeup on +20	Signal level (VAC) on TP1=1.5VAC,  3VAC TP2=0.4VAC,  0.5VAC TP3=1.5VAC,  3VAC TP4=0.2VAC    0.24VAC DC voltage (VDC) on TP11=-3.5VDC,    0VDC TP12=+1.2VDC,  +1.6VDC TP13=+1.7VDC    +2.1VDC

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CP4500 Stereo Bus Compressor / CP4500 second channel (PCB B) low gain

« on: June 15, 2021, 11:03:21 AM »

Hello,

I built my CP4500 kit, and the first channel is just working fine, but not the second one (PCB B). When I feed the unit with a 2VAC, 1kHZ signal, the max output level i get when the "in" control is engaged si about 1,5VAC at maximum. This level is also not affected by the "thresold" or "makeup gain" controls, contrary to the first channel.

I checked the solder and cleaned the whole PCB in an isopropyl dip since it seems to be a frequent issue. Nothing changed for now. All the ICs seem to be in the good spots and in the right directions.

Here are the results i measured  following the troubleshooting procedure .

Channel 2

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, +16VDC V-  =-15 to -16VDC),   -16VDC +12V = +11.1 to +12.9VDC, don't know  where to measure it -12V  = -11.1 to -12.9VDC  same
2	Step 1 conditions plus: Input signal = 0V Threshold on +15 Makeup on 0	TP6, TP7, TP8, TP9 = 0VDC  0VDC
3	input signal = 3VAC Threshold on +15 Makeup on 0	Signal level (VAC) on TP6=1.5VAC,  1.16VAC TP7=1.5VAC,   2.02 VAC TP8=1.5VAC,   1.16 VAC TP9=0.06VAC  1,09 VAC DC voltage (VDC) on pin 1 of U16 (white dot) = 0V.  -0.023 VDC
4	input signal = 3VAC Threshold on -15 Makeup on +20	Signal level (VAC) on TP6=1.5VAC,   1.16VAC TP7=0.4VAC,   2.02 VAC TP8=1.5VAC,   1.16 VAC TP9=0.2VAC    1.09 VAC DC voltage (VDC) on pin 1 of U16 (white dot) = +0.2V  -0.023 VDC

Thank you guys,