How hot should the Crack + SB resistor be?

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Just installed the SB onto the crack and am trying to work out a few problems. The crack w/o SB was working perfectly.

How hot is the white resistor (below the transformer) supposed to be? Mine is burning hot such that I can only keep my finger on it for about 2 secs before it gets too hot.

Occasionally, I also get extremely loud exploding crackle sounds in the left channel with the left channel LCD on the bigger of the three SB boards flickering. This happens with volume knob on zero and no music playing. I'm certain that this is not interference as I've had some interference with the non-SB crack before that was alleviated by moving away surrounding electronics.

EDIT: This was my first build, a friend helped me with it. We accidentally used conductive flux when soldering and had to clean it off with isopropyl alcohol because the board initially started smoking when turned on. But now no more smoking.

[Paul Birkeland]

What are your voltage readings after installing the Speedball?

Those white resistors will be about as hot as they were without the Speedball, and I would expect them to be between 150 and 200 degrees Fahrenheit.  Also, when the amp is running, the highest voltages in the circuit are around these 270 Ohm resistors, so if you're touching them while the amplifier is running or very shortly after it has turned off, then you are bound to shock yourself eventually.  Also, the voltage measurements given in the manual will actually tell us if those resistors are running too hot.

The crackling that you describe is a broken wire or a bad solder joint, and you have that reasonably well narrowed down based on where it's happening in the amplifier. 

-PB

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Voltage measurements were all within limits published in the manual.

Thanks for your reply, I'll re-examine the joints tmrw evening when I have some free time and get back to you.

[fullheadofnothing]

The problems stemming from the conductive flux may have permanently damaged your power transformer. Post pictures of the area between the lugs of the transformer.

The lingering effects of the conductive flux are a probable source of the popping noise.

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The problems stemming from the conductive flux may have permanently damaged your power transformer. Post pictures of the area between the lugs of the transformer.

The lingering effects of the conductive flux are a probable source of the popping noise.

Sorry dumb question, but what are the lugs of the transformer?

Another rookie mistake: I used plumbing solder (97% Sn, 2.75% Cu, 0.25% Ag; brand name is "Forney" 1/8", lead-free) instead of proper electronic solder. Will this be a problem? This is the solder used: https://www.forneyind.com/store/detail/830/solder_soldering_irons_flux/4931/solder_lead_free_18_14_lbs/

The flux paste used was Nokorode Regular Paste Flux: https://www.amazon.com/C-R-Laurence-NSP2-Nokorode-Soldering/dp/B000KZUT60

From reading other forums online, it sounds like a catastrophic error. Sorry, I'm a little developmentally challenged and dyslexic, I thought I read everything thoroughly but sometimes I have a hard time understanding certain things.

[Paul Birkeland]

Ah, I didn't see the bit about conductive flux.  Yeah, that basically ruins your build completely.  The flux in plumbing solder can eat holes in the aluminum chassis, and the conductive flux will create bridges across every adjacent terminal in the amplifier.  I hate to say it, but you need to start over completely and use the correct solder for the job.

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Ah, I didn't see the bit about conductive flux.  Yeah, that basically ruins your build completely.  The flux in plumbing solder can eat holes in the aluminum chassis, and the conductive flux will create bridges across every adjacent terminal in the amplifier.  I hate to say it, but you need to start over completely and use the correct solder for the job.

Ah, thanks for your help; that was what I was fearing. Just to clarify, even disassembly the SB upgrade and thoroughly washing everything with alcohol, the damage is most likely already done? If so, I'd like to thank everyone on this forum for their help. Of course it was unfortunate to destroy a perfectly good non-SB Crack, but I guess this was a good learning experience.

[Doc B.]

I have a different view. Yup, you screwed up. But it's not clear just how much damage has occurred. Since you said voltages were in spec I doubt it's catastrophic - yet. You have nothing to lose at this point. The flux is conductive and oily, but it isn't acid core so it probably wont eat holes in the chassis or thru the terminals underneath the solder like some kits we have seen. So clean the bejeezus out of the thing. Pull the tubes and remove the chassis from the base. You can buy a gallon of denatured alcohol and dip the chassis in it and scrub. It will probably knock off the labels and possibly soften any finish you applied or discolor the chassis panel. And it will need to dry for quite some time. The transformer bell might rust as any protective coating will be washed off. Baking in the oven at 200F for an hour to dry it out probably wouldn't hurt.

This may or may not fix everything. You may still have to go over all of your joints with a little of the correct 60/40 or 63/37 tin/lead ROSIN CORE electronics solder. But you have nothing to lose except a few bucks for the alcohol and some time spent cleaning it up.

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Here are some images of the board. After letting it run upside down, I noticed that one of the LEDs on the SB board with the two heat sinks will start to flicker and then eventually shut off. This happens after it's running for maybe 15 mins or so. Before 15 mins, everything works beautifully. When it's flickering, this is when the very loud crackles begin to go through my left channel. Oddly, when the RCA inputs are not connected, there is no crackling in the headphones.

http://imgur.com/a/rSHcR

You can see in the overhead image that one of the LEDs is no longer lit up. When I shine a light on the board, I see this liquidy stuff around the soldering joints. I can carefully wick this stuff off with a tissue paper - it's yellowish in color. My guess is that for the first ~15 mins, the temp isn't high enough to melt the flux and then after 15 mins, the temp IS high enough to melt the flux and cause some kind of short?

@Doc B., would it be reasonable to submerge just the SB components into a tub of 99% isopropryl alcohol and then let it air dry? Because the original Crack was built with the help of another friend using proper electronics solder. It's only the SB upgrade that was built and installed using the wrong materials.

[Doc B.]

Yup, pull the PC board and just soak it in alcohol and scrub with a toothbrush. Let it dry very well before reinstalling it.

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Yup, pull the PC board and just soak it in alcohol and scrub with a toothbrush. Let it dry very well before reinstalling it.

Thank, will do this tomorrow and report back with results. I did a quick cleaning around the PC board with some alcohol on a Q tip and the crackling already sounds less loud.

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Took the 3 PC boards out and soaked and scrubbed them in alcohol per Doc. B's instructions and then went over everything with proper solders.

The loud exploding crackles are gone, but there are smaller quieter crackles in the left channel still, sounds like interference. With the amp turned on, I began to gently tap at the different components and think I narrowed it down to the TIP50 attached to the left channel heat sink.

However.... during this process I think I shorted something as I heard a loud crackle and now the pair of LEDs for the left channel heat sink no longer lights up and no sound comes out the L channel at all. Pretty certain I shorted the TIP50 as that was what I was poking at when it happened.

Is it possible to order another TIP50 from Bottlehead?

[Rocketman248]

What were you poking it with?  Best thing to use is a wooden chopstick.  You don't want to use anything conductive.

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What were you poking it with?  Best thing to use is a wooden chopstick.  You don't want to use anything conductive.

Oops, sorry my post didn't go through for some reason.

I was using a plastic triangle, the one found in geometry kits in elementary math class. I think there might have been some conductive material at the tip from all the poking around I did. I think I shorted two of the three pins of the TIP50.

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Update:
Bought some extra TIP50's and re-soldered them on, and the left channel still wasn't lighting up. I tested the LEDs and figured that I had blown the red LEDs. Bought some spare LEDs and soldered them on and the amp is working again.

There is still some crackling after about 45 mins of listening. It is only in the left channel and sounds sort of like a river of soft flowing crackles. Been cleaning the solder joints with some more 91% alcohol and the crackling is happening less often.

Overall pretty satisfied with the current state of the amp. Thanks everyone for the help!