Blown Fuse :(

[Derrick1642607670]

Ok so I wake up today eager to bust out some STP (Went to their first "official" reunion gig and they were nothing short of amazing). I play through an AC30 custom classic, (the newest reissue of the ac30) I turned it on heard a quick grumble and then it lost all power. I checked the fuse and it definatley looks blown. Could you guys give me an idea of the best way to go about replacing it and finding the cause?

 

Thanks,

Derrick

[Strategery]

It's fried.

You'll probably have to buy a new one.

 

Too much Tofu in the circuitry.

 

Randy

 

 

[Fumblyfingers]

Well you need to find an electonics supply house and get the exact same fuse and if it is a Slo Blo make sure you get that..exactly the same. Get a few, perhaps a small case of them..like 5 in a case or so.

 

Then disconnect the power cable and change it out, reinsert the holder and tighten...not too tight if it is a screw in.

 

Plug the wall plug back in and turn on the amp. If it blows again you need to stop and take it to a specialist or if it is under warranty talk to the store you bought it at.

 

Do not attempt to open up the amp yourself.

 

Also, buy a small circuit tester from Home Depot the one that has the 3 green lights that tells you if your wall socket is wired correctly and if there is a good ground. They are inexpensive and should go into your guitar kit bag along with your cables, batteries, small tools etc.

 

Use it to check the wall socket you plug into.

[paully]

Derrick,

 

You should test the external fuse if you can(multimeter). If you don't own one or know what a multimeter is, don't even think about fixing it yourself.

 

There are an assortment of internal fuses in the power supply. Any one of them could also be the culprit. Not a safe place to muck around.

 

Best, Paul

[Fumblyfingers]

Yes I was talking about the external replaceable fuse...usually found on the back in the black plastic fuse holder. Never go inside unless you are a pro at it.....you could get nailed hard.

[miroslav]

Get a bunch of the exact same value fuses (I keep a large assortment of various amp fuse values on hand)and then if you want to do some preliminary checking on your own before you send the amp back...also get some new tubes.

 

Replace all the tubes and replace the fuse...see what happens.

You can even start by just replacing the rectifier tube and then the fuse...as a blown rectifier tube would create the symptoms you describe...a little rumble, and then nothing...

The rectifier is what converts your AC power into the DC voltage that the amp/tubes need...and some of the cheaper/newer reissue tubes can blow.

 

If it's not the rectifier...replace all the other tubes too...but after that, there is nothing much you will be able to do (and you will void your warranty if you start poking around inside).

It could be something else...like the power transformer...

 

[Fumblyfingers]

Just a thought Miro but that seems an expensive out of pocket expense buying all new tubes......especially if the amp is under warranty still.

 

It will be cheaper for him to go directly to either the store or amp repair and get a quote.....the diagnostic might even be applied to the repair if it is out of warranty.

 

I also do not think Derrick should be putzing around with replacing tubes just yet.

[Caevan O’Shite]

The fact that you "heard a quick grumble" before the amp "lost all power" strongly suggests that some component(s) in the amp have failed. Likely candidates include tubes (particularly the rectifier tube, and the EL84 output-tubes), and the large filter-capacitors for the power-supply.

 

It's a good sign that there wasn't smoke, and that you didn't smell the distinct odor of burning electronics. Tubes and filter-caps can often go on you without burning or catastrophic failure, and fortunately, they're relatively innexpensive and easily replaced.

 

You should most DEFINITELY proceed with caution, both for your own safety, and so as not to cause further- and possibly more extensive- damage. (Boy, do I know about that- been there, DONE that!)

 

And most definitely go with the exact same specific type and rating of fuse AS SPECIFIED FOR THAT MODEL OF AMP by Vox. It's almost certainly a slow-blow type, for sure, like Fumbly' said. Wear shoes when replacing the fuse and powering-up, and be sure to et the amp sit in "standby"-mode for a few minutes before you go full-on. Be at the ready to flip off the power-switch and pull the AC-plug if there are any alarming incidences...

 

Make full use of the "Feel free to ask Myles"-thread near the top of the first-'page of this forum, too... Myles has this stuff down cold, we're talkin' to a science... !!

