[Maeshiro]

After assembling I did the short circuit test, the general power check, and the bias adjust. All with the expected values.

Then I connect the XT500 extender to my Cranborne Audio 500r8. After powering on I tried 3 different mics with no success. Just little clicks when I move the switches or the main potentiometer.

I have rechecked all positions and solder points (except those relays below the input transformer) and I found some things:

1. The output transformer has a closed circuit between blue and green cables: is that normal?
2. When assembling I didn't found the C26 4n7 100 capacitor, the last film capacitor in the box was a WIMA 4700 400-, so I put this on the C26. Did I do it correctly?
3. I didn't found the C21 1n100v, so I put the supplied WIMA 1000 100-. Is this correct?
4. The C27 wasn't in the box. I bought a  100uf 25v -40 +105c: is this OK?
5. I left to the end the thermistor because it hasnt a code in the part list. And the last piece the seems to be a thermistor was a RA30 OBAO so I put this in the PTC1.
6. I read this blog and found that a lot of people talk about a troubleshooting guide with some measuring points like:
A: 2v70
B: 4v16
C: 23v
D: 13v92
E: 2v08
F: 13v33
G: 0v50
H: 1v07
I: 0
J: 4v27
K: 0v41
L: 0v15

Where I can find that troubleshooting guide?

Please help me, I'm frustrated because it's my first DIY gear but I bought the CP5176, EQ573 II and the LA502 and now I'm a little bit scared!!!

[JPK]

After powering on I tried 3 different mics with no success.
Check you didn't forget the jumper on CN1

1. The output transformer has a closed circuit between blue and green cables: is that normal?
The resistance should be 21 ohms. Do you have a short circuit with the transformer disconnected? Make sure you don't have a wire thread touching the next wire (these 2 are adjacent).

2. When assembling I didn't found the C26 4n7 100 capacitor, the last film capacitor in the box was a WIMA 4700 400-, so I put this on the C26. Did I do it correctly?
Yes correct: 1n=1000p

3. I didn't found the C21 1n100v, so I put the supplied WIMA 1000 100-. Is this correct?
Yes correct.

4. The C27 wasn't in the box. I bought a  100uf 25v -40 +105c: is this OK?
Sorry for that. Yes OK.

5. I left to the end the thermistor because it hasnt a code in the part list. And the last piece the seems to be a thermistor was a RA30 OBAO so I put this in the PTC1.
Correct.

6. Where I can find that troubleshooting guide?
This is in the forum: https://www.soundskulptor.com/forum/index.php?topic=5.msg5#msg5

[Maeshiro]

Thanks for replying Jean Pierre,

The jumper in CN1 is in place (the two right most pins).

The resistance betwen blue and green is 21 ohms. I just asking because the multimeter beebs with lower values. 

I will download thebtroubleshooting guide and post the values soon. 

Thanks in advance

[Maeshiro]

Hi Jean Pierre,

I made the troubleshooting measure:

WITH THE OUTPUT TRANSFORMER DISCONNECTED:
A: 2.53
B: 4.09
C: 22.3
D: 13.3
E: 1.99
F: 12.79
G: 0.004
H: 1.092
I: 0
J: 0.422
K: CAN'T MEASURE DISCONNECTED
L: 0.014

WITH THE OUTPUT TRANSFORMER CONNECTED:
A: 2.52
B: 4.07
C: 22.3
D: 13.2
E: 1.98
F: 12.71
G: 0.92
H: 4.08
I: 0.33
J: 3.51
K: 22.4
L: 2.9

OUTPUT TRANSFORMER RESISTANCES:
YELLOW - ORANGE: 11.7
RED - BROWN: 11,0
BLUE - GREEN: 24.9
VIOLET - BLACK: 24.4

INPUT TRANSFORMER RESISTANCES:
2 - 4: 28.4
3 - 5: 28.5
7 - 9: 137.7
8 - 10: 137.8

Still having no sound

[Maeshiro]

I have new information:

I conected the DI module and the DI works very well; the electro acoustic guitar sound amazing trough it, but the other source some times sounds (after powering off the chasis), but at extremely low volume and like a HPF applied.

[Maeshiro]

More information:


When the other source (not the DI) doesn't sound, I insert and disconnect a plug in the DI, and the other inputs start to work but without low frequencies, like a high pass filter applied and at a very low volume. Then if I move the main potentiometer or a switch, the sound almost disappear. So I need to insert and disconnect a plug to hear some sound again (after hearing a relay click). Can it be a relay problem?

I moved a little bit the bias and the same thing happened. So again with a plug insertion and disconecting the soind returns but like a hpf applied and at low volume.

[JPK]

Did you cut short the header pins which connect the input transformer to the main PCB?
If true, it looks like a bad RLY1 relay or a bad relay solder joint.
You will need to remove the input transformer:

• Remove the 4 screws on the Carnhill transformer (2 in front and 2 in the back).
• Remove solder on the 7 pads of the back daughter board and remove it. Use a desoldering pump.
• Remove solder on the 9 pads connecting the transformer in/outs on the front daughter board and remove the transformer. Be careful when removing the front daughter board not to pull the transformer front plate with it because it is not attached anymore.

[Maeshiro]

Hi Jean Pierre,

I do that last night and reinforce the solder points, but this morning before your response, I start hitting gently the relay and it works when I hit it. I will send you a video to your mail. It's funny, like a touchbar or touchscreen but a "touchrelay" jeje. ¿Do I need to replace that?

[JPK]

Bad relay or bad solder joint.

[Maeshiro]

Hi Jean Pierre,

I finally replace the relay, that was so difficult because the instructions didn't mention about solder the relay with a space between the relay and the board, so the relay was totally stuck to the board, when I finally took of the piece, the board was damage and I needed to make some bypass with little cables. Well, the preamp now works like a charm. It sounds amazing, really silky and creamy. The signal goes into my Logic Audio with a lot of gain. I compared the recording with my Millennia STT1 and the MP 573 sound much more warm and punchy.

I'm so happy with this stuff. Now I will start assembling the EQ 573, then the CP 5176 and finally the LA502.

Thanks for all Jean Pierre, it wasn't the best experience because of the relay, but the rest was really fun.

Merry christmas and a happy new year!!!