Amp turning off and on again quickly

[Hathor]

Hello!

Just registred, first time poster - I hope I don't violate the rules.

I have a problem I experience with my MESA MARK V that is driving me nuts and I can't find anything anywhere on the internet describing my problem. I'm posting here in an attempt to get at least a hint as to what could be the cause of the problem.

Put short, my amp will at random times suddenly switch off and the on again very quickly. The power light will turn off and I will hear a loud click (not a pop), like if the power switch is flicked – and the second after the amp will switch on again and the power light comes back on – it is like a very short power failure, or so it seems. Also - it happens only a few times a month. I can have the amp switched on for 5 days straight without it happening so it is completely unpredictable.

I can't know for sure is that the amp loses power - all I can say is that the power light shuts off and on again and that there is a loud click.

It is literally a second – maximum two seconds but I believe it to be shorter – the amp will be switched off. It is not the footswitch chatter, I heard that on YouTube and this is completely different.

However, the sound from the speaker never stops or gets lower in volume – I don’t really notice any changes at all in the sound and I suspect this is because the off/on again switching happens so fast that the power in the tubes is enough to play through the short time the amp is off - if it actually turns off. I don't know how I could meassure if the amp really switches off or it just is the power indicator that turns off.

I would have liked to include a short video demonstrating the problem but this would require me to have the amp running for a very long time and filming it with a camera on a stand, as it only happens rarely and it seems to happen at completely random times. At least I have not been able to pin point the problem to a specific channel or to link the problems occurrence with a behavior of mine so it seems random to me. I have had this happen at all channels.

I would estimate this happens a handful times a month.

I run the MARK V into a Torpedo Live load box in the 8-ohm input. I use the 8-ohm output on the amp.

The amp is bought in April 2016 new from a Danish dealer. It is using the original tubes equipped at purchase. I bought it used December 2016 and I really have no idea how many hours it has been played. I have the serial number but don't know how to get the manufacture date.

The tubes do not show the visual signs of fatique that I find described on the internet and the sound has the low end.

As I am from Denmark and it would be very difficult shipping this in for service in the states and would take a very long time to document, troubleshoot and repair I hope that you are able to advise me as to how to solve this problem, or just give your thoughts as to what MIGHT be the cause. Any input is greatly appreciated!

Can anyone tell me how I can examine the foot switch for errors besides simply disconnecting it and see if the problem persists?

Please feel free to ask follow up questions if I have left out any missing information.


Best regards,
Hathor

 

[Authorized Boogie]

Hello!

Just registred, first time poster - I hope I don't violate the rules.

I have a problem I experience with my MESA MARK V that is driving me nuts and I can't find anything anywhere on the internet describing my problem. I'm posting here in an attempt to get at least a hint as to what could be the cause of the problem.

Put short, my amp will at random times suddenly switch off and the on again very quickly. The power light will turn off and I will hear a loud click (not a pop), like if the power switch is flicked – and the second after the amp will switch on again and the power light comes back on – it is like a very short power failure, or so it seems. Also - it happens only a few times a month. I can have the amp switched on for 5 days straight without it happening so it is completely unpredictable.

I can't know for sure is that the amp loses power - all I can say is that the power light shuts off and on again and that there is a loud click.

It is literally a second – maximum two seconds but I believe it to be shorter – the amp will be switched off. It is not the footswitch chatter, I heard that on YouTube and this is completely different.

However, the sound from the speaker never stops or gets lower in volume – I don’t really notice any changes at all in the sound and I suspect this is because the off/on again switching happens so fast that the power in the tubes is enough to play through the short time the amp is off - if it actually turns off. I don't know how I could meassure if the amp really switches off or it just is the power indicator that turns off.

I would have liked to include a short video demonstrating the problem but this would require me to have the amp running for a very long time and filming it with a camera on a stand, as it only happens rarely and it seems to happen at completely random times. At least I have not been able to pin point the problem to a specific channel or to link the problems occurrence with a behavior of mine so it seems random to me. I have had this happen at all channels.

I would estimate this happens a handful times a month.

I run the MARK V into a Torpedo Live load box in the 8-ohm input. I use the 8-ohm output on the amp.

