NO sound through the AMP even though the power light comes on

Question edited for clarity (with a guess at model).
Question moved from Television and Video.

If you want to check inside it, look for damaged components or blown or bulging capacitors. The best solution is to take it to a local electronics or audio store for repair.

https://www.google.com/search?q=crate+yellow+amplifier+no+sound

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1. Sounds like it's the input jack., but it could be the volume knob. Have you tried turning Gain1 and Gain 2 or the Clean Channel volume? Try them first when you're plugged in to the jack on the left , then when you're plugged in the back. If none of these work, it's most likely the preamp. 2. Even if the preamp is shot, there's a quick fix - get a guitar preamp or an effects pedal - they have volume and tone controls. 3. Finally - many pros just plug into the aux jack(on the rear panel) and control the volume and tone through their instruments. Hope one of these works. Good Luck.

If sure that power is reaching and getting into unit, then confirm that a signal is also reaching unit. If both are positive, then your gear is FUBAR if signal is going into correct input.

Clean the volume and tone pots with de-oxit cleaner

That is probably a momentary switch that is dirty and sticking. These onboard effects on guitar amps are usually nothing more than a computer sound card and I've found bad connections going to and from them as well. I do think that switch is dirty and sticking, though.

Hi,

This would only mean two things:
1. you have a bad capacitor in the circuit or the grounding on the circuit is broken and not filtering the obvious line noise from the circuit.

2. You have what is called, dirty power. That is when you have some kind of electrical device plugged that generates line noise which can be even a florescent light as they generate line noise.

Please take the following steps to narrow down the issue.

Take your setup and plug it in some where you know others can setup their rigs and it is using clean power. If, the humming goes away then it is dirty power where you originally setup.

If, it is still humming then you will need to take your equipment to a qualified marshall dealer have them look at it.

What could be an issue is if the cabinet is a 4 ohm cabinet and you plug it into the 8 ohm output. of the RT100 ... IT WILL BE LOUDER that way... for a LITTLE while... till the power tubes get gassy from overheating and the sound will GO AWAY. VERIFY the impedance of the cabinet and plug into the correct jack on the RT100. Every RT100 will do this... it is GROSS abuse of the amp if you plug 4 ohm speakers into the 8 ohm jack. Some of the power tubes may conduct so heavily when they get gassy that they will cause a hum before total failure. The tubes will first get red, then orange plates and that drives metal ions out of the plates, then they get a purple glow and eventually blow the fuse or something in the power supply.

This is likely a power supply failure OR the amp chip is bad, It is probablly in the TDA family such as a TDA2050

Power light means very little. If unit has a preamp output, plug a set of headphones into it and see if you can hear anythin going through. (it will be weak). If you can, the power amp section is bad. Take in for service.

NEVER use switch cleaner such as DeOxit on pots !!!!!

I have used CRC226 available at Home Depot electrical dept.

I SUSPECT that the resistance element in that pot is cracked. This is common if the knob sustained a hit. Replacing the pot is the only cure if the element is cracked.

Reviewing the schematic, ALL audio passes through the wiper on the HIGH tone pots. If the wiper is intermittent, so will be the sound.

If your unit is solid state amp, the pot looks like a 10K ohm LINEAR taper.
If you have a tube type, then the pot is a 250K ohm LINEAR.

Note that the other tone pots in the units are AUDIO tapers, but the high is a linear taper.

Get repair parts from either DigiKey.com or Mouser.com