[Dr. Ellwood]

Filter cap.

[miroslav]

Just a thought Miro but that seems an expensive out of pocket expense buying all new tubes......especially if the amp is under warranty still.

 

Mmmmm...not really.

 

You always need some spare tubes. Like imagine if your rectifier blew out at a gig and you had no spare.

Or you can use some extra/different tubes for tone experimentation...and eventually most will need new tubes to replace aging ones.

So even if all the tubes turn out to be good...nothing is wasted in the long runIMO.

 

I think a set of fresh tubeslike JJ's from Eurotubes...will probably cost less than the packaging and shipping of said amp back to Vox.

But hey...if there is a repair shop near buy...they can do the tube-swap-check easy enough at only a minor tech cost if purchasing a whole set of tubes is not desirable.

 

[Caevan O’Shite]

Yeah... I'm with Miro here!

 

Veering slightly off-topic here for a moment, you can never have enough good tubes on hand- let alone too many. Amassing a healthy sized stash of spares and alternate-flavors has been something on my things-to-get-around-to list for a while now...

 

You can be pleasantly surprised from time to time if you look inside old scrapped TVs and radios and the like for tubes; I've still got a few such useable "pulls" in a box, most pulled from curb-side junk on the streets of Rochester, NY! (Once I found- and still have- an antique all-tube 2x6V6 power-amp made by "The Radio Craftsmen"!)

 

And having some so-so, run of the mill, OK-but-nothing-to-write-home-about tubes to use when you're trying to diagnose amp troubles by a trial and error process of elimination could save you from accidentally frying some more expensive tubes that might be more sorely missed...

[miroslav]

...you can never have enough good tubes on hand- let alone too many. Amassing a healthy sized stash of spares and alternate-flavors has been something on my things-to-get-around-to list for a while now...

 

I've kinda' become a bit obsessed with tubes... I have a couple of cases full of tubes! :grin:

And I just bought a few EL84 tubes last night on eBay!

I tend to keep an eye on eBay tube sales all the time...and will pick up anything that's a good price and that looks to be of good quality. Sometimes what I get isn't top-shelf at max specs.but they all work fine. I've only gotten a few dead ones over the last few years when buying old stock.

 

I have about 4 dz. power tubes, a bunch of rectifiers and maybe about 10 dz. preamp tubes...all kinds of assorted types and brands...some "NOS", some used and some new manufacture.

Ive done a lot of tube swapsand yes, you can hear differences most times. I also have a good tube testerwhich is almost a must if you have a lot of tubes and want to compare them.

[Derrick1642607670]

Well replaced the HT fuse and that blew as well. This is really agitating considering the footswitch of the amp just went bad around a month ago. It looks like I'll call vox tomorrow and see what they reccomend, the amp is still well under warranty. Hopefully customer service actually comes through this time... when the footswitch went bad the employee was rude, made a huge deal out of the simple task of confirming im the owner of the amp (showing him the receipt), told me he would send a response within the next couple days. This guy completely blew me off, I never even got a response from my email sending him the receipt, I double checked the email was to the right address and even resent it weeks later. If they can't simply help me with fixing a footswitch it doesn't look very good seeing as now the amp is bad. And the dealer (guitar center) tells me that its irrelevant that I bought the amp through them and they don't want to do the slightest thing about it while treating me as though the amp being faulty was my own fault as if I rolled the amp down a flight of stairs.

[Fumblyfingers]

I gigged for the better part of 23 years and never, ever had a spare tube on me. I have had a fuse or two blow and I have replaced tubes in a couple amps because of noise or what have you. I have toured and played tons of Hollywood gigs which are quick in and out deals...basically my amps have had a fairly hard life.

 

The other point is his warranty. There is absolutely no reason for him to dick with the amp at all....just take it in and get it fixed. When it is out of warranty play around all he wants, but why risk a problem.

 

Derrick, if you get treated badly at the dealer send an E to the manufacturer and tell them of your plight. You will get results. Just make sure you are not rude in it.

[mdrs]

Derrick...who at Guitar Center was rude to you?? Was it a sales person?

