What Needs Replacing/Maintenance in my Amp?

[supergenius365]

I got this Boogie MKIIC+ used and have no idea of it's maintenance history. The amp was made in 1984. I have read filter caps need to be replaced every 10 years or so, but I don't know what they are.

I AM NOT GOING TO DO ANY WORK MYSELF! :nono I WILL TAKE IT TO A PRO. I JUST WANT TO GET AN UNDERSTANDING OF THE LAYOUT OF THE AMP
What else usually requires maintenance/attention? Thanks.
http://i100.photobucket.com/albums/m9/supergenius365/mesainside001.jpg

[phsyconoodler]

See those silver capacitors on the left side of the picture?They ALL need to be replaced.All the blue caps as well,including the one on the far right of the picture.You do not need to use sprague atoms like the originals are(blue caps)or the exact same Mallory caps(silver ones),but use good quality replacements capacitors of the same values.They require board removal to replace,so unless you are experienced,I suggest taking the amp to a good tech.

[Blue Strat]

The caps are the only thing that should be changed routinely unless there's a problem. The electrolytic caps are the big blue and silver cylidrical items in your photo.

[Blue Strat]

Ooops Psychonoodler types faster than me :D

[supergenius365]

Thanks.

So I am looking at replacing:

2 big silver caps
2 small silver caps
4 big blue caps

Is that correct?

[Blue Strat]

Yes, unless there are others that aren't visible. The amp tech should know.

[John Phillips]

Personally I would leave it alone at this stage unless there are obvious signs of problems - physical leakage, hum, loss of bass definition, ghost notes.

10 years is WAY too soon to replace filter caps. 20 years at a minimum unless they have actually started to randomly fail (in which case I would still replace all of them). Especially since more modern filter caps - 1980s onwards - seem to last a lot better than old ones did.

Remember that very many amps are still working quite happily with filter caps up to about 40 years old... there does seem to be a fairly big increase in failure rate about there though.

I don't replace any filter caps less than 20 years old unless there's a very good reason to, and between 20 and 30 years I go case-by-case. 30 years and upwards, replace if any other work needs doing. 40 years and upwards, replace even if that's the only thing that needs doing.

Just my opinion of course.

[Swarty]

Just my opinion of course.

Mine too, FWIW. If the amp does not display any symptoms of failed filters, leave it alone. If anything put some quality glass in it.

[Exothermia]

Well I'm going to disagree with the previous two posters. Replacing filter caps on an old amp just makes sense- and waiting for them to fail is pointless. Old capacitors are ticking time bombs. They are not that expensive. I look at electrolytic capacitors like motor oil in a car. Sure, you could wait 10,000 miles without changing the oil, waiting for the oil to literally "fail", ie, display visible signs of failure, when it in fact has not been functioning within specs for 7,000 miles, or you could simply do it on time and save yourself and your machine from the headaches.

If all you do with your amps is sit in your bedroom and noodle away then I suppose it doesn't really matter if your amp happens to fail the next time you use it. But if you use your amp with a band, at gigs, or in the studio, when you turn it on it needs to work, correctly, it needs to be able to be counted on to function correctly and you need to be able to focus on playing the amp and not worrying about when the next part is going to fail.

Like Psychonoodler pointed out, the silver and blue caps are the ones to be replaced. If you take it to a tech they shouldn't have any trouble finding them.

[TheAmpNerd]

At a minimum at this juncture,
I'd definitely replace the bias caps,
the smaller silver ones.

And as long are you are in there you might
as well replace the Longer silver mains caps.
If I recall I don't think these were the better
ones that Mesa used. I think these have
the fiber disk type ends.

The blue caps with the expoxy red disc last
a good long time and are all probably okay
for another 10 years or so.

Yours is a base MIIC+ model,i.e.,
vinyl cab
no 100 watt chassis and fan
no Simul-class
no Reverb
no graphic Eq
no int'l power tranny

Someone has repace some of resistors grids, plate and power cord too.
I'm not so sure if someone fooled around with the preamp.

I assume it is a combo what speaker can in it?

[John Phillips]

Someone has repace some of resistors grids, plate and power cord too.Ah... I couldn't see the pic earlier. Yes, ideally the carbon screen resistor on the power board needs to be replaced with a ceramic/wirewound like the other one. (I'd probably replace both with a pair of even better ones.)

