Speedball install voltage issues [resolved]

[Paul Birkeland]

I'm interested in seeing the same shot that's on page 46 of the build manual.

If your Crack was functional for that long, please recheck the voltages at terminals A3 and A8.  If they are that high, can you check where the black wires meet at the headphone jack to be sure one isn't loose.

[Dr. Soot]

here you go

A1 = 184.7 v
A2 = 169.6 V
A3 = 180.9 V
A4 = 0 V
A5 = 0 V
A6 = 184.1 V
A7 = 169.8 V
A8 = 174.5 V
A9 = 0 V

@ the headphone jack

Red = 168.0 V
White = 168.6 V
Black = 169.9 V

Not sure if all of those are helpful, but figured I would add them just in case. 

[Paul Birkeland]

Put the 22.1K resistors back and remeasure your voltages.

Are you sure you aren't seeing mV instead of V? 

Which terminal are you using as a ground reference?

When we see a set of voltages like this that are impossible, generally it's a loose, missing, or broken black wire.

Also do be aware that the Alps Blue pot is designed to be installed onto a PC board, and soldering wires directly to those pins will often cause the pins to snap off.  You can buy mounting PC boards for a few bucks on eBay.

[Dr. Soot]

I cannot find the 22.1K resistors since removing them.  Can you suggest a place for me to purchase them, perhaps the item specs so I can get the correct ones?

I am using 12 as the grounding terminal.

A3 = 183.1 V (see photo)

A8 = 178.4 V (see photo)

Other random voltage measurements

18 = 97 V
20 = 0 V
14 = 0 V
Center of 9 pin socket = 172.4 V

On the pot... (see attached photo for pot labels)
Ground top row = 172.4 V
Ground bottom row = 0 V

[Paul Birkeland]

The ground lugs on the pot are connected with a piece of wire to terminal 12.  Since you have 180V between those two points, there is a discontinuity in your black ground wire that is causing your amp to not work properly.  As I suggested before, it's extremely common to find this exact issue where the two black wires connect to the headphone jack, and commonly one will not be captured by solder.

From what you are showing, we can be 10000% sure that you have a loose/poorly soldered black wire in your stock build that has nothing to do with the Speedball installation (other than likely being disturbed in the process of fitting that first PC board).

There are only a small handful of solder joints on the ground bus, why not reheat them all?   That would be terminal 3, the junction of the black wires on the HP jack, terminal 12, terminal 14, and terminal 20. 

[Dr. Soot]

Thank you for all the help. I finally found the poorly soldered joint on the pot, it was one of the ground wires.  I have since repaired that but was still getting some goofy numbers and started trouble shooting all the solder joints on the 9 pin socket.  I accidentally ended up breaking one of the LEDs (the one at A3) and replaced it with one from the Speedball kit.  That fixed that.  I am still getting about twice the voltage I should be getting at A1 and A6.  I believe it is probably an issue at the pot.  And your suggestion about putting the pot on a breadboard was something I had actually done but for whatever reason, swapped the pot for one without the breadboard.  I have another couple pots, I will put one on a breadboard and go from there.  Again, thank you for all the help.  You guys are awesome.

[Paul Birkeland]

Can you please repost the voltages at terminals 1-5?

[Dr. Soot]

Voltages

1 = 73.9V (seems to have fixed itself or I just mis-measured before)
2 = 0 V
3 = 0 V
4 = 176.7 V
5 = 166.7 V

A1 = 167.6 V
A2 = 0 V
A3 = 1.634 V
A4 = 0 V
A5 = 0 V
A6 = 72.5 V
A7 = 0 V
A8 = 1.576 V
A9 = 0 V

The A3 and A8 LED now glow (they didn't before) but on the Speedball breadboard, only the LED closest to the 1B connection glows.

[Paul Birkeland]

Well half of your Speedball is working at least.  I would expect at least two lit LEDs on the front PC board. The higher than expected voltage at A3 tells us that the half of the C4S feeding A1 is likely attempting to source too much current.   It would be a good idea to see some more photos of the PC board itself, especially the bottom.  You can also remove the wires at IA, OA, IB, and OB, then rotate the board 180 degrees and hook it back up.  If that high voltage moves to terminal 1, then you know you have an issue to deal with on that half of the PC board.

The voltages you posted now show that you do not have the voltage issue you had before.  If you didn't do anything specific to resolve the issue, then you are still going to have to find the loose wire/flaky solder joint causing this issue.

Ultimately I would still suggest finding a pair of 22K/1W resistors just in case, because it's more difficult to debug stock Crack issues once the Speedball is installed.

[Dr. Soot]

Thanks for the suggestions.  I did resolder the connections on the pot and on the 9 pin, that is when I saw the voltage correction.  I am reasonably confident that solved that issue.  I will do what you suggest on the PC board.  I am sure I just didn't solder well.  I don't have the best vision and even though I use magnifying glasses and whatever else I can use, it still isn't that clear.  I am attaching images of the underside of the PC board.  I may desolder and desolder it all, not sure.  But once again, thank you for all your help.

[Paul Birkeland]

This is likely your problem.  These two pads need to not touch.

[Dr. Soot]

I took care of that solder bridge but have been following all the lines to see check all the connections and currently, I find that OB reads about 10-11 V and I cannot pinpoint the where the voltage drop occurs.  At this point, I am almost re-soldered every connection.  I just may give up and buy a new kit and do it better the second time.  I assume 120 V is coming in and the transformer and at some point, I am getting about 230 V.  I need to check the jumper wire between 14 and 16 on the transformer to make sure it is OK. But I don't think that would explain the voltage drop across the speedball board.  I would assume if I am getting 74 V at at OA and then read about 10.5 V at OB, something must be wrong on the board, not necessarily the crack itself.  Anyway, any chance I can buy a few parts of the speedball and not the whole thing?  Just the one board I have built so far and try again.

[Paul Birkeland]

Leaded solder and more heat will be really helpful.  You can contact replacementparts(at)bottlehead(dot)com regarding purchasing a new front PC board and electronics.

[Dr. Soot]

I am using Quad Eutectic Solder with rosin core and I have my solder set to 675 F.  Should I use different solder and go hotter?

[Paul Birkeland]

Way, way hotter.