#1
Hi everybody,

I have a Laney GH50L and lately the volume is cutting out sometimes.

It happens when I turn it on. I have it on for a couple of minutes (warming up) before playing. Then when I start playing, for a few seconds, it's sounds low on volume and fizzy before coming back up and after a while (let's say a minute) it sounds fine and stays that way.

My first thought was cables, but I've replaced them and the problem stays. Is this my power tubes in need of replacement?

Thanks in advance for your help!
"Don’t be a guitarist. Be a musician."

Steve Howe
Last edited by von gelb at Jan 24, 2012,
#2
Sounds like powertubes. Grab a new pair and swap em out.

edit: make sure you bias it/have it biased.
Gibson Les Paul Studio
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Last edited by LaidBack at Jan 24, 2012,
#4
Thanks, I thought that would be the problem. Going to replace them with JJ 6L6GC's soon!
"Don’t be a guitarist. Be a musician."

Steve Howe
#5
That amp has built in "delay standby" feature, it's there to avoid breaking power tubes with instant power+standby,

maybe something is wrong with Your element and it's delaying Power Tubes operation no matter how long You warm up the tubes, it works similar to Your description, delays preamp signal keeping it on low fizzy level before it reaches full power. I guess it waits for them tubes to reach certain temp... Maybe there's something wrong with Your sensor or whatever...
#6
Thanks for the tip BartekBeben, but I don't think that is the situation at hand.

Maybe my explanation of the problem wasn't complete to begin with. In the beginning the sound cuts in and out, so that made me think that it was bad cables or power tubes.
"Don’t be a guitarist. Be a musician."

Steve Howe
#7
Mmmhh, I could use some more help now if somebody has any advice...

Yesterday during rehearsal the following things happened (haven't changed tubes yet):

Taking it of standby I got low volume with the master turned down all the way?

Then the problem with low volume, fizzy sound until I switched to the drive channel. Sounded fine after a few minutes of playing...

At one time the amp made a faint hissing sound a few times (coming from the amp itself), sounding like a gas leak or air escaping from a balloon (if that makes any sense).

Then after a while it made a ticking sound (like tapping a pencil on a desk) for a few minutes.

All the while I had no problems with my sound or volume, but this made me worry a lot. Could this still be the power tubes, or do I have other problems I should worry about?

Thanks in advance for your help!
"Don’t be a guitarist. Be a musician."

Steve Howe
#8
You should have spares anyway but try simply pulling out all your tubes and plugging them back in first. They do rattle loose occasionally and it's often not obvious. Pull 'em out and plug 'em back in. If that does nothing try your spares.
Gilchrist custom
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#9
Thanks! I was gonna try that anyway, but could it cause the other weird stuff as well?
"Don’t be a guitarist. Be a musician."

Steve Howe
#10
yes
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#11
Okay, my amp had a cleanup and I have changed the powertubes. It sounds way better now, but the volume problem remains (the other strange noises are gone). Could this be a potentiometer, like the volume knob?
"Don’t be a guitarist. Be a musician."

Steve Howe
#12
Oddly enough, the same volume thing happened to me about two weeks ago. I thought it was the power tubes. I gave it to a co-worker, who I was going to let borrow it, and he was gonna change the tubes for me.

Well, he checked it out, and the tubes were biased too hot. That wasn't the issue. He also said that when he was playing, a small wisp of smoke came out the back. He took it to a tech and the tech said that the power tube socket was loose. Now, he talked to the tech, not me so I don't have all the details, BUT, you said your amp had a "cleanup". What does that mean?
Gibson Les Paul Studio
Highway One Telecaster
Dean Evo
Mesa F-50
Laney GH50L
Vox AC30 C2
Ampeg V2
pedals
#13
A cleanup in this case, means that all the dust and other dirt were removed from the inside. They told me the sockets were fine, though V4 (phase shifter) was a bit loose.

Could be the preamp tube not connecting enough, but I have my doubts. Mainly because the problem goes away after half a minute and than the amp works fine...?
"Don’t be a guitarist. Be a musician."

Steve Howe
#14
Check how well the tubes are seated anyway. Just pull 'em out and plug 'em back in and make sure they go in properly.

It could be a pot. Those things have PCB mounted pots so it could also be a dry joint to the board. It does happen. Depends on how it's all mounted. JCM900's are a bitch for it. Jiggle the pots a bit and see what happens, nothing should happen. If it's the pot itself it will usually be a certain part of the track so it will work in some positions and not others, you can usually feel it anyway. Will be scratchy as you turn it too.
Cleaning them can work as a stop gap measure at times. It will be hard to see without a dentist's mirror on that, but between the contacts and the housing of the pot there is normally a little gap. You squirt contact cleaner in there, preferably while twisting the knob to help it spread.
Really, once a pot starts to go I rip it out and put in a new one. PITA with PCB mounted pots though because you have to lift the board.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#15
Thanks again Cathbard! You may be grumpy, but you give the best advice on UG.

I will try and use contact cleaner on the pots and see if that works after I have checked the tubes first.
"Don’t be a guitarist. Be a musician."

Steve Howe
#16
Okay, problem found... The base (holder) for V4 is loose and the connection with the pins is therefore not 100%.

One last question for Cathbard and I hope his answer will be no: Do you know if these are surface mounted? I hope not...

Edit: After some searching I have found out that the tube sockets are not surface mounted, but mounted to the chassis. Makes me worry a lot less, as it will be an easier fix that way.
"Don’t be a guitarist. Be a musician."

Steve Howe
Last edited by von gelb at Mar 20, 2012,