#1
Hey guys STEVE HOLT! back from the dead.

As some of you may know I got a lovely rockerverb 50 mkii head some months ago. Everything has been going great... Until now.

While at practice the other day I noticed some really annoying humming when playing with my gain up high. Today I checked up on it and it seems there's a constant high-pitched whine whenever I turn the gain past 3 o'clock. Now at first I assumed it was just a bad preamp tube, but luckily the guy who sold me the amp also gave me a brand new set of tubes, as well as the originals.

So I set about trying to isolate which tube was bad, replacing each one by one. Nope, issue still remained. I then tried replacing all of the new EHX tubes I had put in with the original ruby tubes. Still there. I tried so many combinations of these two sets of tubes that I almost went insane trying to figure out the problem, I even changed the power tubes in the unlikely event something was going on there... Nothing.

Now everything I've read still points me towards this being a preamp tube issue, but that would mean that of the two sets of preamp tubes I have the majority of them are microphonic, which I have a hard time believing.

My other suspicion was that it may be a grounding issue. So I've recorded the sound (which is annoying as all hell) with the recording interface I finally received today!! This is the sound I'm getting...

http://profile.ultimate-guitar.com/Steve+Holt/music/all/play1177953

You can hear it phasing in and out as I adjust the guitar's volume. That sound is coming through even when the guitar's volume is at 0. But it only happens with the gain past 3 o'clock.

So what do you guys think? Should I drop the cash for a completely new, third set of preamp tubes, or do you think this is a much more sinister issue??
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#2
That sounds horrid.

To me, it doesn't seem indicative of a bad preamp tube. It doesn't seem like it is a grounding issue either though. I'm not an amp tech, so free bump for you.

Try the 'tapping' test in the link I'm going to give you below. Also, get some Dioxit contact cleaner and spray the tube pins with it an work the tube in and out to clean the sockets.

At this point I'm leaning toward a power section problem but like I said, I'm not an amp tech. You've got your ohms match up with cab right? Can you try a different guitar or a different cab? I was also going to suggest checking all of the solder connections on the RV board but that can be dangerous and I'd doubt that kind of a problem with a Rockerverb anyway.

Good luck man,

#3
I would plug an active pedal into the FX return and if the noise is gone then the problem is in the preamp. Still there... it's in the power amp. Results will vary with a parallel loop.
#4
That's some crazy ass (<- technical term) oscillation!

As fly suggested: zero the reverb, and plug your guitar into the return jack of your effects loop. Is the sound still happening? That will at least narrow it down
Epiphone Les Paul Plus Top
Jet City JCA5212RC (SLO Modded)
Ibanez WD7 Wah
Mad Professor Sweet Honey Overdrive
TC Electronic Flashback Triple Delay
TC Electronic Trinity Reverb
#5
Should have mentioned, I did actually try bypassing the effects loop and the problem was gone altogether, which I suspected because it seems to be because of the gain stages. Though while going through the loop it bypassed even the master volume on the dirty channel.

I also tap tested and a few do seem to be microphonic, but it's weird that this kept happening with every tube arrangement I tried... I'll try another cab at some point soon though.
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#7
Fix my amp, Tim!!
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#8
I get the impression you are an oldie round here, in which case, hey!, but I don't know you so I'll ask you the basics before I continue to help...

Are you electronics savvy?

Do you know about testing/discharging the power supplies in amps and operating safely on them?

Do you have access to a multimeter?
Epiphone Les Paul Plus Top
Jet City JCA5212RC (SLO Modded)
Ibanez WD7 Wah
Mad Professor Sweet Honey Overdrive
TC Electronic Flashback Triple Delay
TC Electronic Trinity Reverb
#9


Yes to electronics savvy (to an extent)
Yes, sort of but don't have THAT much experience
Yes

Not sure which solder joints to check really D:
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#10
We're not checking solder joints.

Open the amp up, make sure it's safe to poke around, multimeter on high voltage (DC), ground to ground, test each of the pins on the power tube sockets is a good start. <10V is safe, 12v can still hurt you.

There should be a big fat capacitor with a value like 22000uF on the side, is there any swelling on the top (or any of the capacitors, but we're mainly going to focus on this big one) If there is stop here and report back.

If not we have to work on it while it's live. So be CAREFUL, don't touch anything except with your multimeter probes, and you may want to pull the power tubes to a) kill the noise b) so you don't have to worry about having a load plugged in

The next step is to measure the DC voltage on Pins 4 or 5 on the preamp valves you can test in relation to pin 9 if you want as that should be grounded (going off the Mk1 schematic, I don't have the Mk2). It should be somewhere between 5.8 and 6.5V

The next step is to measure the AC voltage on the same points. Report back with the figure.

Here's how the pins are numbered from the solder side for testing.
Epiphone Les Paul Plus Top
Jet City JCA5212RC (SLO Modded)
Ibanez WD7 Wah
Mad Professor Sweet Honey Overdrive
TC Electronic Flashback Triple Delay
TC Electronic Trinity Reverb
#11
It's only been 20 minutes, but I always get that sinking "Oh crap! I've killed him!" feeling every time I give out this kind of advice... just felt I needed to share that.
Epiphone Les Paul Plus Top
Jet City JCA5212RC (SLO Modded)
Ibanez WD7 Wah
Mad Professor Sweet Honey Overdrive
TC Electronic Flashback Triple Delay
TC Electronic Trinity Reverb
#12
Not dead! Just at uni. Will perform tests when I get home tonight, or probably tomorrow morning since I may be drunk tonight.
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#13
yeh, please don't attempt while drunk
Epiphone Les Paul Plus Top
Jet City JCA5212RC (SLO Modded)
Ibanez WD7 Wah
Mad Professor Sweet Honey Overdrive
TC Electronic Flashback Triple Delay
TC Electronic Trinity Reverb
#14
Will do my best!

Also to clarify, are you saying that it's safe to remove the power tubes while the amp is on as long as the speaker load is disconnected?
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#15
Yes you can do that.


One key I will share is to never unplug a mulitmeter while attached and amp is on.

Quote by GABarrie
yeh, please don't attempt while drunk

Big Fat Plus One


or even a slight buzz. not worth it. walk away and do it when you are completely sober
#16
I've taken a hit from filter caps before and that alone hurt like a bitch. Not planning to get hit by a live amp!
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#17
Also, thanks for the advice guys, I'll let you know what happens
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar
#18
my theory is, as I've seen it before in the Mk Is, that the filter cap on your heater rectifier circuit has gone funny.

The messy combination of DC and AC current on the heaters leads to this high pitch oscillation noise on top of loads of 50/60 cycle hum and just sounds terrible.

I could be wrong but the sound is similar and I've had it in two Mk Is before.
Epiphone Les Paul Plus Top
Jet City JCA5212RC (SLO Modded)
Ibanez WD7 Wah
Mad Professor Sweet Honey Overdrive
TC Electronic Flashback Triple Delay
TC Electronic Trinity Reverb
#19
Very, very drunk right now so I'm glad I haven't done any work. Scaring a bunch of girls off is much less harmful than working on a live amp with very little hand eye coordination

Will definitely check filter cap first thing when I wake up. Thanks for the great advice
[quote="'[BurnTheDusk"]']Better than my plan, look at those perfect little dick suckin' lips!
Kid's a natural I tell yah!Orange Rockerverb 50 MKII
Marshall JCM 900 SL-X
Gibson Les Paul Studio Faded
Fender Mexican Standard Telecaster
Hey I built a guitar