MARK IV Problems. Please Help!

[visualrocker69]

Hi, the guy who bought my Mark IV is having issues with R1 volume.

Do you know any reason why rhythm 1 would suddenly go much quieter than rhythm 2? I now have to max out the gain to even hear it where previously gain in the lower half of the spectrum was fine. I checked all the other volume controls and they're all the same as they were; all other channels function normally. I'm waiting on a response from Mesa now; what's the state of the warranty on this amp?

Any ideas what could be causing it? My initial thoughts are either the GEQ kicking in on R2 with frequencies boosted, or a bad preamp tube perhaps?

Please help! I want to be the perfect seller who considers it his duty to assist with troubleshooting

 

[Nick_cor]

When I had my mk IV I noticed volume drops as well, then i changed the power tubes and it was fine...tubes do tend to break or go microphonic when you ship them.

 

[visualrocker69]

But mine was shipped from another seller, yet I never had this problem

 

[fpoon]

I'm curious as to why you sold it. I remember a couple weeks ago that you just got it and was really happy.

The volume decreases might be because of the tubes.

 

[MusicManJP6]

But mine was shipped from another seller, yet I never had this problem

It doesn't always happen, but all it takes is just one careless person to drop it from too high up and jar the tubes too much. Hopefully the buyer has enough sense to know it is out of your control and you did not sell it with the clean channel not working correctly. Hopefully it is just one tube that got damaged in shipment...

 

[visualrocker69]

I'm curious as to why you sold it. I remember a couple weeks ago that you just got it and was really happy.

The volume decreases might be because of the tubes.

Maybe you're confusing me with someone else? I bought it in June and sold it almost a month ago. The reason being instead of a widebody combo, I need a head, a cab at college, and another cab for home. It's just too difficult to transport a large combo back and forth.

Since then, I changed my mind a bought a Triaxis. Still deciding between a 2:90 and 20/20. The latter seems more practical for now. The transition isn't that difficult between them, anyway. 20/20's go for about $500 on ebay and 2:90's for about $800. It's just an issue of size, number of tubes, and wattage that makes me wonder if a 20/20 isn't just more suitable for me, even though I'd miss out on simul-class power, modern, deep, half-drive, etc.

Also still deciding between a 1x12 Thiele with EVM12L or a 2x12 Recto with V30's. Whichever one I don't buy now (for college) I'll buy later in the year when I need one at home for the summer. So if I get the Thiele now, I'll get the recto cab for home later on, and visa versa.

But mine was shipped from another seller, yet I never had this problem

It doesn't always happen, but all it takes is just one careless person to drop it from too high up and jar the tubes too much. Hopefully the buyer has enough sense to know it is out of your control and you did not sell it with the clean channel not working correctly. Hopefully it is just one tube that got damaged in shipment...

The impression I get from his message is that this problem just started recently, not when he originally recieved it and started using it. He said himself he had no problems whatsoever with it at the start. "Everything works great" or something.

So I'm definately not taking any responsibility for it, beyond written advice.

 

[wesarvin]

First post here. I'm normally on Gearslutz.

I'm having the same issues with my early 90s MkIV. The R1 channel is really low in volume compared with the other channels.

Other than this issue, the amp sounds great. I'm actually looking at Craigslisting it as I'm thinning out my amp collection, but I'd rather get a better price for it in perfect working order than sell something in need of repair. Thanks!

 

[doctadre]

I once had a short head that has a similar problem.. when at live playing volumes, switching from r2 or lead to r1 yielded a huge drop in volume. Slightly turning the r1 gain forward n back brought volume back, but it was intermittent.

Def try tube swaps, preamp and power tubes.


Dre

 

[wesarvin]

Thanks. I did a tube swap when I bought the amp, and it still had the same issue. Turning the pot didn't help either. The tone is good from R1, but the master has to be on 7 or 8 in order to get the same level as the R2 or Lead channels when they're on 3.

 

[Blueracer]

One thing to try is varying the R2 and LD master volumes while in the R1 mode of operation. The channel master controls are under the R1/R2/LD indicator LEDs. Neither of these controls should affect the volume of R1. If either one of these controls does affect R1 volume it could indicate a bad LDR and will lead to lower than expected volume. Also check that the R1 master volume is just set low. This is something a newbie to the amp might encounter.