The amp is bought in April 2016 new from a Danish dealer. It is using the original tubes equipped at purchase. I bought it used December 2016 and I really have no idea how many hours it has been played. I have the serial number but don't know how to get the manufacture date.

The tubes do not show the visual signs of fatique that I find described on the internet and the sound has the low end.

As I am from Denmark and it would be very difficult shipping this in for service in the states and would take a very long time to document, troubleshoot and repair I hope that you are able to advise me as to how to solve this problem, or just give your thoughts as to what MIGHT be the cause. Any input is greatly appreciated!

Can anyone tell me how I can examine the foot switch for errors besides simply disconnecting it and see if the problem persists?

Please feel free to ask follow up questions if I have left out any missing information.


Best regards,
Hathor

First, be absolutely sure that the removable AC cable is firmly seated in the receptacle on the amp. Also, check the fuse cap to be sure its completely seated.

Have you confirmed this issue happens in other locations as well? Friends house, rehearsal space, work, etc?

 

[Hathor]

First, be absolutely sure that the removable AC cable is firmly seated in the receptacle on the amp. Also, check the fuse cap to be sure its completely seated.

Have you confirmed this issue happens in other locations as well? Friends house, rehearsal space, work, etc?

Thank you very much for your answer! I appreciate it!

The AC cable have been checked and double checked. It sits as firmly in the socket as possible. The fuse I have not checked.

I have not confirmed the problem anywhere outside of my home. I believe it is because of the limited time I have had to test the amp on other locations, as the problem occurs rarely - but of course I can't rule out that it is my power outlet in my home, I get your point. Everything could be the cause and this should be tested.

However nothing else in my living room shuts down at any point. A desktop computer or TV would instantly shut of, I believe. But as I say, I get your point I'm just thinking probability.

When you talk about the fuse - as I am not a native English speaker - do you mean that I should check if the fuse is mounted absolutely correctly and thight, or are you talking about something in the fuse that would require a new fuse? I'm uncertain what exactly the fuse cab would be in Danish.


Have you ever heard of anything like this before?


Best regards,
Hathor

 

[APEMAN]

-

 

[Hathor]

I think this is the good old diode problem in the low voltage (relay control) circuit. You might need a diode job.

Could you please elaborate just a bit? I have very little technical knowledge about the amp. I'm completely willing to read up on the subject, but if you would take a little time to explain this in just a bit more detail I would be very happy. If you can link to an article about the issue, please do!

Now when you say 'low voltage' - this has nothing to do with playing 10, 45 or 90 watts, right? Am I correct assuming it is another part of the amp?

Diodes if I recall correctly can be used to convert AC to DC. Are you saying this problem might be related to the power supply?

Have you ever heard of anything like this before? I am just curious as to how you had the idea that this may be the issue. I don't mean to argue I just try to learn.

Thank you very much for your answer! It is highly appreciated.


Best regards,
Hathor

EDIT: Corrected typos.

 

[IronSean]

I think this is the good old diode problem in the low voltage (relay control) circuit. You might need a diode job.

Could you please elaborate just a bit? I have very little technical knowledge about the amp. I'm completely willing to read up on the subject, but if you would take a little time to explain this in just a bit more detail I would be very happy. If you can link to an article about the issue, please do!

Now when you say 'low voltage' - this has nothing to do with playing 10, 45 or 90 watts, right? Am I correct assuming it is another part of the amp?

Nothing to do with that, correct. He just meant there's a set of circuitry in the amp that controls the signal path and amp modes by using relays (a way of switching from this path to that). That relay circuit is low voltage(maybe in the 5-12v range) compared to the audio signal path through the tubes, (which is in the 2-500V range).

Diodes if I recall correctly can be used to convert AC to DC. Are you saying this problem might be related to the power supply?

Diodes can be arranged in a clever way to do that, but at their simplest they're just a device that lets current flow one way but not the other. They get used as protective mechanisms all over in electronics, preventing voltage from going too high or too low, preventing signal from flowing in directions it shouldn't, etc.

Have you ever heard of anything like this before? I am just curious as to how you had the idea that this may be the issue. I don't mean to argue I just try to learn.

