Amp turning off and on again quickly

[jaslan]

I have very similar symptoms with my amp. Very random but probably once a week the amp will shut down and back on. I hear the fan shut off, the relays click, and then everything starts up again, all within a second or less. Occasionally it will do it again within a few seconds. It seems once the amp is warmed up for a few minutes it doesn’t happen, it seems always within a minute of turning it on from a cold start.

One detail that I did not see in the OPs original description of the problem is this: when it happens to my MK V, the foot switch immediately goes into “power up” mode, whereby all three channel LEDs are illuminated at once. The amp reverts to the clean channel. Does this also happen when your amp momentarily shuts down and back on again?

Thanks for any updates on your situation and best of luck!

This sounds exactly like the failing diodes I had. Eventually, the amp just died and wouldn’t come back on. It was under warranty so they sent me to a tech who replaced them in about 2 hours (actually let me stay and watch/assist) and it has been good every since. I recommend you just go ahead and talk to Mesa service and schedule the diode replacement.

 

[royslead]

I have not noticed the foot switch symptoms, just the clicking, lights at the amp cycling rapidly; and usually just once, then it's ok.

 

[notyalcer]

I have very similar symptoms with my amp. Very random but probably once a week the amp will shut down and back on. I hear the fan shut off, the relays click, and then everything starts up again, all within a second or less. Occasionally it will do it again within a few seconds. It seems once the amp is warmed up for a few minutes it doesn’t happen, it seems always within a minute of turning it on from a cold start.

One detail that I did not see in the OPs original description of the problem is this: when it happens to my MK V, the foot switch immediately goes into “power up” mode, whereby all three channel LEDs are illuminated at once. The amp reverts to the clean channel. Does this also happen when your amp momentarily shuts down and back on again?

Thanks for any updates on your situation and best of luck!

This sounds exactly like the failing diodes I had. Eventually, the amp just died and wouldn’t come back on. It was under warranty so they sent me to a tech who replaced them in about 2 hours (actually let me stay and watch/assist) and it has been good every since. I recommend you just go ahead and talk to Mesa service and schedule the diode replacement.

That is helpful information! Thank you. I have only owned my Mark V for a few months, got it used with 2 years left on the tanferable warranty. I have not playing this amp live yet, not gigging that much but have some gigs coming up in late summer/fall. If the amp did this routine during a performance, it would reset to the clean channel which could be disconcerting while playing, but not a total disaster.

Probably need to get this fixed while under warranty. You may have already mentioned, but which diodes were failing? Thanks!

 

[jaslan]

...which diodes were failing?

All I know is they were in the power supply section... I think...

 

[Rockstarlineman]

from bandit2013
It could also be associated with the 12V voltage regulator which is connected to the chassis for thermal dissipation. this circuit is formed from a separate power tap on the PT and supplies power to three preamp tube heaters, cooling fan and 5v voltage for the channel controller. I believe that the relays also run on the 12v supply as well as the diodes to indicate function. If this circuit is dropping out it will be basically shutting down the amp even though there is power to the power tubes and preamp tubes. There are three preamp tubes that use the 12Vdc heater circuit : V1, V2 and V5. I If there is a fault in the heater of either of these tubes (shorting out intermittently) you could replace all three with new tubes and see if the problem is persistent. The power light is also an LED and most likely is supplied by this circuit.

I looked up the LM2940 (12V voltage regulator) data sheet. In its description, it has an overvoltage protection ciruit that will momentarily shut down the regulator in the event the intput voltage is exceeded. This could be related to a gound loop transient voltage spike or from the power transformer or associated circuits.

This I reposted is exactly what I think is wrong with mine as well. so now Im wondering how to fix it? anyone have a video on how to fix it? mine is out of warranty. the reason why I think it is this and not diodes is because the description fits perfectly . the fan quit, no led on the power, the tubes are all lit up so I believe its a low voltage issue. Please help...

 

[jdgebha]

Had the exact same symptoms. Took to an authorized mesa tech and he a diode replacement and a power supply upgrade recommended by mesa. No probs a year amd a half later.

 

[Giz-Tone]

The same thing happened to my amp. The diodes in the LV power supply needed to be replaced. It seems like a common fault with the Mark V

 

[richprice79]

Well my 2017 Mark V 90 is having the same issue. I don't have any local Mesa repair shops so I called and they recommended I mail it to California from St. Augustine Florida. I asked if they could send me a factory box with the form fitting packing material for a cost and they will do that for around $40.00. It sucks but seeing others have the same issue makes me feel less unlucky. I can't imagine what the shipping to Mesa bill will be as I will want it there fast to avoid damage.

