Resistance check failed [resolved]

[oltmb]

I assembled the Beepre and started the resistance check.

There is a problem with the resistance check for T10. The resistance does not start low but starts at around 500 KOhm and then starts dropping.
During the voltage check, the leds of CS4  A board do not light up.

The same is for the resistance at T15. The measured value is 330 KOhm. However the leds of CS4 B board do light up.

I have checked a connections and examined the solder joints.

Where should I look for a possible problem. Can the 220uF capacitor at U9 and U10 be faulty?

 

[Paul Birkeland]

Provided you don't get really low resistance at terminal 10, you can ignore that resistance issue.

Telling us that LED's don't light up lets us know that your BeePre isn't working.  Posting your voltages will help tell us why.

-PB

 

[oltmb]

Thank you.
I checked the adjacent circuitry and just re-soldered the joints and that worked. The unit is now working well, but with some hum in one channel. I will upgrade the unit first with the BeeQuiet that I ordered and after that I can do the fine tuning. I am very pleased with the result as I have the limited edition of the BeePre.

 

[Paul Birkeland]

No, please finish debugging your build before installing any other upgrades, otherwise you may have to remove them for us to help you debug the stock build.

-PB

 

[oltmb]

Here are the voltage measurements for my 230 Volt unit. The values between brackets are negative voltages (how can that be?)
First colum is the listed value and last column is measured value. Variance means unstable value.

    List Measured
1 5V 4.94
2 90-110V 92.8
3 0V 0.1 mV
4 9.85V 9.83
5 0V 7 mV
6 146V +/- 1% 145.9
7 0V variance
8 0V 0
9 0V 0
10 186V 175.3
11 146V +/- 1% 146
12 0V variance
13 0V 0
14 0V 0
15 186V 174
16 5V 4.94
17 90-110V 94.4
18 0V 0
19 9.85V 9.77
20 0V 7.3 mV
21 0V 0
22 213V  202.5
23 0V   (6.7 mV)
24 0V   (6.7 mV)
25 213V  202.1
26 0V   0
27 0V   0
28 0V   (46 mV)
29 6.8V   6.38
30 6.8V   6.38
31 13.6V 12.8
32 0V   0
33 0V   0
34 13.6V  12.8
35 6.8V     6.39
36 6.8V     6.39
37 0V   (47.4 mV)
38 0V   0
39 0V   9
40 213V  202.2
41 0V   (10 mV)
42 0V   (10 mV)
43 213V  202.3
44 0V   0
45 0V   0
46 213V  202.2
47 N/A
48 0V 0
49 0V 0
50 N/A
51 0V 0
A1 Too risky to probe.
A2 90-110V 93.1
A3 0V         0
A4 Too risky to probe.
B1 Too risky to probe.
B2 90-110V   94.6
B3 0V           0
B4 Too risky to probe.
Terminal Voltage (DC)
C1 ,D1 N/A
C2, D2 0         (6.1 mV) (9.3 mV)
C3, D3 3.5-4.5V 3.48   4.2
C4, D4 N/A
C5, D5 N/A
C6, D6 N/A
C7, D7 147V 146         146
C8, D8 N/A
C9, D9 147V 145.6 145.7

 

[Paul Birkeland]

When you see -6.1mV, that is -0.0061V, which is plenty close to 0V in a high voltage circuit.

 

[oltmb]

I ran a sound check and noticed a buzz coming from the left channel and decided to do a complete resolder as I thought that would help. After doing the resistance check I noticed that the resistance at terminal 7 is around 270 Ohms instead of the 470K and don't know where to look for the problem. I resoldered everything around terminal 7 but that did not help.. All other resistance values are within spec. Any suggestions?

 

[Paul Birkeland]

Terminal 7 is the output of the preamp, that goes through the twisted pair to the output jacks at the back of the BeePre. If you have 270 Ohms of resistance from 7 to ground, I would check the 475K resistor connected to that terminal, as well as the build that goes from the unbalanced output jacks to the balanced output jacks.

-PB

 

[oltmb]

I did check in that direction and resolved the issue. After the voltage check I hooked it up to my system and it is playing fine. The only issue is the microphonics, but I will first do the BeeQuiet upgrade and then work on making the unit less susceptible to microphonics. Thank you for your great support!