Crack 1.1 OTL Voltage Check Issue

[bozemblem]

Hi all. Appreciate the help in advance. I finished putting together the Crack 1.1 OTL Headphone Amp Kit. I'm having two issues that I'd like help with.

One, the LED attached to A9 does not light up. The other LED does light up.

The second issue some of the voltages are significantly higher than what the documentation states. I've attached some photos of the build, and the resistance tests all passed. Here are the voltages:

Contact	Measured Voltage	Expected Voltage	High/Low/Normal
1	154	50-100	High
2	168	170	Normal
3	1.1	0	Normal
4	169	170	Normal
5	76	50-100	Normal
6	1	0	Normal
7	153	90-115	High
8	1	0	Normal
9	104	90-115	Normal
10	1	0	Normal

Any pointers to where I should look would be appreciated. I traced back through the circuit and I *think* I have everything connected correctly. Thank you!

 

[Paul Birkeland]

There is no LED that goes to A9...

After you fix that, I'd watch this:

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You want maximum heat on your iron and solder with lead in it. All of those joints will need more solder/heat to flow out and work properly.

 

[bozemblem]

Thanks for the response Paul, I will improve the soldering on those joints. Regarding the LED, on page 64 of the documentation it states to attach and solder the unbanded lead to A9. Am I misreading or looking at the wrong thing? Thanks again for your help!

 

[Paul Birkeland]

I'm not sure how that has never been noticed. It needs to go to A8.

 

[Jameson]

I'll make the update in the manual tonight.

 

[bozemblem]

Thanks guys very much for your help, and for updating the manual. I've resoldered the joints and the voltage readings are stable. The LED attached to A8 still won't light up, and the one attached to A3 blinked a couple times and now won't turn on when I tried to measure the voltage across it. Are there other voltage readings that I could take to help pinpoint the problem? I've attached updated pictures.

 

[Paul Birkeland]

The solder joints I'm seeing are still not going to work. Please watch the soldering video I posted on YouTube, then you'll know what you need to do and what you need to look for in a solder joint.

(Note that this is not the solder joints on the LEDs, don't focus on those, they have low thermal mass and solder easily, but rather focus on the rest of the kit)