"No Problem Found"
If you have ever had a noise or rattle in your car and taken it to the mechanic, only to find that the noise will not occur when the mechanic is watching, you know about one of the greatest frustrations of our business.
In order to diagnose a failure, we must be able to duplicate and observe the symptom. If all appears to be working properly, it is practically impossible to locate the cause of the problem. (It's like chasing a ghost.)
When we test a piece of equipment that appears to be working normally, we generally assume that the user knows how to properly operate the unit, and that they would not have sent it for repair unless they did indeed have a problem with the unit. For this reason we usually go to considerable effort to identify the reason for the problem. We initially connect and test the unit in a basic arrangement. We operate all the controls and exercise the unit to its maximum limits. Then we test for failure due to vibration by any of several methods. We also use heat or cold to see if the problem occurs due to changes in temperature. We disassemble the unit and inspect for loose cabling and bad solder connections on any exposed circuit boards. We flex the cables and circuit boards. If the manufacturer has provided a test verification process, we perform those tests. We may also do a more extensive disassembly of the unit to expose and inspect circuit boards for cracked solder connections (a common failure causing intermittent operation). If the failure still does not occur, we will set the system up for extended operation and run it for hours or days (known as 'Burn-in') at various power levels over the time period.
At some point during this process, we will contact the user to obtain more information about the nature of the symptoms, under what conditions they occur, and with what other equipment the unit is being used. We try to determine if the problem could have been caused by other equipment or cables in use at the time. We also find out if the user is experienced with the unit or whether it was newly acquired, along with any other information they may be able to provide in order to help us duplicate the symptoms.
If we are still unable to duplicate the symptoms, we generally come to the conclusion that the problem was caused by oxidation on jack switches or cable connectors, so we clean and treat them with an antioxidant, as well as clean and recondition all accessible controls. Finally we reassemble the unit and perform a final check.
All of this usually requires more labor time than if the symptoms were initially obvious. While it may appear on the invoice that we didn't do anything to repair the unit and that you aren't getting anything for your money, we have in fact done as much or more work on your unit than if the problems were obvious.
You can help ensure that we repair your equipment properly the first time by carefully observing what conditions cause the symptoms to appear. Has it occurred more than once? What control settings do or do not cause it? Does it only appear at certain volume levels, or certain notes, or at all times? Does temperature affect it?
If the signal is intermittently cutting in and out, take a look at the article entitled "Solving intermittent signal dropout/noise problems" and try treating the jacks with antioxidant. (Call us.... we can supply it.)
Any information you can provide that will help us reproduce the symptoms will save you money and our frustration.