Crackly IIC+

[alistair]

Hey everyone,

Haven't been on this board in a while! Seems to still be going strong.

I've got an early-ish MKIIC+ (cream combo, 60W, Rev), that's been sounding great for a few years, but is having some issues. It's been regularly serviced, but issues are still popping up.

At the moment, I've noticed that the cleans have been getting very muddy, and I'm certainly losing a lot of definition. Even with the first gain control set at around 3, I still can't get a really clean sound. Once the control is up to 7-8, it's chockers with gain, and very 'solid-state' ish. This was annoying me, but the amp still sounded good with the gain on lower settings.

However, today it was sounding even more muddy and distorted on the clean side of things. I unplugged my guitar so I could just listen to the amp, and I noticed that if I bumped it or tapped the amp on top, a crackle was coming out the speaker. Could this be a cold solder/dodgy tubes/time for a cap job? Anyone had a similar event occur?

Cheers!

 

[Shep]

Yeah best to start with new pre amp tubes. V1 first!!!! I just re capped my C+ and i have to say that it sounds AMAZINGLY better. huge improvement.!!!so maybe that would be on the cards soon.

 

[Elpelotero]

The crackle may be the reverb springs.

 

[alistair]

I'll check out the preamp tube- the crackle is so bad that if touch any of the knobs, or even walk near the amp I can hear it! It's annoying cause the preamp tubes are pretty new (less than 2 months- and I weeded out the bad ones first).

I dont think its the reverb as its present even when the reverb is off

 

[DaveP]

If you turn the reverb up does the volume increase? The reason I ask is I had an issue where the amp was sounding the way you describe and the issue was the reverb connection not being grounded and causing a floating ground. I soldered a ground wire to the shields of both reverb connections (front and back RCA jacks) and that corrected the issue. Sometimes you have to open the reverb tack and ground that as well but I didn't have to in my case.

 

[alistair]

It's def not the tubes- just replaced them all and the sound was exactly the same.

In terms of the reverb- I tried turning the reverb to 0 and unplugging the reverb tank. Would this stop the noise or does it need to be soldered?

 

[DaveP]

I think at this point your best bet is to call Mesa and talk to the man himself. Mike B. If he can diagnose it over the phone he will, if not he is the guy to talk to about sending it in for repair.

 

[alistair]

Would do, but I'm in Australia, so it's a bit of a trip to ship it home!

 

[av8or3]

You know, I had the very same problem with my C+ when I got it and described it to Mike when I shipped it to him for a cap job.
He told me it was the Presence pot, said they get very dirty/noisey because of where they're located in the circuit (or something) and that a good cleaning would fix it. Heck, get some Desoxit and clean ALL the pots and the jacks too! Can't hurt and you might get lucky.
After getting mine back from Mesa, it's been good as gold.
Jim

 

[alistair]

Thanks Jim, I'll give that a shot. Are there any specific cleaners I shouldn't use inside the Boogie?

Thanks for all your help guys!

 

[av8or3]

I would think it would be safe to use any electrical contact cleaner in there, I recommended Desoxit because I'm familiar and it's great stuff. Good Luck!
Jim

Also, if it's never had a cap job it will make a big difference (read GOOD!) once thats done. Any amp with electrolytic caps that are over 10 years old will benefit from replacement. There is an oil that is used in those caps as an insulator between the plates that dries up over time, reducing the performance of them. In worst cases those plates can short out once the cap has dried up and cause really serious problems. If you have any doubts about their age (or know they're original) get 'em out of there.

 

[Platypus]

DeOXIT is the one, but make sure if you're cleaning the pots to use the DeOXIT Fader Lube... you need a lubricant in there for sure in the pots because of the moving parts. You can get this stuff at a hardware store most likely... just be careful.

Also, stay far away from the GEQ if you have one, don't clean it or touch it. It's very prone to static.

 

[Boogiebabies]

The problem is, when the reverb ground goes bad either by oxidation of the washer holding the reverb output jack
or the cable grounds as shown in the repair illustration are dirty/oxidized.

When the reverb circuit loses ground at either point it turns the series effect of the reverb into a small
1 Watt tube amp. It behaves like a mini booster in the signal path and can cause crackling to full on fuzz.
The tank is an input and output ground circuit, but 99% of the time it's the output ground that goes bad.
This is the connector under the preamp PCB and you cannot get to it, so the jumpers on the cable is
the realistic and easy fix. I should note that even if you do this mod and your cables and tank connectors are heavily oxidized
the issue may come back soon, or not repair it at all, so cleaning the cable ends, and tank connectors inside and out should be done as well.
Lastly, your EQ/Reverb foot switch jack must be clean. If it is dirty, both the EQ and Reverb signals can
be poor. Both function go through the on stereo shorting jack. If the ground again are dirty on this jack,
you may experience a similar issues with poor Reverb function and noise.

In regards to cleaning the Presence pot, like the Slave pot they have a very thick lubricant in them. If you clean them with De-Oxit,
I would highly recommend using De-Oxit Fader Lube with 100% solution. If you use the 5% solution, it will never feel right again and may wear out
quickly from being under lubricated. I never clean either the Presence, Slave or EQ faders unless 100% necessary.