Part two, where we try and fix it.
Well the garden blinkenlight thing worked intermittently for a while and then didn’t. The first problem was fairly obvious. The positive lead from the DC / DC converter had fallen off.
You can see the state of the board. It’s been wet for some considerable time. The mode switch has fallen apart and I’d already had to bridge the power switch out.
After I soldered the wire on it was back to being intermittent. The next thing I noticed was that if I pressed on the microprocessor it would work and if I didn’t it wouldn’t. So the processor is dry jointed on the board.
The processor is this thing in the handy red circle.
It’s only got eight legs, but they are really small legs. Really really small.
I have played with surface mount stuff in the past but not often. I actually have a surface mount FM radio kit that I want to build but I’ve not got round to it yet. But I did get some solder paste to build it with so I tried it.
Basically it comes in a syringe, you squirt a bit of it on the pins of the chip and heat it with an iron, or preferably a heat gun. It flows onto the pins. There is much less chance of blobbing pins together. When you blob your pins together it’s a real git to unblob them.
So now it’s fixed right!?
Nah.
It powers up reliably now but it changes flashing mode every time. I’d like it to stay on the static setting.
So I took a closer look. The end pin is the one that is attached to the mode switch, or rather, the remains of the switch.
If you look carefully at it the solder hasn’t flowed over it very well. So I cleaned it up with a fibreglass pencil and resoldered it.
Fixed right!?
Nah, it’s still switching mode when it powers up.
Then I noticed this further up the board.
So there are two pins in the board and one solder pad where the pin has dropped out. This is labeled T2 so it’s a transistor. Let’s look at it and see if we can reconnect that pin.
Oh. It’s gone completely. It has (or had) wires going to the processor and a capacitor on it.
My guess is that this was the reset system for the processor. When the power comes up there is a point where processors do some weird stuff until the power stabilises. There is normally a reset pin that you hold until the power has stabilised. It just halts the processor. My guess is that without it the processor is running amok for a moment.
The problem is that I have no idea what this transistor was so it’s going to be hard to replace. And let’s face it, this thing’s not going to last much longer whatever I do.
I think we are done. Disappointing though. I don’t like being beaten.
James
Well the garden blinkenlight thing worked intermittently for a while and then didn’t. The first problem was fairly obvious. The positive lead from the DC / DC converter had fallen off.
You can see the state of the board. It’s been wet for some considerable time. The mode switch has fallen apart and I’d already had to bridge the power switch out.
After I soldered the wire on it was back to being intermittent. The next thing I noticed was that if I pressed on the microprocessor it would work and if I didn’t it wouldn’t. So the processor is dry jointed on the board.
The processor is this thing in the handy red circle.
It’s only got eight legs, but they are really small legs. Really really small.
I have played with surface mount stuff in the past but not often. I actually have a surface mount FM radio kit that I want to build but I’ve not got round to it yet. But I did get some solder paste to build it with so I tried it.
Basically it comes in a syringe, you squirt a bit of it on the pins of the chip and heat it with an iron, or preferably a heat gun. It flows onto the pins. There is much less chance of blobbing pins together. When you blob your pins together it’s a real git to unblob them.
So now it’s fixed right!?
Nah.
It powers up reliably now but it changes flashing mode every time. I’d like it to stay on the static setting.
So I took a closer look. The end pin is the one that is attached to the mode switch, or rather, the remains of the switch.
If you look carefully at it the solder hasn’t flowed over it very well. So I cleaned it up with a fibreglass pencil and resoldered it.
Fixed right!?
Nah, it’s still switching mode when it powers up.
Then I noticed this further up the board.
So there are two pins in the board and one solder pad where the pin has dropped out. This is labeled T2 so it’s a transistor. Let’s look at it and see if we can reconnect that pin.
Oh. It’s gone completely. It has (or had) wires going to the processor and a capacitor on it.
My guess is that this was the reset system for the processor. When the power comes up there is a point where processors do some weird stuff until the power stabilises. There is normally a reset pin that you hold until the power has stabilised. It just halts the processor. My guess is that without it the processor is running amok for a moment.
The problem is that I have no idea what this transistor was so it’s going to be hard to replace. And let’s face it, this thing’s not going to last much longer whatever I do.
I think we are done. Disappointing though. I don’t like being beaten.
James