Mark III Maintenance

[SnS77]

hey guys,

I got turned onto mesa's and bought a mark IV which I have gigged for 5 years now and feel I know the amp pretty well. I have done minor maintenance on it like tube changing and speaker swap and stuff. My lead guitarist recently upgraded to a mark III, it really rips and when set up properly the two come together amazingly. The III is an 89 I believe, and the kid we bought it off of had very little knowledge about the amp, so IDK when or if it has been serviced.

No here's my question.. It squeals/feeds back pretty bad, worse than it should, and yes the gain is high. I can never tell if pre/power tubes need to be changed because to me its like getting fat..you look at yourself in the mirror everyday and you don't notice it, but if you look at a picture of you 5 years ago your like WTF!? Ya know?, you just don't notice the gradual decline til you put new tubes in. Also I have read a lot of posts regarding amps needing re-capped. Do you think it could be time for a cap-job and how would you be able to tell? Besides tubes and caps, what else would be common maintenance on a 25 year old amp? Should we take it in to get serviced? Thank you

 

[wezzley]

if you don't know how old the tubes are, and more importantly, how much usage they've seen, it never hurts to try a new set. especially with the noise you describe, might wanna start with the v1 / v2 preamp tubes.

 

[snorkel54]

If you feel there is a lack of bass in the amp, that you need to turn it to a higher setting, that is a indication that the caps need to be replaced.

 

[kekam35]

If you feel there is a lack of bass in the amp, that you need to turn it to a higher setting, that is a indication that the caps need to be replaced.

Actually its not lack of bass, a good sign is when the bass gets flabby sounding but an even bigger indication of bad caps is getting weird harmonic overtones.
In any case filter caps are only good for about 10-15 yrs so he might want to change them anyways.

 

[stokes]

With an amp that age,I would suggest new filter caps.You will notice an improvement in the over all response of the amp.Might even help the squeeling,but that is most likely a preamp tube.Mesa's are pretty hard on the pre's,more so than a lower gain Fender type amp and the newer preamp tubes just dont hold up like the old stock pre's will.

 

[BlackBoxy]

Hi,

I would change all electrolitycs caps on you Mark IV + blue voltage 50v PS 5w resistor with 500v spragues or F&T caps !
and check pre tubes, putting somes NOS US tubes !

would turn you Mark to a sturdy young bloody horse :wink:

 

[SnS77]

Can anyone give me an idea about the cost of a cab job? I know tube prices and such. Besides pre/power tubes and Caps, what else is normal maintenance on an amp of this age? P.S do you think if I am going to change the V1 and V2 preamp's to cut down on the squeal that I should just change all of them? Thank you

 

[stokes]

For a cap job on a MKIII,I get $65 plus cost of caps,I will only use Sprague and/or F&T's.Cant speak for anyone in your area.To check which preamp tube,if any,are microphonic (usual cause of squealing),just turn the volume up till you get the squeal,then back off just till the squeal stops.Now tap each tube with a pencil or chopstick,when you tap the problem tube the squeal will appear or the taping will cause noise.But it is best to change them all if they are all very old,but you can likely keep the ones that arent noisy.As for other maintenance,I would suggest cleaning and re-tensioning the sockets and cleaning the pots.