LSS Loop - ok to engage with no efx? (tube problem)

[A440]

I have an LSS, and most of the time I have been running it with the loop hard bypassed.

I do have an old Nanoverb I've tried running in the loop, but I had a few questions in relation to the loop.

Is it ok to run the loop engaged with nothing plugged in?
Which preamp tubes are added into the circuit when the loop is engaged?

Unfortunately, now the amp sound is cutting out when I have the loop engaged
It operates fine in hard bypass mode. I checked all the preamp tubes (especially V3 which I replaced).

Sadly, this hasn't fixed the problem with sound cutting out/no sound at all.

any advice is appreciated.

thanks in advance,

Mike

 

[plan-x]

I never run the loop dry so I'm not sure. But it's supposed to work dry for the solo function. Yeah V-3 according to my manuel. Maybe put that nano in there and see what happens.

 

[djw]

I don't run anything in the loop, but I engage it for the Solo function and it's all good. You don't need to run anything through it. Ditto what plan-x said, it sounds like V3 is bad; but I'm not clear if you're saying you have sputtering only when you run fx thru the loop; or only if the loop is engaged but with nothing in it; or just whenever you engage the loop either way.

 

[A440]

thanks for your replies

initially, I heard no problems when I was running the nanoverb in the loop.

after I took it out of the loop, I experienced the sound cutting in and out.

I think I am to blame on this one, I flicked the bypass/loop switch and I wasn't in standby (duh).
I heard a pop when I went to hard bypass mode

I replaced V3, and now there is NO sound when I have the loop engaged. I'll have to try switching in another tube when I have the chance.

 

[plan-x]

Yeah, try another tube that is known to be working. Maybe V4, reverb valve. Put V3 in its place and see if the reverb fails. And if V4 works in V3. I've switched in/out of hard bypass w/o the SB on w/o any problems. But if a tube is ready to go, that might have been enough of a surge to do it.

 

[A440]

I'm bummed/po'd

I switched in a bunch of preamp tubes I had around, and also pulled one from another amp that I know is working fine (it's an EH).

for about 5 mins, I thought I had the problem licked with the tube from my other amp, but now the same problem has come back. the sound keeps cutting in and out. when out, I can barely hear what I'm playing thru the amp. almost as if I have the master vol set very low.

this amp was shipped to me, and I had previously dealt with a broken preamp tube for the reverb. I'm worried something else might have been damaged in transit.

I thought maybe the rectifier was on it's way out, but the problem still occurs even in 30 watt mode. I am aware there is an issue with LSS rectifier tubes blowing.

I'm going to give the local boogie repair shop a call to see if they can take a look at it.

 

[plan-x]

Keep us updated on the shop's findings.

 

[thirstypirate]

Although this isn't likely it's a possibility that there is a wad of dust or dirt in one of the loop jacks. Especially if you bought it used.

It caused the same symptoms in another amp I have and was cleared up by simply spraying Deoxit onto a cable plug and working it in and out of the jack. I figured this out on my own after two 45 mile trips to the Fender repair shop that turned up nothing.

 

[lostcause]

Although this isn't likely it's a possibility that there is a wad of dust or dirt in one of the loop jacks. Especially if you bought it used.

It caused the same symptoms in another amp I have and was cleared up by simply spraying Deoxit onto a cable plug and working it in and out of the jack. I figured this out on my own after two 45 mile trips to the Fender repair shop that turned up nothing.

+1. happened to a fender amp and a nomad. Dirty jack plugs and dust.
I could give the amp a bang with my fist and it would come good for 30 seconds then start fading again.
A quick spray of deoxit and all was good.

 

[thirstypirate]

+1. happened to a fender amp and a nomad. Dirty jack plugs and dust.
I could give the amp a bang with my fist and it would come good for 30 seconds then start fading again.
A quick spray of deoxit and all was good.

Mine was also a Fender amp, Acoustasonic SFX II. It's never had a problem since and it get some pretty heavy use.

 

[speedy mcfeely]

does the send level pot make any scratchy noises when moved? the pot could be dirty.

 

[Octavarius]

I assume you've read the memo that Mesa recently gave out about V3?

In any case, here it is:

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

Lone Star & LS Special: V3
Stiletto: V3 & V4
Road King I: V3 & V4
Road King II: V3 & V5
Roadster: V3 & V5
Dual & Triple (2ch or 3ch): V3 & V4
Tremoverb: V3 & V4


BASS AMPS

Venture: V2
M-Pulse: V2
Big Block 750: V4
Titan: V4
M2000: V2
Bass 400+: V2


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.

