Did You Get The Memo?

[Brewski]

Has anyone else heard about this one? My Road King was working fine, and then the volume started to drop and then go into volume swells, sort of like a slow tremolo. Then, at times, it would give an ugly static buzz. Finally, the volume totally dropped. I first thought that it was a pre-amp tube, however, when I flipped the solo switch, on the back of the amp to bypass, I got volume on all channels, but no effects or reverb.

Well, I decided to just send it in to Mesa for Repair, so dropped it off at an excellent local music shop, to send in for me. I was thinking that it must be the circuit surrounding the switch.

I got a call from, Doug at Guitar Showcase, who gave me the following info. After trying to get an RMA from Mesa. The Mesa service rep told Doug that the problem sounded exactly like an issue that they had sent a memo out on. On Road Kings and some other amps, the effects circuit is partial to the Mesa Chinese tubes, rather than the Russian made tubes. So he recommended that I try to put a Chinese tube in and see if the problem clears up. The v5 slot is the one closest to the fan and furthest from the transformer. That actually solved the problem and the amp is back up and running. I'm not sure what it is that makes the Chinese made tubes special, but a $16 pre-amp tube is a much less costly resolution than sending the amp in for repair. I just thought that I'd put the information out there. If this is redundant to another thread, sorry, but I tried searching for it first.

I tried searching the Mesa site for this memo, and couldn't find it. And tried searching the BB for it with no luck. I did get a verification that Mesa Techs got this memo. Anyone else hear about this?

 

[Charlie]

I had a problem with the volume on my Stiletto - it was WAY low in spongy mode. I had to switch a Tung Sol tube out of one of the slots (forget which one) and that cleared the problem up.

Seem like these Mesa circuits can be tempermental with certain tubes.

 

[Brewski]

Yeah, I didn't realize that they were THAT sensitive, where even if it's a Mesa tube, the point of origin matters. At least the fix is simple if you know what to look for.

 

[Ang3lus]

so i have to ditch my mullard and siemens when i get my road king II?

 

[Brewski]

I don't know. I have an early series 1.

 

[Boogiebabies]

Mesa was pretty public about this about a year ago. The Russian 12AX7's would just blow in the cathode follower positions of V3B and V4A. The plates see about 422V and the cathode 213V. The issue was supposed to be solved by using the Chinese 12AX7, but these had issues as well. They could handle the cathode follower posistions, but would crack upon cooling down. Mesa moved away from the 7025 Silver Specials and to the 12AX7C9 and both problems appear to be handled. It's only a matter of time for any tube in the V3 and V4 of any Road King or Dual Rectifier.
I would hope they meant V3 or V4 on your RKI as the V5 is the phase inverter and I have never had an issue with the V5 on the RKI or DR.

 

[Silverwulf]

I would hope they meant V3 or V4 on your RKI as the V5 is the phase inverter and I have never had an issue with the V5 on the RKI or DR.

+1 to that. I've never heard of the V5 giving anyone problems before.

 

[wastoid]

Do you guys think new Roadsters would have this problem? I just ordered mine about a month ago and they are still building it.

 

[Boogiebabies]

Do you guys think new Roadsters would have this problem? I just ordered mine about a month ago and they are still building it.

It's more of an annoyance than a problem. Every Dual Rectifier design uses a cathode follower for the tone stack and effects send. It's more a matter of getting a preamp tube that will have a short life span. Some run for years and some run a few days. It's not a bad design as it is almost the same as the Soldano SLO 100, but it's prone to making weak tubes very evident. Welcome to Tubeville.

 

[wastoid]

Do you guys think new Roadsters would have this problem? I just ordered mine about a month ago and they are still building it.

It's more of an annoyance than a problem. Every Dual Rectifier design uses a cathode follower for the tone stack and effects send. It's more a matter of getting a preamp tube that will have a short life span. Some run for years and some run a few days. It's not a bad design as it is almost the same as the Soldano SLO 100, but it's prone to making weak tubes very evident. Welcome to Tubeville.

So I'm a little confused then. If the Russian ones are horrible and the Chinese ones have some other problems, what's the ideal tube type? Should I preemptively swap out the tubes as soon as I get it or just see how long of a ride I can get out of the stock ones before doing anything?

 

[Brewski]

I would hope they meant V3 or V4 on your RKI as the V5 is the phase inverter and I have never had an issue with the V5 on the RKI or DR.

Hey Boogiebabies, Good info. I was told specifically V5, and that the notice wasn't that old. I'm just repeatin' what I got 2nd hand from a Mesa Service Rep. I replaced V5 and it did fix my problem, well, at least for the time being. If I can get my hands on a copy of the notice, I'll post it.

