Smoke/Burning Smell after Speedball Upgrade [solved]

[gemini14]

As the title would indicate, I've unfortunately got some serious problems after performing the Speedball upgrade. I received the Crack & Speedball for Christmas and had absolutely no problems putting the Crack together - it worked on the first try and sounded fantastic. I decided to use the Crack for a few days before adding the Speedball kit. All the readings were spot on and there was no humming or other noise.

Unfortunately, the problems started after I added the Speedball. I got very weird results while checking the voltages. A lot of terminals showed 0 when they should have had a nonzero value and some terminals showed less than half of the correct voltage. What's worse is that after a couple of minutes, the amp got really hot (pretty sure more than usual), there was a burning smell coming from the amp, and a wisp of smoke appeared. Needless to say I shut it off immediately. I should note that the tubes started glowing right after I turned on the amp, both before and after the upgrade, as they should. I couldn't precisely identify where the smoke was coming from, but it originated from the area near the transformer.

I spent over a week trying to identify where a wire may have crossed another, if there was a bad joint, etc., but with one exception I kept coming up with nothing. The exception was the B6/B7/B8 area. The red and black wires may have been touching due to some melted plastic and the constricted area, so I rearranged the wires and resoldered each connection. Nothing was working so I decided to go back to the drawing board and redo the entire amp. I realize that since at least part of the amp was working before, it might not have been the best idea, but it did allow me to redo a couple of problematic spots and resolder every single connection.

Bad news is that the same thing is happening - tubes light up, burning smell, and messed up voltages. On the plus side, I didn't detect any smoke after rebuilding the amp. I had shaken the amp before (when it was smoking) and again after rebuilding it to see if something had gotten lodged inside and was burning, but I didn't hear or see anything. I also checked the fuse with a loupe to be doubly sure it hadn't blown, but it looked perfectly fine.

I could really use some help getting this sorted out. It's driving me crazy! I'm assuming this is simply user error, as most problems with these kits seems to be, but I just can't figure out what the problem is. I've linked an album with shots of the amp. Some areas don't look as pristine as I would like, but I did my best to make sure there were no unwanted connections or bad joints. If you need to see a specific area more closely/clearly, please let me know and I'll upload additional pictures.

Album: http://imgur.com/a/7XSmg

[Paul Birkeland]

The jacketing on most of your wires is pulled way back, which will very likely cause shorts.  See the wire going to B4?  The end poking out the tube socket pin looks like it could easily touch B5.  Same with terminal 18, there's a long component lead just sticking out there, hanging in the air. 

I would encourage you to remove the Speedball and put the resistors back in the circuit, then do everything you can to make your build look like the manual. 

Based on your photos, there is a short in the amp that is sucking the power supply voltage down (the first 270 Ohm resistor has gotten hot enough to burn the writing off).  I would be suspicious of the wiring going from T14 to power transformer terminal 4.

[gemini14]

Is it just that since the wires are more exposed that the chance of them causing a short is higher? Right now, the wires don't seem to actually be touching anything they shouldn't.

I'll remove the Speedball and do some triage on the problem spots, as you suggested, and see if I can get it back to a working state.

[STURMJ]

The pins in the tube sockets have some movement to them.  It may be possible that the little wiggle room it has may get it just close enough.

[gemini14]

OK, the Speedball is out and I touched up a few of the joints. Checked the voltages and, lo and behold, it works again. All readings were spot on, just like when I initially built it. There is a hum at ~75% to 100% volume, but at least it works again. Apart from the hum, which, from what I understand, could just be the RCA wires needing some insulation or additional twists, the question now is, what part of the Speedball kit is causing the trouble? Other than going over every single joint again (which I've now done twice), is there some way to test the individual circuit boards (before reinstalling them) and determine where the issue lies? Check resistances perhaps?

[Paul Birkeland]

You can just remove the 22K resistors and reinstall the smaller PC boards, then recheck with just those small PC boards first, then move on to the 3K resistors separately.

[gemini14]

Sorry for the delay in getting back, I've been extremely busy.

The piecemeal installation was an excellent suggestion - thank you! I'm pretty sure now that the problem is in the larger circuit board. Voltages seemed OK, if not 100% correct, with only the small boards installed and there was no burning smell or smoke.

After adding the larger board, I noticed that the left LEDs (on the large PCB) hadn't turned on, even though they had before. I was once again getting sound out of my headphones, albeit only on one side and at a reduced volume. The orientation was correct, so I decided to re-solder both left LEDs. Unfortunately, I melted one, so I'm waiting on replacements atm. Will update when I receive and install them.

[gemini14]

Got the new LEDs today, installed them, and...no go. The problem is the same as before. The LEDs on the left side (left as in looking straight down at the underside of the board, with it installed in the Crack) of the larger PCB simply do not light up. All the other LEDs turn on fine. I assume that means that electricity is not able to reach them at all.

I'm linking a photo of the underside of the PCB. The orientation is with the word Top on the left side and the troublesome LEDs are on the top side of the board. Is there anything that sticks out as being wrong? I've resoldered all the joints at least two times, some three. Some joints may look dull, but they are all shiny from the right angle. Would it perhaps help to add solder to some of the joints which currently have minimal amounts of solder on them?

http://imgur.com/x4Px1M4

[Paul Birkeland]

I'd hit all the solder joints on that board again.  One of the TIP50's on that board looks like it needs a lot more heat applied to the center leg to get the solder to wick in properly.

[2wo]

It is hard to see but check that one solder joint is not touching another (bridging)...John 

[gemini14]

Ugh, still nothing. Resoldered all the joints on the board, checked for potential bridges, and double checked the TIP50 legs. Same result: only right channel works at reduced volume and left LEDs still don't light up.

This might be a dumb question, but is there a way to isolate the problem using a voltmeter and checking voltages on the Speedball PCB circuit by circuit?

[Paul Birkeland]

Hello Gemeni,

Can you post the voltages that you currently have that are out of spec?

[Paul Birkeland]

Just an update to this thread:

This Crack came in for repair, and the absence of mechanical wire connections allowed the red wire to slip out of T13 and short out the power supply.

-PB

[Doc B.]

Lesson here - be sure to bend the wire around after you slip it through a terminal. Military spec is to wrap the wire around the terminal twice. That may be difficult in a lot of situations on these kits, but getting a simple bend after inserting the wire is very easy and should be done in such a manner that the wire won't move while being soldered.