My marshall vs 225 combo amp pops and make loud noise when turn on and cnot get sound from amp

Hi J Wade. I'm Dave P. I'm not a guitar amp expert or technician but I've been using amps and effects for 35 years and there are a couple things I can suggest.

That kind of periodic noise/switch noise can be a symptom of having the polarity of the amp reversed. If your amp has a 3-position OFF/ground switch, try reversing the ground. If it doesn't, take the plug and turn it around. Just don't get near a microphone unless you're sure your amp is grounded the same as the P.A. It could fry your lips off.

Dirty switches to that too. You said the noise is in time with the delay's tap time which is set by a foot switch. If tapping that switch the first time generates a pop, the delay may have catch it and is repeating it. Turn off the amp, remove the delay foot switch and turn it back on. Still noisy? If not, give the foot switch a good cleaning.

When you turn the EFFECTS knob up, is it scratchy? Might need the potentiometer cleaned. What happens when you specifically turn the DELAY level down all the way while using the other effects? Noise still there?

That's all I've got. Hopefully, it was helpful. Don't wrack your brain over this too much. There could very well be an internal problem with your amp that will require a trip to the shop. You don't want to open it up yourself. Rock on but be safe.

Dave P.

My high pitched noise was due to a resistor not being soldered enough to make a good connection at the back of the input jack.

may be one of the electrolytic capacitors in the power supply has become leaky...this is a common problem among amplifiers...so you let it cool down..then after a period of time the capacitor heats up and then causes the hum...the power supply caps filter out the 60 hertz ac line noise...which is probably the frequency of the sound it is making...this is a good indication of these caps going bad....another thing you can check is to see if the amp is properly grounded(eg: the ground pin on the plug is present) and that you dont have an open cord or input

I may be missing something but i cant see what amp you have? Is it a valve or solid state marshall?

Have a look at this link:http://www.geofex.com/ampdbug/squeal.htm then Back to the Home Page. You may have a bad solder joint some place on the circuit board also. Unless you have experience with electronic repairs you are best served by consulting an accredited Marshall dealer and repair person as there are voltages present that can kill or injure you.

One of the tubes COULD be microphonic.

Take back off and use a pencil to lightly tap each tube to see if one causes noise.

I suspect the power supply for the effects processor has failed. The effects unit will "go crazy" when power supply is too low voltage.

If the amp has loud noise, then the power amp portion is PROBABLY OK.

I had a similar problem in a Behringer amp caused by a bad electrolytic filter cap.

Your welcome. I'm glad I could help and if it came that way marshall should do it for you.

Could very well be the fan. The motors can cause interference. There may be a solution to get rid of the noise. Some copper shielding tape may help. You could rule out it being a microphonic preamp tube by turning the amp on as normal and tapping the tubes with something non-conductive. If you hear the tapping noise coming thru the speakers while doing this to a particular tube, replace it. With power tubes, the tops of them turn white on the top when they become microphonic, along with plenty background noise.

Before you bring this into a shop, try spraying out all of the controls. Use an electronics switch cleaner that contains a lubricant. Spray into the control and work the control back and forth a number of times to loosen up any dirt inside. Then spray it again.

Let me know if that resolves the problem.

Thanks,
Dan