Firing up an amp after a long dormancy?

seajay

Member
Messages
2,671
Hi everyone. I haven't fired up the ol' Mark III in a few years. Any precautions that I need to take before turning this amp on after such a long time? Isn't this a common scenario for blowing a capacitor?
 

vintagelove

Member
Messages
2,691
If you can, try to bring it up slowly with a variac.

I'm not sure it's as important in 3 years as it is when its 30 years.

Best,
 

Steppin' Wolfe

Silver Supporting Member
Messages
5,369
A Variac is a good tool for this purpose....start out at 20VAC output and bring that voltage up in stages over a 6 hour period or so. IF you don't have that or some other voltage controller, a current limiter is advisable. that said, most people would have already fired it up and lived with the risk/results.
 

DiPa

Constant GAS
Messages
14,653
3 years ain't that too long, turn it on and play.
You may have some initial noise ramp but that should hopefully stabilize over 10 mins or so of playing it.
If the caps are gone bad, you will know.
 

seajay

Member
Messages
2,671
I don't have a variac but that's good to know...I hadn't thought of that.

I think the go ahead and try crowd has won me over. Especially with the 3 years vs. 30 year argument. Yes the amp is almost 30 years old but it has only been sitting for 3.

I'll report back.
 

lemonpaul59

Senior Member
Messages
2,065
Hi everyone. I haven't fired up the ol' Mark III in a few years. Any precautions that I need to take before turning this amp on after such a long time? Isn't this a common scenario for blowing a capacitor?

Been there done that. Typically I will leave them powered for a few hours before playing. In other words, just idling. Another thing I do is twist all the pots vigorously before applying power, to shake out the dust and corrosion.

I've got a similar problem with an old Crown CE-1000 PA amp. Hadn't fired it up in years. Now a channel drifts on and off. Most likely an electrolytic cap. I broke the amp in for days, still get the channel dropping out. She's going back to Indiana soon.
 

Steppin' Wolfe

Silver Supporting Member
Messages
5,369
30 year old caps....3 year dormancy.....things will probablywork out by just turning it on. IF not, don't say I didn't warn you.
Here is a video from Uncle Doug. Please note the blurb below the youtube screen as to why one would want to utilize one of these. IF there is a problem with an old cap, the current limiter will indicate that problem and limit any possible damage. Simple tool....it is useful for a player...a necessity for a tech, imho.

 

FFTT

Member
Messages
28,352
If you listen closely, you'll hear the screams of dust mites roasting.

Hopefully there aren't any mouse turds in your chassis or reverb pan.

Stink Bugs love to hide and die.

These days you have to consider bed bugs, fleas, cockroaches, all kinds of hitch hikers.


 

seajay

Member
Messages
2,671
I played the Mark III last night and it was fine. I started it on 1/2 power mode, thinking that would be safer than full power. I later switched to full power and it worked just fine.

It's still a righteous sounding amp. It must have been the highest gain amp available at the time because it is still plenty high gain by today's standards. I'm surprised every thrash band of the day wasn't playing through one. Palm mutes sound excellent through this amp.
 

seajay

Member
Messages
2,671
Been there done that. Typically I will leave them powered for a few hours before playing. In other words, just idling. Another thing I do is twist all the pots vigorously before applying power, to shake out the dust and corrosion.

I've got a similar problem with an old Crown CE-1000 PA amp. Hadn't fired it up in years. Now a channel drifts on and off. Most likely an electrolytic cap. I broke the amp in for days, still get the channel dropping out. She's going back to Indiana soon.
I did the twisting of pots thing as well as working the pull-out pots too. Some controls were still scratchy. I think about sending it to Mesa for a checkup or tuneup. Maybe get the Mark III+ mod done.
 

Steppin' Wolfe

Silver Supporting Member
Messages
5,369
IF they are still doing mods. The last time I inquired about modding an old MK amp, they said that they did not do that any longer. I am sure that they will refer you to someone who has that experience for the job, though.??
 




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