Loud hum and no output - Fender Frontman 212R 100W 2x12 Guitar Combo Amplifier

While it is possible (probable) it is caused by the AC mains modulating the output due to a power supply fault, it could be caused by inadvertently creating a hum loop due to poor grounding - check out the link below...

https://www.google.com/search?q=hum+loop+audio&rlz=1C1CAFB_enGB673GB676&oq=hum+loop&aqs=chrome.4.69i57j0l5.8500j0j8&sourceid=chrome&ie=UTF-8

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

One of the power supply voltages is bad... either a short or the regulator is blown. Follow my instructions for a previous poster:

http://www.fixya.com/support/t10013559-mackie_1604_vlz

If this monitor is humming without nothing connected to it, maybe the electrolytic capacitors from its power supply are bad - they are responsible for filtering the fluctuation at the output of the internal voltage rectifiers that transform the AC input voltage into a DC voltage to feed its internal amplifier.

When they fail, the supply voltage for its internal amplifier that should be flat, continuous, now presents a pulsating profile, according to the mains frequency (generally 60 or 50 Hz, depending on the country you're in). So, the output of the amplifier will be varying at the same rate, producing the humming.

Another possibility is that one internal cable connection that should be shielded is now disconnected or loose and is picking the hum from the internal power supply.

Anyway, maybe you should take it to a service center and have it checked.

Hope this info may help you!

i) Disconnect one lead of loudspeaker & insert an open-ended guitar cable into headphone socket.

ii) Put a dc voltmeter across open end jack then turn Frontman ON for a few seconds.

iii) The reading should be about 0volts - if the voltage is high (27v), then it is likely that the PA chip TDA1514A has blown.

iv) If,however, the voltage is correct in iii) , then reconnect speaker & put guitar cable into the POWER AMP IN socket & connect other end to guitar...Turn on briefly, if there is still hum then fault is in the output stages & will require chassis removal to solve.

Likely the power adapter has failed if it uses one. Try a new one first.

If half the rectifier blows out, a very impure DC voltage is applied which will be heard in the audio output.

sounds like the solder on the connections has either dried and cracked or come loosse if the wrigling of cables works its the connections if you unpluig and remove the back panel look where the cable connect check the condition of the wiring at source point of contact you may need to resolder or reconnect..

Hi there. The final output IC (big and black with 15 pins? attached to heat sink) is shorted and needs to be replaced. If you can still see color bands on R63, it should still be good.
Thanks
Paul

output caps. dont beat up your amp. crazy
yostamplifier.com

I would also be inclined to check all the larger electrolytic capacitors in the power circuits as well for AC bleed.