[Ewaja]

I recently finished my MP573 unfortunately without succes.

After testing (TP2 with V+) I measured 23.9V (on 200V scale)

The same 23.9V was also measured with output transformer connected.

I thought it would be close enough to test the module, unfortunately no input signal.

When I went through the troubleshoot checklist i measured the points
A till L

The points were all good except the following points:
D= 12.83V (within 10% range but still)
H=1.71V
I= couldn't measure within power supply
J =couldn't measure within power supply
K= don't know how to measure
L=0.0

What can i do to fix it?
Does this mean i have some weak or missed solders?
Does this mean some components are not placed correctly?

I hope you can help me out!

[Ewaja]

I soldered about every solder again to make sure everyrhing was good, even though i did not see something strange.
I plugged it into my power supply and for 5 seconds my mic input came through.
I was so happy that i immediatly took it out and screw everything together, to eventually find out: no input again..

I really don't know whats wrong. I measured again and again, but  after point G, i'm measuring way different then it should (I guess).

A=2.62
B=4.11
c=22.0
D=12.81
E=2.02
F=12.20
G= 0.82
H= 1.71
I= 1.10
J= 1.80
K=23.10
L=1.31


hope you can help me out.

[JPK]

The issue is around Q4...Q6, R40...R47, C24...C29.
Check the value, direction and solder joints on these components.
Check the connections of the output transformer (no short circuits between adjacent wires).
Check the output transformer coils resistances (unplugged: Yellow-Orange : 7.6 ohms, Red-Brown : 6.4 ohms, Blue-Green : 21 ohms, Violet-Black : 21 ohms)

[Ewaja]

I checked the values as much as i know how to do, nothing strange.
I resoldered al the  old points again, a few times the TP2 with V+ dropped till 13.8V.
After trying a lot I got the main voltage on 23.9V again.
But the measurepoints after point "G" still get the same volt values.

No shorts at the transformer and the ohms were all correct.

Measurements:
Yellow-Orange : 7.8 ohms,
Red-Brown : 6.6 ohms,
Blue-Green : 21.3 ohms,
Violet-Black : 21.1 ohms

I do get some output now. The mic is coming through and the mp573 knobs are working.
Unfortunately it does not amp enough.

My audient has +60db built-in pre amp.
The MP573 has +70db (60 + 10) but does not get half as loud as my audient.

[JPK]

I- 1.10
Your value in point I: is it negative or positive ?

[Ewaja]

That was a little mistake the '-' should have been a '='. It is positive. Any suggestions about what else i can do?

[JPK]

There is something really wrong in the DC values in H, I, J, L.

I repeat: The issue is around Q4...Q6, R40...R47, C24...C29.
Check the value, direction and solder joints on these components.

With the output transformer disconnected, what DC values do you get on G, H, I and on the left side of R42?

[Ewaja]

The values are as described.
The directions are right.
and the solder joints are checked like 50 times and reheated a couple of times to make sure the solder flows deep enough.

with output transformer disconected 
G- jumps around between 0.00 and at max 0.06 that does not look good.
H=0.33
I=0.33
J=0.35
Left side of R42 stays at 1

what does this mean?

[JPK]

Left side of R42 stays at 1
1Volt DC ?

This point should be 24V.
Please measure the DC voltage of both sides of R24 against 0V.
Also measure the DC voltage on TP2 against 0V (should be -9V).

[Ewaja]

excuses me i used the 20V scale so nothing happened on the MM.. 
The left side of R42 says 23.9V
Both sides of R24 with OV = -14.9V (- on R24 L/R and + on OV)
TP2 against OV is 8.98V (- on TP2 and + on OV)

[JPK]

These values are all good.
I start being short of ideas, maybe it's time for you to send us the unit for a check?