Mini Rec Possible Preamp Tube Problem?

[paulg2uk]

Hey guys,

I been playing about with my mini rec the last few days and I took it to rehearsal last night and noticed some weird behaviour. I think it might be a preamp tube. It's in chan 2 when I flick from 25 watts down to 10 watts it makes a high pitched squeal. This will come and go and will only happen when the guitar is not played but chan 2 is left switched on. This must of happened for the first hour and a half and then it disappeared which I thought was kind of strange. Do you reckon it could be a preamp tube messing around?

Should I try and swap it out?

Thanks

Paul

 

[elvis]

I'm not convinced it's a preamp tube, since it's the power tube condition that makes it happen. The amp is perfectly happy in 25W mode.

Try tapping all the tubes, including the power tubes, with a pencil eraser in 10W mode to see if that affects the oscillation (squeal). I would bet it's a power tube that's microphonic or unstable in triode.

 

[paulg2uk]

I'm not convinced it's a preamp tube, since it's the power tube condition that makes it happen. The amp is perfectly happy in 25W mode.

Try tapping all the tubes, including the power tubes, with a pencil eraser in 10W mode to see if that affects the oscillation (squeal). I would bet it's a power tube that's microphonic or unstable in triode.

Thanks for the reply. I did try tapping the power tubes earlier and they were pretty silent. That's the problem though is I never know when the squeal will occur. And when I was testing the tubes the squeal wasn't present but shortly after. It didn't occur to me to test them when the squeal was present. I did notice a noisy v2 preamp tube but that was the socket and it needed a bit of switch cleaner.

I did hear back from mesa and they said the same thing it could be the power tubes as its only present when switching wattages. I'll have to get some spare power tubes and swap them out. I've only had it 2 weeks surly I should get a set of tubes from mesa for free?

 

[elvis]

EL84s are cheap. Get a set of Mullards, you'll probably love them.

You should also have a spare set of preamp tubes. Tubes are notoriously unreliable. I've had brand-new tubes that lasted less than 10 hours, and one that lasted only 10 minutes (all Mesa brand).

 

[paulg2uk]

EL84s are cheap. Get a set of Mullards, you'll probably love them.

You should also have a spare set of preamp tubes. Tubes are notoriously unreliable. I've had brand-new tubes that lasted less than 10 hours, and one that lasted only 10 minutes (all Mesa brand).

I just tried tapping the tubes with a pencil like you said while the squeal was present. Not a thing both the preamp tubes and power tubes are dead silent during the squeal. Its kind of weird the squeal doesn't happen straight away the amp has to warm up for an hour or so and then when the squeal occurs it will only go away when switched to 25 watts and it doesn't happen again when switched back to 10 watts straight away.

I think I'm gonna get some new power tubes and see if that makes a difference.

 

[paulg2uk]

Some good news for me anyway. The store I bought the mini rec from have said they will just change the amp over for another one. That saves messing around with tubes I suppose. I still need to buy a spare set though just in case.

 

[RR]

Some good news for me anyway. The store I bought the mini rec from have said they will just change the amp over for another one. That saves messing around with tubes I suppose. I still need to buy a spare set though just in case.

Cool, care to give us the store name? We like to hear good news too.

 

[paulg2uk]

Its a store in the UK called Andertons. They are a very helpful. I thought they were just gonna give me some power tubes to change out but no a new amp is on its way.

 

[paulg2uk]

Well I think I might have problem with the replacement min rec. I took it to rehearsals tonight and it just seemed like it was struggling to keep up with the rest of the band. I did notice a big volume difference between the one I sent back and this one which is a lot quieter in comparison. It actually came to a point where my bass player couldn't hear me and had to mic the cab up.

I don't know if its a tube maybe or am I going mad? I had both clean and dirty channels on 25 watts and on the one I sent back I remember it being super loud only on the 10 watts setting.

Anyone got any suggestions? Is this normal?

