Re: QCX TROUBLESHOOTING


Bob M.
 

Can you disconnect the secondary of T1 to check that 2.5V bias voltage? I don't know if the IC it feeds is passing that bias voltage to the circuitry to its right (on the schematic) but I suspect everything along that signal path is DC coupled so if you remove the chip, there won't be 2.5V present for the stuff after it. If you're going to remove that IC anyway, it's worth measuring the bias voltage with it out.

A product called Chip-Quik is amazing for removing SMT ICs. It alters the melting point of solder such that it stays molten long enough for you to grab a component and lift it right off with no damage. It's not cheap but you use so little of it, it's worth the price. They sell it in kits with some liquid flux included. You apply the flux, heat the connections, apply a tiny amount of Chip-Quik (it looks like solder) to all the joints, then lift the part off the board. In the case of an IC, flood the leads and pads with Chip-Quik, even if it's just one row at a time. Reheat it and lift the part off. Clean the board with solder wick or vacuum desoldering equipment then some isopropyl alcohol, and you've got a new clean place to install a new part.

Join QRPLabs@groups.io to automatically receive all group messages.