[hasanova]

Hi there,

The first time I was ready to fire up the the CP4500, it was with only the 1st channel in (PCB-A).
No IC's plugged in. Compressor was off.
When I turned it on, I saw a short light flash in the meter and than a super high high pitch and than C18 exploded. Was the wrong way in. First time that happened to me.

I cleaned the board and I saw that I forgot to pull out U7 (THAT 1646) before turning on for the first time. I put a new capacitor in C18. Checked all solder joint and re-flowed some of them. Cleaned again all the flux.

Measured all the voltages without any IC's in:
• V+ =+15 to +16VDC, +16.04
• V-  =-15 to -16VDC), -16.13
• +12V = +11.1 to +12.9VDC, +11.89
• -12V  = -11.1 to -12.9VDC -11.84


Now I'm going through the setup guide:

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, +16.04  • V-  =-15 to -16VDC), -16.13 • +12V = +11.1 to +12.9VDC, +11.89 • -12V  = -11.1 to -12.9VDC -11.84

2

Step 1 conditions plus: Input signal = 0V Threshold on +15 Makeup on 0

TP1, TP2, TP3, TP4, TP11, TP12 = 0VDC TP1= 0V, TP2= 0V, TP3= 0V, TP4= +15.6V, TP11= -15.17V, TP12= +14.26V (all VDC)

I'm stuck in the this step of the setup. Only TP1, TP2 and TP3 gave 0VDC.
I don't know if anything else got damaged when C18 exploded? Or IC U7 got damaged? I don't know.

Also: When I turn compressor on (IN pressed), the meter light turns on and the meter hits MAX, way passed 20dB compression.

Can someone point me in the right direction?

Cheers!

EDIT:
From datasheet OPA2134:
1 out A
2 -in A
3 +in A
4 V-
5 +in B
6 -in B
7 out B
8 V+

From the CP4500 schematic:

TP4 --> IC U10 (OPA2134) pin7 = out B
R40 = measured in circuit = 33k?

TP11 --> IC U21 (OPA2134) pin1 & pin2 = out A & -in A

TP12 --> IC U22 (OPA2134) pin2 & pin1 = -in A & out A --> ACV1

Why do I get DC voltage on TP4, TP11 en TP12 when input signal = 0V?

[JPK]

What is your PCB revision number?
Can you report the DC voltages (against 0V) on the 8 pins of U9?

[hasanova]

What is your PCB revision number? CP4500 REV1.3

Can you report the DC voltages (against 0V) on the 8 pins of U9?
DC Voltages on U9 pins:
1   0.00
2   0.00
3   +0.75
4   0.00
5   -2.88
6   0.00
7   +16.04
8   +15.61

[JPK]

What is the DC voltage on TP5, with no input signal and threshold at +15?
Check the resistors value and solder joints of R36, R37.
Is TP4 going to 0 if you remove U9?
If yes try putting the other 2180C in U9 and check if it changes.
If not try putting another OPA2134 in U10 and check if it changes.

[hasanova]

What is the DC voltage on TP5, with no input signal and threshold at +15? +16.03VDC
Check the resistors value and solder joints of R36, R37. R36 = 815?, R37 = 47?
Is TP4 going to 0 if you remove U9? No
If yes try putting the other 2180C in U9 and check if it changes.
If not try putting another OPA2134 in U10 and check if it changes. No change, still +15.6VDC

[JPK]

Please report the DC voltages on the 8 pins of U10.

[hasanova]

Please report the DC voltages on the 8 pins of U10.

DC Voltages on U10 pins:
1  0.00
2  +15.56
3  +15.59
4  +16.04
5  +15.52
6  +15.51
7  0.00
8  -16.13


EDIT:
I'm an idiot... U10 holder was wrong way in... sorry! I think I fried two OPA2134 IC's I put in U10, maybe the THAT 2180C is still okay(?).... I never had these hick-ups before, and I've built a lot of modules... I'm getting old...

Correct orientation: VDC on U10 pins:
1  -0.161
2  0.0
3  0.0
4  -16.09
5  0.0
6  0.0
7  0.0
8  +16.06


STEP 2: all voltages are 0V!
Thank you for your time, I will continue from here

[hasanova]

I'm stuck again... @step 5.

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   +0.003VAC TP5 goes from +0.35VDC to a negative value   +0.396VDC TP11 goes from 0VDC to -3.5VDC   +0.003VDC TP12 goes from 0VDC to +3.5VDC   -0.004VDC

The voltages I measured don't change when rotating Threshold between -15 & +15.

[hasanova]

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  YES TP5 goes from +0.35VDC to a negative value  YES TP11 goes from 0VDC to -3.5VDC  YES TP12 goes from 0VDC to +3.5VDC  YES

I replaced U1, U6, U7, U9 and U10 with the ones from channel 2. For channel 1, I now have the correct measurements in step5 and all the remaining steps. I cannot use the same IC's for setting up channel 2, because there have to be IC's in channel 1, right?

So I guess I have to determine which ones of the IC's I swapped are not working:
- U1 = THAT1246
- U6 = OPA2134
- U7 = THAT1646
- U9 = THAT2189C
- U10 = OPA2134

How do I know that in a "safe" way without ruining anything? Or should I just buy new IC's and be done with it?

Thnx!

[JPK]

because there have to be IC's in channel 1, right?
Yes right.

Insert the doubtful IC's, one by one on the working board and check rapidly the +/-15V and if the board is working.
If one of the power rail goes down, turn off rapidly.

[hasanova]

Took some time (months1!) for me to source the parts I wanted to replace:

- U1 = THAT1246
- U6 = OPA2134
- U7 = THAT1646
- U9 = THAT2180C
- U10 = OPA2134


I was able to setup the 2nd PCB. I used two extenders which made my setup easier, highly recommend it. It took me back and fort between the two channels to get set both trimmers for unity gain. I realized I had to wait several minutes for the voltages to settle.
Now everything is balance and I put some audio through it. I like it, for a very nice and subtle, but noticeable effect.

Thank you!

[JPK]

Congratulations!