BlueTube clean up

[TarheelTechinTraining]

Hey folks. I recently acquired a tubeworks BlueTube pedal. Its currently not working but my problem is the "brown glue" tubeworks covered the PCB in. How can I remove this crap? Its not hot glue but its much harder. I was thinking a heat gun but I'm afraid it'll mess up the traces. A wire brush would probably hurt stuff as well. Any advice is greatly appreciated. Thanks to all and Merry Christmas, Greg

[TarheelTechinTraining]

A picture would help, don't ya think.

[J M Fahey]

No big deal
If hard and can be scratched, 95% possibility is it's Epoxy.

Very hard, insoluble in solvents and sticks very well, BUT there is a certain temperature above which it crumbles, turning into coarse "brown sugar" lookalike.

You'll need to get an old thin screwdriver and sharpen its point into a needle tip and a hot air gun, if you have an accesory mouthpipe to narrow the hot air jet to something thumbsize, even better.

Set air temperature to Max, the one which will quickly brown paper and even light it if held for some time, we need to heat the Epoxy to over 200C .

Heat one small area and start pricking with your steel needle tip, in, say, 20/30 seconds it sgould crumble under pressure and blown air carries small pieces away, so don't do it in a carpeted Living Room or tghe Mizzuz will object.

Once you catch the proper heating and crumbling sequence (you never put the heat away, the needle works submerged in the hot air flow) , you'll clean that patch you show in around 5 minutes.

You're lucky it's on the solder/tracks side and at worst holds a diode inside, it's worse when you have small transistors or delicate ICs or electrolytics *inside* the Epoxy, because it's easy to damage them.

FWIW when I pot something , I design the PCB so some tracks are replaced by short strips of very thin (think guitar pickup type) copper wire, which then get encapsulated.

Removing Epoxy is *guaranteed* to destroy them and lose lots of connections, my gooped modules can not be copied, he he.

[Enzo]

Why is the goo a problem? Do you need to solder things under it?

[Mick Bailey]

You could go to a lot of trouble removing this only to find the fault lies in an uncovered part of the circuit. My approach would be to power the circuit and input a signal, then use an 'audio probe' to determine what's happening. You may at least narrow it down so that you don't need to attack both areas and increase the risk of damage.

[TarheelTechinTraining]

Thanks fellas. Unfortunately Juan the component side has the "goo" on it as well. The pedal turns on but no output. Also its not switching when the button is depressed. I tried changing the tube with a good tube but still nothing. I was hoping that heat wouldn't be the way to remove this crap but oh well. Thanks again

[DrGonz78]

Looking over the picture there is one solder joint that jumps out at me. Now it probably is my imagination playing tricks on me due to the detail that can be made just by looking at that picture. Still what I see is a through hole with no solder and what looks like a component leg sticking through. At least compared to other empty solder pads this one jumps out at me looking it over.

[Jazz P Bass]

Here is the schematic.

Blue Tube.pdf

I suggest that you check the opamp next.

It appears that it runs off of a dual supply so the output pins should sit at zero volts.

[TarheelTechinTraining]

First Jazz thanks for the schematic its better than the one I have, a jpeg. Secondly Dr.Gonz I also noticed that but this board says RT-901 and the BlueTube is an RT-903. So I figured that this board covered a few pedals. Thanks again, Greg

[TarheelTechinTraining]

Also its a double sided PCB, oh the joys of DIY.