I don't remember the details, but there may have been some diodes that commonly failed on the earlier Mark Vs. There are definitely some jFets in the Reverb circuit that tend to do bad. I had my amp totally die on my and it turned out to just be a couple components Mesa knew were a problem that had to be replaced. Can't remember now if it was Diodes or JFETS.

I will say, it sounds like you're just learning about some of this stuff, so before tackling it yourself I'd consider that Tube amps are very high voltage devices, and have very large capacitors inside which can store that power even when they're unplugged. They have enough power to kill you even when disconnected from the wall. The Mark V series are also very complex, and very cramped to work in, and the complete schematics aren't even available unless you're a Mesa tech (there's a partial on the internet, but it doesn't cover the switching system, and it's incorrect about the circuit in a couple place because it's either for a prototype, or for models sold in the first year before the design was updated.).

So if your amp is less than 5 years old, the easiest path would be to make use of your Warranty and let a professional hunt down the problem and fix it for you. They get a couple Build Your Own Pedal kits if you want to start learning electronics yourself, then a simple amp you can do some mods to (classic fender and Marshall style circuits tend to be very simple and easier to understand and work on. Or the Jet City amps tend to have good circuit boards and large spacing and relatively simpler layouts if you want something new, cheap, and easy to work on.

 

[Hathor]

I think this is the good old diode problem in the low voltage (relay control) circuit. You might need a diode job.

Could you please elaborate just a bit? I have very little technical knowledge about the amp. I'm completely willing to read up on the subject, but if you would take a little time to explain this in just a bit more detail I would be very happy. If you can link to an article about the issue, please do!

Now when you say 'low voltage' - this has nothing to do with playing 10, 45 or 90 watts, right? Am I correct assuming it is another part of the amp?

Nothing to do with that, correct. He just meant there's a set of circuitry in the amp that controls the signal path and amp modes by using relays (a way of switching from this path to that). That relay circuit is low voltage(maybe in the 5-12v range) compared to the audio signal path through the tubes, (which is in the 2-500V range).

Diodes if I recall correctly can be used to convert AC to DC. Are you saying this problem might be related to the power supply?

Diodes can be arranged in a clever way to do that, but at their simplest they're just a device that lets current flow one way but not the other. They get used as protective mechanisms all over in electronics, preventing voltage from going too high or too low, preventing signal from flowing in directions it shouldn't, etc.

Have you ever heard of anything like this before? I am just curious as to how you had the idea that this may be the issue. I don't mean to argue I just try to learn.

I don't remember the details, but there may have been some diodes that commonly failed on the earlier Mark Vs. There are definitely some jFets in the Reverb circuit that tend to do bad. I had my amp totally die on my and it turned out to just be a couple components Mesa knew were a problem that had to be replaced. Can't remember now if it was Diodes or JFETS.

I will say, it sounds like you're just learning about some of this stuff, so before tackling it yourself I'd consider that Tube amps are very high voltage devices, and have very large capacitors inside which can store that power even when they're unplugged. They have enough power to kill you even when disconnected from the wall. The Mark V series are also very complex, and very cramped to work in, and the complete schematics aren't even available unless you're a Mesa tech (there's a partial on the internet, but it doesn't cover the switching system, and it's incorrect about the circuit in a couple place because it's either for a prototype, or for models sold in the first year before the design was updated.).

So if your amp is less than 5 years old, the easiest path would be to make use of your Warranty and let a professional hunt down the problem and fix it for you. They get a couple Build Your Own Pedal kits if you want to start learning electronics yourself, then a simple amp you can do some mods to (classic fender and Marshall style circuits tend to be very simple and easier to understand and work on. Or the Jet City amps tend to have good circuit boards and large spacing and relatively simpler layouts if you want something new, cheap, and easy to work on.

Thank you very much for your reply, it is very helpful to me.

I can assure you that I have no intentions of trying to fix this issue myself, for several reasons, number one being I am not qualified to do so, number two because of risking to do it the wrong way and blow up the most expensive amp I have ever owned.

I have however in a tech class some twenty years ago build a diode bridge, so I knew that diodes had some say in making a one way street for electrical current.

Here's the case and my problem with regards to sending the amp in for repair: First of all, I live in Denmark. Initially I took the amp to the Danish retailer, but they had no clue about what the problem could be.

While I was in the store they did a Google search, found some online messages boards, read a few posts and then said maybe it was the tubes, maybe it was the power cord not correctly inserted to the socket. They also explained that with this type of periodical error, and me not being able to document it and them not being able to reproduce it, what would basically happen was that the amp would be sent to MESA in the states, it would take several months to be sent back and the issue would not have been resolved when I got it back.

I then wrote MESA from a form on their website explaining the problem as I have here, my OP was pretty much copy and pasted from that form.

MESA then forwarded my email to the nearest authorized tech, a guy in Finland. He said the same thing, power cable, tubes maybe the fuse.

I'm a computer technician and I know that the worst thing to fix is an error that is poorly described and not possible to reproduce with ease.

So while I absolutely want to send the amp in for repair in a service center, I HAVE to do some research so that I am able to describe the error in more detail than a loud click, power light of, and back on.

I have really tried to find someone or something on the internet resembling my problem but to no avail. I'm at a loss. There is for sure a problem with the amp and given my background in computer maintenance I have the methodology for testing multiple possible errors and ruling them out one by one wired into my way of thinking. Obviously I don't know very much about tube guitar amps and that is a major problem.

This is why the suggestion of the diodes is a nice thing to hear because it is the first time I hear anything other than power cable and tubes.

It really annoys me that I have no idea what the problem is, and therefore cannot describe it adequately.

Also, if I have to send my amp around the globe and wait for it to get back for months I really want it fixed when it comes back, so I don't have to send it to the states one more time.

At the same time I worry that it will get worse at some point leaving the amp useless and that the repair will be very expensive.

According to E.U. law I have two years warranty - I'm not sure if I as a non US citizen also have five years of warranty as mentioned earlier.

Assuming that the problem is this diode thing - is there any way to test that to confirm or deny?

Is this repair an expensive one, again assuming it is in fact the diodes.

Do you know of any video online demonstrating this issue? I can't seem to find any.


Thank you all so much for your time and effort. It is highly appreciated!

Best regards,
Hathor

 

[IronSean]

I understand very much, and as a Software Developer who's built many computers as well I'm familiar with the troubleshooting skills. I just wanted to add the caveat in case you weren't aware, or someone else who reads this thread later.

I looked into the warranty for you, and it does appear the 5 year is USA and Canada only, with distributor specific policies otherwise. So you would need to contact whatever distributor serves Denmark to see if anything more than the 2 year required by law applies.

The good news, if it's diodes or switches, is that they are very inexpensive components. It's the time to track down the problem diode which is expensive. So much so that many amp techs will just replace every diode in an amp rather than replace and test specific ones.

As for a means to test and reproduce... I'm not sure right now. I'll comment again if anything comes to mind later.

Mesa did let you know about a tech in Finland, I assume they are an authorized Boogie repair technician. If so, perhaps you could see if you dealer would send it to a closer authorized tech instead of Mesa Boogie in California. When mine (in Canada) went in for repair, it was sent to a technician not far away who did the work.

 

[kreatorkills]

I'm going to throw something out here that hasn't been mentioned. I'm assuming that you have a mark v, if you do you might want to try putting in a new rectifier tube. Sometimes they can go bad or have intermittent problems. I had one go bad and the amp shut down and turned on by itself really quickly, which is the only reason i mention this. It's a long shot but might be worth a try.

 

[Hathor]

I'm going to throw something out here that hasn't been mentioned. I'm assuming that you have a mark v, if you do you might want to try putting in a new rectifier tube. Sometimes they can go bad or have intermittent problems. I had one go bad and the amp shut down and turned on by itself really quickly, which is the only reason i mention this. It's a long shot but might be worth a try.

Yes, I have a MARK V.

I have actually been researching this issue for months and I have been suspecious about the rectifier tube for some time, as I understand correctly this tube is related to powering the amp. However the tube had no signs of fatique so I dropped the thought of the problem being caused by that tube again.

Thank you very much for this info.

 

[Hathor]

I understand very much, and as a Software Developer who's built many computers as well I'm familiar with the troubleshooting skills. I just wanted to add the caveat in case you weren't aware, or someone else who reads this thread later.

I looked into the warranty for you, and it does appear the 5 year is USA and Canada only, with distributor specific policies otherwise. So you would need to contact whatever distributor serves Denmark to see if anything more than the 2 year required by law applies.