 

I'd politely ask for the manager, and deal direct with the manager.

 

Nobody should be rude to you. That's just not right.

[Caevan O’Shite]

Yeah, that's right- under the warranty you should NOT do anything beyond what you've done, and it should be corrected pronto. And the GC people should DEFINITELY be involved and helpful... WTF? That's ridiculous, p!$$-poor service...

[Fumblyfingers]

LOL I think the reason many of us carried no spares is because it was expensive....I seem to remember a set of Groove Tubes being around $200.....does that sound right? I mean I knew of no guitar player buddy that had tubes spare.

 

Nowadays it is s different story perhaps....I imagine the tubes are becoming harder to find and the whole concept of changing tubes for tone has become somewhat of a boutique experience.....I have seen some of the Myles posts about what tubes are warm, softer sounding, bright etc etc.

 

Back in the day we used what was available. My rig was "stereo" for the longest time, the nice thing about that was if a head went down I could still finish the gig with the other amp. I have only had one am crap out on me...a Bassman that was a loaner....someone had wrapped silver foil from a cigarette pack around the fuse because it was blowing I guess, well it smoked the head....I disappeared in a cloud of noxious smelling thick white smoke....LOL, thank goodness it was a dress rehearsal.

 

What sucked is when I took it back to the store they tried to blame it on me, that I had compromised the fuse.

[miroslav]

YeahI played for many years too, and one amp went for 30+ years and I never changed the tubes in it! Heck, back in the days, I NEVER even thought about the tubesI just played. :grin:

Luckily...they never let me down.

 

But really...carrying spare tubes is no different than carrying a spare fuse. I mean...it may be even more important, 'cuz if the fuse is blowing because of a bad tube...then those spare fuses will be useless without a fresh tube.

 

And I don't have two cases of tubes because I'm worried about my amps blowing tubes...I have them because 1) tubes are only being made by a few companies now (some rather unreliable) and most of the venerable brands are only available as leftover stock that won't be around forever and 2) I like to try different tubes for different flavors.

 

With several guitar amps, and a few microphone preamps, compressors and not to mention microphonesall that require tubes...I just feel better having a decent supply for the future.

And whatever I dont use, I will be able to resell on eBay 10 years from nowprobably for a profit (the out-of-production brands).

 

AFA this Vox issue...it appears that he is going to have to package and ship the amp back to Vox....which will not be cheap...so I would at least try fresh tubes before taking that step...YMMV.

[Fumblyfingers]

I get what you are saying, but during a show if an amp craps out you are pretty much screwed. You are not going to have the time to diagnose and change out a tube.....it is just not going to happen. Even changing a fuse is iffy. In Hollywood it is back to back 3-5 bands a night. Your best hope is that someone in another band will bale you out with a loaner.

But as far as at home or in the studio, yeah, absolutely.

[miroslav]

Yes... you are rightin a very tight back-to-back 3-5 band night where everything has to move fastyou won't have time to diagnose and do major repairsetc.

 

But I remember a few technical SNAFUs back in the day :grin: when we often played as the only band for the nightdoing 3-4-5 sets.

We had blown fuses....blown horn diaphragms...broken wiresand other assorted mini-nightmares.

Heck...I remember firing up my soldering iron a few times during a set-break to repair busted connectors.and for some gigs, we use to leave one plugged-in on the sidelinesjust-in-case!

 

Most issues were dealt with during the 15 minute set-breaks (which sometimes came unexpectedly if there was a malfunction ). And then there were a few really bad nights where we chewed up 30-40 minutes diagnosing and fixing a problembut the crowd was always appreciative, and we always made up for it.

A lot better than just shrugging it off and telling them youre amp blew up.and you couldnt go on any more.

And we also use to carry at least one or two spare amps...

 

Its all relative to the size, and importance, and type of gig you are doingand sometimes, if you know you are going to get only 10 minutes to do 3 songs at a showcasethen there really aint no point in worrying about stuff breaking. You just bang it out and hope for the best!

But for the bigger/longer road tripsyou gotta have some backupsome spares, IMO.

And yesin the studioits an absolute necessity!

