having some crack problems

[waheey]

I'm having some issues with the Crack + Speedball kit. My voltages are way off, and there's almost no sound coming out of the left channel

I first built the crack, and the voltages we all within tolerances, and it was working fine.

With the speedball, though:

1- 80
2- 103
3- 0
4- 103
5- 75
6- 0
7- 84
8- 0
9- 73
10- 0
11- 0
12- 0
13- 103
14-
15- 147
19- 80
20- 0
21- 191

A1- 75
A2- 0
A3- 1.5
A4- 0
A5- 0
A6- 80
A7- 0
A8- 1.5
A9- 0

B1- 80
B2- 102
B3- 83
B4- 75
B5- 170
B6- 73
B7- 0
B8- 0

I also think I may have accidentally shorted the 18-20 and 18-21 rectifiers on the top side (between 20 and 21) briefly. Any ideas?

[Grainger49]

It will help if you only post those voltages that are out by more than 15%.  Also post the expected voltage to help us from having to go back and forth to the manual.

Since you suspect your rectifiers were shorted use the diode checker on your meter and see if they check out.

[waheey]

Alright, I did a little troubleshooting of my own, and I've gotten it mostly working again with the speedball.

Here are my current voltage reading discrepancies. They will read like Terminal - Reading (target)

5 - 112 (75)
9 - 130 (100)
18 - 85 (not specified)
19 - 85 (0)
20 - 0 (200)
21 - 215 (not specified)

A1 - 115 (75)
B4 - 115 (75)
B6 - 130 (100)

It's playing on both channels, but there's a pretty strong hiss in the left channel.

[Laudanum]

Im not one of the techie braniacs and beyond visual, not great at troubleshooting,  but this has come up before. It hasnt been unheard of to mix up the little transistors and resistors.  In fact, it seems pretty common.  So for starters, if you havent already, check the speedball boards, make sure you didnt mix up the little can transistors (2N2222A and 2N2907A) between the large and small boards and that orientation is correct (with a little space between them and the boards)   Make sure you installed the small 1/8 watt metal film resistors (31.6 ohm and 237 ohm)  in the correct locations (that you didnt mix those up).  Also, double check orientation of the LED's (are they all lighting up?).

[waheey]

I've double checked all the resistors, transistors, and LEDs you're talking about. They're all correct. The LEDs are all lighting up, but the ones on the little boards are really dim. All the others are pretty bright.

I reflowed all the joints in the left channel where my voltages were high, and now my voltage readings are even higher for those terminals. Terminals 3, 9, A1, B4, and B6 are now about 15V higher than they were in the last list. They actually start another 15V higher, but gradually fall to those (still high) levels.


I think the speedball manual has a mistake for the voltages of terminals 19 and 20. They should be 20 and 21. The voltages for those match the crack manual, but seem one terminal off in the speedball manual.

[magnafuzz]

There are a few sticky threads for manual corrections at the top of the Crack forum. It looks like terminal 20 should be 0V and 21 should be 206V which look ok for your measured values. Terminal 19 doesn't need to be measured.

http://www.bottlehead.com/smf/index.php/topic,1398.0.html

Sorry i can't help out with the other terminals. hopefully that will narrow the scope of your troubleshooting.

[waheey]

There are a few sticky threads for manual corrections at the top of the Crack forum. It looks like terminal 20 should be 0V and 21 should be 206V which look ok for your measured values. Terminal 19 doesn't need to be measured.

http://www.bottlehead.com/smf/index.php/topic,1398.0.html

Sorry i can't help out with the other terminals. hopefully that will narrow the scope of your troubleshooting.

Ahh, gotcha. That clears that up.

Edit: After reading up, at this point it seems like it might be a tube issue. I ordered 2 different replacements for the output tube and a replacement for the input tube. We'll see how that goes when those get here next week.

[Paul Birkeland]

After reading up, at this point it seems like it might be a tube issue. I ordered 2 different replacements for the output tube and a replacement for the input tube. We'll see how that goes when those get here next week.

You are correct, the 100+v where you would want to see 75 indicates an issue with the 12AU7 (though the LED's should glow strongly). 

Let us know if the tube swap doesn't help.  I would also hit the solder joint on the middle leg of the MJE-350 while you're waiting, along with the joint at "O" on the offending channel. 

-PB

[Grainger49]

See, this is a guy who understands the circuit well enough to say the middle leg on the MJE350. 

Paul, can you add to the question about CCS in Tech Topics?

[waheey]

Thanks for the help, guys! The tube switch resolved the issue. Now, I'm seeing normal voltages and there's no hissing in the left channel.

Sounds phenomenal too!