The good news, if it's diodes or switches, is that they are very inexpensive components. It's the time to track down the problem diode which is expensive. So much so that many amp techs will just replace every diode in an amp rather than replace and test specific ones.

As for a means to test and reproduce... I'm not sure right now. I'll comment again if anything comes to mind later.

Mesa did let you know about a tech in Finland, I assume they are an authorized Boogie repair technician. If so, perhaps you could see if you dealer would send it to a closer authorized tech instead of Mesa Boogie in California. When mine (in Canada) went in for repair, it was sent to a technician not far away who did the work.

I am absolutely aware of the good intentions you had by cautioning me. It is always nice to warn people that they might die if they do a certain thing.

If in any way that was not clear I do apologize sincerely. Not being native in English can sometimes be a bit tricky to me when trying to communicate that I agree because of having some experience and/or knowledge myself on a given subject. Small differences in wording can change a sentence from a positive acknowledgement from having the same experience with a given thing, to the sentence having a rude or arrogant tone to it, something in the way of 'you don't get to tell me, I know perfectly well that...'.

The big problem of course being that I am unable to tell beforehand if I come off as rude. Also punctuation with commas are a pain

Thank you very much for looking up the warranty issue. That means quite a lot to me as the 2 year warranty will expire in April. I better get this thing shipped! I will try to find the supplier also and email them about the warranty.

There seems to be only one service center in Europe - in Helsinki, Finland. Thats 980 kilometers away - and that's way better than the US.

I wound just love to be able to test it so I had some way of telling the tech what the problem is. I will have to try to dig through YouTube again, with regards both to the diodes and the rectifier tube.

Thank you very much for your time and effort, it gives me hope that in the end I get it fixed and just don't have to live with it - I have been really close to giving up, especially after the almost indifferent attitude from the guys at the Danish retailer.

 

[Hathor]

A quick question about the fuse:

Is it a digital or thermal fuse that can shut down on failure without blowing, or will the fuse always blow and have to be replaced before powering up is possible again?

 

[Hathor]

I found this thread.

http://forum.grailtone.com/viewtopic.php?f=33&t=70633

What happens for the OP in this thread is exactly my problem as well.

Click, power down, 1 second, power on, no noticeable loss of sound, all lights off until power on.



I am not the only one. What a relief!!

 

[bandit2013]

If this issue cannot be manages with preamp or power tube replacement or by operating the amp with the footswitch controller removed, I would seek Mesa technical service for repair if it is deemed the issue is caused by an internal issue. I may point out some issues I have had but mostly was tube related (5U4G). What may be listed in my response may not be the actual issue with the amp. I am not a Mesa tech so I can only assume the problem. Best to call Mesa tech service on this issue. If you get voice mail, leave a message and return phone number, they do call back. They may be able to guide you if it is an easy fix, cable or tube or other. If you still have an active warranty with the amp, definitely make the call :!:

The fuse on all Mesa boogie amps is the traditional thermal link slow blow fuse type. When it goes, it goes and does not come back to life. It is not a resettable fuse like a PTC thermistor type.
I have had this issue myself but the cutout was sometimes accompanied with a pop but not on all cases. It does not matter what power mode you are using when this problem becomes apparent. What I did to correct the problem, replaced the Rectifier tube with a new one. It runs parallel to the silicone diodes but it can pull the power supply down if there is a discharge between pins 4 and 6 (this will be evident with a light show within the tube and will be noisy as well. I have had issues with the rectifier tube on occasion and the fuse remained intact. However if this is the root cause of the issue, pull the fuse out and look at it. It may not be blown but you will see small metallic balls on the filament caused by thermal stress and eventually it will fail.

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.

Another cause of abnormal behavior which places the amp in a mute condition could be related to the footswitch or footswitch cable. The DIN connector on the back of the amp is not the best part of this amp in general terms. I have had more problems with this aspect of the Mark V such that I no longer use the footswitch. I would try disconnecting the footswitch and use the rotary controls on the back pannel to select your channels for a short term test. If you cannot get the amp to exhibt the issue of random turnning off it may be related to the footswitch, DIN connector on the amp or the cable itself. However, the power light should not be turning off if it was footswitch or cable related.

