Peavey pa 120

I would check the caps on the power supply. They are rather large electrolytic capacitors that will look like they burst and/or leaking. When these die, the caps ground and the sub will make a loud buzzing sound. If you are handy with a soldering iron you can replace them yourself. Replace them with the same voltage or a little bigger and same with the size.

If the cap. says 16v 4700pF on it, for example, a 20v 5300pF or a 16v 6200mF cap. will work for this application.

Hello,

I need a bit more information but from what i can tell it's about the power supply capacitors issue, as this devices are known to develop such kind of humming annoying noise when they go under the specified value, let me know further,
Regards.

That sounds like mains hum! Most amps have large electrolytic capacitors to take it out. They can go faulty and let it in. They are high value often around 2,200 or 4,700 UF or higher.

2 Channel Peavey CS-800 Amp (800 Watts) ... Peavey CS-800x 800 Watt PA Stereo power Amplifier. The Part in question Q4025P is an alternistor. Two SCRs back to back that may have shorted out if it is not working.

You would send high as well as low to the sub and unless the sub had a built in crossover it COULD get muddy sounding. The specs SEEM to indicate the 118 DOES have a low frequency crossover so it SHOULD be OK... How would it sound? An 18 inch sub normally adds to the sound of a system... You MAY need to PAN over to send more power to the one side with the extra load on one side. Often people use two sub's... one for each side so it is balanced.

if you mean effects loop try graphic out to ultraverb input and output to power amp in. this will effect all channels of the xr500c

FIrst of all, in bridge mode there is only one channel. The "bridge" means that you combine the two channels together to get a single more powerful amp. The swollen part is probably nothing. Sometimes the plastic caps cup like that. Unless there is a specific problem with the amp, don't worry about it. Try placing the amp into stereo mode and testing each channel. If both work, there is no problem with the amp. If for some reason you need repalcement capactors, contact Peavey directly. They supply replacement parts.

Dan

The Peavey A/B controls are output gain controls. Your mixers stereo output goes into the amps inputs, channels A & B. The Peavey is the output stage to your speaker system. If you you connect the outputs from a power amp to the inputs of a mixer you will blow the mixers input stage, amongst many other things and possibly damage the amplifier too. The bias (Bass, Mid, Treble controls) are on the mixer, not the amplifier. Unless you are using a mixer amp, which you are not. A PA system DOES NOT work in the same way as an intergrated hi fi amp.

Hi There,
Hum can come from all sorts of places in an audio amp system......
The shielding on the input cables may be broken.
An earth somewhere can be broken....which then allows "ground loops" to form and unbalances the earthing...causing HUM....

Your note about reducing the controls to zero and the hum is still there leads me to believe that the power filter capacitors or some other filter capacitor in the DC supplies have dried out.
Capacitors can also go "open" which can cause low level sound and HUM.

The motto is "Capacitors get "old" and cause hums"....
It looks like its time for a full service....the amp has done you very well over the years and its like anything else needs a service now and then to maintian the quality of sound expected...If there is one capacitor showing you its getting "HUMMY" then there will be others in there as well needing replacement....

High heat can kill an amplifier so while its getting a check over there will be checks for other problems in there as well..Hot running resistors which can dry out adjacent Capacitors...

Cheers for now YUBEUT

What type of noise is it making? If it sounds like a load hum, you may have a 60 cycle hum issue. This is caused by a capacitor not filtering out the 60 cycle ripple on the DC voltage supplied by the power supply. If you have this problem I would suggest measuring the power supply with a DC voltmeter first and writing this measurement down. Then I would suggest you plugging the amp into an isolation transformer and taking an oscilloscope (plugged into the wall)and measuring the DC voltage while the oscilloscope is set to AC if you see an AC ripple voltage higher then .1mv you have a bad filter capacitor or a bad voltage regulator.