Speedball upgrade fail after a month, voltages way off [resolved]

[goldencalves]

Hi, I put together the speedball upgrade and was very much enjoying it for a month or two (all of the voltage and resistance readings checked pre and post upgrade), when all of a sudden one channel started popping and gave out.  Popping was able to be manipulated by touching/slightly shifting the large tube.

I smelled some burning plastic and noticed the sheathing on the black wire running from U14 to U20 melting to the 270 ohm 5W resistor connected to 15U and 21U, so I pulled it off (still maintained its sheathing) and put some space between the wire and resistor. 

When I tested it out a month or so later (when I had a few minutes), I got it turned on again it appeared to have fixed itself and worked very well for a couple of weeks until the same thing happened, one channel giving out entirely and the other one extremely quiet.

Voltages:
OA - erratic, will be 0, sometimes climb slowly to 140-160, then drop back down to around 0 and stay there mostly
OB - 40-42
G - 0.0-3.0
B+ -48-51

Two LEDs are out, pictured below along with some general pictures of the surrounding build.  Please let me know if any other pictures would be helpful from anywhere I didn't get.

Thanks,
Chris

[Paul Birkeland]

Can you post a picture of the solder and/or flux that you used to complete this build?

[goldencalves]

Paul, thank you so much for the quick response.

Below are the pics, in order of the soldier, the flux that I definitely used (Sterling), and the flux that I may have used on just a couple of spots (Oatey).

[Paul Birkeland]

The solder you have is fine.

The fluxes you have used are for plumbing.  They are both conductive and corrosive.  I could tell that you used these because of the corrosion that's already started on your bottom panel.

I would remove the tubes from your kit and pop it out of the base, then run it through your dishwasher with no detergent.  This will discolor the plate a little bit, but it's the only way I've ever recovered kits that have ended up in this situation.

[goldencalves]

OH JEEZ.  I had no idea I have been using plumbing flux for years!

So run the whole thing through the wash, circuits and everything?  Will I have to re-do any of the soldiering or anything like that, or the wash should fix it? 

And should I run with extra heat?  Or just a normal cycle?

Thanks again,
Chris

[Paul Birkeland]

Hot water and the top dish rack.  It may fix the kit, or you may have to bin it.  Plumbling flux is really, really harmful to this stuff.  Since you used rosin core solder, you shouldn't have to redo any of the solder joints.

[goldencalves]

Thanks again, I appreciate the instruction.  Will run tonight and test it again tomorrow after it dries.

...you may have to bin it.  Plumbling flux is really, really harmful to this stuff.

However, I don't understand why, especially as this issue has apparently come up before in other people's builds, that this isn't mentioned in the manuals.  I read both very closely, line by line repeatedly during fabrication, and checking back the Crack Manual I have (from 2015 or so) doesn't say anything about plumbers flux (or soldier for that matter).  The Speedball Manual mentions to not use plumber's soldier but makes no mention of flux-types to use or not use.  I personally, as a very casual hobbyist, had no idea that there was any real differences between fluxes, and had no idea that the use of the wrong kind of flux could potentially destroy my kit.

I also double-checked the packaging on both fluxes and neither make any specifications on their use, not even oblique inferences for plumbing.  They are just "flux".  I have also seen other, more invested, hobbyists (and professionals) use these same types of flux on electronics.

[Paul Birkeland]

Yes, this has happened before, maybe once every 2-3 years.  The solder you used has the correct flux in it.  The manual never mentions anything about using extra flux as it's completely unnecessary.  We are happy to answer questions like these as they come up in the future, but do be aware that we do call out in the manual not to use plumbing solder to build electronics.

You might also take note that the flux containers say not to use them with leaded solder, so that should also have raised some questions.

[scblock]

One of those cases references ASTM B813 on the front.

ASTM B813: Standard Specification for Liquid and Paste Fluxes for Soldering of Copper and Copper Alloy Tube

[goldencalves]

Ran unit through the dishwasher.  Brought it into the shop to scrub some of the residual rust/corrosion spots off of some terminals with a tooth brush and 99% isopropyl and noticed this 5w resistor (attached picture) had cracked. 

I am assuming I should not test this out without replacing this?  What is the best resource to find a replacement?  This is the same resistor that was melting some of the sheathing on a wire that was touching it, not sure if that is relevant info or not.

Re: Non-leaded flux, neither of these flux containers say to not use them with leaded solder, just that they work with non-leaded solder.  I originally used non-leaded solder when I bought all of this kit for craft projects, and switched to leaded when I started messing with more electronics.  The flux seemed to work just as well getting the leaded solder to stick to metal just as well as it did with the unleaded solder. 

Re: unnecessary flux, I recently did a job soldering PCBs and the client required flux to be used even though we were using rosin-core solder (and flux was actually necessary on a laser-etched board, the solder would absolutely not stick anywhere without it).  The instructional videos I watched to catch-up on electronics soldering also universally suggested flux in combination with rosin-core solder.  I was not aware the rosin core would work just as well or better without flux, and neither is this delineated in either of these manuals.

@ scblock Re: ASTM B813, good to know for the future, but I did not even realize that this was a standards code as opposed to just a product or batch code.

[Paul Birkeland]

Yes, replace that resistor.  You can e-mail replacementparts(at)bottlehead(dot)com to inquire about this.

The flux you used is like running a wire between everything it touches, and it likes to spread around as heat is applied to it, so you'll have to fire the amp back up and see what the voltages look like once that resistor is replaced.

[goldencalves]

Thanks Paul.

[scblock]

I really hope everything works out. Posted that just in case it helps anyone else in the future.

[goldencalves]

@scblock Thank you.  It is useful information.

[goldencalves]

OK, so:

1) Unit went through dishwasher
2) isopropyl/toothbrush scrub of most reachable solder joints
3) replaced cracked 270 ohm resistor b/w U15 and U21

Large speedball readings basically the same:
OA : 0
OB : 44.5
G : 3.0
B+ : 50

And the 2 LEDs on the large board in front of Q2A are out (rest of LEDs are working).

Anything else I can do? Would it be worth it to do a full resistance/voltage check?
Should I replace the other 270 ohm resistor as well (does not appear damaged from the exterior)?

Thanks,
Chris