Well I'm going to disagree with the previous two posters. Replacing filter caps on an old amp just makes sense- and waiting for them to fail is pointless. Old capacitors are ticking time bombs. They are not that expensive.
I'm not advocating waiting for filter caps to fail before replacing them - I do think it's worth waiting until there is at least some evidence that they're a risk, and not just changing them because they're a certain age (at 40+, it's pretty certain you will find warning signs though). If there's no evidence that any of them are on the way out, it's fairly unlikely that any will actually fail suddenly. I've also noticed a big drop-off in the failure rate of caps starting in about the early 80s - the technology may have changed slightly - although I agree with TheAmpNerd that the Mallorys are more of a risk than the blue Spragues.

Even with the older ones, some are much more long-lasting than others - the large radial cans that Marshall used seem to last far longer than the axials in Fenders for example. It also drastically depends on the pattern of use - if the amp has been used regularly, the caps are likely to be in much better condition than if it's been sitting doing nothing for years.

A full cap job is not that cheap either, and I wouldn't do it on that amp at this stage unless there's at least some reason to. But if there is, you might as well do the lot if you've got to have the boards out.

[supergenius365]

At a minimum at this juncture,
I'd definitely replace the bias caps,
the smaller silver ones.

And as long are you are in there you might
as well replace the Longer silver mains caps.

Someone has repace some of resistors grids, plate and power cord too.
I'm not so sure if someone fooled around with the preamp.


Sorry for my ignorance, but where are the replaced resistor grids?

It had an EMI 150 Watt MS-12

[teleamp]

Be careful with what you read.

How does the amp sound?

Has the amp set unplayed for 5-10 years, or more?

MikeY

[supergenius365]

There is some crackling and occasional whooshing sounds, but otherwise sounds great.

From what I was told, the amp has been heavily gigged since it's original purchase in 1984. The original owner replaced by it with 2 Victorias.

My main concern was reading that filter caps should be replace every 10 years or so. I am sensing from here and the Boogie Board that that is not always true.

I really like this amp and just want to take care of it. If it needs a little help after 23 years, I am willing to do it. I just want to know what kind of care it needs.

[John Phillips]

My main concern was reading that filter caps should be replace every 10 years or so. I am sensing from here and the Boogie Board that that is not always true.It's almost never true. 10 years is ridiculously short. Unless a cap has actually failed due to some construction flaw (it does happen, although rarely) I would never even consider changing them that soon. About the only case I can think of where there would be even any question of it is if the amp has sat more or less unused for the whole ten years, and even then it should be fine, especially if powered up slowly. I'll even install NOS unused caps that are up to at least five years old, if they've been stored properly, and I wouldn't if I thought there was any chance they'll need doing again within a few years.

[Popoon]

What about the whooshing sounds,is it a failing orange cap?

[phsyconoodler]

More than likely a bad preamp tube.
I am not a fan of saving a few bucks by leaving old caps in.As was mentioned previously,new style caps have improved over the years and have surpassed the ones in that amp as well.They are smaller and have higher temp ratings too.
If it was my amp I'd change them.That amp was built around 1984 or so?That means it is over 23 years old.It may last a few years longer,but why wait?Do it now and don't worry for another at least 23 years.
I am so old myself,that I think a 1984 car is not that old.When it goes up on the hoist,the holes in the floorboards make me wince a little.
Your boogie is old and decrepid just like me

[supergenius365]

As was mentioned previously,new style caps have improved over the years and have surpassed the ones in that amp as well.They are smaller and have higher temp ratings too.
I am so old myself,that I think a 1984 car is not that old.When it goes up on the hoist,the holes in the floorboards make me wince a little.
Your boogie is old and decrepid just like me

Thanks again for that DRRI pot!

What are some of the brand names of the newer caps I should use? Any brands to stay away from?

[phsyconoodler]

TAD caps are good.(tube amp doctor) Phillips,new style Sprague's,CD's(Cornell Dublier) Illinois and Xicon are all fine.Sprague Atomes WERE the benchmark in the past,but they have been obsolete for quite a while now.
Sure someone will pipe in and say they are the best on the planet,but that has been disproven by people over the last few years.The Atom technology has stood still while the other makes have kept improving.Of course the new Spragues are fine too.

Did you get the pot into the DRRI?Glad to help out!

[supergenius365]

TAD caps are good.(tube amp doctor) Phillips,new style Sprague's,CD's(Cornell Dublier) Illinois and Xicon are all fine.Sprague Atomes WERE the benchmark in the past,but they have been obsolete for quite a while now.
Sure someone will pipe in and say they are the best on the planet,but that has been disproven by people over the last few years.The Atom technology has stood still while the other makes have kept improving.Of course the new Spragues are fine too.

Did you get the pot into the DRRI?Glad to help out!

Thanks again.
DRRI works great.