Crack not glowing on startup - shorted diodes? [solved]

[Paul Birkeland]

Voltages were looking perfect until terminal 6. It was always changing and I couldn't get it to stay on one number,

Your meter may wander a little bit, what numbers does it show you?  (Hint - your meter may have a mV that shows up on this terminal, which would mean that a 1 is 0.001V, which is adequately close to 0)

[adydula]

The voltages in the manual are with the tubes in the sockets. But you can check some voltages without the tubes in the sockets which what I was asking for you to try...if the tubes were not glowing, which is what you reported then I would leave them out and find out why you were not getting heater voltage to the heater pins/terminals on the sockets. Once you get the tubes to glow and heat up then you of course should have the tubes in to check the remaining voltages....

The one solder joint I thought was "in need of re-flowing was the one that went from the IEC power to one side of the primary winding of the transformer, if that wasnt solid you wouldnt get any voltage to the transformer and hence no secondary heater voltages and no glowing tubes. If you re-soldered that one then that could have been that specific issue.

Alex

[Doc B.]

if the tubes were not glowing, which is what you reported then I would leave them out and find out why you were not getting heater voltage to the heater pins/terminals on the sockets.

Actually it makes no difference if the tubes are in or out with respect to measuring whether there is voltage at the heater pins.

[adydula]

Ha! That is very true!

I was thinking that he possibly had more issues...

Its good they glow, glow is good!!

lol
Alex

[Todd]

Hey guys, great news!

I powered it on with the tubes again, gave the voltage tests another go with an alligator clip, making sure that the negative probe couldn't move, and things are looking really good.

Three questions:

1) Terminals 6 and 10 don't seem to settle on a value, it's always moving up and down, but don't seem to go beyond + or - 10, which I assume is within the 15% safe limit, right? Just wanting to be sure that the fact that it never stops moving isn't a bad sign.

I do have an mV symbol as Caucasian Backplate mentioned, but it seems like it's always on. To clarify, I'm testing DC volts.

2) Terminals A1, A6, B1, and B4, which should be 90, are getting 74-76 instead. Is this too far off?

3) And finally, would it be worthwhile to complete the headphone jack grounding mod before moving forward?

http://bottlehead.com/smf/index.php?topic=2946.0

Voltages (tubes in)
Terminal / Suggested / Actual:
1 / 75-90 / 77.6
2 / 170 / 169.7
3 / 0 / .7
4 / 170 / 170.3
5 / 75-90 / 74.9
6 / 0 / 10+-
7 / 100 / 103.2
8 / 0 / 1
9 / 100 /102
10 / 0 / 10+-
11 / 0 / 1
12 / 0 / 0
13 / 170 /170.1
14 / 0 / .1
15 / 185 / 191
20 / 0 / 1.1
21 / 206 / 212

A1 / 90 / 74.6
A2 / 0 / .6
A4 / 0 / .1
A5 / 0 / .1
A6 / 90 / 76.9
A7 / 0 / .6
A9 / 0 / .2

B1 / 90 / 76.9
B2 / 170 / 170.2
B3 / 100 / 103.2
B4 / 90 / 74.4
B5 / 170 / 170.4
B6 / 100 / 102.1
B7 / 0 / .1
B8 / 0 / .2

[Paul Birkeland]

1) Terminals 6 and 10 don't seem to settle on a value, it's always moving up and down, but don't seem to go beyond + or - 10, which I assume is within the 15% safe limit, right? Just wanting to be sure that the fact that it never stops moving isn't a bad sign.

I do have an mV symbol as Caucasian Backplate mentioned, but it seems like it's always on. To clarify, I'm testing DC volts.

If you have a 10 on your meter, and mV shows up, that's 0.010V, which is very close to 0.  If your meter has scales, and you are on the mV scale, then that will also be 10mV.

2) Terminals A1, A6, B1, and B4, which should be 90, are getting 74-76 instead. Is this too far off?

That's indicative of a stronger than normal 12AU7.

3) And finally, would it be worthwhile to complete the headphone jack grounding mod before moving forward?

Don't modify an amplifier that you aren't sure is working.

[Todd]

Holy smokes, guys! It works, and it's glorious!

Thanks so much for all of your replies. All of them were very helpful in helping me get it straightened out.

The only thing left for me to do is to pick a stain and assemble the housing.

I'll also be selling off my Fiio e09K + e17 combo and will likely be upgrading to a Schiit Modi 2 Uber for a DAC.

I was able to test the Crack using Sennheiser HD600s by connecting the Crack to the Fiio e09K + e17 combo, and from that to my PC.

I'll update the original post with my solution for any other novices stumbling across this thread looking for help, but in short, taking note of these amateur mistakes may do the trick:


• Reflow and add more solder to any of your potentially suspect looking joints. Flip the board to see if the joints look good from the other side.
• Use alligator clips so that your multimeter probes don't move--I got sparks without one.
• If you see an mV on your multimeter when testing voltages, it means milivolts, 1000 mV = 1V, so your larger looking numbers may be perfectly fine.