Mark V briefly loses power, then comes right back on?

[bandit2013]

It is good to hear you may have a resolve on your issue. Did you send the amp with the power tubes installed or did you remove them when you shipped it for repair?

I have had other issues with my Mark V but nothing like what you have experienced. I did have a similar problem but was related to rectifier tube and power tubes and eventually a screen resistor. I have not had any issues since the repair.

 

[tele_jas]

It is good to hear you may have a resolve on your issue. Did you send the amp with the power tubes installed or did you remove them when you shipped it for repair?

I had the option of sending the tubes to have them tested as well, or just the chassis without the tubes. I did send my tubes in and they all tested fine...... It was my power supply with the additional possibility of something in the footswitch jack causing issues. But more than likely, the power supply.

I played a 4 hour show last night, plus sound check and a quick practice pre-show... A total of almost 5 1/2 hours and it did not give me any problems.

 

[kreatorkills]

I had the same problem last year but it only happened once, and right after the power came back on the rectifier tube started smoking and then died. I took it to an authorized repair guy and he checked the amp out completely and replaced the rectifier tube. The amp had no problems that he could find and since replacing the rectifier tube i have had no further problems.
So if you haven't already, try replacing the rectifier tube.
Good luck.

 

[tele_jas]

I had the same problem last year but it only happened once, and right after the power came back on the rectifier tube started smoking and then died. I took it to an authorized repair guy and he checked the amp out completely and replaced the rectifier tube. The amp had no problems that he could find and since replacing the rectifier tube i have had no further problems.
So if you haven't already, try replacing the rectifier tube.
Good luck.

I already sent it in and got it back right after Christmas.... They found some bad components in the power transformer and some issues with the footswitch jack and re-tensioned the input.

I did replace the rectifier tube prior to sending it in, no fix.

 

[jaslan]

I started experiencing this a few months ago. My amp is about 6 months old. It would happen once or maybe twice a day playing 2-4 hours per day or, sometimes not at all for several days. At first, it was very quick and i wasnt even sure what was happening. Then, once it went off for about 2 seconds and when it came back, the channel had reset to channel 1 and all 3 channel footswitch lights were on (like i had just turned on the power from a cold start up). This is when i started to suspect power problems. I talked to support and they said i may be experiencing low voltage in my house. So i tried to keep an eye on that (i have a rack mount power strip with a voltage readout but the amp was plugged directly into the wall per supports recommendation). It continued to cut out occasionally and then, the other day, it cut out and reset to channel 1. There were no lights on the front panel of the head or footswitch and the sound faded out over the 15 seconds or so. Now the amp wont come on at all. I can see when the power switch is on, that the power tube filaments are getting power and glowing orange but no sound or lights anywhere on the amp or footswitch.
I talked to support again and they seemed fairly certain of low voltage condition at my location and he did mention that they have been seeing this problem. He said there is a "tech order" update that replaces some components in the power supply that should fix the problem by making it less sensitive to momentary low voltage conditions (or at least that was my understanding).
I contacted the nearest repair shop and he ordered the components and once he gets them i will take the head in and he said it should only take an hour or two. I am hoping that fixes everything and will post the results here.
I live a a town of about 45,000 people in an area with plenty of new development and our house is less than 20 years old and i have never had any trouble so far in our 8 years of living here with appliances or my old amp, etc. i am hoping the diagnosis is correct and it just needs a more robust power supply. I guess if that doesnt do it i may have to look into a voltage regulator.

Anyway, back to Guitar Rig for, hopefully, only a week or two...

 

[jaslan]

I got my amp fixed. I was fortunate enough to have a qualified repairman within driving distance from my home. He was very accomodating (New Orleans repair location) and allowed me to coordinate bringing in the amp at a time when he was able to work on it immediately. In fact, he let me stay and watch and actually taught me some things about handling the tubes and taking the chassis out in case I ever need to send it somewhere, etc.
Anyway, when we plugged in the amp at his shop, it was still "dead" with no lights on the front panel at all but the tubes were getting power as indicated by the orange glowing "filaments". There are 4 diodes that the support tech had instructed him to replace with new ones that they sent to him. Before removing the old ones he tested them and 2 of them did, in fact, fail the test. After replacing all four diodes and putting the tubes back in, the amp powered up and worked flawlessly. We tested all the channels, etc. I have had the amp back at home for four days now and have put about 6 hours on it and have not had any "cutouts" so far. Mesa support was right on with the diagnosis and the fix.

In total, my amp was only out of commission for six days. The repair tech had the parts in hand the day AFTER in called support. The extra couple of days was actually my waiting for a day I was able to take it in.

