[tilman]

Hi there!

I am stuck in the setup. Here is the problem: No signal on left channel when engaged ("In" pressed") 

To be precise: there is a very low output readable/audible 

• Right channel works fine when "In" is engaged (PCB B)  - problem must be on PCB A
• Everything on the front panel works as expected (VU meter, LED, etc.)
• Soldering and component placement double checked
• There are only minor deviations in "In case your CP4500 doesn't work as expected" measuring procedure - especially on TP 2 & TP4 when small values were expected (step 6 & 7). However, my simple DMM might not be precise enough?

Photos and measurements: https://we.tl/t-YxjaN58oQD
Thank you so much for all recommendations or tests to find the issue!

[JPK]

Try putting U17 (THAT1646 from right channel) into U7 (left channel), in case U7 is damaged.

[tilman]

Thank you for the suggestion. However, the problem remains even after exchanging U7 & U17...

[JPK]

In step 6 of the voltages tests, you said you got 1.5VAC on TP2. This means that the signal is present just before the output amp U7. 
Check the solder joints on C23, C24, C25, U7.
In the same conditions as step 6 check the AC signal level on TP2, U7-pins 4, 1, 8.

[tilman]

Great that helped me find a broken solder! I could repair it and and first channel now was easy to set up. Thank you!


However, it seem I have a second issue -now with the second channel. It is significantly louder than the first: 2 VAC on the Input and more than 3 on the output - even when IN not engaged/bypassed.


measurements: 

Channel 2, Step 3:
Signal level (VAC) on

• TP6=1.5VAC,
• TP7=1.5VAC, (2,5VAC)
• TP8=1.5VAC,
• TP9=0.06VAC (1,3VAC)

Signal level (VAC) on

• TP6=1.5VAC,
• TP7=0.4VAC, (2,5VAC)
• TP8=1.5VAC,
• TP9=0.2VAC (1,3VAC)

Any suggestion on where to start looking? I couldn't seem to find any flaw on PCB B. Could it be on PCB (c)?

Thank you so much for helping out!

[JPK]

Channel 2 steps 3 and 4:
Check if you also have any DC volts on TP7 and TP9.

What is the DC voltage (VDC) on pin 1 of U16 (white dot) in the 2 steps?

[tilman]

Channel 2 steps 3 and 4:

Check if you also have any DC volts on TP7 and TP9. --> it reads -0.02 on TP7 0.00 on TP9 for step 3&4

What is the DC voltage (VDC) on pin 1 of U16 (white dot) in the 2 steps? --> -0.02 for both steps

[JPK]

2 VAC on the Input and more than 3 on the output - even when IN not engaged/bypassed.
This sounds impossible: When bypassed, the input is directly connected to the output by a mechanical relay.

[tilman]

Ok, the tread can be closed - I solved the issue. 

It was a misunderstanding from my side: I was trying to set up the second channel with only one expander cable. Now that I simply installed it to the 500 case it work perfectly! Just minor trimming - and it works great!

So to sum up: I had a broken soldering connection which I could locate with your help JPK. Thanks again! The second issue was my work understanding.

Now I can start working with it. And I will order a next kit immediately

[JPK]

Congratulations!