Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: ghostyjack on September 23, 2018, 12:14:50 AM
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I've been running the standard Crack for a while now, but decided to install the Speedball upgrade.
After fitting the first PCB I did the voltage check and got got the following voltages.
OA: 76v
IA: 181v
B-A/B: 238v
IB: 181v
OB: 55v
Also, the LED immediately under IB does not light.
Also, before starting the upgrade, I forgot all about a noise I was getting from the amp that became a loud pop when I twisted the headphone jack in the jack socket. Suspect that was a bad joint but forgot to look for it before starting the upgrade.
Could the original issue I had be what is causing this Speedball issues?
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Yes, I would consider it very likely that these are related.
When you examine the black wires entering the headphone jack, are they all well soldered, or perhaps is there one that's loose and one that's well soldered?
It would also possibly help to see some photos of the top and bottom of the small PC board, just to be sure that everything is looking OK there.
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I found the dry joint, it was a black wire in the jack socket. I re-flowed it and not it is attached not.
I retook the voltages and have these now:
OA: 80v
IA: 182v
B-A/B: 0v
IB: 182v
OB: 55v
I still have one LED not lit though.
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Do both LEDs on the 9 pin socket light up?
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yes
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What voltages do you have at A3 and A2?
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Both are about 0v.
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Reviewing your photos, you have a backwards transistor.
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Ahh, Yep, I see it.
Q1B?
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Well I can't see how I can desolder 3 legs at once.
Looks like I may need to cut it off and buy a new one.l
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Do PN2907A only come in one type? Or do I need to look for some specific version?
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Do you not have some solder wick? With solder wick you can remove the solder one leg at a time, or if you are good at soldering all three legs at once.
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Yeah, or a solder sucker. The Japanese one I bought does an excellent job at removing molten solder
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I have some, but never used it before, always used a solder pump, but that doesn't seem to be working on it.
I'll try the wick and see if that helps.
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A spring-loaded desoldering pump (not the kind with the squeeze bulb) will suck the solder right out of the hole. You just have to heat the top of the board and suck the solder out from the bottom.
Any old PN2907 will do the job. If you can get the one out that you have, it should take the heat without receiving any damage, and being installed backwards also shouldn't destroy it.
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Well it turned out I wasn't very good at removing the solder, it just wouldn't come out of the holes.
I ended up snipping the legs and replacing the transistor.
Afterwards, all the LED's lit up fine and the voltages were good.
Fitting the second PCB was straight forward with no mistakes this time and its LED's lit and had good voltages.
Powered it up and worked fine.
I even have the problem with the sound and jack plug I mentioned earlier fixed, it was definitely a loose wire which is properly soldered now.
The amp sounds fantastic now, seeing as I loved the sound before the upgrade, not sure how much of an improvement it is, but will have to listen to it for a while. The bass did sound a bit tighter though.