New Member, Mark IV issues

[kingvpro]

Hey everyone. I've been surfing this forum for months and it has been extremely helpful in my decision to buy a Mark IV Widebody which I just received today.

I'm totally stoked to dial this thing in although I did come across an issue. I bought this used and when I picked it up the guy mentioned that one of the pre-amp tubes went bad so he "Replaced it with a Groove Tube". So I'm thinking there are 4 mesa boogie pre-amps and one GT Pre-amp. Nice... I plugged this thing in and its getting a lot of noise, a lot on R2 and a weird sound when clicking to Lead. I also noticed that sometimes R1 will float from sparkling clean to a real gainy sound without even touching anything. Anyways I was looking to replace the Preamp tubes and when I looked behind the amp I noticed that the Power tubes aren't matched. There are 3 Blue and 1 Green 6L6GC. I'm wondering if that has anything to do with any of the noise issues I have. I'm contemplating getting a set of Mesa pre's and 1 Power Blue.

Since the Mesa tubes are so expensive is there a good substitute to use instead. I can't even tell what the Mesas sound like because of the current mismatch and noise in my amp. Are the Mesa Tubes worth giving a shot?

One more thing. I've read the manual about 4 times now and the effect loop still has me confused. Can anyone give me a brief run down on how to use it with the multiple channels?

Thanks for all the infomation you've supplied me in the past and any input would be greatly appreciated.

Take it easy

 

[marklyn]

Congrats on the Mark IV purchase and welcome!

Don't worry about feeling overwhelmed with stuff, there is a lot to figure out.

Here's how I use the loop on mine. I go from the out of the switchable loop the the in of my effects. (I only use 2 a delay and a reverb/tremolo.) From the out of the effects I go in on the switchable loop. I use the footswitch to turn the loop on and off.

Some other effects, (like a wah pedal) would probably be better in front of the amp, between the guitar and the amp input.

If the noise happens on certain channels more than others, it may be an indication of a preamp tube problem.
As far as the matched power tubes, you could put 2 of the same set in the outside power sockets and switch the amp to Class A (which only uses the outside 2 tubes.)

There are several reliable tube sales places on the internet. Here are a few.

http://www.dougstubes.com/
http://www.eurotubes.com/index.htm
http://www.nebsnow.com/LordValve

email or call any of these and explain your situation and they should be able to offer good suggestions.

Good luck!

 

[Phendaphil]

Hi Congrats on getting the mark iv, it really is a fantastic instrument. Worth putting the time in with. I know it's a pain after parting with cash to buy it, but a complete re-tube would put you on a fresh start with it. You never know how the amp's been treated before you got it.

No need for pre-amp tubes to be mesa, and if you go to a good supplier like marklyn suggested they should be able to supply power tubes to mesa specs at a cheaper cost. A lot of people seem to like JJ's but it's personal choice, doing a search on here will bring you up lots of info on this.

With the fx loop i just connect mine from the send, into the effects unit then out of the effects, into the return right (mono) You can then choose if you want to be able to turn the loop on and off by the mark iv footswitch, or if you want the loop on permanently. All the other sockets are if you want to run a second amp and have your effects running stereo - as far as i know.

Again as marklyn said keep delays, chorus, etc to the fx loop and use everyting else before the amp.

Good luck, let us know how you get on.

Phil

 

[kingvpro]

Thanks for the replies guys. Its nice to see a forum where people take some time to help out the new guys.

I've dealt with Bob at Eurotubes before he seems to know his stuff very well. I got some tubes for a Marshall DSL 50 head a few months ago and it did make a difference in tone but it wasnt enough difference to keep me from wanting a Mesa instead. Hopefully if all goes well with this Mark IV I will probably off-load the Marshall to help pay for the Mark. After reading the article on Mesa's website about the fixed biasing it got me kind of paranoid to go with anything else besides Mesa tubes.

I guess I was reading more into the effects loop than was really there.


Thanks guys

 

[kingvpro]

Well I just replaced all the preamp and power tubes and I'm still having a problem. In R1 & R2 the tone will be muffled really bad and there won't be any gain on R2(sounds like total crap), I'll just keep hitting the same chord over and over then it will start to crackle and snap into an incredible tone and gain. Also, in R2 if it is in that muffled stage and I turn the treble all the way up the amp goes silent, no volume on that channel. Is there any other reason it may be doing this besides the tubes?


