#1
Problem
My Laney GH100L- After 1/2 minuets of playing it pops and then makes a horrible loud buzzing noise bzzzzzzzzzzzzzzzzzzz like feedback but a lot lower pitch

I re tubed it yesterday and before re tubing i didn't have a problem, i played it last night after re tubing and it was fine

I changed my bias from 37 to 40.5?

I replaced tads with JJ's and changed the preamp valves too

The Power tubes all light up so surely they haven't popped?

Really don't have a clue as to what the problem could be?
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#2
Check your leads.
#3
Have done, its not leads it works but pops after a min or so and then buzzes VERY loudly
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#4
check the connections to the speaker in the back. Sounds like a problem my friend had a few weeks ago.
#5
hmm I've re plugged the speaker connection in as well as the power cable, its so late now and parents are in bed so i can't really try and fix it but please keep posting with suggestions as ill try them out tomorrow
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#6
I know exactly how you feel man. Just don't freak. There's nothing on your amp you can't fix. Oh, and don't screw with it till you're sure you know what your doing.
#7
What kind of tubes are you using here, 6L6 I take it?

You may have set the bias too high. Your idle current should be set to about 70% of the maximum bias current. This depends on what plate voltage you're measuring.
#8
I'm using E34L'S is it possible that i set the bias too high? I didnt measure the plate voltage as I don't know how i know i know...i suck!
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#9
Well, 40mA isn't abnormal for el34 or 6l6s, but it's definitely biasing on the slightly hot side.
#10
ok thanks man, Ill drop the bias down to 38 and report back later
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#11
That being said, check for red plating (orange spots on the gray plates themselves) when you're running the amp hot. It might be hard to see so turn out the light and check to make sure the plates themselves aren't glowing.
#12
could be a leaky coupling cap... i fixed one this week...
master the beginner's mind
#13
also, just in reading the first post, the power tubes lighting up doesn't mean that they're not bad. It just means the heater filaments are working.
#14
Ok think I've found the problem, decided to take everything out today and just re check bias/make sure tubes are all in and i started playing and YAY it worked find for 20/30 mins UNTIL i plugged my laney footswitch in and BZZZZZZZZZZZZZZZZZZZZZZZ started again :S
Suggestions?
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#15
I just removed the new jj pre-amp tubes and installed the old ones and the problem is gone but they don't sound as good I'm guessing my problem is the pre-amp tubes?

i have a high gain balanced phase inverter in slot V4, is there a chance that if this is in the wrong slot it would cause this problem?
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#16
Just put the new JJ phase inveter in slot 4 with all old pre-amp tubes and it brakes, put it back to all old pre-amp tubes including the old tube in slot 4 and it works :S, I'm presuming its my phase inverter that is faulty?
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12