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Equipment/PCB etch station: Difference between revisions
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The pump was replaced with a heavier duty medical unit mostly because it was cheap & available. The original was a fishtank pump and is still mounted on the front of the tank. It worked, but seemed not to have enough pressure available to overcome backpressure if the aeration tube had partly filled with etchant. Fitting it involved a few peculiarities, though. | The pump was replaced with a heavier duty medical unit mostly because it was cheap & available. The original was a fishtank pump and is still mounted on the front of the tank. It worked, but seemed not to have enough pressure available to overcome backpressure if the aeration tube had partly filled with etchant. Fitting it involved a few peculiarities, though. | ||
* There is a clamp on the tube near the pump, which can be used to restrict | * There is a clamp on a branch of the tube near the pump, which can be used to restrict a controlled pressure relief and hence the vigor of the bubbles. | ||
* The pump is no longer fitted to the tank, but instead rests in the cabinet | * The pump is no longer fitted to the tank, but instead rests in the cabinet | ||
* It is still possible to remove the tank for maintenance: the cable and pipe connecting to the pump are very long but if they need to be detached the cable can be unplugged from the back of the pump and the pipe unplugged from the | * It is still possible to remove the tank for maintenance: the cable and pipe connecting to the pump are very long but if they need to be detached the cable can be unplugged from the back of the pump and the pipe unplugged from the pump. | ||
* There is now a one-way valve between the pump and the antisyphon trap to reduce the possibility of etchant flowing into the pump. | * There is now a one-way valve between the pump and the antisyphon trap to reduce the possibility of etchant flowing into the pump. | ||
* The power connection to the pump has no earth wire connected and apparently swaps black/white colour coding. This is not just carelessness : the original black/white wiring apparently had black as neutral, white as live to the fish tank pump. The IEC lead to the new pump uses conventional euro colours : black is live. So black and white swap at the join. | * The power connection to the pump has no earth wire connected and apparently swaps black/white colour coding. This is not just carelessness : the original black/white wiring apparently had black as neutral, white as live to the fish tank pump. The IEC lead to the new pump uses conventional euro colours : black is live. So black and white swap at the join. It's not very important as the pump doesn't have a preferred live connection. | ||
* The earth pin in the cable to the pump is not connected at the pump end (it's a 2-pin connector) so there was no point connecting it at the tank end. | * The earth pin in the cable to the pump is not connected at the pump end (it's a 2-pin connector) so there was no point connecting it at the tank end. | ||
The piping requires some care. Because of the increased pressure available from the pump, if the bubbler is blocked it's possible for the pump to blow the pipe off the bubbler. This can then lead to etchant leak. | |||
At present, there are cable ties around the most important joints but NOT where it links to the pump. This tends to result in that joint breaking rather than any other, which is good because it's easily accessible and doesn't cause leaks. If there are problems with it blowing off too regularly, look into the cause : just fitting it more solidly is likely to lead to etchant leaks. | |||
Originally, I restricted the airflow into the tank (to avoid excessively vigorous bubbles) by pinching the air tube with a clamp. This often caused the pump connector to come off, prompting the use of cable ties. When the bubble tube silted up, it was that joint that came undone instead of the pump joint. This was a bad thing. | |||
A new configuration places a T joint near the pump with the clamp fitted to the additional open outlet. The idea is to make a controlled leak so that excess pressure is bled off rather than overpressurising the joints. It's likely that this will need to be adjusted as the bubbler silts up. | |||
==Instructions== | ==Instructions== | ||
