Interesting Problem with hum in my Mini Rec in 10watt mode.

[Hank75]

Hi, this is my first post about a fanastic little beast with a small issue
Haven't had this amp too long but it is/was brand new. Tried searching the forum but came up empty.
Right from the start I noticed a substantial hum in 10watt mode only, on both Channels (louder in channel 2)
I unplugged everything except the speaker connection and noise is still there.
I had an extra set of JJ- El-84 tubes so I plugged them in and noise was completely gone. Put Mesa power tubes back in and noise was back. I guess I have a bad tube.
Took it back to dealer and showed them and they agreed the noise was bad and sounded like the "60 cycle" hum, so we put in a set of brand new Mesa power tubes and rechecked.The noise is still there :?:
I put in my JJ tubes to show them I wasn't crazy and proved to them that the JJ's made the noise go away.
I left the amp with them to have their techs check it out.
It's interesting that the noise only happens with Mesa branded tubes.
Any thoughts or experiences?

Thanks
Henry

 

[Third Age Amps]

Could be some microphonics going on with the Mesa tubes. JJ's are built with more mechanical dampening in them.

 

[11justin22]

Well I have an odd story about hum with the mini rec. I had it about 2 months and it developed a "60"cycle type hum on both channels. Wasn't the tubes I swapped all of them and it was still there. Sent it in to Mesa to have them check it out. They called me the next week and said they couldn't find anything wrong! They said no hum. How the heck can they not hear it. It was as loud as the guitar being played. They shipped it back and.......no hum :?: I don't know if they fixed it and didn't want to tell me(don't know why they would do this) or something got knocked back in place during shipping..... But it's back to normal now and hasn't acted up again in 3 months.

 

[D2dark]

I has the same problem, it's bad power tube, I've send my mini to my amp tech and he find a good pair of mess tube and... No more hum!

He told me its a bad paired set ( only on pentod side?! )

 

[Hank75]

We'll see what the techs say.
Maybe just have to use the JJ's, although I just read an article published by Mesa about why you should only use Mesa Tubes,its basically written in all the owner manuals around the section about why they don't put bias adjustments in their amps.
Thanks for your input.

 

[elvis]

Mesa tubes are rebranded JJs as I understand it. That is why they have so many problems.

 

[ken361]

keep the JJ powers in, more low end and more chime. Stocks are cheap Sovteks. I get my JJ from the tube depot rating at 26

 

[ratter]

That's one big upside of a low-wattage amp - retubes are nice and cheap compared to a 100w head.

 

[Hank75]

Got the amp back and was told that the original tubes were no good. I asked why a new set of mesa tubes off the shelf had the same issue and was told basically that Mesa doesn't do a very good job of matching their tubes and allow high tolerances when they match them.Its basically hit or miss with their tubes,so I'm told. He basically stated that "Mesa" branded tubes were junk.
Tech confirmmed that the JJ-tubes were very well matched.So his solution was put in JJ tubes. I'm not sure if I really like his diagnosis but will stay with the JJ's.
It occured to me later that evening that I had provided the JJ's for them,so I basically paid for my own replacment tubes on an amp thats a week old. I am going to contact them and ask that they provide me with a set of decent tubes, JJ's preferably.
I also asked that when they do get more of that particular amp in that I would like to see if the other amps do the same thing, if they don't I will ask for an exchange based on my original concern.

 

[ratter]

Got the amp back and was told that the original tubes were no good. I asked why a new set of mesa tubes off the shelf had the same issue and was told basically that Mesa doesn't do a very good job of matching their tubes and allow high tolerances when they match them.Its basically hit or miss with their tubes,so I'm told. He basically stated that "Mesa" branded tubes were junk.
Tech confirmmed that the JJ-tubes were very well matched.So his solution was put in JJ tubes. I'm not sure if I really like his diagnosis but will stay with the JJ's.
It occured to me later that evening that I had provided the JJ's for them,so I basically paid for my own replacment tubes on an amp thats a week old. I am going to contact them and ask that they provide me with a set of decent tubes, JJ's preferably.
I also asked that when they do get more of that particular amp in that I would like to see if the other amps do the same thing, if they don't I will ask for an exchange based on my original concern.

FWIW, my mini is dead quiet with the stock tubes. I dont think you're out of line to request an exchange if another set of Mesa tubes is still noisy.

 

[pegagos]

Fyi, I had the same issue you describe here. The stock el 84 that came with amp made a hum in 10w mode. I already a had JJ el-84 on the way. When I changed it to the JJs the hum went away. At a later time I put the mesa back and used them for a while and didn't care about the hum because I was mainly using 25w mode. Ater a month or two, one of the stock tubes went out on me. I called mesa for a replacement and the sent me a new set of el-84 at no charge. The new ones did not hum in either mode.

Hope this helps.

 

[bumblefunk]

Ditto on the Mini Rectifier 10W hum. I let the tubes burn in and after about an hour the hum at 10W became significantly louder. With the case off I could see that one of the EL 84s was flaming red in perfect correlation with the hum. I had a couple Sovtek 84s around and the hum was gone - plus the amp sounded much better (more high end clarity).

 

[bendo]

Ditto on the Mini Rectifier 10W hum. I let the tubes burn in and after about an hour the hum at 10W became significantly louder. With the case off I could see that one of the EL 84s was flaming red in perfect correlation with the hum. I had a couple Sovtek 84s around and the hum was gone - plus the amp sounded much better (more high end clarity).

If you haven't had your Mini longer than 3 months, call Mesa and get a replacement set of tubes for free. Always good to have a spare set on hand.