Just got a free amp. Repair advice?

Let's see some guts

Then we can see what work has been done to it (and the quality of the work)

 

It's definitely worth fixing. Get it fixed by a professional. Tube amps hold lethal voltages even when turned off, unplugged and the tubes removed.

But, if you didn't know, Leo Fender was a slient partner in Music man until 1975, when he became president of the company. The amps were designed by Leo and Tom Walker. They were extremely loud, and quite clean.

 

Wow, what a score. Take it to a amp tech. He/She can tell you what it will cost when they get into it, I'd bet it's going to be worth a lot more than the repair bill. I just wonder if it's just a loose tube/ wire, solder joint etc., since it woke up and sang loud and clear for a bit. Good luck!

 

Amp tech.
Don't stuff with it, take a shot of the tray if you must, but don't second guess the ability of an amp to send you into the ether, even when unplugged.

it'll be a great amp once it has been serviced.

 

That's a great/classic amp dude! Those things were made to a pretty high standard and its delightful to see it still has the original speakers.
If its nice and clean inside, that would be a wonderful thing to fettle and pass down to future generations.
Given the age, if nothing has been done, it will need the filter caps replacing and probably a few other current passing electrolytics. Coupling caps etc.
Grid resistors usually need to be tested and old carbon comp ones likely replaced. No biggie! Not sure if that is P2P or PCB? Be interesting to see inside her!
Its not dangerous IF you are aware of and understand how to discharge the caps prior to poking around. If you don't or its your first time, please do some research!!!

That said, as the jingle says, "If you don't know what the **** you're doin', ask an amp tech!"
But don't just ask ANY amp tech. Seek out a reputable fella. Far too many muppets and thieves (guys who will strip old tubes and caps and call it maintenance work etc) out there. Also far too many amp techs have zero regard for aesthetics or maintaining vintage integrity and will put ****ty orange drops in as replacements etc. If that stuff matters to you, definitely have "the talk" beforehand.

 

If you take the amp to someone to go thru it and it needs output tubes or has a output stage problem be sure to confirm on the phone that they know that in these amps the output stage is biased in class B, not class A/B as is the norm as they have very high plate voltage!

These amps can make good use of KT90 or KT120 output tubes for extended life over 6CA7 or EL34 type output tubes like they came with.

Most of these amps I have worked on just need tubes and all the power supply filters replace, even in the two solid state preamp sections they need the filters replaced!

At times they have bad regulator Transistors and as a repercussion of that a bad 60 cent IC chip.

Nice find by the way!

 

yeah that amp is worth fixing.
solid state pre amp with an all tube power section..... eminence made speakers.
i think these amps first came out in 1975 and the first models(not sure for how long) had a 12ax7 phase inverter.
these are the ones they say sound better, so if yours doesnt have that, you know you have a later model.
i saw a used 1975 model for about $799, so its worthva hell of alot more than you paid for it.

 

If you don't know what capacitors look like, or how to trace a circuit, you have no business poking around inside a tube amp. Many guitarists have died from doing just that.

If you are savvy, and know how to handle them safely, the job may be straight forward. It's even possible there's nothing wrong with it, could have been the previous owner had a bad guitar cable.

As others say, it's probably due for a filter cap replacement anyway.

 

Nice !

 

He shoots; He Scores !!!!

Get it fixed by someone good. Loud and clean. Great platform for pedals. Friend owned one years ago and always says he wishes he still had it.

While that is my advice. My reality would more likely be to just play it until I noticed a problem. Do as I say; not as I do.

 

Is a Music Man amp worth fixing? Dude those are some of the best amps ever made. Ooooo! Your has the one 12AX7 phase inverter tube... those are the older
more desirable models.

oh I’m a big MM user since 1975... those amps a monsters...

 

Too cool of an amp to let it self-destruct, take it to your tech.

 

Major league score there. Congrats! It may not ever had the caps replaced so that should be considered. I've owned a HD130 and also a RD 1x12 One Hundred. Music Man's are great clean, they are not overdrive machines. You've got something akin to a Fender twin there...I'm sure the weight is in the same neighborhood too...a real back breaker

Reverb/eBay listings are, like most things, higher than actual selling price in the wild but it's likely easily worth $500 to someone locally,,,in other words with no commission and shipping

The experts are here: http://pacair.com/mmamps3/forum
It's not like the Strat forum, like a social media platform, it's mostly just MM amp info but there's some real experts there. Should be some good reading if you want to know a bit more about the amps.

Here's my Strat talk thread of the refurb I did on my RD. I swapped out the speaker for an Emi V128 which sounded very close to what was in mine and shaved off somewhere around 8 or 9 pounds. If you keep the amp you may consider lighter speakers but keep the originals and put them back in when you sell.
'
Have fun with it.

 

There may be about 700V of fun in there. Music Man amps ran with very high B+ voltages.

 

In about 1980, I persuaded the company I worked for to stock MM amps. Good grief they were loud!

EDIT: I've just checked out what these amps sell for in the UK on eBay. There are sellers asking £900 ($1,152) for a really tatty example, right up to £2,500 ($3,209). TBH, I think the highest price is probably a classic eBay: "Honey, you know I've tried for weeks to sell that amp..." None the less, that's an enviable amp you have there and fully deserves looking after.