question about my dead guitar amplifier

[maxxkagato]

So, one day I show up to the studio and low and behold, my Framus Cobra is on, not in standby and not connected to a speaker cab. Studio owner is doing some promo video shoot or something.

I yell at him, turn the amp off and put it away.

I'm setting up for a recording session, pull out the amp, plug it in to the speaker cab, turn it on. Its on for a few minutes and then dies. The mains fuse had blown, so I try swapping it but to no avail.

Is there a direct correlation between what the studio owner did and my amp dieing or is it just a fluke? I spoke with a buddy who is a gear head and he said that problems can arise down the road if someone does that to their amp.

I'm taking it to a repair shop tomorrow, but any speculation is welcome.

[dwoz]

There's a pretty decent chance you've got a damaged output transformer.

Does it pass signal?

[maxxkagato]

I swapped out the mains fuse but it still doesn't turn on.

[G. Hoffman]

I swapped out the mains fuse but it still doesn't turn on.


The big issue with what he did is to the output transformer, but it is entirely possible that this caused the OT to draw too much current from the power transformer, which may have burned out the the PT.

My question is what kind of studio owner doesn't know that is stupid? Or was it just a camera crew who did this without his knowledge?


Gabriel

[maxxkagato]

No it was the studio owner, the camera crew hadn't showed up yet.

The other question I have is that, if the output transformer is blown, is that something that can be easily fixed? Will that hurt how the "sound" of the amp?

[otek]

if the output transformer is blown, is that something that can be easily fixed?

It can be fixed, but it's not gonna be cheap.

Framus are using high quality components, and the output transformer is likely the most expensive one of them in your amp.


otek

[Tommy Fobia]

Amp heads (or more specifically the output transformers) are not designed to be turned on without a load (a set of speakers).

Without a load OTs literally melt.
:Thumbdown:

[dwoz]

The other question I have is that, if the output transformer is blown, is that something that can be easily fixed? Will that hurt how the "sound" of the amp?

sure, if they don't put in the same one. I've seen that myth in the guitar forums...that changing the output transformer somehow "castrates" the amp. Bollocks. Get OEM parts, and there you go, good to go.

[maxxkagato]

My big worry is that if it is a transformer problem, is that the amp sound will change, that the amp could have more problems down the road from this incident or ultimately the amp loses resale value because the transformer has blown.

Thanks all for the helpful information.

[Tim Halligan]

If you love the amp, why would you be worried about re-sale?

It's not like you're going to sell it...is it?


Cheers,
Tim

[John Eppstein]

Just make sure the service place uses exact replacement parts. It won't be cheap. With luck the power transformer will be OK, but you won't be able to be certain untill the tech looks at it. Doing a quick online search it looks like the output trannie will run in the ballpark of $250 and most likely you'll have to replace the output tubes as well.

Good luck!

[otek]

My big worry is that if it is a transformer problem, is that the amp sound will change, that the amp could have more problems down the road

What Eppstein and dwoz said.

Get it serviced by a qualified tech, who uses original parts, and you should be fine.


otek

[maxxkagato]

I just dropped it off at Savage Audio, who make some distorted and not so distorted gtrs from hell btw, and the tech there sounded rather optimistic about getting it back to good as new.

If you love the amp, why would you be worried about re-sale?

It's not like you're going to sell it...is it?


Well, looks like I need to. The studio I was working out of isn't an option anymore and I don't own any actual gear so it looks like I'll have to sell this amp and another, which also dearly love, to pay for monitors and a computer.

Thanks everyone for the advice. You've all been incredibly helpful.

[John Eppstein]

The studio I was working out of isn't an option anymore and I don't own any actual gear so it looks like I'll have to sell this amp and another, which also dearly love, to pay for monitors and a computer.

Thanks everyone for the advice. You've all been incredibly helpful.

Man, that's a real drag. What happened, the guy blew up your amp, refused to pay for the damage and kicked you out of the studio for trying to get him to pay for the gear he broke?

[G. Hoffman]

Get it serviced by a qualified tech, who uses original parts, and you should be fine.



That could be kind of tough, if its an old amp.

But as long as you get one of the same size, it really shouldn't be a problem.

Oh, and the power transformer is usually more expensive than an output transformer, but the two are usually the most expensive parts in an amp. The folks out at Savage should be able to take care of you, though. Are they making guitars, now? I thought they just made amps?


Gabriel

[otek]

That could be kind of tough, if its an old amp.

It's a Framus Cobra. Currently produced, German high-gain amp. Parts should not be a problem.


otek

[Tim Armstrong]

I'm interested to hear what the tech says about what's wrong. While it's absolutely NOT a good idea to turn on an amp without a speaker load, it's usually not an amp-killer unless you actually run signal through it.

Although I guess if they then left the amp on for hours, that could lead to thermal problems...

Tim

[brunopolski]

I'm interested to hear what the tech says about what's wrong. While it's absolutely NOT a good idea to turn on an amp without a speaker load, it's usually not an amp-killer unless you actually run signal through it.

Although I guess if they then left the amp on for hours, that could lead to thermal problems...

Tim

I agree with Tim here. The problem with output xfmrs not collected to a load happens when you run signal through it. The reflected impedance to the power tubes goes real high and the signal voltage across the primary does the same.......usually arcs a tube socket as one of the heater pins is next to the plate pin. Transformer can be damaged during an episode like this, as well. This all assumes the output jack is not wired to short to ground, or they left a speaker cord plugged in but not connected to a cab.