Top 20 Marshall Amplification Marshall MG15 15 Watt Combo Music Instrument Amp Questions & Answers

Hi, I have repaired loads of these kinds of amps. The first thing to check is if the input jack socket is still soldered to the circuit board properly. These have a tendency to break. They all have a dual opamp and a 15 watt power amp chip. Invariably it is the power amp chip that fails IF it is an electronic fault. Both chips can be bought for a few pounds. The variations, aux input, spring reverb and this, digital effects are extremely unlikely to cause this kind of failure. At one time anyone with a screwdriver and a soldering iron could fix these, but in the days of health and safety, find someone who knows what they are doing. It should take half an hour and about £3 worth of bits. All the best, Chris the Fader.

I would test by first trying a different guitar cord. If the fault is still there, try jumpering the effects in and out jacks with a patch cord. If there is sound now, clean the two jacks with contact spray and working a 1/4 inch plug in and out of the two jacks.

Internal failure... take in for repair. It is NOT DIY unless you are electronically adept and have necessary equipment to repair it.

FixYa Subscribers have access to unlimited tech support, articles, and Experts!

Make sure you are using this on a three wire grounded receptacle. If you are on an old two wirepower system, have a ground installed in the receptaclel you are using. If you are on a grounded circuit, then exercise your warranty for repair/replacement.

It sounds like you bought a defected amp. You should contact Marshall and tell them the problem. You should have some kind of warranty.

Open the unit and restore the jack to the proper place. Do NOT overtighten the input jack mounting nut.

https://www.dropbox.com/s/6spu98r39t2wvcr/Marshall%20G30RCD%20Schematic.pdf

Most likely cause for this is an intermittent potentiometer. Check to see if any of them are mechanically loose as this is a sign that they have been damaged and could have cracked the wiper surface inside the pot causing this problem. Alternatively, any switch that controls any gain setting could also be intermittent or dirty. Gain of the amplifier should be stable, but is controlled by the feedback and signal injection at the pots so that is where to look first. Good luck, as intermittent problems are tricky, but sometimes better than no function at all which can be more costly.

Hi. Doesn't look like it as the speaker is a 4 ohm one and the head needs at least 8 ohm as far as I can see.

What type of Marshall, please? First of all, control the fuse and let me know.

clean switch connections

Make sure speaker cable works and is connected then check fuses. If it has a master volume, make sure it's turned up.

Does anything happen while you turn the knobs on the amp? I had a similar problem with a yamaha amp. It turned out a couple of knobs went bad. Soldered new pots and it works fine for me now.

http://www.manualslib.com/brand/marshall-amplification/amplifier.html Scroll down alphabetically.

Some Marshall serial numbers might tell you the year your 3005 was made, Marshall stamped the different years of the micro's in different spots, your number could either be on the back metal plate stamped right above the AC power cable port, or barely visible on the front gold plate above the power switch just under the Tolex, at least that's where my 1988 3005's serial number is stamped. But it should have one on it somewhere, could even be inside the head too, my sis plays and has an old 1977 50watt tube head with an interior serial number. I've been a huge fan of the Micro stacks since they came out in the mid-80's. I believe the 3005's were only produced from 1985 or so till around 1988 or 89 in Black, White, Red, Orange, Blue, Purple, and Grey, a Camo Tolex was a custom option as far as I remember. 1987 was Marshall's Silver 25th Anniversary, so a Silver Tolex Jubilee edition was made that year only. Than the newer MG15-II's were made from around 2004 till 2010 along with the Zakk Wylde signature series micro stack,. And now they make the newer MGD's since 2010, I just tried one last week at my local guitar shop, I liked it a lot, it's very different sounding than my old 1988 or my 2009 micro's and has a few built in effects which weren't great, but not that bad at all, I have a 1988 3005 stack that came with Celestion G-10's in the cabs and an MG15-II series micro stacks, that one came with some no name 10's, but believe it or not they sound better than the G-10's! Mine are all in black, I have been after an original micro stack in white for many years.Did your old 1x10 cabs come with Celestions too?

First check the preamp valve in that curcuit

Open the cabinet (remove back panel). Either a wire came loose or one of those 2 speakers is blown.

https://www.manualslib.com/manual/99237/Marshall-Amplification-Mg15msii.html