I've previously cured a problem with an old Humax 9200T PVR (where the clock module stopped working) by cleaning the relevant circuit board (PCB) with isopropyl alcohol. This is a well known problem with the Humax 9200T and the "fix" is well establish (I've done it a number of times on my machine and that of a relation - all successful). It seems that over time, some residue builds up and bridges some circuits allowing low level tracking across the board.
Well, just recently my ancient Denon DRA-545RD Stereo Receiver started playing up. The left channel was very faint and lacking in bass. By playing with the controls I guessed that the problem lay in the area of the Variable Loudness (VL) control (slight pressure on the control temporarily rectified the problem). As that wasn't a permanent fix I deemed it necessary to dismantle and investigate further.
I could see that slight pressure on the PCB that the VL was connected to would again resolve the problem (but soon dropping back again). My initial thought was a dry joint of some other such soldering issue.
However,having looked at the underside of the PCB (the solder side), I could see some slight traces of black right by the VL connections. A quick swab with isopropyl alcohol seems to have solved the issue (at least for now).
So, my question is this: Is it that common for dirty PCBs to cause such problems? If so, it makes me wonder how many pieces of equipment are binned when a quick swab with isopropyl alcohol might fix the problem.
"So, my question is this: Is it that common for dirty PCBs to cause such problems? If so, it makes me wonder how many pieces of equipment are binned when a quick swab with isopropyl alcohol might fix the problem."
Taking your questions in order, my response would be 'reasonably' and 'probably quite a few'.