 

[Hathor]

I think I need to make it clear why I don't just contact MESA directly. It is because I alreade have.

They gave me this response:

Hello [Name Removed],

Your request was forwarded to Levytukku (Finland) which is the Scandinavian Distributor for Mesa/Boogie.

Your description of the issue is very detailed and good. Thank you for the time and effort you put to do that. It´ll make the process easier.

I may need to ask you to check few things before going further in this matter. First thing to check is the mains lead(power cable). I believe your MarkV is head format and not a combo? Most cases like your are caused by power cable loosening just a little bit. It looks like it is in but in fact it is a little loose. You cannot see this as the plug that goes into amp goes in so deep. Usually the power cable is attached to the inside of head cabinet with a clip. This is to prevent the cable from coming loose but handling the amp on the road means it will come loose at some point anyway. Having the power cable ”almost” connected usually causes the power to go on/off like this.

As the power light goes on/off I do not believe this is a tube issue. If you have already checked the power cable and the problems persists let me know.

This is why I am gathering information - just to pass it on to the tech, that is all.

I have no intentions to try the repair myself, nor am I qualified to do so. I litterally have no idea what I would be looking at if I took the amp apart. I do not have any illusions that I know how to fix this - and while I am still under warranty it would be pointless.

I have emailed MESA again last night, I am now waiting for them to respond.

 

[bandit2013]

I see. I hope you get a resolve on your issue.

 

[Hathor]

I see. I hope you get a resolve on your issue.

Thank you!

With the help provided by all you friendly and knowledgeable people on this board, I feel like I am ready to send the amp in for service.

In a second reply from MESA the tech writes:

HI [name removed],

Yes, I did receive your message. One of our workers dislocated his shoulder in hockey game (how delightfully Finnish by the way:-D) . Now I have to do most of his work too for awhile so I´m a bit overbooked. Sorry for the delay.

Power cable is checked. The only possible thing I see is power tube badly seated(not fully in) in its socket. But symptoms dont really point there though it´d be easy to for you to check. Not much more you can do for yourself really.

Of course there can be outside issues like badly regulated power. This happens sometimes in training rooms as the current available fluctuates and affects the amps inner voltages which confuses the amps relays. Or short circuits elsewhere in the signal chain(most usually in speaker cabs).

Denmark has been difficult market for us as no dealer is willing to give effort to Boogie. This means your closest Official Service Station is in Malmö, just over the Bridge. Great store, knows Boogie and they have Service Station inside with exclusive access to Mesa/Boogie Tech Support. You don´t have to ship your amp to USA. I´ll include Malmö contact info here:

As the diodes as mentioned in a previous post by another user affects the relays I really think I have come closer to a solution and a fix.

I will update this thread with information about the outcome of all this, and try to get the tech to give an explanation of what caused this issue, for future reference in case that some MESA owner in the future will face the same problem and have the same troubles I had getting a grasp on how to understand and describe the problem to a service center.

Also, this tech from Finland, whoever he may be is a very friendly and professional person and that is simply a great feeling when you are frustrated and troubled by the thought of just having to make do with a malfunctioning amp.

I thank you all.

 

[royslead]

So, are there any updates to report on this issue? I ask, because I just noticed the same behavior with my Mark V (90) head. EXACT symptom.

 

[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!

 

[Hathor]

So, are there any updates to report on this issue? I ask, because I just noticed the same behavior with my Mark V (90) head. EXACT symptom.

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!

My amp has been in a repair shop for nearly 3(!) months - since the beginning of March until now. I haven't got it back yet. The tech was able to actually see the issue with his own eyes which by itself was almost a miracle.


They soldered everything off and back on, and they believe that the issue is located in the diodes in the 12V circuit and have replaced that but they also say that they have no way of testing and reproducing the error, so it is anyone's guess if it is actually fixed.

It is very, very frustrating.

With regards to the foot switch, I simply haven't noticed if it behaves odd when it happens - the time is too short and all my focus has been on the amp itself.

All I can say about the foot switch is that when the amp comes back on, the foot switch will turn on on the same channel as it was before shut down.

I hope you guys get it fixed but be prepared for a lengthy and frustrating experience.


Best regards from Denmark.