IIC+ Problems persist

[Soundstorm]

I got my IIC+ head back from Mesa about a week ago and they didn't seem to fix one of the primary problems that was supposed to be fixed.

When I turn the amp up to practice/gig levels I get this ugly scratchy staticky noise the sometimes comes in at the same time, or a second after I hit a low power chord.

I've heard this sound through 2 EVM 12L's, 1 G12H30, 1 Swamp Thang now, so I don't think it's the speakers.

I've swapped out all my pre and power tubes.

When it came back from Mesa there were a few small resistors and caps they had changed along with installing a new reverb tank, cleaning all the contacts, and supposedly giving it a good look over.

So what gives??

 

[Tuna141]

It seems like it might be a chassis vibration that's getting amplified, or a cold solder joint, or a high resistance connection such as tube socket oxidation, reverb jack/cable connection etc.

With the amp on, try banging on the top with your fist and see if the rattle/noise corresponds to your banging. If it does, then you just need to track down the source - try gently tapping components with something insulated until you find the offender.

Good luck.

 

[phyrexia]

I'd call Boogie and complain. Although it's a pain in the *** to ship the thing back. Maybe they could give you a partial refund or something.

 

[Soundstorm]

Tuna, that's a good idea.

UPDATE: I'm only getting this noise on the lead channel. I cranked the rhythm channel up to master 6 and couldn't get anything but face meltingly loud sweetness with no breakup. So that rules out the speakers.


I'll try bashing it.

 

[Soundstorm]

UPDATE

Ok, I tried bashing it wish my fist while on at a good healthy volume. Nothing. Problem with your suggestion, Tuna, is that it *just* came back from Boogie and they supposedly checked/cleaned all the contacts.

The thought of having it sent back to Boogie for another two months makes me cringe, and I don't think I'm gonna do it. I'm waiting to hear BoogieBabies recommendation on this, and seeing what I can do myself before I start thinking about sending it somewhere.

 

[Soundstorm]

Also, I never noticed this before (I guess I haven't had THAT much playing time with it), but is the volume supposed to swell out then back in when footswitching from Lead to Rhythm?

Is there something that can be done to fix this?

 

[Buddy]

Check your pots . tap/wiggle them while holding a chord and see if that causes it . It seems strange that the boogmeisters could have missed this though . You can also pull the chassis , run a signal through it , and with a nonconductive probe ( a chopstick works good for this ) poke around . Keep one hand in your pocket !
That volume swell sounds like an optocoupler acting up . If they replaced one it may be defective or coincidentally going bad . I had a similar problem , but it seems to have corrected itself . Go figure .
Oh , and if you never pulled the chassis before , remember to pull the mounting screws out , when you slide it back in you can scratch the faceplate .

 

[danyeo1]

Double check and make sure it's not your guitar, cables, cabinet, or anything else in your signal chain.

 

[JOEY B.]

When I turn the amp up to practice/gig levels I get this ugly scratchy staticky noise the sometimes comes in at the same time, or a second after I hit a low power chord.

So what gives??

Try moving the head away from the speaker cabinet and see if this problem persists. If so, push/pull each pot and test for the noise. I had a similar noise in my combo when I first got it. It was much worse with the combo speaker engaged than playing thru a seperate speaker cab. I then tracked it down to the "bass" pot. It would only make the noise if the bass pot was pulled out. The same scratchy crackle that you speak of, and only occuring on a few low notes. I sent the amp to Mike B. to have him give it the once over. The noise was being caused by the ground braid that connects the back of the pots to the preamp board. It was frayed or something, if I remember correctly, causing an intermittant grounding issue. Good luck, man.

 

[sundaypunch]

You paid good money to have Mesa service the amp rather than trusting it to a local tech. You still have a problem with it. Unfortunately intermittent problems can be hard to fix.

Still, you should call Mesa and let them take care of the problem. I would think at a minimum they would try to get to it quickly and also not charge you for return shipping. It can't hurt to call them and see what they say.

