My Fender Quad Reverb just died. Why?

[C/G]

While tracking guitars last night, my beloved Quad Reverb decided to pack it in. It was *blackfaced* a few years back, has all new tubes with very little hours on them.

The amp simply stopped working. No noise, smoke or burning smell, it just stopped and had no power.

I checked the fuse and it had blown, but what would cause this? The amp has never had any issues until now. The room was very hot and the amp was getting pretty darn toasty as well. Would overheating cause a fuse to blow?

I have not tried putting a new fuse in yet, but should I try putting a new fuse in and see what happens?

I'm no amp tech so I don't want to damage anything further by turning it on again.

BTW, the transformer near the power tubes was really damn hot when I touched it. Is that normal for the amp being on for an extended time (4 hours in a very hot room)?

Thanks.

I need this thing running to finish tracking tonight or I'm screwed.

[AdamJay]

had you rebiased the power tubes ?

[C/G]

Yes. Everything was done professionally when it was blackfaced by a very amazing amp tech/builder. Unfortunately he now lives 2000 Km away from me now.

I might just try to pop in a fuse and see what happens. I am going to make sure the power tubes are seated properly ect. This is boggling my non-electronically adept mind.

Now if I could only find a 2A slow blow fuse in this city. What a shit show.

[amorris]

hot transformer is not good. drawing way too much current. new fuse will undoubtably blow. pull power tubes and try fuse. if it blows, transformer shorted. need new transformer. no other way.

[C/G]

Originally Posted by amorris

hot transformer is not good. drawing way too much current. new fuse will undoubtably blow. pull power tubes and try fuse. if it blows, transformer shorted. need new transformer. no other way.

Pull tubes. Got ya. I'll do it after work as I just bought a handfull of fuses. I did check to see if any of the tubes were glowing abnormally hot before it went, and nothing was out of the ordinary. I am thinking a power tube probably went.

If my tranny is screwed, is it possible to find nos Fender Transformers? I do not want to change the sound of this amp, unless it is for the better.

Transformer brand suggestions just in case?

[dementedchord]

whoa ....whoa there are other reasons it can blow without the outputs in... diode stack and filters immediately come to mind and are WAY more probable.....
dont suppose you just happened to see if the tubes were cherry before the fuse blew???? was the thing biassed "special" for a particular response.... starved/overbiased? either can severly degrade tube life.....

[Sounds Great]

I once had a Marshall that just died, nothing coming out at all. Turned out that the transformer was fried. With yours getting all hot and bothered, wouldn't surprise me if that were the case.

[C/G]

Seems as though whomever owned the amp before me, had a 2A fuse in there instead of a 3A. It never stopped or blew a fuse before so I never bothered to check.

I went to my local music shop and they did not have any 125V, 3A fuses, only 250V, 3A fuses. We had to finish tracking so I popped that one in and everything was cool, no red glowing tubes, tranny wasn't excessively hot to the touch. Things were going well.

The amp just stopped again, no power. I took out the fuse, it looked ok, popped in another 3A, 250V fuse, and it worked again. We finished the track and I quickly turned it off and have not touched it since.

I am going to get the prper 3A, 125V fuse in there today. Would putting that 3A, 250V fuse in there hurt anything? We were in a jam so I had to use it to get the track done.

It still confuses me why the amp would just shut down, then work, then shut down, then work again. At least the transformer is not blown.

[Matt Syson]

Hi
Fuse VOLTAGE rating is sn indication of the amount it can withstand when it has blown (to keep you safe) and a 250 volt variety should be safer than 125. The relevent thing is whether it is a slow blow or antisurge type which generally has a capital T as part of it's rating. Thus it would say 3AT. If it is not a slow blow type it will tend to blow for no 'good reason' and may survive switch on a few times or if the equipment stayed on permanently it would probably last for months.
Put the correct fuse in and keep an eye on the thing, otherwise take it to a tech and get it checked out. It is possible to have one or two turns shorted on the mains transformer which will heat things up a bit but will still basically work. www.tubesandmore.com probably have replacements or a Fender dealer.
Matt S

[C/G]

Originally Posted by Matt Syson

Hi
Fuse VOLTAGE rating is sn indication of the amount it can withstand when it has blown (to keep you safe) and a 250 volt variety should be safer than 125. The relevent thing is whether it is a slow blow or antisurge type which generally has a capital T as part of it's rating. Thus it would say 3AT. If it is not a slow blow type it will tend to blow for no 'good reason' and may survive switch on a few times or if the equipment stayed on permanently it would probably last for months.
Put the correct fuse in and keep an eye on the thing, otherwise take it to a tech and get it checked out. It is possible to have one or two turns shorted on the mains transformer which will heat things up a bit but will still basically work. www.tubesandmore.com probably have replacements or a Fender dealer.
Matt S

It is just a regular slow blow I have in there now. I should take it in to a tech as my reverb channel has an annoying hiss in it as of late. Weird thing is, the amp quits while it is in use and not when turning it on or taking it off standby. It is like someone hits the power switch.

[KingDaddyO]

I am not an electrical engineer, but this is what I learnt on my summer vacation: Generally speaking about fuses, you are safe if you use the higher rated 250VAC fuse than the 125VAC fuse. But you should NEVER use a higher amperage rated fuse for any given equipment. This is why it is always OK to replace any capacitor with a higher voltage rated version of itself.

Current on the other hand, is the 'business end' of the power equation. I can pretty much guarantee your survival with 25,000 volts flowing across your body at 10 microamps (.000001A - appx. what you feel when you walk across a carpet, touch a doorknob, and see a spark discharge), but I would wish you a fond farewell if that was even a tiny voltage at 3A (searching for a ground path through your chest, down through your arms or legs, and out through your feet). It only gets worse from there - damp hands, bare feet, standing on concrete, holding a mic stand in one hand and a well grounded guitar in the other... at 15A? Ouch! People simply suck at pretending to be resistors. And this is why equipment tends to burn when you treat it this way - even resistors suck at pretending to be bigger resistors than they really are.

Almost everyone knows someone who once stuck a higher amp rating fuse, or worse... aluminum foil into a fuse socket 'in a pinch' (this would be the 'dead short' type of fuse rating). They were then shocked of course (figuratively speaking) when the bloody thing POPS!, or simply bursts into flame! True story -- I once worked with a so called electrical engineer at a well known satellite agency who did just that. Turned a very expensive equipment prototype into a very expensive arc welder. And she had a proper college degree!

Voltage tends to flow on the outer skin, while current tends to flows through the body. Hence the reason Tesla could survive public demonstrations (ok, that plus the extra thick, cork soled shoes he wore!) where tens of thousands of volts of AC, but very little current appeared to flow 'through' him (actually across the surface of his skin) and on to the flourescent tubes that he held in his hands... which lit up... without wires! Pretty damn cool trick. YMMV of course

[Matt Syson]

From the description a couple of posts ago, it sounds like your mains transformer is goosed.
A proper Tech can determine how much power is being consumed and whether the transformer really is the culprit. I presume the amp seems to be working fine until it overheats. Continuing to use it without resolving the true cause risks damaging many more parts so I am afraid it needs taking to the vet.
Matt S