This keyboard amp repair was for a Worksop based violinist who uses the full range speaker with his electric violin.
The amplifier was obtained second hand and had developed an intermittent problem in which the amp would drop out almost completely, leaving only a tinny high frequency signal. At first, I suspected that the LF driver or the crossover had become damaged, leaving only the HF driver active in the coaxial speaker. Normally, you would expect an HF driver to be damaged first, but LF drivers are still possible to damage.
However this wasn’t the problem. In the end I fixed the amp by replacing the corroded FX send jack and phones connectors. The shunt contacts on both of these interrupt the audio signal so they must be kept clean. To complete the Keyboard amp repair I then put the amp on soak test for 2 hours to verify that there were no further problems – there were none!
I shot a quick video part way through diagnosis:
If you need a keyboard amp repair, please drop me a message.