Anyway, incredible support from Mesa and the repairman!

I hope this post helps someone.

 

[tele_jas]

Awesome, thanks for the update!

There's nothing worse than having a dead, expensive, amp! Luckily, it was an easy fix (for both of us)

 

[bandit2013]

I will buy that..... It is good to see there is a resolve to your issues......

 

[Rocco Siffredi]

I got my amp fixed. I was fortunate enough to have a qualified repairman within driving distance from my home. He was very accomodating (New Orleans repair location) and allowed me to coordinate bringing in the amp at a time when he was able to work on it immediately. In fact, he let me stay and watch and actually taught me some things about handling the tubes and taking the chassis out in case I ever need to send it somewhere, etc.
Anyway, when we plugged in the amp at his shop, it was still "dead" with no lights on the front panel at all but the tubes were getting power as indicated by the orange glowing "filaments". There are 4 diodes that the support tech had instructed him to replace with new ones that they sent to him. Before removing the old ones he tested them and 2 of them did, in fact, fail the test. After replacing all four diodes and putting the tubes back in, the amp powered up and worked flawlessly. We tested all the channels, etc. I have had the amp back at home for four days now and have put about 6 hours on it and have not had any "cutouts" so far. Mesa support was right on with the diagnosis and the fix.

In total, my amp was only out of commission for six days. The repair tech had the parts in hand the day AFTER in called support. The extra couple of days was actually my waiting for a day I was able to take it in.

Anyway, incredible support from Mesa and the repairman!

I hope this post helps someone.

Thanks! My Mark V is having this exact same issue.

 

[tele_jas]

Thanks! My Mark V is having this exact same issue.

Give Mesa a call...Or have your tech call them. When I spoke to them, they said there were several from a few years ago that they have narrowed it down to the components they got from their supplier (or something like that), but they know which SN's have these parts and replacing them will fix the issue.

 

[Giz-Tone]

Here's an update on my situation. After sending my amp to my closest Mesa tech to be repaired, they sent it back to me saying the amp was A okay, nothing wrong. The day it returned it cut out again. Talk about frustration. I reported it to the store I bought it from and they said they would not refund my purchase as Mesa said the amp was fine. So I recorded the fault on video and returned the amp for a second time. This time the store checked it out before sending it on to Mesa. They witnessed the fault and agreed to have it repaired before sending it back to me again.

In the end Mesa replaced the entire amp chassis. Their tech couldn't find what was causing the fault.

 

[guitarsawicki]

This happens also when the reverb tank cable is loose. It happened with Mark III many years ago and with Mark V last week.

 

[bandit2013]

That is odd, I have not lost power with the tank removed (unplugged). If your amp does not have the stability it would point at a few components on the circuit board or the voltage regulator that is mounted to the chassis. Does it get worse when you select variac power? If you have a bad component in the 5V supply circuit (note that V1, V2 and V5 heaters are supplied by the 12V regulator that feeds into the 5V regulator. Could be a bad heater element on one of the preamp tubes. Just a suggestion.

 

[Hathor]

I know this is an old topic but I'm having the exact same problem.

I wish I had a video recording of it happening but the random occurence and quick revert back to normal operation makes it almost impossible to document.

After searching for months this is the first time I find some describing the exact same issue as I'm having. I seriously thought I was the only one in the whole world!

EDIT: Link to my thread about the problem: http://www.forum.grailtone.com/viewtopic.php?f=33&t=74584&p=504950#p504875

 

[Hathor]

Here's an update on my situation. After sending my amp to my closest Mesa tech to be repaired, they sent it back to me saying the amp was A okay, nothing wrong. The day it returned it cut out again. Talk about frustration. I reported it to the store I bought it from and they said they would not refund my purchase as Mesa said the amp was fine. So I recorded the fault on video and returned the amp for a second time. This time the store checked it out before sending it on to Mesa. They witnessed the fault and agreed to have it repaired before sending it back to me again.

In the end Mesa replaced the entire amp chassis. Their tech couldn't find what was causing the fault.

Dude, I'm sorry for being forward but I will PM you in the hopes that you see it and that you still have the video and you will share it with me. I really need to be able to document this error and given I don't play every day and not for several hours at a time it is just impossible for me to record on video.

