[PACO]

Good morning Jean Pierre,

I have just to finish the EQ573II but I'm afraid there's something wrong with the assembly.

The checking figures are:

A -2,1V
B -14,6V
C -13,2V
D -11,1V
E -7,9V
F-5,6V
G  -0,7V
H -6,8V
I -13,2V
J -13,8V
K -7,9V
L -5,6V
M -6,1V
N -6,8V


I have to say that in the point A there's some sparks when I conect the O volts and the R48 resistor.

Could you guide me?

Thank you very much!

[JPK]

I have to say that in the point A there's some sparks when I conect the O volts and the R48 resistor.
Normal, A is the positive supply rail for the circuit

Check V+ test pin (against 0V) : +16V
Check V- test pin (against 0V) : -16V
Check the solder joints of R48.
Check that R46 is still conducting.

[PACO]

I have to say that in the point A there's some sparks when I conect the O volts and the R48 resistor.
Normal, A is the positive supply rail for the circuit

Check V+ test pin (against 0V) : +16V
Check V- test pin (against 0V) : -16V
Check the solder joints of R48.
Check that R46 is still conducting.

V- gives -16V but V+ is -0,7V
I have checked ans resolder R48 and R46 is not conducting

Should I replace R46 and R48?

Thanks Jean Pierre!

[JPK]

Yes you should replace them.
They were probably destroyed when you created these sparks.

[PACO]

Yes you should replace them.
They were probably destroyed when you created these sparks.

Hi Jean Pierre,
I replace the resistors and finally every the parameters seems to go fine. (Except the point G, I'm not sure what resistor I have to measure)

*Read the second column, the first one was before the replacement.

A -2,1V    13,3V
B -14,6V  -13,3V
C -13,2V  -10,5V
D -13,8V  -11,1V
E -7,9V      -2,6V
F-5,6V        3,7V
G 
H -6,8V      2,5V
I -13,2V  -10,5V
J -13,8V  -11,1V
K -7,9V      -2,6V
L -5,6V      3,7V
M -6,1V      3,1V
N -6,8V      2,5V

I have just to test it and I verify that the signal drops more than 20 dB in XLR Mode

[JPK]

Looks good ! 

[PACO]

Looks good !

Trying to trace follow the signal (100Hz at 2VAC) the results are:

TP1 0.20 VAC
TP2 0.16 VAC
TP3 1.62 VAC

Are there normals numbers? in that case, I'm not sure why en XLR mode the signal drops more than 20dB

Many thanks, JP!!

[JPK]

Not normal.
Do you also have an attenuation when the EQ is OFF ?
Check solder joints of R1 to R4, R10, R11, U1, U2.

[PACO]

Not normal.
Do you also have an attenuation when the EQ is OFF ?
Check solder joints of R1 to R4, R10, R11, U1, U2.

yes, the attenuation is always, even if the EQ is ON or OFF

I have checked the joints you told me but nothing changes

[JPK]

When bypassed the signal path is really simple: U1 receiver followed by U driver.
Check that the relays are in the correct direction.
Check you didn't swap U1 & U2.
Did you do something that could have damaged U1 or U2?

[PACO]

When bypassed the signal path is really simple: U1 receiver followed by U driver.
Check that the relays are in the correct direction.
Check you didn't swap U1 & U2.
Did you do something that could have damaged U1 or U2?

The relays are well installed and the amps also well.

I don´t know how to check how to test if they are working right

[JPK]

In bypass (OFF) mode, you should get half of the input voltage on U1 pin1 and U2 pin4.
With 2VAC you should get 1VAC.

[PACO]

In bypass (OFF) mode, you should get half of the input voltage on U1 pin1 and U2 pin4.
With 2VAC you should get 1VAC.

Hi again Jean Pierre,

Sorry for bothering you again, but this makes me mad.

The current situation is:

- In Pre Mode everything is OK. The EQ works fine with the MP576
- In XLR there's no return signal from the EQ to the DAW



So, I can't trace the signal.
I don't know if the solution is to change U1 and U2, check the reles or how to check. The only problem is that it seems that in XLR mode goes to bypass

[PACO]

JP,

Forget the last poat. Everything seems to work 100%. The problem is the slot of the lunchbox!!

Thank you for four patience!

[JPK]

Great, I was about to reply!

[PACO]

Great, I was about to reply!

I Jean Pierre,

Solving all the problems of before, now I'm testing the EQ.

The HP Filter, Low and mid Shelf seems to work properly, but I feel not with the High Shelf.

The shelving in 10K seems to be excessive (Look at the pic)



Same in the other frequencies.

Can be related with this abnormal results checking the signal?

TP1 0.20 VAC
TP2 0.16 VAC
TP3 1.62 VAC

[JPK]

Is this with the high shelf pot at min?
It doesn't look that much different from this:


Can be related with this abnormal results checking the signal?
TP1 0.20 VAC
TP2 0.16 VAC
TP3 1.62 VAC



The values with the black PCB version are (for 2VAC at the input):
TP1: 1 VAC
TP2: 1 VAC
TP3: 0.9 VAC
TP4: 0.8 VAC

Your values seem to be wrong.
Do you have an attenuation when the EQ is OFF ? There should not be any.

[PACO]

Correct! It’s at minimum. Is it normal to start to attenuate at 2K?

This numbers are with 2VAC. There’s no signal attenuation in bypass

[JPK]

Is it normal to start to attenuate at 2K?
Yes, normal.

Do you confirm TP1 0.20 VAC instead of 1VAC?
What is the AC voltage on U1 pin1? It should be the same as TP1.
And what is the AC voltage on U1 pin1 in bypass?

[PACO]

Is it normal to start to attenuate at 2K?
Yes, normal.

Do you confirm TP1 0.20 VAC instead of 1VAC?
What is the AC voltage on U1 pin1? It should be the same as TP1.
And what is the AC voltage on U1 pin1 in bypass?

Yes, TP1 is 0,20 VAC, same that U1 PIN1. in bypass, U1 PIN IS 0,985VAC (same than U2 pin4)

[JPK]

Something is pulling down the output of U1-pin1.
Look for a solder bridge on J2, J5, RLY1, RLY2.
Check that the relays are inserted in the correct direction.

[PACO]

I have checked visually the right orientation of RL1 and RL2

Also checked the joints of J2 and J5.

Checking with DMM, none of the pins has to have continuity, right?

[JPK]

No continuity except pins 3-4 on J5 which are connected.

[PACO]

I detect continuity between pins 8, 10 and 12.

Should I desolder with care and solder again?

[JPK]

This is normal, sorry.
J5 pins 8, 10, 12, 14 are connected to ground.