 

[MetalMatt]

Thats interesting and good to know, thanks! My RKII has the Mesa russian 2's. They are the stock preamp tubes, so for 2+ years they haven't given me any trouble.... yet.

 

[JAZZGEAR]

Well, this problem is not unique to just the Road King. I have a brand new 2008 LSC that had the exact same problem...and got the exact same fix from Rich at Mesa Boogie. Sent me a Set of 5 Preamp tubes to for V3/V4.

Issue is, the problem creeped up again momentarily at a recent gig.

Will have to place close attention to this if it happens again. :evil:

 

[Ang3lus]

that is good info
what's the point of having a 2500$ amp if you can't fit good tubes in it, i know the mesa tubes are ok, but they are nowhere near as good as the siemens tubes i use in my current amps, not being able to change sucks.

 

[Brewski]

I did get a copy of the notice. I was given wrong verbal info, V3 and V4 are the cathode follower locations on the series 1 and v3 and v5 on the RK 2. Boogiebabies was right. In any case, I'm still up and running. Sounds like I'm going to get my hands on a few more of them tubes, just to be sure.

 

[blakkspider]

Hey everybody

Any one knows what's the v3 and v4 on a Roadster? and what's the bias level or uhm the voltage?? i need to run to my local music store and they don't carry MESA tubes so i have to buy a pair of fender tubes or electro harmonix, i have a show in about 55 min.

i need to change those preamp tubes in order to find out if this is the problem i got on my amp.

-spider-

 

[Brewski]

Hey Blakkspider, I hope that you got your amp back up and running. Here's the info from the Mesa Memo...


SOUND “DROP-OUTS” / INTERMITTENT SIGNAL

One Possible Cause



Most (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.



Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.



For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.



In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).



Below is a partial list of Mesa amps and cathode follower tube locations:

GUITAR AMPS BASS AMPS

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure.

 

[gumbymage]

The other day, I noticed I had to crank the Output and Master way beyond 12 O'clock to hear anything from my Stiletto Deuce. Plus, the low E string was almost non-existant. No bass at all, with a crackling sound thrown in. Very thin and tinny. I was baffled. :?

The next day I plugged it up and played some and it seemed better. I was getting louder volume and crunch with Output and Master between 10:00 and 11:00. However, after 20 minutes of playing, I switched up to Bold and nearly blew my eardrums out! :shock: I went to Spongy and it was lower volume and seemed to change on it's own! I flipped back and forth and finally I was getting nothing but ear splitting volume and put both Output and Master down below 9:00 and it was still incredibly loud. In fact, I don't think the Output knob even affected the volume, but the Master (all channel 2) could barely go to 9:00.

Sheesh, I was baffled. So I searched and found this thread. Is this the same issue all of you have had? Tube change for v5 then?

Thanks

Has anyone else heard about this one? My Road King was working fine, and then the volume started to drop and then go into volume swells, sort of like a slow tremolo. Then, at times, it would give an ugly static buzz. Finally, the volume totally dropped. I first thought that it was a pre-amp tube, however, when I flipped the solo switch, on the back of the amp to bypass, I got volume on all channels, but no effects or reverb.

Well, I decided to just send it in to Mesa for Repair, so dropped it off at an excellent local music shop, to send in for me. I was thinking that it must be the circuit surrounding the switch.

I got a call from, Doug at Guitar Showcase, who gave me the following info. After trying to get an RMA from Mesa. The Mesa service rep told Doug that the problem sounded exactly like an issue that they had sent a memo out on. On Road Kings and some other amps, the effects circuit is partial to the Mesa Chinese tubes, rather than the Russian made tubes. So he recommended that I try to put a Chinese tube in and see if the problem clears up. The v5 slot is the one closest to the fan and furthest from the transformer. That actually solved the problem and the amp is back up and running. I'm not sure what it is that makes the Chinese made tubes special, but a $16 pre-amp tube is a much less costly resolution than sending the amp in for repair. I just thought that I'd put the information out there. If this is redundant to another thread, sorry, but I tried searching for it first.

I tried searching the Mesa site for this memo, and couldn't find it. And tried searching the BB for it with no luck. I did get a verification that Mesa Techs got this memo. Anyone else hear about this?

 

[CudBucket]

Interesting stuff. I wonder if my LS doesn't suffer from the same thing. It's about 4 years old and I'm the 2nd owner. I get noise (hissy, sizzly popping) in the clean channel only. I changed V2 with a new Mesa tube and it went away for about 2 weeks only to start again a couple of days ago.

 

[gumbymage]

OK, the loop switch in back was down so the output and solo knobs were bypassed.

But still, I can't explain the strangeness from the other day. Crackling, no bass, thin/tinny sound, low volume even past noon.

Yesterday when I messed with it I removed each tube and put 'em back one by one (not replacing them). Maybe that did something... :?