Thanks

 

[jukesgtr]

kingvpro, welcome to this forum from another new member too!

Sorry to hear about the trouble you are facing with your amp. Did you have a chance to test it before you decided to take it? If yes did it sound OK then? How "reliable" is the seller?

Does the lead channel seem to work fine?

 

[kingvpro]

Unfortunately I didnt get a chance to test it before hand, Ebayed. The seller is reliable and I'm sure I can work something out with him if it needs to be sent in. I really want to keep the amp because it sounds amazing when its working right. The Lead channel is working perfectly and it sounds gnarly as hell, maybe just some light noise at idle. I was hoping maybe someone had some insight or had a similar problem in the past and knew what direction to point me.

 

[jukesgtr]

Could this be from a bad solder joint or component somewhere in the R1/R2 circuit (I have not looked at the shematics so I do not know how many common components these channels have actually)? If the lead channel is good all the time perhaps that area is worth looking at. Also, as it has been said many times, even new tubes may be bad.

Edit/add: bad solder joint or other contact may cause a similar problem as bad contacts in pots too, treat them with a contact spray!

 

[Greystoke]

As Jukesgtr suggested, cleaning the pots with contact cleaner is a good next step to take. You could also move your tubes around to different sockets and/or mix in new/old tubes to help rule out a bad, new tube. You can also clean and retension your tube sockets.

If you're confident inside a tube amp, there are a couple other things you can do. If you're not familiar with the internals of tube amps, DO NOT try this - take it to a good tech - touching the wrong component in there can be lethal. While the amp is on and in the playing mode giving you problems, use something like a wooden chopstick to peck and poke around on the circuit board and gently move the wires. Do not come in contact with the components inside - use only the chopstick for this. If there's a cold solder joint or component failing due to vibration, this will often find it by producing static/crackle through your speakers when you peck on or around the trouble spot.

Again, DO NOT do this unless you are familiar and confident with the internal workings of tube amps.

Greystoke

 

[Boogiebabies]

Unfortunately I didnt get a chance to test it before hand, Ebayed. The seller is reliable and I'm sure I can work something out with him if it needs to be sent in. I really want to keep the amp because it sounds amazing when its working right. The Lead channel is working perfectly and it sounds gnarly as hell, maybe just some light noise at idle. I was hoping maybe someone had some insight or had a similar problem in the past and knew what direction to point me.

These guys have you going in the right direction. Knowing that the R1 and R2 share a tone stack and have and LDR to switch in the revoiced R2 treble, I would first start with the pot. With the old Fender style tone stack, the treble pot controls the rest of the signal to the mid and bass. If you put them all at 0 you should have no signal. I would surmise that the resistor element in the pot is either really dirty or shot. If you have ever seen a pot that was bad, the resistive layer for the pot to sweep over has rubbed off and the wipers only contact the board leading to a short circuit. Try a cleaning. You can get Caig's De-Oxit and Pro-Gold at Radio Shack for $ 12.95 or you can call Mesa on Monday to talk it over with them.

Good Luck.

 

[kingvpro]

Thanks alot for all your help guys. Unfortunately I called the guy I bought it from to let him know what was going on and he said he would rather buy it back from me for what I payed and call it even. I had 2 days with my first Mesa.... . I will definitely keep an eye out for another Mark IV. Thanks again.

 

[Phendaphil]

Shame that mate, hope you find another real soon it'll be worth it.

 

[kingvpro]

Boogiebabies, you hit the nail on the head... I got a call from the guy I bought the amp from, he took it to a authorized Mesa Tech and found out that the treble pot was shot. Even better news, I'm going to get this amp back from the guy. Can't wait to blow out my windows!!!!

 

[jukesgtr]

Boogiebabies, you hit the nail on the head... I got a call from the guy I bought the amp from, he took it to a authorized Mesa Tech and found out that the treble pot was shot. Even better news, I'm going to get this amp back from the guy. Can't wait to blow out my windows!!!!

Cool! My guess about a bad contact was near... :lol: