[kotrag]

Hi guys, cheers to everyone...and I need some help here...

I built two CP554 modules, did the power voltages check in step 4 and the 3V Bias adjust in step 5.
I am stucked at step 6, with the 1kHz sine signal - can't get any voltage reading between pin 2 and 3 on the XLR of the output, or between TP1 or TP2 against OV. No change if I turn the Gain Knob. 

When the unit is bypassed ( no green light) I read 1VAC at the output (XLR), but no voltage between TP1,TP2 and OV. 

Checked all the joints and solderings many times, orientation of components, tested the diodes and the visually the capacitors, traced the PCB 1 and 3 and can't find anything suspicious...nothing touches the board. I can't see why the two units have the same problem...I checked the colour wires and the joints of the output transformers J1 J2 connections, everything passed with continuity tester. Can't find any short circuits.
I red all the topics 3 or 4 times and can't get any idea how to proceed.

Any help will be highly appreciated!
Thanks in advance!

Best Regards!

 

[JPK]

You can increase the input voltage to 4VAC to make measurements easier. You will need to remove the chassis plate.
Check that you receive the input signal voltage on the secondary of T1 between pins 7 & 10 (? 0.9 VAC)
Check that you receive the input signal voltage on the primary of T2 between pins 2 & 5 (? 0.1 VAC)
Check that you receive the input signal voltage on the secondary of T2 between pins 7 & 10 (? 0.19 VAC)
Check that you receive the input signal voltage on TP1 against 0V (? 4.7 VAC)
You may keep the output transformer disconnected for all this test.
Check that 

[kotrag]

Hi Jean Pierre,

Thank you so much for your support!

I did the tests as you proposed:

Check that you receive the input signal voltage on the secondary of T1 between pins 7 & 10 (? 0.9 VAC) - Unit OFF - Yes, Unit On - No

Check that you receive the input signal voltage on the primary of T2 between pins 2 & 5 (? 0.1 VAC) Unit OFF - Yes 0.07-08VAC, Unit On - No



Check that you receive the input signal voltage on the secondary of T2 between pins 7 & 10 (? 0.19 VAC) Unit On - Yes 0.13VAC, Unit On - No


Check that you receive the input signal voltage on TP1 against 0V (? 4.7 VAC) - No - with or without bypass engaged.

Thanks so much again!

[kotrag]

I was wandering about the unit, does it have to be switched on for these tests, or bypassed in order to get these values?

What could be the possible reason for not receiving the 4.7VAC between TP1 and 0V? 

Thanks!

[JPK]

The unit was supposed to be ON for the measurements.
Can you measure the DC voltages, against 0V, on :
- U1 pin 14 (0VDC),
- U1 pin 7 (0VDC),
- U1 pin 8 (0VDC),
- Q2 collector (the pin closest to U1) (? 4 VDC),
- Q4 collector (the pin closest to C6) (? 4 VDC).

[kotrag]

Hi JPK  I did the test:

- U1 pin 14 (0VDC), - Yes
- U1 pin 7 (0VDC), - Yes
- U1 pin 8 (0VDC), - Yes
- Q2 collector (the pin closest to U1) (? 4 VDC), Yes - 3.49 VDC
- Q4 collector (the pin closest to C6) (? 4 VDC), Yes - 3.55 VDC



thank you so much!

[JPK]

All this is correct.
Did you check the ususal suspects ?

[kotrag]

Hi JPK,

thanks for your input - yes I did all of that many times , but didn't make it to point 9, I am still stuck on point 6. 

I suppose that firstly I have to figure out why I can't get any input signal (voltage (VAC) on TP1 against 0V, and why I can't get these other voltages between pins 7&10 T1,T2 and 2&5 on T2 from the input signal with Unit On.

All the components that have directions are checked and OK, capacitors, diodes. I am not sure about the ICs and transistors, but at least they are positioned as they should on the schematic.

[JPK]

I suppose that firstly I have to figure out why I can't get any input signal
Absolutely.
I am not sure about the ICs and transistors
The part name is marked on the devices. You must check them.

[kotrag]

Hi JPK, still struggling here...

when the SW2 switch is pressed (Unit On) it shuts down the input signal on  the primary of TR1 ( pins 2,5) ( there is no voltage there:0.00V). When it is on position Up (Unit Off - bypass) the signal comes in - 4 VAC (sine wave). The switch is positioned correctly and the RLY1 is working ( clicks). Is that normal to not have input signal on pins 2&5 in these conditions? 

Thanks in advance.
Konstantin

[JPK]

Not normal at all!

