Tube amp failure... damn it!

[DURBANS]

Hi

I got a Laney GH100Ti Toni Iommi head and matching cab.

It's really awesome.

Worked wonderfully for about 4 months now but suddenly something "wicked" this way arrived...

Last night I was playing at a normal volume (say, 3 or 4) for about 20 mins and then when I finished, I accidentally turned off the POWER switch without putting the STANDBY switch ON, (I then turned it ON so that next time I power up the amp there will be no harm on the power tubes). I've done this a couple times before accidentally but nothing happened. Actually I've read a lot of "trouble-shooting" stuff and none mention this as a bad thing, they usually say that before turning the POWER on, the standby switch should be ON, but that had nothing to do.

Thing is this morning I wanted to play for a while so I lugged my guitar, turned the power on, waited for a couple minutes then let the stand by switch OFF as usual so I can play...

There was no sound!!! I then discovered that there was a sound if I turned the volumen to the MAX and still it was a scratchy tinny and of course, low volume sound. Damn!!! The 4 power tubes are all glowing equally, I can't see the preamp tubes since they're housed inside some metal tubes.

What could be wrong??

 

[egan.]

1. check your Ht (dc power) fuse
2. check your cabling (all of it). Honestly the sound you're describing reminds me of the sound you get from a tube amp w/ no cab attatched (or a bad speaker cable).
3. ask laney. They may have a simple solution. Certainly they can refer you to a certified tech.

These suggestion are by no means the be all end all, but it's what I would do for starters.

 

[DURBANS]

thanks! now, what do you mean by "check"? I see there is a little tube inside the "Ht" fuse screw, looks okay, but dunno what do u mean by checking.

Speaker cable was checked twice (its monster cable) and I used another speaker cable and I even tried with an instrument table, all 4 times I got the exact same sound.

 

[egan.]

thanks! now, what do you mean by "check"? I see there is a little tube inside the "Ht" fuse screw, looks okay, but dunno what do u mean by checking.

Did you take the fuse out? Basically you turn that screw and the whole thing pulls out. The plastc screw is part of a caddy that holds the actual fuse. Inside the glass part (the actual fuse) you will see a little metal fillament running from one side of the fuse to the other. If this is severed in anyway the fuse is bad. Typically if the fuse is burned out it would be black towards the center so it should be pretty obvious....But I've had them look 'ok' but actually be bad before. If you know how to use a multimeter to check for continuity I suggest this.
If the fuse is bad, in small letters on one of the ends of the fuse will be small letters/numbers which indicate the type and rating of the fuse you need. You'll just need to call around and find one. Good luck.

 

[Andy Sneap]

check your cab input jacks and speaker output jacks on the head. Try another speaker cable also. Is the sound (scratchy when turned up full) coming for the head or cab?? Like the tubes are resonating?

 

[silverwulf]

Definitely check your cab inputs and head unit outputs like Andy mentioned, and the speaker cables too. Try a different speaker cable, and try them in all the outputs of your amp into all the inputs of your cab (that are usable for the load). The sound you are describing sounds like what happens when the signal doesn't get properly transferred to the cab and the load is backing up in the power transformer. Check all of the aboove and see if it helps.

 

[DURBANS]

yep, I found the sound to be like you guys describe it, but, as I said, I checked with 4 different speaker cables.

My amp has a lot of speaker outputs but my cab only has a 16 OHM input, meaning I have to connect the head via the "16 OHM" output jack to the cab. Should I try a lower impedance if the cab says 16? I mean, won't it be bad?

I took the Ht fuse aout and it looks ok as egan said, no burns, filament okay, etc, I should get a tester to see.

 

[DURBANS]

yep, I found the sound to be like you guys describe it, but, as I said, I checked with 4 different speaker cables.

My amp has a lot of speaker outputs but my cab only has a 16 OHM input, meaning I have to connect the head via the "16 OHM" output jack to the cab. Should I try a lower impedance if the cab says 16? I mean, won't it be bad?

I took the Ht fuse aout and it looks ok as egan said, no burns, filament okay, etc, I should get a tester to see.

 

[egan.]

Do you have another cab available to test w/?

 

[DURBANS]

Nope

Can I connect the amp head through the 8 OHM output jack into the cab's 16 OHM input jack? (it's the only input option it has btw)

 

[KeithRT99]

some guy on harmony central said the Gh sounds like a bogner ubershall, any truth to that?

 

[006]

LOL completely wandering from the point, that was funny. My friend owned a GH100, not the Iommi model, and it didn't sound much like an Uberschall to me, but I have only ever played one once. I like the XTC over it from that one experience, although biased since I played the XTC a lot over about a month's time and the Uberschall only once for about an hour. Back to the point at hand...

From what I know with sub woofers for car stereos, when you drop the impedance level down, the subs hit harder and are louder, well on the lower frequencies anyway. With subs you can take an 8ohm 12" and run it a certain way to get it to 4ohms, which makes it hit hard. But then you run it parallel (or in series, I don't remember) and you can drop it to 2ohms, making it bump like nobody's business. And then you do some tricky wiring and you can get it to go to 1.5ohms which is the mother of all thump, depending on your gear anyway. As far as this working for guitar cabs, I've never heard anything about it. But I know that as many times as I've accidentally put a 16ohm load into the 8ohm jack on my cabs, nothing bad has ever happened. Didn't sound different either. I would say try it just to *see*, but don't leave it on there just because it works. I would still take it to an authorized tech as soon as possible. Hope that helps.

~006

 

[DURBANS]

Well I haven't ever tried an Uberschall neither a Recto, remember I'm in Peru where the sun don't shine lol

Some people say it sounds like aperfect blend between a Marshall JCM800 and a Dual Recto. I think it's great actually, sounds unique and with a lot of character, just put a Tube Screamer in front and all it's magic.

I'm taking the amp in today since I have a warranty, I hope all goes well.

 

[estigma2001]

good luck piggy lol