Crack with Speedball Troubleshooting

[Mstyle]

Hello everyone,

I just built the Crack and got it working. I tested it out, and everything passed inspection. I plugged in headphones and sweet music poured through them.

I then proceeded to install the Speedball kit. After installing it, I plugged in headphones and the sound had a lot of hum and sounded very distorted.

So I figured I'd better do some thorough voltage checks:

Pin 1 -- voltage much higher than spec
Pin 2 -- voltage much higher than spec
Pin 3 -- huge spark shot out and scared my poor Pug

I noticed that the LED lights on the small PC boards were not lit. Upon closer inspection, one of the MJE350's were installed facing the wrong direction (facepalm!).

So I removed it and faced it the correct way and re-soldered. Now after I fire it up, the LED lights on the small PC boards still will not light up. The LEDs on the big boards are lit, as are the LEDs on the 9-pin tube socket. Tubes are glowing just fine.

Have I possibly blown something? (the fuse is still intact). It seems I have a grounding issue? Any ideas on what to troubleshoot for. I'm scared to check voltages again because of the previous gigantic spark incident.

Please help!

[Loquah]

I'd suggest (from recent experience) double checking and possibly re-soldering the joints created during the Speedball build and install. You might just have a poor connection. Be sure that all joints have ample solder, but not too much, and that the solder joints are nice and shiny. If in doubt, re-solder.

[Grainger49]

On the PC board the solder joins the component lead to the circuit board trace.  A key to getting this done right is to be certain that the soldering iron tip is touching (heating) the component lead and the trace. 

A general statement not associated to this post directly is that solder isn't glue, it needs to bond to the metals being joined.

[Mstyle]

Thanks guys for the tips so far. I'll start by double checking all of my solder joints to see if there is anything that I missed or didn't do properly. I was in such a rush to get this project done that I may have failed to properly solder some joints.

Will keep you guys posted on the progress!

[Paul Birkeland]

No current is flowing through the C4S.  This can happen if you mix up transistors (2N2222A and 2N2907), swapping orientations, reversing LED directions, or mixing up the red wires connecting to "I" and "O".

[Mstyle]

Hey guys,

Thanks for the replies and PMs so far. Been trying unsuccessfully to figure out what is going wrong with this thing. I'm resorting to uploading pictures so that hopefully another pair of eyes can spot any errors I've made.

To recap, I had a fully functioning Crack, and then it started giving me issues when I installed the Speedball.

Here you can see that the LEDs on the tube and the big board are lit. The LEDs on the small "A" and "B" boards are not lighting:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi44.tinypic.com%2Fwlduft.jpg&hash=b55cd05f2fd0e4536e5e0ccb58edda80ad9ab471)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi41.tinypic.com%2Fd6se8.jpg&hash=541f0d8744461d2d4a0bb37ee9dcdd37754a6b09)

Connections from A Board:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi41.tinypic.com%2F25ajipk.jpg&hash=8786b6148de8ac1cea9be23f38095e71a987fa43)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi40.tinypic.com%2F351alh3.jpg&hash=d07bdcc2785436d76e9a9af33756743975690d80)

Connections from B Board:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi44.tinypic.com%2F23r49ig.jpg&hash=a9b715527679c8f0549e44de1222d6fd2c95d5f4)

Top side of A Board:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi42.tinypic.com%2F2lctg86.jpg&hash=e7a1b66bd67a9b00e88ad12230553d5d3e932f2f)

Top side of B Board:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi43.tinypic.com%2F24q1k6d.jpg&hash=dc9551fa6dd60467a42de0d8613096c6dbe7483a)

Bottom of big board:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi41.tinypic.com%2F2nvzbs8.jpg&hash=437ce404e2ed2b86caf8f973973e55b6a4a91564)

The 1U joint was registering 250V when the expected value should be 75V. So something isn't quite right there.

Any help would be appreciated!

[Paul Birkeland]

Can you double check that the 2N2222's and 2N2907's are in their correct sockets?  (Trim those leads on the TIP50's while you're in there)

Are the MJE350's facing the correct way?  The writing should face the outside of the PC boards.

[Mstyle]

Just double checked, the 2N2222's are on the big board, and the 2N2907's are on the A and B board.

Also, yep the writing is facing the outside (left) of the PC boards. The smoother side is facing the inside.

[Paul Birkeland]

The 237 Ohm and 31.6 Ohm resistors are not in the correct positions.

[Mstyle]

Holy moly you're right! Thanks so much! I'm going to swap those bad boys right now.

[Mstyle]

Thanks for the heads up, Caucasian Blackplate! Now we're getting somewhere.

Now the LEDs on the small board actually light up, but the two on the A board are very dim, and the right one on the B board is dim. The left LED on the B board (right side) is nice and bright though.

One that that did happen was that a lead from the resistor on the B board got broken, so I just reattached with solder. Probably not the smartest thing to do, but I'll order more of those resistors and replace.

Anyway, I was brave enough to do some voltage testing:

Joint) Value (Expected)
1) 106 (75)
2) 222 (170)
3) Big blue spark (0)
4) 226 (170)
5) 223 (75)
6) 0 (0)
7) 141 (100)
0 (0)
9) 219 (100)
10) 0 (0)
11) 0 (0)
12) 0 (0)
13) 227 (170)

Looks like everything is running higher than expected.

Thanks!

[Paul Birkeland]

Tell me about the big blue spark?

Do you happen to have a different 12AU7 on hand?  Having those resistors swapped, you demanded an incredible amount of current from your 12AU7, and it'd be good to know that it survived.

It looks like half the amplifier is mostly working, I'm wondering if you shorted either terminal 2 or terminal 4 to terminal 3?

[Mstyle]

I really appreciate the feedback, CB. It's been frustrating, but you give me hope for a light at the end of this tunnel!

It was a blue-ish spark with a big pop sound. It happened on my first go-around with voltage testing (before I swapped the resistors) at the same spot (terminal 3). This time I was halfway expecting it, so it was not quite as frightening.

I'll check later tonight to see if I somehow shorted those terminals.

Unfortunately, I don't have any other 12AU7's on hand, but I'll see if I can grab some locally off craigslist. I did check the tubes afterward yesterday and both tubes gave off a nice glow afterward, so they seem to be fine.

Anyway, will report back later!

[Paul Birkeland]

Terminal 3 is the chassis ground, so it's likely that you shorted something else out to this terminal.

I'm suspecting that the one smaller PC board may be fried (if the 12AU7 is still fine).  To test that, you can swap the small boards side-to-side to see if the high voltage changes sides on the front 5-lug terminal strip.

[azrockitman]

The photo could be deceiving but are the solder points at A2 and A3 (on the tube socket) touching?  The angle of the photo makes it look like they might be making contact.