Sound Skulptor forums

Build help and troubleshooting => MP573 Microphone preamplifier => Topic started by: PACO on January 29, 2023, 04:34:36 PM

Title: No Input
Post by: PACO on January 29, 2023, 04:34:36 PM: Hi!

I just finished the assembly and I'm with the tests.

at point 3 I get 24.67V and 24.58 connecting the output of the transformer.

At point 4, I get 3.0V with the trim.

The problem is that I don't have output.

I have checked and got the following results:

A.2.6V
B.4.1
c. 22.6
d.13.6
e.2
f.13
G.0.9
h.4
I.0.34
J.3.4

I don't know how to measure point K, but I realize that at point L I get 0 Volts.

Can you help me?
Thank you!
Title: Re: No Input
Post by: PACO on January 30, 2023, 07:26:28 PM: Hi again Jea Pierre,

My check figures for today are very normals, I guess..

A. 2.6V
B. 4.1
C. 22.6
D. 13.6
E. 2
F. 13
G. 0.9
H. 4
I. 0.34
J. 3.4
K. ? 22.8
L. 3

But the results are the same. No input in the preamp.
Title: Re: No Input
Post by: JPK on January 31, 2023, 09:24:37 AM: I guess you already checked the usual suspects:
- Check you didn't forget the jumper on CN1,
- Check you didn't leave the polarity switch on the center position (=mute).

Try to follow the signal as described here (https://www.soundskulptor.com/forum/index.php?topic=5.0).
Title: Re: No Input
Post by: PACO on January 31, 2023, 11:36:07 AM: Thanks Jean Pierre,

Should I put off the 2 jumpers?
Title: Re: No Input
Post by: JPK on January 31, 2023, 12:08:47 PM: The jumper on CN1 must always stay in place.
The jumper on JPM3 is necessary when the DI board is not installed yet (but must be removed afterwards).
Title: Re: No Input
Post by: PACO on January 31, 2023, 12:55:27 PM: In that case, I have all correct. Jumper in CN1 in place and in JMP3 installed because the DI board is out at this moment.

Any other thing I could check?
Title: Re: No Input
Post by: PACO on January 31, 2023, 07:35:43 PM: Jean Pierre,

I am trying to test in the next way, but probably wrong:

I use Reaper and I insert the preamp in a track with "Reainsert". The problem is there is no return signal. (with other modules everything is OK). By the way, DI doesn't work either.

I put some pics:

With a MIDAS Compressor:

(https://i.imgur.com/Xx1DReb.png) (https://i.imgur.com/rJEY4mh.jpg)

With the MP573

(https://i.imgur.com/J35Sval.png)
Title: Re: No Input
Post by: JPK on February 01, 2023, 09:16:56 AM: Did you try to follow the signal as described here (https://www.soundskulptor.com/forum/index.php?topic=5.0)?
Title: Re: No Input
Post by: LKL on February 01, 2023, 05:19:58 PM: Quote from: PACO on January 31, 2023, 07:35:43 PM
Jean Pierre,

I am trying to test in the next way, but probably wrong:

I use Reaper and I insert the preamp in a track with "Reainsert". The problem is there is no return signal. (with other modules everything is OK). By the way, DI doesn't work either.

I put some pics:

With a MIDAS Compressor:

(https://i.imgur.com/Xx1DReb.png) (https://i.imgur.com/rJEY4mh.jpg)

With the MP573

(https://i.imgur.com/J35Sval.png)
I don't mean to interfere, but since I use Reaper (and Reainsert), I thought I would comment. Your hardware return looks incorrect. Your hardware return should be the analog Return on your interface. For instance, mine is Analog 1 using the Audient ID22. However, I know you can name these whatever you want, and maybe you just have a different naming structure. Hope this is helpful, and if not, please ignore. Best of luck
Title: Re: No Input
Post by: PACO on February 01, 2023, 08:34:23 PM: Hi,

Yes, I renamed the I/O. The routing is: The preamp is in Slot 1 of my MIDAS L10. So, OUT 1 of the MIDAS goes to IN 1 of the Interface, and OUT 1 of the Interface goes to INPUT 1 of the MIDAS. That's the same routing of my other modules.

In Reaper, I create a track and insert a Reainsert Plugin. As I show in the pic, there's no return signal. Is like doesn't detect the module.

I am trying to do the test Jean Pierre asks in the post before, but I'm not sure how to so it. Sorry about that!

Cheers!
Title: Re: No Input
Post by: PACO on February 02, 2023, 07:34:39 AM: Quote from: JPK on February 01, 2023, 09:16:56 AM
Did you try to follow the signal as described here (https://www.soundskulptor.com/forum/index.php?topic=5.0)?
Title: Re: No Input
Post by: JPK on February 02, 2023, 09:32:34 AM: You must send a constant sine signal to the input.
Then measure the signal with your DMM in AC volts mode in different points of the circuit.
You can control the correctness of your measurements by varying the source amplitude. The meter reading should follow the variations.
Title: Re: No Input
Post by: PACO on February 02, 2023, 10:24:18 AM: Jean Pierre, I have detected i have solded wrong R28. It could be the cause? Should I have to desinstall the input transformer?
Title: Re: No Input
Post by: JPK on February 02, 2023, 05:47:06 PM: Yes it may be the cause. What value did you put there?
It is not necessary to remove the transformer to replace this resistor. You can cut out the wrong one and solder directly the proper one to the pads.
Title: Re: No Input
Post by: PACO on February 02, 2023, 09:37:58 PM: I put 4K7
Title: Re: No Input
Post by: PACO on February 03, 2023, 06:45:51 AM: Great! I replace the resistor and now works fine!

Now, I have issues with DI

There's no sound. The relay works, I hear the clic connecting it. No sound when I move the jumper.
Title: Re: No Input
Post by: JPK on February 03, 2023, 04:45:03 PM: Check that you placed the transistor 2SK170 in the good A position and direction.
Check your solder joints.
Title: Re: No Input
Post by: PACO on February 03, 2023, 06:57:38 PM: You were right! Transistor in B position :-[

Now tested and working!

Thank you so mucho for your big support, Jean Pierre!