I left my fender frontman 65r on for over a year and yesterday a gentle hum for a few seconds then a loud hum for a few seconds more then no more power to the unit. I opened it and troubleshooted it around the power supply, fuse 3.15A is ok, diodes are ok, the power resistors are ok, the power supply tansformer's primary winding is open. I substituted it for a similar one and powered the amp up and again the smooth hum for 2-3 seconds and then the louder hum. I turned it off. I had my guitar plugged in with it's volume turnd up but no amplification at all while the amp and its volume turned up. I assume there is a short in the power unit but the output transistors seemed ok
Music - Fender - Frontman 65R 65W 1x12 Guitar Combo Amplifier
Answers & Comments
Why was it on for over a year :D Has anyone replaced the fuse? In the service manual I found it has to be only 2 Amps! Okay let's solve the problem. The power transformer was overloaded which caused the broken winding. It is still overloaded what can be heard by the hum sound. First thought was to check main capacitors or better just replace them! If the hum gets louder, they might also become warm. Check voltages after bridge rectifier and smoothing circuit. They should be +/-42 V (TP3, TP4) and +/- 16 V (TP5, TP6) Let me know which of them is faulty Cheers