Mini Rectifier big hum problem

I know there's a problem with many amps around and i'm borrowing a mini rectifier i consider buying. But i need to know if there's fix before i even think about handling over the money to the seller.

The problem is as follows:

A little hum on the clean ch 25 w and a bit more when in pushed mode.
More hum on the clean ch 10 w in both modes.
A lot hum in both modes on the overdrive channel in both 10 and 25 w modes. Most in 10 w mode. In other words not useable as it is right now.

I'm quite experienced as a musician and have played a lot of different amps and know this is not working as it should. I've tried every tweak without modding the amp so now i'll ask here.

The amp is looked over by a really good pro service tech next to where i live. He can fix and mod everything as long as there 's a schematics for the mod. He has a couple of soultions but they are too big to fit inside the housing of the amp. The tubes are all good and all the rest seems good.

Is there a fix for this hum problem ? And is there a schematics for it ? I need it fast since the seller is unpatient. I've read about a 10w osc fix and several other fixes.

Btw, i live in Norway.

Thanks.

Sarge 1970 said:

I know there's a problem with many amps around and i'm borrowing a mini rectifier i consider buying. But i need to know if there's fix before i even think about handling over the money to the seller.

The problem is as follows:

A little hum on the clean ch 25 w and a bit more when in pushed mode.
More hum on the clean ch 10 w in both modes.
A lot hum in both modes on the overdrive channel in both 10 and 25 w modes. Most in 10 w mode. In other words not useable as it is right now.

I'm quite experienced as a musician and have played a lot of different amps and know this is not working as it should. I've tried every tweak without modding the amp so now i'll ask here.

The amp is looked over by a really good pro service tech next to where i live. He can fix and mod everything as long as there 's a schematics for the mod. He has a couple of soultions but they are too big to fit inside the housing of the amp. The tubes are all good and all the rest seems good.

Is there a fix for this hum problem ? And is there a schematics for it ? I need it fast since the seller is unpatient. I've read about a 10w osc fix and several other fixes.

Btw, i live in Norway.

Thanks.

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Have you tried a new pair of power tubes? More hum in 10w (triode) than in 25w (pentode) suggests the tubes are out of balance.

The first thing we tried was to replace the powertubes with new ones. TAD tubes have really good quality and are nicely matched in pairs. I tried several pairs with the same result and no improvement. We even tried the tubes in a tube tester to check if they deliver what they're supposed to and the tubes we tested are all ok and in perfect working condition.

It seems like there are a lot of different fixes for these amp's and it seems like the build quaility differs a lot. This particular amp is almost not used and it has a really bad humming especially on the overdrive channel, but also in the clean channel. I finally got hold of some of the official service partners in Norway which had a lot of experience with faulty Mini Rectifiers. But since they are located about 550 km from where i live it's not just to drop by. I have to send it by mail. Since i haven't bought the amp yet i would like to know what the fault is and how much it would cost before i use money on anything. So thats my dilemma.

Do any of you guys have any mod schematics so i can try to find the right fix ? I know there's a lot of different fixes for different faults but someone should have experienced the same thing and might have the right schematics. The norwegian service partner won't help me since they only want me to send the amp so they can do the repair and make the money.

You do realize that "Authorized Boogie" is a representative from the actual Mesa factory?

I would work directly with Mesa in this case - if you are going to ship the amp anywhere why not just ship it to them? Or someone that THEY (Mesa) recommend in your country.

Is the hum present with no lead attached to the input?

Is the hum present with a voltage regulator between the amp and the mains?

My MkV25 has a lot of hum under certain conditions. I know it's not the same amp but they are very sensitive. I keep my gain less than noon and only use a compressor when absolutely required. My guitars are all copper plated to reduced interference. When I am at rehearsal, the studio I am in suffers from a lot of voltage fluctuation that can cause a significant amount of hum and or volume fluctuations. I use an AC voltage regulator (UPS) in front of it to mitigate that. A simple power conditioner does not help.

Right now there's no official Mesa representative in Norway and that might be the reason why it's so hard to find someone who can help me here. I have found the former service tech shop but they can't promise anything and cost a lot just to diagnose

I did try the amp through a Furman Powerconditioner and with nothing else attached to it than a speaker cab 2x12. The humming was still the same. The humming has the same high level whatever adjustments to the preamp. I have different Mesa amps and have tried them in the same outlets and there's no humming in them so it has to be the Mini Rectifier.

Since i still haven't bought the amp and nobody has come up with a fix, i will just return the amp to it's owner and let him figure out what to do. I have so far used about three days and many phonecalls without being close to a soultion and since i don't know if this is a monday product i will just try to find another amp and hope its in better shape..

Anyway... Thanks for your replies.

The distributor for Norway and Finland is in Finland - contact them for assistance in locating a technician. Thanks!

Levytukku

HERNEPELLONKUJA 9, 00560 HELSINKI, FINLAND

P: +358 9 7 57 1344
F: +358 9 7 57 0066
http://www.levytukku.fi/mesa-boogie-scandinavia

Authorized Boogie said:

The distributor for Norway and Finland is in Finland - contact them for assistance in locating a technician. Thanks!

Levytukku

HERNEPELLONKUJA 9, 00560 HELSINKI, FINLAND

P: +358 9 7 57 1344
F: +358 9 7 57 0066
http://www.levytukku.fi/mesa-boogie-scandinavia

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I've contacted them in couple of cases and they have been really helpful