 

[Giz-Tone]

Well my 2017 Mark V 90 is having the same issue. I don't have any local Mesa repair shops so I called and they recommended I mail it to California from St. Augustine Florida. I asked if they could send me a factory box with the form fitting packing material for a cost and they will do that for around $40.00. It sucks but seeing others have the same issue makes me feel less unlucky. I can't imagine what the shipping to Mesa bill will be as I will want it there fast to avoid damage.

I was going to send my amp back to my nearest mesa distributor. There's none in my country, I'd have to send it abroad (not the USA) to be repaired.

It turned out that the Mesa distributor would lease the repair work out to a third party. Some local dude near the distributor in other words.

My point is that if you can find a good local tech, go with him. He can order the diodes and tech info from Mesa. It will be a lot cheaper.

It's a quick fix, and a good tech should have the necessary parts already.

 

[Zakkmylde]

This issue just happened to me yesterday and has happened many times since buying new. Often seems to be when on 10watt more cranked. Maybe just coincidence. I’ve had bad rectifier tubes before so good chance it could be that. Also had my footswitch go at the 10 pin connector which had to be re soldered. So I’m never sure if it’s foot switch or tube related but thinking more towards bad tube. I have tube tester but will just buy new tube since amp has been sitting around few years and not much play. Maybe just needs a refresh of tubes. Not sure if replacing just the one or should be doing all pre amp and power but will try just rectifier and see it it helps the on off thing.

 

[Giz-Tone]

Hopefully it's just the tubes. It wasn't in my case. Here's a link to my thread: https://forum.grailtone.com/viewtopic.php?f=33&t=84989

Let us know how you get on.

 

[guijs]

Did anyone who had this problem ever experienced a burning smell when the amp turned off and did not turn on immediately after?

 

[G Mac]

Hey, all! I'm new to the forum and I'm having this problem as well. I have the Mark V combo that I bought new in August of this year. I just talked to the folks at Mesa today and they gave me a number of things to try in order to help diagnose the issue. Since I only run the amp in 90 watt mode, they told me to remove the rectifier tube and see if the problem still occurs. Apparently, the rectifier tube is not being used in 90 watt mode but, could still cause this problem if it is shorting out. Next, they told me to unplug from my Furman power conditioning power strip and plug straight into the wall as that has been known to cause this problem if the strip is failing. They also mentioned that the diodes are a known issue. I hope that one of the simpler solutions will fix the mess! Also, to guijs, fortunately, I have not smelled anything burning...that's never a good sign! Anyway, I'll keep you up to date on my progress and hopefully provide some additional useful information on this problem. I hope that you all have a great Holiday season, regardless of what holiday you celebrate! Peace!

 

[G Mac]

Hey, all! Just a short update. I've ruled out the rectifier tube; the problem occurs whether it is in or out. I've ruled out the power conditiong power strip; it still happens when plugged straight into the wall. I took it to another outlet; the problem still occurred. The power tubes show no obvious signs of shorting; no burn marks inside or out. I've tried bridging the FX loop; no effect. I reseated the footswitch plug at both ends...no problem during my last hour and a half of practice! Perhaps that is/was the culprit. Tomorrow I'll do a tap test on the preamp tubes to check them. If none of that works, I'll be on the horn to Mesa on Tuesday. They've been Super Helpful by the way! Anyway, I hope everyone is enjoying the Holidays despite these crazy times!

 

[G Mac]

Okay, another brief update. I took the amp to an autourized tech yesterday. We/he didn't find anything obvious. He cleaned up a few solder joints in the area of the known diode issue but didn't replace them as my amp is outside the known serial numbers that had the bad diodes. We played it loud, soft, clean, and dirty for about two hours with no problem so, I came home. I set it up here and, during my practice, she did the thing! I'm flummoxed! Now I'm thinking that maybe it is my house power. Anyhow, I'll test it for a few more days and then I'll take it back to him. If anybody has some more ideas about what I can check to help diagnose this, please chime in! Just to reiterate, the amp shuts off then comes back on very quickly; the footswitch does not reset and the amp plays normally both before and after the glitch. Thanks for all your help and suggestions so far! Happy New Year to all!