Thanks again

Paul

 

[ken361]

I would retube anyways stocks suck, JJ power tubes tunsol in the v1 at least loop bypassed sound better

 

[paulg2uk]

I would retube anyways stocks suck, JJ power tubes tunsol in the v1 at least loop bypassed sound better

Really I was thinking retubing but was told that JJ's are just the mesa tubes but just rebranded. Is that right?

Does it sound like a tube fault to you what I'm describing?

 

[ken361]

JJ are really decent, there not stock mesa those are sovteks. I had a preamp tube fart out but there was a lot of sound lost. The amp should be loud no matter what, if you can get another one right away go for it. If you plan on keeping the mesa get some tubes at least

 

[paulg2uk]

JJ are really decent, there not stock mesa those are sovteks. I had a preamp tube fart out but there was a lot of sound lost. The amp should be loud no matter what, if you can get another one right away go for it. If you plan on keeping the mesa get some tubes at least

Thanks for the post. I'm gonna get them to change it for another amp this will be the 3rd one. But I'm gonna troubleshoot the tubes tonight and see if I can find the fault.

I think I will change the tubes out though when I get a replacement amp. Which JJ's do you recommend? Power tubes and preamp tubes?
There are a few different ones as far as I remember.

 

[ken361]

Jj el84's are good, for preamp I use a mix of old stock and new. Tungsol is a good v1, v2 and 3 maybe JJ 803's, mullard,v4 PI sovtek lps v5 loop maybe JJ again you gotta play around and see what you like best. I find the NOS baldwin slyvania Ebay has them works great as a v2, v1 gold lion,v3 old stock Mullard japanese, v4 penta M v5 EI I have a bunch so I always ended up using these over stock it sounds better and smoother.

 

[paulg2uk]

Jj el84's are good, for preamp I use a mix of old stock and new. Tungsol is a good v1, v2 and 3 maybe JJ 803's, mullard,v4 PI sovtek lps v5 loop maybe JJ again you gotta play around and see what you like best. I find the NOS baldwin slyvania Ebay has them works great as a v2, v1 gold lion,v3 old stock Mullard japanese, v4 penta M v5 EI I have a bunch so I always ended up using these over stock it sounds better and smoother.

Thanks again for the info. I managed to cure the problem is was the V4 driver preamp tube causing the volume loss. Its back to normal now. I'm glad I found it.

I have stumbled upon another problem though. I connected my TC g system up as I wanted to test the switching relays and I've found on channel 2 a very subtle volume fading in and out. Its not drastic but enough to be noticeable. Whats weird is if I disconnect the g system I don't get it and I also connected up my nova sys and it doesn't do it either. I tried switching out the fx loop pre amp tube but it didnt make a difference.

I think I just need to swap the tubes out for another brand they are really unreliable for a new amp.

 

[domct203]

JJ are really decent, there not stock mesa those are sovteks.

FYI-
The current (since '09 or '10) Mesa "Russian" 12AX7 is in fact a JJ ECC83.

Previous to that was the Mesa "Russian-2" 12AX7 made by Electro-Harmonix (New Sensor).
Sovtek (New Sensor) has not supplied the standard Mesa 12AX7 since the "Russian-1".

Dom

 

[ken361]

JJ are really decent, there not stock mesa those are sovteks.

FYI-
The current (since '09 or '10) Mesa "Russian" 12AX7 is in fact a JJ ECC83.

Previous to that was the Mesa "Russian-2" 12AX7 made by Electro-Harmonix (New Sensor).
Sovtek (New Sensor) has not supplied the standard Mesa 12AX7 since the "Russian-1".

Dom

Sorry I meant the 12ax7

 

[domct203]

JJ are really decent, there not stock mesa those are sovteks.

FYI-
The current (since '09 or '10) Mesa "Russian" 12AX7 is in fact a JJ ECC83.

Previous to that was the Mesa "Russian-2" 12AX7 made by Electro-Harmonix (New Sensor).
Sovtek (New Sensor) has not supplied the standard Mesa 12AX7 since the "Russian-1".

Dom

Sorry I meant the 12ax7

:?:

Now I'm really confused, I thought we were talking about 12AX7's

:?

Dom

 

[ken361]

I was trying to say that stock mesa ax7's are the same as JJ as you stated