 

[Don McNevin]

This is old an old thread, but relevant and can't be stressed enough for folks with old Mark V 90's.
I had the same diode problem with my 2009 V90 Combo.
I purchased it used in 2018, and it died in 2019, and I finally got around to getting it fixed last month.
The bank of 4 diodes had fried out.
I had the symptoms of momentary shutdowns, pops, white noise on the gain channels and eventually complete failure of any kind of meaningful output.
Weighing as much as this amp does, it's not easy to transfer, or ship. So I tried a "highly recommended" amp tech locally first.
That tech I brought the amp to was so bad he couldn't even find the burnt out diodes, or didn't bother looking.
I also was experiencing issues with the foot switch connector prior to the diodes dying.
But anyway, he claimed after 3 weeks he found no issues. Charged me $100 and gave me my amp back. I took it home and had the same issue as I brought it to him with.
So I decided I was going to deal with Mesa instead.
Before getting around to actually removing the chassis myself and troubleshooting, I had purchased a new foot switch and cable at first thinking it could be the origination of the problem based on Mesa tech support advice. I also purchased an entire set of preamp and power amp tubes and a new bezel to replace the discolored "purplish" bezel that had turned color over time and looked strange and out of place on the amp. So at least it looked better. The amp cabinet is in fantastic shape and I had purchased a new C90 from Mesa as well to replace the speaker someone had installed at some point. So everything is newish at this point.
I did ship the chassis to Mesa for repair and it took about 6 weeks to get it back.
They were actually very good to deal with and I have appreciation for the job they have done to salvage my amp.
It's been expensive to get this amp up and running properly. Not to mention not being able to use it during the downtime.
But they do sound sweet. Amazingly so.
Hopefully this info might help keep someone else from needing to invest several hundred dollars and a ton of time in their Mark V in the future.
My advice is, if you have the symptoms, find the diodes bank and get it repaired immediately.

 

[mace]

This is old an old thread, but relevant and can't be stressed enough for folks with old Mark V 90's.
I had the same diode problem with my 2009 V90 Combo.
I purchased it used in 2018, and it died in 2019, and I finally got around to getting it fixed last month.
The bank of 4 diodes had fried out.
I had the symptoms of momentary shutdowns, pops, white noise on the gain channels and eventually complete failure of any kind of meaningful output.
Weighing as much as this amp does, it's not easy to transfer, or ship. So I tried a "highly recommended" amp tech locally first.
That tech I brought the amp to was so bad he couldn't even find the burnt out diodes, or didn't bother looking.
I also was experiencing issues with the foot switch connector prior to the diodes dying.
But anyway, he claimed after 3 weeks he found no issues. Charged me $100 and gave me my amp back. I took it home and had the same issue as I brought it to him with.
So I decided I was going to deal with Mesa instead.
Before getting around to actually removing the chassis myself and troubleshooting, I had purchased a new foot switch and cable at first thinking it could be the origination of the problem based on Mesa tech support advice. I also purchased an entire set of preamp and power amp tubes and a new bezel to replace the discolored "purplish" bezel that had turned color over time and looked strange and out of place on the amp. So at least it looked better. The amp cabinet is in fantastic shape and I had purchased a new C90 from Mesa as well to replace the speaker someone had installed at some point. So everything is newish at this point.
I did ship the chassis to Mesa for repair and it took about 6 weeks to get it back.
They were actually very good to deal with and I have appreciation for the job they have done to salvage my amp.
It's been expensive to get this amp up and running properly. Not to mention not being able to use it during the downtime.
But they do sound sweet. Amazingly so.
Hopefully this info might help keep someone else from needing to invest several hundred dollars and a ton of time in their Mark V in the future.
My advice is, if you have the symptoms, find the diodes bank and get it repaired immediately.

That worthless tech wasn’t in Indy, by chance?

 

[ATR1]

I just had the same issue. I sent it back to Mesa they did the fix/mod and mailed back in about a week.
Awesome!

 

[Sicman71]

I just replaced all four diodes in my MarkV 90 last week. Now it works like a charm. I'm so glad some people posted this on another gear post. Hope this info gets out to people. Diodes 16-19 can, and have gone bad before.

 

[MarkV User]

I only saw this old thread now, but I had the same problem last year and fixed it by replacing the low voltage diodes also. For me the symptoms were the footswitch being flaky and then the amp cutting out randomly and finally no sound.

I don’t like the diode choice Mesa used. They picked diodes good for 1000V but only one amp for the low voltage power rectifier. Without making a power budget I guessed that the 1A rating could be pushing things. I picked a different diode in the same series with a lower voltage spec and several times the current rating. When I called Mesa support to tell them what I’d found and what I was doing about it they were not helpful and didn’t try to answer my questions about the problem or the circuit or the current assessment of the design relative to the failures that people have very often with those diodes.