 

[rarebitusa]

Okay, another brief update. I took the amp to an autourized tech yesterday. We/he didn't find anything obvious. He cleaned up a few solder joints in the area of the known diode issue but didn't replace them as my amp is outside the known serial numbers that had the bad diodes. We played it loud, soft, clean, and dirty for about two hours with no problem so, I came home. I set it up here and, during my practice, she did the thing! I'm flummoxed! Now I'm thinking that maybe it is my house power. Anyhow, I'll test it for a few more days and then I'll take it back to him. If anybody has some more ideas about what I can check to help diagnose this, please chime in! Just to reiterate, the amp shuts off then comes back on very quickly; the footswitch does not reset and the amp plays normally both before and after the glitch. Thanks for all your help and suggestions so far! Happy New Year to all!

curious, but when you tried the other outlet in the house, was it on a different circuit/breaker? If not maybe try a few different outlets physically distanced from the current room ie: opposite end of the house or garage. Yea, could be a possible power dip. Wondering if there are there any appliances that are starting up when it happens? One other thought is to test at a different house, a 3rd location.

 

[jaslan]

My amp does this too. I would really like to know what causes it if you ever do find out.
I have had mine for about 6 years. I DID have the other "bad diodes" problem and had that repaired at about the second year.
It is a different issue I think.... The diode thing would reset the footswitch with all three channels lit on the footswitch and channel one active (like when first powered up). For a while it did it and came right back on then, one day, it just died and wouldn't come back. That is when I had it repaired and haven't had that exact same problem since (i.e. the footswitch and channels don't reset).
BUT, I do get this other problem like you are describing. It is not very often. Maybe once or twice a week? (I play an hour or two a day but sometimes use other amps). There is just a very quick "click" and I can even hear the fan wind down for a split second and then it comes back up to speed. But the channel selection does not reset like it did when I had the "bad diodes". It has been doing it for a couple of years now and it seems like it stops for a while when I replace the power tubes but I haven't kept track well enough to say that for sure. I am not sure if the fan runs on DC downstream of the power rectifier tube or AC but I suppose it could be the power rectifier tube having an occasional hiccup or the power transformer if it uses a low voltage AC tap from there. I don't really know enough about the design of the amp to figure that out.
I don't play in a band or anything, just in my own house, so I basically just figured I would wait until it gets to a point where I could take it to a tech and know that they won't get a "could not duplicate the issue" moment.

I didn't think about major appliances starting up causing a momentary dip in the power supply. Our house is only about 20 years old in a residential neighborhood of the same age so I don't think it has "bad power" but it is possible the MV is just very sensitive to voltage dips. I do have several other amps and haven't had anything like it happen while playing those amps though...

 

[SCSurfAddict]

I had this “power blink” problem as well.

About once per week the amp would power off/on in a blink and on reset to channel 1. Everything else was fine.

My amp was manufactured just after Mesa fixed the diode issue (2015/16). I live in Northern California so I took my Mark V to Petaluma and had Mesa check it out. Diodes were ok. Evidently I had an issue with the power switch solder joints. They resoldered everything and im back in business. If the problem resurfaces I’ll post something. Hope this helps someone

 

[guijs]

I also took mine to a tech, and obviously, he found no problems and the amp didn't "power blinked" even once... He replaced the diodes and the regulator anyway. From the post above I also asked him to check and resolder the power switch solder joints.

 

[G Mac]

Hello, all! An update as the saga continues. I talked to my tech after the last post and he suggested that I run the amp without the footswitch. I ran it like that for a week and; no problem! I replugged in the FS and, within about ten minutes, the problem occurred! My guy says that he now suspects either the switch itself or the DIN cable that connects the FS to the amp. Apparently, there are some known issues with the FS and/or cable and/or the FS DIN jacks. I have been practicing/playing as usual (2 to 3 hours a day) without the switch and, as yet, no problem. I'm taking the amp back to the shop next Friday so that we can suss it out while we have a Mesa tech on the phone with us. Thank You all for your help and suggestions; you've all been great! To jaslan...you may want to try unplugging the FS and see if that works. At this point I think I've ruled out the diodes, the house current, any appliance-based surges, the power switch, the rectifier tube, the power tubes, the outlet I'm using, and the JFETs malfunctioning. The rotary channel switch is working fine as far as I can tell, sooo...I'll keep you posted.