 

Getting back to the OPs Vox issue

The time it took for me to type out this reply and check for typos...I could have swapped out a fresh set of tubes in his amp to see if the fuse issue went away. Not to mention...you would probably kick yourself when it came back from the Vox repair shop...and if they said,"It was just a blown rectifier tube."

I'm not trying to be argumentative...I just feel that having spares...having some backup...is always better, then not. You may never need it...but it's there for that one moment!

 

[Caevan O’Shite]

Truth be told, this reminds me a LOT of the symptoms of rectifier-tube issues that a friend of mine had with his Vox AC30TBX. Sounds a lot like it may well be the rectifier-tube has gone.

 

Get a copy of Tom Mitchell's How To Service Your Own Tube Amp; there are a number of EXCELLENT flow-charts for trouble-shooting in there, very plainly, very logically laid-out, and very easy to follow for a step-by-step process-of-elimination to diagnose the source of such problems.

[Dr. Ellwood]

Filter cap (x2)

[Caevan O’Shite]

Filter cap (x2)

 

You may very well be right; I'd be much more inclined to think so, too, if it weren't a brand-new amp, new enough to still be under warranty. And it's not uncommon for rectifier-tubes (especially the ones being made now-a-days) to get KO'd in a Vox AC30, and it would have similar symptoms. Could still be a filter-cap like you say, though.

[miroslav]

Yup...rectifier tube...or filter caps...or power tranny...or...?

 

But trying a different tube is about the easiest check to make.

 

One thing with a bad rect tube...sometimes the amp WILL power on in Standby and everything looks good...then you flip the Standby and the fuse blows!

 

[BadLife]

Where exactly is this Guitar Center? The guys here practically fall all over themselves trying to be helpful. They even call after the purchase to check and see how things are working out. I would send an email to corporate headquarters and rat them in if they tried to pull that crap on me. I would probably escalate to the store manager first and let him or her know in no uncertain terms that they were about to have a boat load of crap fall on them if I did not got an apology and things sorted out immediately . There is no excuse for them to treat customers like that.

[Fumblyfingers]

Uh yeah I went over the managers head at a local huge music store, I won't say who, and had the big guy himself E mail me from New York. The regional manager then contacted me and they went in and cleaned up...well kinda, at least an effort was truly made. I should have gone to the manager first but I had been dicked around in there so many times I was done. I went straight to the top. The manager kept his job but I noticed he hired a couple older guys to replace one or two of the brain dead kids they had in there before.

 

Not that all kids are brain dead....these were though!

 

Writing to corporate works.

 

I have complained to Home Depot and Vons head office as well. Not that you can do anything about all the "laborers" loitering at Home Depot, but I had several other complaints.

 

The way I look at it, if I am going to spend the money I work really hard for and miss a lot of family time to earn it because I work long hours.......you better treat me decently or I will say something. I want politeness and I expect service.

 

I do not believe it is too much to expect.

 

Seriously, I am so done with bullshit and bullshitters.

[Dr. Ellwood]

Filter cap.

[Part-timer]

New VOX amps uses a valve for a rectifier? If the fuse blows as soon as you turn on the amp, most likely a diode or bridge rectifier (relplaced a valve in the late 60's.) They normally do not short but they would make the fuse blow right away.

 

A filter Cap would take a bit to load up before blowing the fuse. Same with most of the tubes in the amp.

 

Tube amps are much easier to trouble shoot than solid state amp. Some of the modeling amps and the 1980's Peavey amps need a computer tech.

 

It seems the simpler the amps construction is, the better the amp is. (observation)

[Caevan O’Shite]

So, Derrick- how'd you make out there?

 

Find out what the problem was?

 

Get the amp fixed?

[guitarzan6000]

I am an electronics tech, and I agree, my first place I would check is the Power supply filter caps. Fuses only blow if there is a direct short to ground. And caps are the most notorious source. If it's still under warrenty GC should fix it. I tell ya, the last few months since they got bought, I have heard nothing but bad stuff about them. GC used to be my "crack house" but not any more. If you sent in your warrenty registration card to the company, they should be able to tell ya where to take it if GC doesn't honor it. Keep us posted...PS, ASK MILES!!!