There's no harm in switching either power settings or bypassing the loop while the amp is fully on/off standby. You have done nothing wrong, and before you do anything "drastic" (like paying for a tech to check your amp), try putting a new Mesa Chinese 1 12AX7 in V3.

Hope this helps!

 

[A440]

I assume you've read the memo that Mesa recently gave out about V3?

In any case, here it is:

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

Lone Star & LS Special: V3
Stiletto: V3 & V4
Road King I: V3 & V4
Road King II: V3 & V5
Roadster: V3 & V5
Dual & Triple (2ch or 3ch): V3 & V4
Tremoverb: V3 & V4


BASS AMPS

Venture: V2
M-Pulse: V2
Big Block 750: V4
Titan: V4
M2000: V2
Bass 400+: V2


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.

There's no harm in switching either power settings or bypassing the loop while the amp is fully on/off standby. You have done nothing wrong, and before you do anything "drastic" (like paying for a tech to check your amp), try putting a new Mesa Chinese 1 12AX7 in V3.

Hope this helps!

thank you very much!

I wasn't aware of this memo (how do I get in the loop on these?)

I'll give compressed air or de-oxit a try. I've tried a large number of different tubes in V3, but will give it another try.

I did talk to a local repair shop, and he thought it might be something bad in the efx loop. We shall see...

 

[Octavarius]

I assume you've read the memo that Mesa recently gave out about V3?

In any case, here it is:

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

Lone Star & LS Special: V3
Stiletto: V3 & V4
Road King I: V3 & V4
Road King II: V3 & V5
Roadster: V3 & V5
Dual & Triple (2ch or 3ch): V3 & V4
Tremoverb: V3 & V4


BASS AMPS

Venture: V2
M-Pulse: V2
Big Block 750: V4
Titan: V4
M2000: V2
Bass 400+: V2


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.

There's no harm in switching either power settings or bypassing the loop while the amp is fully on/off standby. You have done nothing wrong, and before you do anything "drastic" (like paying for a tech to check your amp), try putting a new Mesa Chinese 1 12AX7 in V3.

Hope this helps!

thank you very much!

I wasn't aware of this memo (how do I get in the loop on these?)

I'll give compressed air or de-oxit a try. I've tried a large number of different tubes in V3, but will give it another try.

I did talk to a local repair shop, and he thought it might be something bad in the efx loop. We shall see...

Not really sure. I saw it posted on these forums and thought I should save it for later. A few months after I bought a brand new Lonestar, so it turned out to be a good find as all the preamp tubes that came with it are Russian 2's. Haven't had any issues yet, though. My best bet would still be to try a Mesa Chinese 12AX7 in the V3 socket in your case, though...

 

[plan-x]

When I recieved my tubes from eurotubes, Bob had instructions with the shipment on how to clean the sockets. Spray some contact cleaner on the tube pins and insert in and out of the socket a couple of times or so. I found that the contact cleaner spray evaporates quickly, so ya gotta move fast. How come this chinese tube thing thats been circulating around this forum forever, doesn't affect say, every Lonestar, or mine.

 

[BobL]

I've had this issue rear it's ugly head on both of my Lonestars. On one it was the tube, now replaced with GT ECC83s, and the other was with the loop jacks. The loop is an easy fix using contact cleaner. Spray a 1/4" plug and the jack then run the plug in and out a few times. Do this for each jack. If it happens on stage, take an effects pedal cable and jumper from the in to the out jack with it. Either way the problem is solved. And keep dirty cables out of those jacks!!

 

[thirstypirate]

When I recieved my tubes from eurotubes, Bob had instructions with the shipment on how to clean the sockets. Spray some contact cleaner on the tube pins and insert in and out of the socket a couple of times or so. I found that the contact cleaner spray evaporates quickly, so ya gotta move fast. How come this chinese tube thing thats been circulating around this forum forever, doesn't affect say, every Lonestar, or mine.

Mine has Russian tubes as well.

 

[A440]

a quick update...

much thanks to Octa and everyone for their posts

I did the contact cleaner thing to the efx loop jacks, and tried a chinese tube I had around in V3. so far, so good. the problem has not recurred.

if it comes back, it's going to the shop for a check up

ps...I think it could be very helpful to sticky some of these known tech issues/repair memos

Happy Holidays to All!

 

[Octavarius]

Glad you've solved the problem! (for now, at least)

I'll also vote for making the memo into a sticky. Could help a lot.