Crack started smoking after installing speedball [resolved]

[Blue]

Hello all,

First of all, I have been running a stock crack for the last week with zero problems.
The only upgrade I did was installing an Alps Blue potentiometer during the initial installation.
The stock crack passed all resistance and voltage tests, as was running smooth for the week, then I installed the speed ball today.

As with the speed ball, I did all the resistance checks and voltage checks listed in the manual, and everything passed, all within the 10% threshold.
I left the crack standing suspended (just incase I needed to look at any parts while running), and set the crack on my desk and turned it on to get ready to play some music.
I left the room for 5 minutes, and when I came back i started to smell smoke. Well im not sure if it was smoke or the smell of wire melting.
Just before turning it off, I noticed that one LED on the SpeedBall board isn't lighting up. I marked it in one of the photos.

I also noticed that the resistor from 21U to 15U on the PT-10 transformer was bloody hot, and it seems the leads have turned slightly blue.
EDIT: Just noticed that the Resistor at 15L and 13L has also blue leads, and that a wires jacket leaning against it also started to melt. Pictured attached as well.
I am hoping I have only destroyed some resistors and LEDs and not the Transformer itself.

I have attached a bunch of pictures to this post. I am guessing I need to disassemble the speed ball, but I would love to hear any suggestions first if anything looks out of the ordinary,
and if it looks like I fried anything else. Also, If I need to buy new parts, could anyone recommend any european websites for such things?
The burned wire jacket from the the RCA wires to the Alps potentiometer was due to me accidentally touching the jacket with my soldering iron (not the most stable hands).

Thanks for the help, and If you need more information or any better pictures, let me know

[Paul Birkeland]

Whenever we have seen this, it's because one of the TIP50 transistors is touching the heatsink and not properly isolated.  The LED that's out is an indicator of which TIP50 you need to check. 

[Blue]

Thanks for the tip blackplate.
I’ll check the transistors and the heat sinks tomorrow as I left my crack at the office.
From the pictures I posted, do you think I need to replace the 270 ohm 5W resistors connected to the transformer? Or is there a way to check the reliability of the resistors now other than checking the resistance itself?

[Paul Birkeland]

You can just measure the resistance listed.

When they are run like this too long, they fall apart physically and open up electrically.

[Blue]

I reflowed the solder for all the components on the Speedball board, and moved the black wires away from the 270 ohm 5w resistors near the transformer.
I also disassembled the transistor and heatsink closer to the base where the headphone jack is and reattached everything.
All the LEDs light up now, although the the left hand LEDs on the smaller board light up faintly. But as I read, they are not meant to be bright LEDs, so I assume they are okay.

My voltage readings are as follows (I am running on 233 volt mains)

OA: 112v
OB: 108.3v
G: 0v
B+: 195.3v

My OA is just 2v off the 10% allowable threshold, but I am assuming that is okay still? So far all LEDs remain on, even after 10 minutes. Not smelling anything smokey, no wires are burning.
Im going to let it run for a little while more before turning it off. But it seems like its good. Just wanted to ask if the OA voltages are still good even though its 12% off the allowable threshold.

[Paul Birkeland]

Yeah, those are acceptable.

[Jimb0]

Sometimes the 12AU7 can influence the voltages. I have a 12AU7 tube that brings my OA and OB to 120v. Your readings are excellent. Good job