Screwed up my Crack upgrade

[Paul Birkeland]

I would be looking for a broken wire.  1L is also not well soldered, but that won't cause the issue you're having.

-PB

 

[flyfisher55]

I appreciate your knowledge in troubleshooting my build but I keep thinking that this amp was fully operational for almost a year prior to my trying the speedball upgrade. It wasn't until my hand slipped and shorted that the LED's went out. Is it possible that the 250 V capacitors would be the culprit? That was where the zap and spark occurred when my probe slipped. What wires would I have to replace? Are we talking about rebuilding the entire amp?

 

[Paul Birkeland]

I appreciate your knowledge in troubleshooting my build but I keep thinking that this amp was fully operational for almost a year prior to my trying the speedball upgrade. It wasn't until my hand slipped and shorted that the LED's went out. Is it possible that the 250 V capacitors would be the culprit?

No, there's absolutely no possibility of this.  A blown cap will short, and a shorted cap will blow its insides out all over the place immediately.  This will also drag your high voltage rail way, way down, and yours is still just fine.

What wires would I have to replace? Are we talking about rebuilding the entire amp?

What I would suggest is getting a wooden chopstick and poking around the 9 pin socket and the small Speedball board with the amp on.  You may find a spot where you can tap with your chopstick and suddenly the LED on the socket that's out lights up, and this can be used to direct your efforts.

 

[flyfisher55]

I removed all the wires from small board and replaced them with fresh wires left over from the build. Voltages at small board remained exactly the same. One note, I used the tip of a number 2 pencil and shorted A3 to A4 with the lead and this caused the LED at A3 to be lit. This had no effect on the LED's on right side of small board.

 

[flyfisher55]

I replaced the existing  12AU7 equivalent tube with a new 12AX7. I had no other  12AU7 laying around. Only the one LED lit at the socket base and none at all on the small board. Upon restoring the provided tube the two Left LED's came back on but right two remain out.

 

[Tom-s]

The Crack is not designed for a 12AX7. It's not a replacement for a 12AU7.
See the tube rolling thread for suitable alternatives.
Since your Crack is malfunctioning, i'd only use it with a good 12AU7/ECC82 for now.

 

[flyfisher55]

Thanks for the reply. As I was instructed to probe around with a chop stick on my last post from Paul I took a stab at trying a different tube. Unfortunately not having much success.

 

[Tom-s]

I'd put the 12AU7 back in and poke around some more with the chopstick like PB said.

Good luck with the trouble shooting.

 

[Paul Birkeland]

You don't have a bad tube.  A bad tube would leave very high voltage at OB if it had no emission and would blow up the LED if it was shorted.

Another likely course of action would be to put the 22.1K resistors back in and remove the small PC board, then continue debugging the circuit.

 

[flyfisher55]

Okay, so after making makeshift extension wires in order to reinstall the 3K resistors and the 22.1K resistors I got them back in and both LED's on the 9 pin socket are lit.

 

[Paul Birkeland]

I would grab the chopstick again and poke around to see if you can disturb any connection to make the socket LED go out.

I looked over your board work again and everything looks great, so it's difficult to imagine how you're getting no voltage out of OB. 

 

[flyfisher55]

Just checked all voltage and these are my readings.

1. 74.4
2. 170.7
3. 0
4. 170.3
5. 78.1
6. 0
7. 102.9
8. 0
9. 104.2
10. 0

 

[flyfisher55]

Faulty board?
Options?

 

[Paul Birkeland]

Though the solder joints on the board look good, it's completely possible that there is one that isn't making good contact. 

A faulty board is usually the result of a shorted transistor, and a shorted transistor will make IB and OB roughly the same voltage.

 

[Deke609]

Just a shot in the dark, but maybe resolder the legs of the transistor on the OB side. The circled leg looks a bit iffy in the photo (but could be perfectly fine).  I'd try soldering it from the top, tinning and putting the tip on one side of the leg/trace-hole and applying solder to the other side.  Might be worth a try

 

[flyfisher55]

Just a shot in the dark, but maybe resolder the legs of the transistor on the OB side. The circled leg looks a bit iffy in the photo (but could be perfectly fine).  I'd try soldering it from the top, tinning and putting the tip on one side of the leg/trace-hole and applying solder to the other side.  Might be worth a try
[/quote

Thanks Deke, I tried what you said. I've put three PN2907's into O1B. all three including original shorted one and two that I ordered  read differently than O1A.
O1A L&R = O.L M Ohms
      L&C =O.L M Ohms
      R&C =40.19 M Ohms

O1B L&R = O.L M Ohms
      L&C = O.L M Ohms
      R&C =00.00 M Ohms

 

[flyfisher55]

here are latest photos of small board.

 

[Paul Birkeland]

The other option is to use the repair service.  Many times the repair only requires resoldering all of the joints in the amp.

 

[flyfisher55]

After all this time and effort, sending it in for repair feels like throwing in the towel, Especially when we've confirmed that the unit was working prior to the upgrade and upon being restored to the original is once again operable. Is it an option to order another Speedball kit?

 

[flyfisher55]

I'm confused, Despite the fact that the unit is operational and reading within the correct parameters presently you still feel that the fault lies with bad solder points?