Marshall 600 silver series bass amp head

A silly suggestion is to plug in a different guitar and see if the problem still happens. Have you checked the link your using to connect to the amp? For example is it a faulty lead, a loose jack plug on the end of the lead or an intermittent signal from a wireless connection? You could also check the pickups on the actual bass guitar.
Pick ups don't often cause issues but they can become faulty because of age, corrosion, short circuits and if they're badly fitted.

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?

Guitar amps have preamp sections (think unpowered audio mixer) and power amp sections (Crown rack-mount amp). An excellent way to isolate audio problems if amp is still producing audio is to check the preamp out (line out). Preamp output distorted = preamp failure. Connect MP3 player to "Power Amp In"...sound distorted = power amp failure. In your case the latter is the case as your "line out" is clean. Also test each speaker for clear sound as speaker cone damage from being overpowered is fairly common. At 300w. I'll assume the failure was not from cranking the volume to loud but a shorted speaker or speaker wiring could zap the power amp in an instant.

Hello,

A common issue with Marshall Amps are generally speaking a low resistor value cracked leg inside the power module, just open up the amp and with the amp unplugged from mains check by a little finger movement the big 2/3W resistors and possibly you will find that one or other will have a broken leg, also cold solder joints do this kind of issue, hope this helps...

I am not sure how you are measuring the power output to verify it is less than 200 watts. With a true RMS voltmeter you should see 28.28 volts RMS across a net speaker load of 4 ohms. If you use only one 8 ohm speaker, you will get 120 watts. If you are getting the 28 volts there is nothing wrong with the amp. You MAY have blown the speakers OR not generating much bass due to processing in an EQ. I assume you are using at least 15 inch speakers if you want to feel bass. Look up your speakers specs... you will need speakers capable of 32 Hz to feel much. With this amp your speakers should have aa total rating not less than 400 to 600 peak watts or around 300 watts RMS continuous power rating. Using a lot of high end EQ will keep the amp busy at the high end and reduce the power available at the bass end.

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

First thing is to verify the MAIN power source is getting to the amp. It may not be the fault of the footswitch at all. Connectors and cables are the usual cause of these problems. Seating of connectors is a common problem...

Well i know ive destroyed a guitar amp with a bass guitar before :-p this is why they make bass amps and guitar amps instead of just amps

The fuse is inside the unit so as to force you to open it and look for damage.

The fuse is likely a 3 amp/250 volt type.

Replace the fuse and then put a 100 Watt light bulb in series with the hot side of the power input. If the lamp stays lit with no load on the unit, then there is damage that requires repair before use. If you just replace the fuse repeatedly you may damage further components.

In the future obey the minimum resistance load on your amps.

You are ultimately limited by the available power of the internal amp. You can set controls for bass boost and turn off the treble but there is only so much power available.

HINT: If you are using speakers smaller than 15 inch, that will limit the bass as well. Use larger efficient speakers.