Dead Mark III - need help!

[scotte28]

Hi there,

Picked up my first Boogie yesterday ( finally!). It's a Mark III red stripe with all the trimmings - simulclass, imbuya cab, 200 W speaker, reverb, FX loop, etc. Looks hot, and GAS was (at least for now) satisfied.

THEN

Got it home, turned it on, checked the clean channel - good-, checked the lead channel -good, then began tweaking. 30 seconds later, boom, went completely dead. There was no noise to act as a warning, no nothing. It was like I had flicked the off switch, except I hadn't. I tried it in some different wall outlets and it just won't turn on at all. Very disappointing to say the least, but now I'm on a mission to fix it!

I'm thinking a blown fuse. Does this sound right? I guess it could be output tubes as well. Does anyone know what type/size of fuse a MarkIII uses? Can you get 'em at Home Depot?

One weird thing that may or may not matter - when I first plugged it in, even before I turned it on, the house lights flickered ever so slightly. Like they might when you turnm on a hairdryer in some houses . I know these Boogies are powerhouses, and our house is a bit on the old side.....Could any of this be a factor as well? Of course the Fender or the Marshall cause no such flickering.

Any assitance on offer here, would be much appreciated! Thank you!!

 

[Neptical]

Definitely sounds like you blew the slo blow fuse. You can get a pack of them for a few bucks at Radio Shack. Give a once over on your power tubes as well, never know.

~Nep~

 

[MrMarkIII]

Fuses are cheap. They blow in order to save more expensive parts from frying and dying. Generally speaking.

It's quite possible the blown fuse is an incorrect rating, so that's why it blew. The replacement fuse you want is a 3 amp Slo-Blo LittleFuse. But take the old fuse with you.

Unplug the amp from the wall before removing the fuse cap holder thingy on the rear panel next to the A/C cable. Juice goes through the fuse even when the amp is "OFF".
(It's not that big a deal. I've been zapped many times with no ill effecccccctttttssss... :lol: )

The blown fuse should look obviously "blown" - the glass cylinder may have charred markings inside, or the wire running from end to end will be melted and, uh, no longer running from end to end.

Just a thought, because this has happened to me:
check the wires going to the speaker. The EV 12ML has push-on connectors, and one or both could have wandered loose.
Especially check this if the fuse looks OK.

When you replace the fuse, turn the amp on, leaving it on Standby for a minute or so. Look at the big tubes. Are they uniformly warm, or is one staying cold? That may be a dead tube. There should be an orange glow inside each one, but not necessarily exactly the same. There may be varying amounts of blue haze swirling around the glass after you take the amp off Standby - it's normal. But look for one tube maybe heating up or glowing orange to red a lot more than the others. Sometimes you will hear a sputtering noise, maybe only when you play a loud bass note, maybe spontaneously.

Unfortunately, if you keep blowing fuses, there's probably something else wrong and it's time for the repair person.

Hope this helps. Keep us up to date.
It's a drag when your amp won't work.
Good luck.

 

[SonicProvocateur]

If a power tube had blown you would have heard the sound of it dying moments before (lack of gain/volume) and if it had taken out the screen grid resistor with it (as mine did in a gorgeous display of tube flashing light followed by the amp dying and smoke!) You would immediately know.

Odds are you crapped a fuse. As others have said - 3 amp slo-blo. Glass type, I believe.

As MrMarkIII also pointed out, since you just got your amp, make sure all your connections are tight too, something may have wandered.

If you suspect the wiring in your house/fuse box is junky, invest in a power conditioner to protect your investment. My vintage electric mistress is ruined from bad wiring in a friends house.

 

[JD]

I had this problem what I had done was have a brain melt and had the 6l6's and el34's swapped this would cause the fuse to blow after about 2 min so make sure you have el34's in the outer sockets.
Also if a power tube has gone get a 2 amp sloblo fuse just for the test you can put the 3 amp fuse back in when everything is ok turn the amp on but don't turn the standby on yet let it warm up while looking at the power tubes turn the standby on and see if any of the tubes flash if 1 does thats the faulty tube with the 2 amp fuse in it should blow quicker than a 3 amp and hopefully not do any damage.
Replace the faulty tube/s put the 3 amp sloblo fuse in and jam away.

 

[Facelift]

NEVER plug straight into a wall socket. ALWAYS use some sort of surge protector, especially in an old house.

 

[>Photi G<]

NEVER plug straight into a wall socket. ALWAYS use some sort of surge protector, especially in an old house.

I don't see a problem with plugging straight into an outlet. Sure, a power strip/surge protector or a power conditioner is a good extra measure, but it is unnecessary for the most part. All Mesa/Boogie amps from the Mark IIB onward had a built in surge protector in the form of a MOV. This could have been the problem. You should replace the varistor if you've had a surge and the amp won't turn on.

 

[kdorsey]

NEVER plug straight into a wall socket. ALWAYS use some sort of surge protector, especially in an old house.

I don't see a problem with plugging straight into an outlet. Sure, a power strip/surge protector or a power conditioner is a good extra measure, but it is unnecessary for the most part. All Mesa/Boogie amps from the Mark IIB onward had a built in surge protector in the form of a MOV. This could have been the problem. You should replace the varistor if you've had a surge and the amp won't turn on.

Facelift's intended message is sound, just not accurately stated. You should, if possible, always use a power regulator or conditioner. This can be a Furman-like product or other device that conditions the AC power before reaching your amp. A surge protector won't do diddly squat to prevent the poster's issue.

And Photi, an MOV fails open, so it wouldn't cause a fuse to blow.

A fuse blowing is not a good thing. It's the last resort before catastrophic failure. The amp should be completely inspected - inside and out - before replacing the fuse and trying again. The next time may not end so smoothly.

If you're electronically inclined, tear the thing apart. Feel free to post pics. Otherwise, seek the advise of a local professional. Don't blow up your new investment.

 

[scotte28]

After reading the helpful suggestions here, I took out the fuse. Sure enough, the filament that runs from end to end, was snapped. So, went to Radio Shack, got the same fuse, put 'er in, plugged into a surge suppressor instead of directly into the wall and she works, hence ushering in a new era of my guitar playing!

It was a long weekend up here in Canada so i got to spend more than the usual amount of time with it, and first impressions are simply, WOW. I started with the recommneded factory settings from the manual and was able to easily dial in lots of great tones, yet I have this feeling that I've only scratched the surafce of what this little beast with the big tone can do! So far, no other issues, and I've put a few hours on it. I'll post some pics when I get a chance, but as of now I am one happy camper!

Anyway, I just wanted to thank all those who responded. Your comments were supportive and educational and made me feel good (insetad of terrified) about seeking a solution for the issue.
This community/board is great! Thanks again folks!

Scott

 

[Neptical]

Scott,

No problem! Glad to see it was a nice easy simple fix. I'm sure you will have a blast with discovering all the tones you can pull out of your Mark III. As you can see, there's alot of folks here that truly believe it was one of Mesa's best amps ever produced! Good to see her back up and running. Enjoy!

~Nep~