Dead mark lll

[make13]

Hello there, i'm new here, well i've been reading this forum for ages but this is my first post. I have a Marklll blue stripe. I did purchase it back in 91 and never looked back, no need for another amp.
Anyway, my friend played with it and he told me that all of sudden it went dead. I checked it and the fuse was blown.
The tubes were rather old anyway so i went and replaced all the power and preamp tubes.
It did do the trick and amp worked just fine. I did play one rehearsal session with it and next rehearsal it worked just fine until i had a cigarette break, when i switch the amp on again it went dead. It blows the fuse immediately.
I wonder what might cause this. Any idea? Anyone?
-Make-

 

[Boogiebabies]

New tubes may not always last long enough to evaluate a problem. you may have a bad new tube. It could also be a short in one of your filter caps. I would have them and the tubes checked out.

Even if the tube blew and took the screen grid out with it, the amp would work with new tubes. It's probably the new tubes have a bad one in the quad or duet.

 

[make13]

Ok, finally i had some time to check my mesa. I took it out of the chasis and cleaned all the tube sockets etc. After the cleaning i put the tubes back and tried to switch it on one more time, just in case.
It didn't blow the fuse and all the tubes seemed fine in standby power, so i thought that it might work.
Next i put it back in the chasis and switched the AC/DC on, everything seemed to be okay. So, I connected the speaker cable to try it out.
Then it happened again, I just flick the power on and it blows the fuse immediately.
I tried it again without speaker cable and it didn't blow the fuse and then with cable and "puff" the fuse is gone again. Now i'm out of fuses and puzzled :roll: .
It's pretty hard to find a good mesa tech here in finland so it would be nice to have some clue what might be wrong with my amp before i start to find a guy to fix it. Any idea? Anyone?

 

[Restless Rocks]

Never never never ever ever loan out your Boogie! Ask your freind how many speakers he had hooked up and if he knew what he was doing if he did. Your problem, if you are not able to test your output tubes for shorts, or a new set still does not fix the problem, will probably require a tech. And remember never never never never ever ever ever ever loan out your amp without proper collateral, ie. his wife or girlfreind or car (provided it's worth as much as your boogie is to you).


P.S. you should test drive the girlfreind first just to give yourself a chance to reconsider. Even then not a good idea!

 

[disassembled]

Maybe you have a bad speaker or bad speaker cable. Is it a combo or head?

Greg

 

[joepopp]

I remember back in the 90's I had the same problem with my Mark III. I sent it back to boogie and it turned out to be only the power tubes. I had TWO bad brand new sets! Bad luck but it happens. See if you can put in a known working set. Take them out of your friends amp!

Speaker cable is a cheap test too. Be sure the fuse is the right value too!

 

[Boogiebabies]

I do a full check up on all of my amps every year. I clean, scrub and tighten the pre and power sockets with a dental pick, clean and lube the pots, clean the reverb cables and soak and clean the star ground. In 10 years, no blown tubes ( Dougs Tubes, GT's and Triode Electronics ), no scratchy pots and totall reliability. I clean any exposed circuit boards and solder connections with PCB cleaner. A Q-Tip is great for cleaning exposed traces and even a shiny trace or joint will give you more dirt and oxidation than you could imagine.. Gently vaccum, or use a micro fiber cloth to get the dust bunnies. A good 0000 Scotch Brite cut like a french fry is the best for cleaning input sockets until they shine like new. I also inspect and coat the transformers to keep them from rusting. Other than an occasional cooky preamp tube, Boogies are awesome.

Whatever you do, do not use contact cleaner on the EQ faders. They are impossible to lubricate. They use a special thick grease that cannot be replaced due to the design of the slider.

I also check voltages at the caps, bias voltage at the caps and plate voltages for the pre and powers. In case anything goes funny, I have a pretty good map of where a critical problem may be. Another trick I use is to test the power and bias caps out of circuit for capacitance. IMO, when they generally read 30uf, 220uf and 47-50uf for the bias caps I leave them. Each amp has it's own medical history and chart. This is also part of my Boogie restoration and revitalization regimen. You would be surprised how an old amp can come to life when it clean and free of multiple little problems.

With this regimen I also get about four to five years of good tube life.
I have been running NOS Svetlana's I bought from Ned at Triode and after 4 years, they still draw exactly the same bias as when they were new and have the same output.

Good Luck, I hope she get back up an ripping.

 

[make13]

Maybe you have a bad speaker or bad speaker cable. Is it a combo or head?

Greg

+1. try a different speaker cable and cab.

