Mark IV probs!!

[Ronnie_Rocker]

i hate my amp. this is the problem. i warm up the amp, push of standby, it sounds awsome...but just for a couple of minutes. then its like some one puts a blanket over the speaker cab. the trible get dull. not like when you cut trible on a tone control, just dull. no precense at all. i had the amp on service. but returned with same fucking problem. when i put the amp on stand by for a couple of seconds and return to "playmode" the problem is gone... but just for a couple of seconds. any ideas? soon i´ll throw the amp out the window.

 

[paleamberglow]

maybe you need new tubes?
if that's not the problem you should take it to a mesa authorized technician...

 

[zeppman]

It really sounds like a tube problem to me, too. How old is the amp? When was the last time you changed the tubes?

 

[Bullen]

Hallå Ronnie!

I had the exact same problem with my Mark IV head. I sent it in for repair 3 times and to 3 different people in as many months. No one could fix the problem. They did fix a few bad solderings, a noisy fan and a broken tone pot, but not the main problem.

It was not the tubes, I changed them when I first got the amp and then ended up buying another set when I noticed the problem.
I bought it used at Musikbörsen in Västerås (Sweden) and it was under warranty so I didn´t have to pay for the repairs, but I ended returning it.

It sounded awsome for the few minutes it worked, but as you say it became very dull when it warmed up. If I turned the standby off for a few seconds and then turned it on again, it would sound good for a few minutes again but then it became very dark and dull again. Very frustrating!

A year after I noticed the same amp for sale in Eskilstuna (not hard to spot because one of the knobs was not original). I borrowed it , just to try it out, but the problem was still there.

Perhaps it´s the same amp. Is it a wide head with one of the knobs
(I think it was the rhy1/rhy2 bass knob) replaced?

I would love to know what the problem was, if you can get it fixed.

 

[Ronnie_Rocker]

yeah dude. its the same amp. the R1 trible nob is changed. i traded the amp with a guy here in Umeå. its was gr8 for a couple of months. then it started to fail. and now i have big problems with it. i have no idea what the problem is. new tubes and all...

 

[Bullen]

It´s a small world sometimes.

It seems that the amp is un-fixable by our local techs. Maybe you should contact the swedish Mesa importers (svensk musik, tror jag det är) and see if they can help. I´m sure that the guys at Mesa can fix it, but it will cost a lot to ship it to the US.

I did mail Mesa at the time, but they just responded that it must be the tubes that caused the problem. I think it´s something bigger.

Otherwise you may have to get rid of it and get another one. There´s usually some used Mark IV´s for sale in Sweden.

Jag förstår hur du känner det, jag hade velat ha en Mark IV i flera år och när jag antligen köpte en så var den trasig. Jag var jävligt förbannad. Den låter verkligen bra under dom minuter då den fungerar som den ska.
Det slutade med att jag köpte en fulladdad Mark III combo istället. Den låter också jävligt bra...och hela tiden.

Lycka till!

 

[Ronnie_Rocker]

ja. jag har mailat till mesa nu. så vi ser vad dom säger. jag ska lämna tillbaka stärkaren till killen som server den nu. han har bla. lött om en massa banor i kretskortet och wirat on den till 240 v. jag tror personligen att det är nått problem med kondingarna eller nått i slutsteget. jag bytte denna stärk med en kille i Umeå mot min Mark IV Combo som jag hade, och det ångrar jag stort nu.

 

[Ronnie_Rocker]

bullen, add me on msn!

[email protected]

 

[Shep]

once tubes warm up the tone tend to brighten down so thats why i let mine warm up and then play it...ten mintues is about right..

 

[Bullen]

True, amps do change thier tone when they get warm, but usually for the better.

The change in this amp is not normal. It´s like you take all the presence and treble frequencies and just turn them down to zero. It gets very muddy and has no cut what so ever. And it effects all 3 channels.

 

[tim6string]

Just a thought. I once had a Mark III with the same problem. In and out of the shop, back to Mesa, new tubes.

The problem ended up being the tube sockets. They were the gold plated ones and the plating had worn off and the tube was arcing causing it to "starve" and act like it was worn. New tube sockets ended up fixing the problem.

Check to make sure the sockets are tight and cleaned. I don't think they used the gold ones in the Mark IV. But I wouldn't be surprised to find out it was a socket problem.

 

[Ronnie_Rocker]

i got this mail from Kris at Mesa Boogie.

Wow, very interesting issue. I spoke with one of our techs here and he felt that the only part that could cause this issue would be a tube, but I would have hoped that the repair station you brought the amp would have checked the tubes. We have not seen any issues with this amp of this nature that we could pin point a certain part. You are always more than welcome to send the amp back to the factory to have it repaired here, but that would be rather costly for you with shipping. Please let me know if I can answer any other questions you may have.
Thanks
Kris

 

[Bullen]

Yes, they replied the same thing to me: "must be the tubes". Perhaps it does have something to do with the tube sockets like tim6string said.

So what are you going to do?

 

[tim6string]

My Mark III went back to Mesa and they replaced a cap I think, but they did not discover the tube socket problem.

It wasn't until I took it to my local tech and said I didn't want it back until it worked correctly that they found the problem.

But it behaved just as you said. Sounded great (like old times) when first turned on, then degraded badly. It was hard to find because good sound doesn't necessarily show up on a scope.

I would think they would be easy to inspect. Probably worth a look.

 

[Ronnie_Rocker]

ok! i´ll check with the repair shop if they can change the powertube sockets.

 

[Ronnie_Rocker]

this is how my tube sockets look like. it seems like they are little burned on some pins... hmmm....

 

[tim6string]

I have also heard people talk about cleaning and tightening them.
I have never done that, but it would be contact clearner and using a tooth pick or something like that to make sure the sockets make good connections. The tech could look them over.

 

[metalmaster]

I've heard a good way to clean the tube sockets is to apply cleaner to an old tube, and work it repeatedly in and out of the socket. If there is a lot of build-up and corrosion, the tube pins should be wiped off, and the process repeated until the pins come out relatively clean. I havn't tried it myself yet because I havn't had to re-tube recently.