 

[Boogiebabies]

The rushing volume is usually from having too high a master volume when switching to a much lower lead volume, or vice versa. The LDR for the lead Master is the quicker VTL5C4, so it switches quickly, but it can get over loaded. If it is going bad, it will fade in, out or swell the volume almost every time you switch channels, but can also bleed signal. In addition, the noise could be a dirty tube pin, a faulty filter cap, a failing resistor, a bad spot in the potentiometer, a faulty cathode cap, or possible oscillation from the high volume. The oscillation is a common issue and is repaired by putting a .047 or .05 1KV poly cap on the terminal strip where the choke and standby connect to the red primary wire. Put the cap on the top terminal to ground. As mentioned earlier, corroded grounds can be just as irritating at making errant noises and problems. I would let Mesa handle the repair due to the nature of the problem. You would basically have to clean all the pots, soak the grounds, jump the loop, clean the tube sockets, try the oscillation cap, look for a loose or bad filter cap, try a new LDR, cathode caps, replace burnt or drifted resistors and try a new speaker. In the meantime you can try a new guitar and cable . Sometimes amps don’t get repaired due to issues not making themselves evident while in for repair. It could have been a no fault found diagnosis.

 

[Octavarius]

I have the swelling from lead to rhythm as well. Oddly enough, not the other way. :shock: Guess it's the LDR...

 

[Boogiebabies]

I have the swelling from lead to rhythm as well. Oddly enough, not the other way. :shock: Guess it's the LDR...

It's a curse for having an export.

LDR 4 for the lead master has been a commonly replaced part in the C+. It's right below the lead master pot.

 

[Soundstorm]

So is the switching between lead and rhythm and vice versa supposed to be fast and quiet? No swelling?

Thanks for the input, everyone. I tried calling Boogie a couple days ago but they're out from wednesday to monday on account of the fourth. We'll see what happens.

 

[Buddy]

these amps are The way they are .
a wonderful sweet howling pain .

 

[Soundstorm]

A wonderful sweet howling pain in my *** until it's working right.

 

[Restless Rocks]

The rushing volume is usually from having too high a master volume when switching to a much lower lead volume, or vice versa. The LDR for the lead Master is the quicker VTL5C4, so it switches quickly, but it can get over loaded. If it is going bad, it will fade in, out or swell the volume almost every time you switch channels, but can also bleed signal. In addition, the noise could be a dirty tube pin, a faulty filter cap, a failing resistor, a bad spot in the potentiometer, a faulty cathode cap, or possible oscillation from the high volume. The oscillation is a common issue and is repaired by putting a .047 or .05 1KV poly cap on the terminal strip where the choke and standby connect to the red primary wire. Put the cap on the top terminal to ground. As mentioned earlier, corroded grounds can be just as irritating at making errant noises and problems. I would let Mesa handle the repair due to the nature of the problem. You would basically have to clean all the pots, soak the grounds, jump the loop, clean the tube sockets, try the oscillation cap, look for a loose or bad filter cap, try a new LDR, cathode caps, replace burnt or drifted resistors and try a new speaker. In the meantime you can try a new guitar and cable . Sometimes amps don’t get repaired due to issues not making themselves evident while in for repair. It could have been a no fault found diagnosis.

We got to get to Buffalo quick

 

[Baconator]

I have the swelling from lead to rhythm as well. Oddly enough, not the other way. :shock: Guess it's the LDR...

It's a curse for having an export.

LDR 4 for the lead master has been a commonly replaced part in the C+. It's right below the lead master pot.

When I spoke with Mike B a few years back he said a short swell from lead to rhythm was normal and that I should only worry if it takes more than 1-2 seconds. He also said the LDRs do go from time to time and that if the swell was longer than 1-2 seconds it would need replacing.

FWIW

 

[Soundstorm]

Thanks, is there any way to get the switch to be *INSTANT* like with the Mark IV?

 

[Restless Rocks]

Here's an idea: remove your foot switch and switch channels by way of the "pull lead" switch and let us know if you still get the volume swell. If this cures the problem try using a speaker cable instead of a guitar cable to your footswitch. Let us know what happens. Some long guitar cables may have a few ohms of resistance seen by the control voltage and a 14 or 16 gauge speaker cable could be a possible fix.