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Old Mar 10, 2012, 01:10 PM
tom66 is offline
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Basingstoke, UK
Joined Aug 2010
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Heating element on the Aoyue 968 died (for hot air)... have ordered a new one. Looked at it and it's arcing between wires and parts are getting very hot but others are very cold, this is causing the temperature to be erratic.

Anyway -

Started work on the power supply but even after several attempts couldn't get it to work. Will need to investigate why in detail. There is a short between SW and GND; and it might just be my layout or a problem with the board. I've replaced the diode and the switcher twice, and it still doesn't work. The short "seems" to disappear when either are removed, but I need to take a closer look at why.

I had to bodge a diode on because the footprints for the original diode were incorrect - this is the diode for the boost pin which generates the gate drive for the fet. It may be simply that this is wired up incorrectly or it may be a hidden solder bridge under the IC or diode, or a problem with the PCB. The main buck diode should be fine.

After several attempts the power supply area is looking very worn from flux so I've decided to prototype the power supply on a spare board.

Regardless it doesn't stop the prototype from mostly working if only fe. I'm going to work on adding the OSD parts soon and getting the two chips to talk to each other.

On the code front I have got the ADC calibration and conversion code working. (This converts an ADC code to a voltage and adjusts the results to compensate for errors in the dividers, reference and the dsPIC's ADC.) I will wait until the OSD is added to the board to test it fully.

Note diode is removed in attached photo.
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