Assistance with Crack Build - Resistance, Voltage, and LED issues [solved]

[beansprout]

Hello,

Thank you for creating and supporting the Bottlehead forum as I don't know where else to turn to when asking for assistance with my Bottlehead Crack build.  As a quick background, I have completed the amp wiring several days ago and have made attempts at both resistance and voltage checks.  Unfortunately, the data I have gathered is not consistent with the numerical guidelines - with respect to resistance and voltage data - found in the Crack manual.  I have provided my resistance and voltage data below with the Crack manual numerical guideline in parenthesis,


Resistance

Terminal	Resistance
1	*
2	*
3	0.2 ohms (0)
4	*
5	*
6	0.2 ohms (2.4K ohms)
7	2.94K ohms (2.9K ohms)
8	0 ohms (0 ohms)
9	2.93K ohms (2.9K ohms)
10	0.2 ohms (2.4K ohms)
12	0 ohms (0 ohms)
13	269.7K ohms (270K ohms)
14	0.4 ohms (0 ohms)
20	0.4 ohms (0 ohms)
22	0.4 ohms (0 ohms)
B3	2.94K ohms (2.9K ohms)
B6	2.94K ohms (2.9K ohms)
RCA Jacks:
Ground Lug	0.2 ohms (0 ohms)
Center Pin	White: 96.0K ohms Red: 88.0K ohms (90K ohms - 100K ohms)

NOTE: In the last step on page 22 of the manual, I extended the black wire from 4.5 inches to 5.5 inches so as to connect the two unsoldered terminals in the headphone jack (http://www.bottlehead.com/smf/index.php/topic,2946.0.html [nofollow]).

Voltage

Terminal	Voltage (VDC)
1	0 (90)
2	0 (170)
3	0 (0)
4	0 (170)
5	0 (90)
6	0 (0)
7	0 (100)
8	0 (0)
9	0 (100)
10	0 (0)
11	0 (0)
12	0 (0)
13	0 (170)
14	0 (0)
15	184 (185)
20	0 (0)
21	207.1 (206)
A1	85.3 (90)
A2	0 (0)
A3	1.55 (1.5)
A4	0 (0)
A5	0 (0)
A6	141.5 (90)
A7	0 (0)
A8	15.43 (1.5)
A9	0 (0)
B1	142 (90)
B2	160.6 (170)
B3	141 (100)
B4	85 (90)
B5	159.9 (170)
B6	104.5 (100)
B7	0 (0)
B8	0 (0)

The numbers highlighted in red are the readings that I thought didn't agree with the ones provided with the manual.  Any assistance in understanding and finding a solution to these issues is greatly appreciated!   

I've checked both vacuum tubes when the amp is powered on and both are glowing.  Initially, both LED's lit up but only one was working after my initial voltage tests.  Could I have wrecked the other LED while testing?

I've also provided images of my Bottlehead Crack build.  If you need more information, please let me know.  Thanks in advance for everyone's help!

Sincerely,
Raphael

[Mike B]

It looks like the lead is sheared off the unlit LED.

[Paul Birkeland]

When you ground those extra tabs on the headphone jack, you will make 0 Ohms at 6 and 10 in the resistance checks, so there's nothing to worry about there.

A6 and A1 connect to terminal strip terminals 1 and 5.  You can have 0V on the terminal strips and high voltage at the tube pins, I'd suggest that there's a measurement issue at work here.

The LED connected to A3 has a long lead hanging off that needs to be cut off, I wonder if the LED connecting to A8 is also touching something else?

The black wire that goes to the center post of the 9 pin socket has a long bare stretch that could hit pins A1 or A9, I would slide the jacket up a bit to prevent that from happening.

Can you recheck your measurements? 

15V at A8 means that the wire at A7 is not well connected on one end, or one of the connections of the black wire to the volume control is not well soldered.

Also, the amp will hum if the paint is not well scraped off under terminal 3.

-PB

[beansprout]

Hi Mike and PB,

Thank you for the quick and detailed replies!

@Mike

I have rechecked the non-functional LED for a sheared connection but thankfully, it's still intact.  The LED was just positioned closer to one of the terminals.  As a result, I have repositioned the LED and  uploaded an updated image showing the connection.

@PB

I will update my measurements as soon as I've followed through with your suggestions.

Thanks again,
Raphael

[beansprout]

Hello,

I'm sorry for the delayed response.  I finally got a chance to redo the recommended alterations.  As suggested, I've inspected the soldered joints in question and "reflowed" (is this the term used to reheat the solder until it liquifies and allow the solder to re-solidify?) the solder in each of these joints just in case I did a bad solder job with any of the joints.

However, the entire solder reflow process wasn't entirely perfect as the lead to the non-functioning LED attached to A8 was severed.  Thankfully, I replaced it with another HLMP-6000 LED from my Speedball upgrade kit which solves the non-functioning LED issue I initially had.  The problem now though is I am short one LED when the time comes to install the Speedball kit.  I will contact Bottlehead and hope they have spares available or can direct me to places that do sell these LED's.

I've scraped the paint from underneath Terminal 3 - thanks again for this helpful suggestion! - and have noticed no humming in my initial listening sessions with the Crack.  I've also slid the sleeve up on the black wire connected to the center post of the 9-pin socket.

The voltage readings have normalized and became consistent with the guideline figures from the Crack manual.  The numbers in blue are the numbers that have normalized when compared to my initial voltage readings.

Voltage

Terminal	Measured Voltage (VDC)	Expected Voltage
1	82.0	90
2	167.1	170
3	0	0
4	167.4	170
5	87.1	90
6	0	0
7	106.0	100
8	0	0
9	107.5	100
10	0	0
11	0	0
12	0	0
13	167.6	170
14	0	0
15	188	185
20	0	0
21	209.7	206
A1	86.6	90
A2	0	0
A3	1.55	1.5
A4	0	0
A5	0	0
A6	81.6	90
A7	0	0
A8	1.55	1.5
A9	0	0
B1	81.6	90
B2	166.4	170
B3	105.7	100
B4	86.7	90
B5	165.5	170
B6	107.1	100
B7	0	0
B8	0	0

After the voltage readings settled down.  I wasn't exactly sure with how to test the voltage of the TRS jack.  What I did was used the red probe of my multimeter to make contact with anything metallic inside the headphone jack chamber (where the jack is inserted) or the exposed metal bands located on the outside housing of the headphone jack (please see the bottom image on page 12 of the Crack manual).  The voltage reading didn't go anywhere near 9v.  If anything, it hovered around 0v.  I repeated this measurement a few times to be thorough.

If I've done anything wrong please let me know and I'll happily do these readings again.

As someone who has little to no electrical and soldering experience it was personally satisfying to build the Crack amp.  I'm looking forward to countless hours of sonic enjoyment and definitely some component tinkering and tube rolling in the future! 

THANK YOU!

Raphael

[Grainger49]

Without getting out a calculator it looks like all your voltages are within the +/- 15% that the manual allows. 

Try some music.

[beansprout]

Thanks!  My experience thus far with the Crack has been sublime!