It's head but i don't think it's the speaker or cable since they are hooked to another amp and everything runs smoothly. And the problem problem occured with another speaker and cable.
The fact that i can put the "basic" power on (standby off) without speaker
but not with speaker appears very weird to me. I mean , if it were bad tube
wouldn't it blow the fuse in both cases. Well, what do i know, i just like to play with that amp. I wish that mesa was a finnish company so i could take my amp to good hands.

 

[Shep]

when you turn standby on you are only putting turning a 6.3v or so heater filament on in the tube....the tube only turns and gets going when you have the power switch on..

 

[Buddy]

Quoted from Boogiebabies :
" Whatever you do, do not use contact cleaner on the EQ faders. They are impossible to lubricate. They use a special thick grease that cannot be replaced due to the design of the sliders .[/quote]

Oop's , I just did that , the sliders were stiff and the center detent was non present . Gave 'em a squirt with c.c. Should I try some immediate remedial action ? They did loosen up somewhat .
Is that a bullet hole in my shoe ?

 

[Ed Mullins]

Boogiebabies,
What do you coat the transformer with to keep it from rusting? If a little rust is present would you cover it up or try to remove it first? Good advice on the cleaning methods. I've also use contact cleaner on my eq. I'll not do that again. Had no idea.
Thanks,
Ed

 

[make13]

I'm not sure if i should share this with you guys because i've never felt this stupid before. My mark lll is up and running now. I just used wrong fuse.
:lol:
I managed to blow up a bag of F marked fuses when all i needed was a T marked fuse. But i didn't realize it because it worked couple hours with fast fuse. Now i just have to take it to rehearsal room and make sure it really works. You live and you learn. And yes, i do have blond hair.

 

[make13]

Never never never ever ever loan out your Boogie! Ask your freind how many speakers he had hooked up and if he knew what he was doing if he did. Your problem, if you are not able to test your output tubes for shorts, or a new set still does not fix the problem, will probably require a tech. And remember never never never never ever ever ever ever loan out your amp without proper collateral, ie. his wife or girlfreind or car (provided it's worth as much as your boogie is to you).


P.S. you should test drive the girlfreind first just to give yourself a chance to reconsider. Even then not a good idea!

Well, he didn't ask to borrow it, he just couldn't keep his dirty fingers off.
And that will be the case with me and his girlfriend too.

 

[Boogiebabies]

Quoted from Boogiebabies :
" Whatever you do, do not use contact cleaner on the EQ faders. They are impossible to lubricate. They use a special thick grease that cannot be replaced due to the design of the sliders .

Oop's , I just did that , the sliders were stiff and the center detent was non present . Gave 'em a squirt with c.c. Should I try some immediate remedial action ? They did loosen up somewhat .
Is that a bullet hole in my shoe ?[/quote]

The best you can do now is use Caig Cai-Lube. It will give it some lubrications. I made the same mistake on my 80Hz slider and it still works fine, but moves very fast. It does not have that usual resistance. They are stiff because they are vertically mounted and could fall from the amps vibration. With that 80lb grease, they don't move.

 

[Boogiebabies]

Boogiebabies,
What do you coat the transformer with to keep it from rusting? If a little rust is present would you cover it up or try to remove it first? Good advice on the cleaning methods. I've also use contact cleaner on my eq. I'll not do that again. Had no idea.
Thanks,
Ed

I use a tooth brush and naptha or denatured alcohol. They evaporate very fast so they will not get into the lams. After that I wipe them down again with naptha until I see no signs of orange. The oxidation needs to come off or you will basically just seal it in. You can coat it with shellac for an impervious barrier. I use a lubricant called Wurth HHS 2000 which is a synthetic lubricant that lasts for ever. A thin layer and it's good to keep the moisture our. I wish Mesa made them all like the one off my Imbuya 84. The whole PT was covered in potting resin and looks like the day it was born.

 

[E_R]

I'm not sure if i should share this with you guys because i've never felt this stupid before. My mark lll is up and running now. I just used wrong fuse.
:lol:
I managed to blow up a bag of F marked fuses when all i needed was a T marked fuse. But i didn't realize it because it worked couple hours with fast fuse. Now i just have to take it to rehearsal room and make sure it really works. You live and you learn. And yes, i do have blond hair.

Oh man I did that before with my DC-5, I grabbed the wrong box of fuses when I went to replace em... I didn't even realize it until I ran out (5 per box) and went for another box in my garage. Then I found I had gone through a box of the wrong ones.....**** I'm lame LOL