The Marshall VS230 is a 30-watt, solid state combo amplifier. It is part of Marshall's Valvestate series of amps. The VS230 has two 10-inch speakers and a single preamp tube. The tube does not power the amp, it colours the preamp tone. The stereo configuration means that this amplifier can generate on-board chorus effects. Solid state amplifiers use transistor technology to amplify the guitar's signal. The use of transistors means the VS230 amp is less likely to break down than a similar all-tube-powered amp, but repairs and maintenance are occasionally necessary.
Replace your guitar cable with a new one and remove all pedals from the signal chain. Faulty cables and pedals with dirty potentiometers can often create sounds similar to those of a faulty amplifier, such as crackling and hissing. Remove this potentially time-wasting distraction from your troubleshooting process by plugging directly into the amp with a new cable.
Troubleshoot your amplifier. Turn the amp off and dial the master volume to zero. Plug in the channel foot switch at the rear of the amplifier. Turn it back on and gradually increase the master volume. If the amplifier powers up, you can eliminate the power section from the troubleshooting process. If it fails to power up completely, it is likely that a transistor or fuse in the power section has blown out. If the amplifier powers up but creates no sound, the problem is likely to concern the preamp section or the speaker.
Remove the rear panel of the amplifier. Inspect the power section for blown fuses. A blown-out fuse will have a brown discolouration. Replace any blown fuses and replace all of the transistors like for like.
Inspect the boost channel tube. Valvestate amps come with a stock 12AX7 tube, located in the preamp. If it is discoloured, replace it with an identical tube or an ECC83 version.
Check the wiring. Disconnect any loose connections with your soldering iron. Melt away the existing solder joint, remove the residue with a dry cloth, and establish a new solder joint. Before reconnecting the wire, pull the preamp out of the cabinet and clean the potentiometers with a plastic-safe contact cleaner. Crackling and hissing is often caused by dust in the back of the dials. Reconnect the wires.
Examine the speakers and chorus module. If the amplifier is pulsing when the chorus effect is disengaged, check for solder bridges. These are caused by poor soldering that diverts audio signal into the chorus module. The pulsing is caused because the signal is delayed by the chorus module. Melt any solder blobs and wipe away the residue.
Test the amplifier before enclosing the rear panel.
Shine a flashlight on the amp's 10-inch speakers to identify rips. Rips in the speaker cause a flapping sound when the amp is cranked up. If the speaker is ripped, order a replacement, as repairs rarely lost long term.
Never use a screwdriver on the amp while the power is on.