Can you remove the relay RLY1 in case it is defective?
Without RLY1 you won't get an output on the XLR but you should have a signal on TP1, TP2.

[kotrag]

Hi,

thanks, I was thinking of doing it or replacing it, but since I made two units which have the exact problem, I thought that probably the problem is not in the relays, because the chances that both of them to be defective is minimal. I also see that they are working ( clicking) and rerouting the signal from the BP+ and BP- outs. I tested them with continuity of the multimeter and the middle pins (2,3 and 8,9) ring as they should. The 3,4 and 7,8 don't ring as it should.

So I decided to check the SW2 switch. It is positioned exactly as it should be and the lower two pins on the right ( looking from the back of the PCB3 ) are engaging the LD1.

LD1 is positioned as it should with the cathode (-) up and lights on. After the check of these circumstances I gave up the idea that I flipped the SW2, Is there any chance that the SW2 is flipped?

Should I anyway remove the relay and do the test without it?

Cheers!
Konstantin.

[JPK]

I agree if you have the same issue on both units.
The relay switches the module XLR output between XLR input and compressor output.
Check if you don't have a short circuit on the output, between hot and cold or beween any phase and ground.

[kotrag]

Just checked, everything is normal on the XLR. On the extension cable too.

With unit bypassed Out- and In- are connected and the same thing with Out+ and In+.

With Unit On- they are disconnected as it should.

No shorts between pins 1,2,3 on the XLR or on the Extension cable on the pins either with unit on or bypassed.

I left the T3 disconnected for now but it does not have to be, because I am trying to find what is going on on the primary on the T1, (pins 2&5) and why the input signal disappears with SW2 engaged.

I checked with continuity test that with unit on and off the connection between In - and pin 5 and In+ and pin 2 on T1 stays, so probably something is happening with the ground... 

[kotrag]

Ok, finally I found the problem (s)

I decided to push softly flom left to right, up and down T2 and saw that the VAC measurements on the output began to change rapidly and going to 0VAC again after releasing it.

The pins of PCB4 which "holds" the T2 need to be pressed and sodered very well from the BOTH sides of the border to make full contact. The weight of TR2 "pulls" down the transformer and if the unit is placed horizontally and meanwhile the weight make some pins to lose contact from time to time, then strange things are happening. After two EQP501 and two EQ573, these are the first units that I assemble that have such kind of PCB to PCB mounting and I consider it to myself as a week point of the design, but anyway.

I resoldered the pins very well, while pressing the two boards one to another. Meanwhile I found that while checking the PCB1 components with continuity test sometimes the connections between pins 2,5 of the T2 and negative pin on C8 and C9 and between C11 and pin 7 of J2A didn't ring although that visually and on previous checks were fine. Resoldered them and now both units passed point6 of the setup :).

Now I am stucked in point 13 on the setup on the treshold setting. After applying 6.15VAC on the input, I got about 4.5VAC on the output and the TR3 does not make any difference. I am going to check the connections between TR3 and the other parts that are connected to it, hopefully find the fault...

Anyway I feel positive now that I went 8 positions of the setup ahead.

Cheers! 

[JPK]

If the threshold control (SW4) doesn't reacts then you should check the solder joints on R56, R44, C31, J3a & J3b pin14 & pin12, SW4.

[kotrag]

Hi JPK



Everything works now . Finally did it!



Except one thing of one of the units. I can't manage to set the meter on -8dB with the TR6 in step 12. I rechecked all of the connections between Meter - J4,a,b, and J3, alb,  but no reaction on the meter with TR6 - it is stucked on - 2dB. Other than that I did the whole setup of the threshold.



I checked all of the connections between the meter - R93, D17,D16, R92,R91,R89,R90.R88, U7, U6.1 and TR6 as seen on the schematic but I can't get any result.



Also checked U6.2 connections on the

schematic.



EDIT:

Well after a couple of days of trying to find the problem I simply put the two CP554 close to one another with one being placed horizontally and the other vertical so that I could plug the PCB6 connector from the working CP554 to the other and saw that the meter went to the same position and wasn't reacting with the TR6 in the exact same way. So mounted back the original meter connector and swapped the U6 op amp, borrowing it from the working one and bingo...everything worked!

I now will have to find one OPA2134 to replace the fault one and getting this big time job done!

Well now I have two working CP554's and the sound is rocking! Although the this was the hardest project of all. I enjoyed it and learned a lot by not giving up the fight and trying to diagnose everything by myself although I am not so good in electronics...

I hope that if needed, this thread will be useful to another user!  

Cheers to everybody!
Konstantin.

[JPK]

Bravo !