Wrong Ohm and Voltage check with first Crack built [resolved]

[chuotcon15]

Hi all!   
First Crack built, and failed on Ohm and Voltage check.
Here is what I have on checking.

Ohm check
Terminal 1 & 2 N/A (No number reading)
Terminal 4 & 5 about 0.6 Ohm
Terminal 6, 7, 9, 10 N/A
Terminal 12 = 0 Ohm
Terminal 13 = 270 K Ohms
Terminal 14, 20, & 22 = 0 Ohm
B3 = 2990 K Ohms
B6 = 2900 K Ohms

Voltage check

Terminal 1 = Linking up from 1 -> 5 V
Terminal 2, 4, 5 = 0 V
Terminal 6 = 71
Terminal 7 = 70
Terminal 9 = 71
Terminal 10 = 71
NOTE: Terminal 6,7,9,10 are linking from 64 Volt to 72 Volt, I just pick a number.

Terminal 11, 12 = 0 Volt
Terminal = 164 V
Terminal 14 = 0 V
Terminal 15 = 184 V
Terminal 20 = 0 V
Terminal 21 = 204 V

NOTE: I have checked many times, but couldn't find a mistake, even check the connection from every connection by Ohm to make sure they were connected properly. I have removed and broken down every single part and rebuilt for 3 times, but still the same.

Note: Test with head phone. It was Ok with low volume, but if the volume went down about 75%, then having a noise
          Test with music. Sound good with  low volume, but if the volume went down about 75%, then having a noise.

Please help me to fix this Crack. Thank you!

[Paul Birkeland]

Please don't turn your Crack on until you pass the resistance checks.  The resistance checks exist to tell you whether or not you should turn your amp on, and there's no reason to attempt to listen to an amplifier that you have measured as not electrically sound.

Now, having said that, are you able to measure 3K worth of resistance between terminal 3 and terminal 7?  This resistor should be measurable by any meter, and would be a good measurement to get comfortable using your meter. 

I think you have a loose ground connection in your amplifier, most likely the connection of the two black wires on the headphone jack.

-PB

[chuotcon15]

Hi Paul!
Thanks for your help.
Yes, from Terminal 3 and 7 = 2.990K. For both almost 6 K Ohm. I rechecked for every connection, but they are good.

[chuotcon15]

Update:
I just found a loose connection and everything looks okay now, but a voltage is a bit low.

Terminal
1   75   (69)
2   170   (164)
3   0   (0)
4   170   (164)
5   75   (70)
6   0   (0)
7   100   (95)
8   0   (0)
9   100   (97)
10   0   (0)
11   0   (0)
12   0   (0)
13   170   (164)
14   0   (0)
15   185   (184)
     
20   0   (0)
21   206   (204)
     
A1   75   (70)
A2   0   (0)
A3   
A4   0   (0)
A5   0   (0)
A6   75   (68)
A7   0   (0)
A8 
A9   0   (0)
     
B1   90   (69)
B2   170   (163)
B3   100   (96)
B4   75   (71)
B5   170   (163)
B6   100   (97)
B7   0   (0)
B8   0   (0)

Are those voltages okay?
The noise still appears at 75% volume and up, but if I move the tube 12UA7, the noise is a bit change (more loud or more quiet).
What can I do to fix the noise? Thanks a lot.

[Paul Birkeland]

Update:
I just found a loose connection and everything looks okay now, but a voltage is a bit low.

Some of those voltages actually are indicative of stronger than normal tubes, so no problems there.

The noise still appears at 75% volume and up, but if I move the tube 12UA7, the noise is a bit change (more loud or more quiet).
What can I do to fix the noise?

I would recommend reading the Crack FAQ stickied post.  If you played audio into the amplifier with the level control set that high, you would risk damage from the amount of power delivered from the amplifier.  Consequently, the signal to noise ratio is still quite good, it's just that you have so much signal that you are bringing up the noise floor.

[chuotcon15]

Hi Paul! Thanks for your reply.
I just installed the Speedball, and here is the voltage check.

Terminal
1   75-90   (60)
2   170   (176)
3   0   (0)
4   170   (177)
5   75-90   (65)
6   0   (0)
7   100   (94)
8   0   (0)
9   100   (182)
10   0   (2)
11   0   (0)
12   0   (0)
13   170   (176)
14   0   (0)
15   185   (189)
     
20   0   (0)
21   206   (201)
     
Some voltages are a bit low, but Terminal 10 and 9 are so weird.
Can tell me what the trouble could be?
Also, at a minimum volume up to 20% is noise and at maximum is noise (this could be ok like you said, but at low can't be accepted).
NOTE: only right headphone works if I put on the way down to the 6.3 headphone Jack. All lights are light up.
What can I do with this? Thank you.

[Paul Birkeland]

High voltage at terminal 9 indicates perhaps a flaky solder joint on the large PC board.

-PB

[chuotcon15]

Hi Paul!
I found a loose wire on the terminal 9 and have soldered, but on the terminal 9, the voltage is 129V. Others are the same. Is that normal? Try to connected to the source and noise appears from low to max volume. The really loud noise appears at the minimum volume. What is the problem? Thanks.

Note: only right channel works.

[chuotcon15]

I just removed the wires from two small boards and replaced by two transistors, then no noise at minimum to 75% of volume, but still right channel working. So what is the cause? Thanks again.

Note: all Leds light up.

[Paul Birkeland]

Can you remeasure and repost all of your voltages?

[chuotcon15]

Hi Paul!

Here is what I test on voltages.
Note: I just re-solder for every wire on the pc boards.

Terminal
1   75-90   (60)
2   170   (162)
3   0   (0)
4   170   (162)
5   75-90   (65)
6   0   (0)
7   100   (90)
8   0   (0)
9   100   (95)
10   0   (0)
11   0   (0)
12   0   (0)
13   170   (162)
14   0   (0)
15   185   (182)
     
20   0   (0)
21   206   (201)

There is a noise on both channels from low to max volume.
Left channel more noise than right.
Note: Stock Crack work well.
Thanks for your help.

[Paul Birkeland]

Is the noise present with a source connected?

[chuotcon15]

No.
I tried without connect to source.

[Paul Birkeland]

No.
I tried without connect to source.

Open inputs will pick up whatever ambient gunk they can.  Try the amp with your source.

-PB

[chuotcon15]

The noise appears even I try with the source. I knew that because I paused the source, even trying with low volume.

Thanks for your help.