Speedball issues [resolved]

[Droo]

Hi,


After receiving my crack with speedball, I first built the stock crack over the course of a day, and have been listening to it for a couple of days now. At this point, all resistances and voltages were correct, so yesterday I decided to do the speedball.

The small board went well, and I was really impressed by how it sounded. When doing the large board, however, two things went wrong: firstly, one of the leads came off of one of the 10W 3K wirewound resistors, so I can no longer revert back; secondly, I somehow lost one of the LEDs on the big board, but being an impatient idiot, I figured the LED was for indication of errors only, and I went ahead with the assembly without it.

When I turned it on to check the  resistances and voltages, something near the rear of the chassis started smoking (maybe the transformer), so I immediately shut it off. I didn't know what to do, so I put in a random led I had lying around and mounted it in place of the missing one (with the correct polarity).

When I checked the resistances afterwards, the resistances of 7,9, 10, B3, and B6 all read 1 instead of their proper values. All else is correct. The led was just to complete the circuit, and I have not applied voltage to anything since. I know I have made a lot of stupid mistakes, but I would like some help in figuring out whether or not I made some irreparable damage to anything (especially the transformer) and how to remedy the situation, if at all possible.

Thank you very much for your help.

[Droo]

I noticed the upper lug of the headphone jack was a little loose, so I resoldered it. 10 is now within acceptable range, but where I was previously getting 00.0 for all 0 values, I now get 00.8 at 200 ohms and 001 at 2000 ohms. I'm worried that this might be too high for safe operation.

[Paul Birkeland]

The LEDs are not for indication; the circuit won't work properly without HLMP6000s installed.

The one resistance check in the Speedball manual checks to see if the heatsink mounting kit on the TIP50 is installed properly.  The DC resistances on terminals 1, 5, 7, and 9 from the Crack manual no longer apply once you install the Speedball.

What smokes near the rear of the chassis is the 270 ohm resistor closer to the power switch.  It will smoke when you don't have the TIP50 heatsink mounting kit installed properly, but since you ran the kit without one LED installed, it's really hard to know what might be damaged on the big PC board.

You can start by setting your meter to check continuity (it will beep when you touch your meter leads together), then look for continuity between any pair of leads on the TIP50 and 2N2222 transistors.

If I had your Crack here for repair, I would pull the LEDs and transistors on that side of the board and throw them away, then measure the R1 and R2 resistances to be sure they were OK, then I would replace the LEDs/transistors on the board.

[Droo]

Thank you so much! The 270 ohm resistor still seems to work, so I'll just replace the transistors and LEDs and go from there.

[Paul Birkeland]

I would recommend testing them... 

The only reason I would replace them all if I had the kit here is because I have a pile of each just sitting around, and I'm impatient.  If you do not have a spare 2N2222, TIP50, and a pair of LEDs, then you should do a little testing to see which are shorted.

[Droo]

Hi,

I replaced the LED. All of my LEDs light up and there is no more smoke coming out. After testing the voltages, however, I got the following results: G:0.00 B+:243 OA: 125, OB: 148. These are all DC (1000 V). I also noticed that for some reason the LEDs on the OA side of the board light up as soon as the crack is plugged in, while the rest take a while to gradually glow brighter. How do I proceed from here?

[Droo]

Sound wise, there's a bit of a buzz in the left channel, and with cymbal hits, there's a very distorted but quiet thump in both rears. Only the left channel plays sound. When I shut the amp off, the distortion temporarily seems to disappear on the left.

[Paul Birkeland]

That's a very good indicator that you have a bad solder joint.  I would reflow all of the joints in the amp.

[Droo]

I reflowed everything in the area, which didn't seem to change too much. When I unplugged the left Jack, there was still quiet music going through the left channel. (The right was even quieter, with mostly just some crackling corresponding to bass.
http://imgur.com/gallery/HD4PwgC

[Deluk]

There are a LOT of wires with excess ends that need trimming back. The preference is to make a mechanical joint by crimping the wire around the tag, trimming off and then soldering. Small long nose pliers help here. B2/B3 touching? I prefer to solder components on both sides of a board to make sure the joint is sound. Electrically this may or may not matter but it helps to reduce the chance of colder solder joints.

[Paul Birkeland]

Proper side cutters will help to trim those leads back.

Can you take a photo of the headphone jack wiring with more light on the jack?

[Droo]

I trimmed the leads and reflowed everything from the top to no avail.

Jack https://imgur.com/a/mgTTIa6

[Paul Birkeland]

Can you post your voltages?

None of the solder joints on that jack look promising.  The middle joint on the outside where the 2.49K resistor connects looks to be unsoldered.  The junction of the black wires doesn't have enough solder, the joint with the white wire hasn't been heated enough, the joint with the red wire has the lead of its 2.49K resistor just poking out and hanging out in the air (bend it around the terminal and crimp).

[Droo]

B+: 248
OA:131
OB:233
G:0.

I think I may have shorted something when soldering the OB TIP50 (with everything off). I may have touched a lead of the big resistor, as I saw a spark and now the LEDs don't light up on this side anymore.

[Droo]

Just went through everything and confirmed that all capacitors and resistors are good except for one of the TIP50. I'll try to find a replacement and see how it goes. Can I just use any generic TIP50 from digikey?