Hi Jola,
That is definitely strange. I have never heard such a noise from the 4 tube amps I’ve owned. Not sure what to tell you but is the Sam Ash store still around to check it out? Keith (GnLGuy) seems pretty knowledgeable about amp electronics and might be worth asking. I can PM him if you haven’t friended him as yet.
John

It could be related to the tubes warming up but I’ve never had that experience. I PM’d Keith and linked your post. Hopefully he’ll throw his 2 cents in within this thread.
John

Yep, I vote for a tube issue. Care and feeding of tubes is part of owning a tube amp, since they don’t last forever, and also a certain amount of tubes are born with birth defects. 2 years of being turned on an off frequently and improperly could definitely annoy those tubes. With luck, Sam Ash may have some spare tubes and it would be easy to just start popping them out and replacing them one at a time and see if it still happens.

When an air-conditioning unit kicks in, it generates some RF for a minute or so due to the initial power demand. I have 6 inside heat pump units in my house, and my Blackstar modeling amp used to complain like that every time one kicked in. Then a couple of years ago I replaced all my Daikin heat pumps with Mitsubishi Electric heat pumps, and it no longer happens.

JoLa wrote:

My newly purchased Fender Pro Jr IV has a very predictable high pitch noise that starts at about 2-3 minutes after being turned on. It lasts about 20 seconds and then stops and does not happen again. Is that normal???

The amp was purchased as new with a warranty from Sam Ash store but I assume it has spent 2 years as their floor model because the sticker inside shows 2022.

I have attached the recording of the noise. The amp’s volume was set at 0 and the input cable was NOT connected.

Jola

That’s a wild sounding amp for sure!! LOL

It could be the power tube as mentioned but I’m going out on a limb here and say that it could be a power supply issue, maybe an issue with one of the bypass capacitors. I think what you are hearing is an oscillation that is being passed into the power section, its noticeable that it is going up in pitch before it reaches a plateau and then stops. Makes me wonder if a cap is having trouble charging

Set the amp on a table where you can easily see the tubes; turn the amp on and check if they are glowing orange while this noise is happening. There are times that tubes, particularly power tubes will glow blue when an amp is going into oscillation.
This is just checking for curiosity sake because it needs to go back for an exchange since it’s under warranty. Since Sam Ash is going out of business, don’t let them BS you that you’ll need to return it Fender yourself. They probably wouldn’t do that but companies going out of business sometimes do things that aren’t right

Hope that helps and I’m glad that its under warranty

Keith
aka GnLguy

sunjamr wrote:

Yep, I vote for a tube issue. Care and feeding of tubes is part of owning a tube amp, since they don’t last forever, and also a certain amount of tubes are born with birth defects. 2 years of being turned on an off frequently and improperly could definitely annoy those tubes. With luck, Sam Ash may have some spare tubes and it would be easy to just start popping them out and replacing them one at a time and see if it still happens.

When an air-conditioning unit kicks in, it generates some RF for a minute or so due to the initial power demand. I have 6 inside heat pump units in my house, and my Blackstar modeling amp used to complain like that every time one kicked in. Then a couple of years ago I replaced all my Daikin heat pumps with Mitsubishi Electric heat pumps, and it no longer happens.

It’s amazing how noise on an AC line will cause such issues and the newer modeling amps are likely very susceptible to that noise. Computers motherboards are running on very low voltages and noise just annihilates those circuits

Curious if New Zealand uses 120VAC as we do stateside or 220VAC like Europe? I’ve read that power in Europe and especially in Asia is very dirty and the noise is horrendous

Keith
aka GnLguy

JoLa wrote:

Thanks for the reply, Keith.
I did what you suggested and the orange light did not change during that noise.

When I was buying it, the salesperson in Sam Ash specifically told me up front to contact Fender in case there was something wrong with the amp being under the warranty. I think I may try to go back there and argue with them once I get a chance but I also sent an email to Fender Customer Service, see what they say…

OK since the tubes continued to glow orange, that indicates that the voltages going to the various pins of the tubes are correct. It could be that a tube is bad but I’m still wondering if there isn’t a power supply issue of some sort

Hopefully it will be as simple as taking the amp to a local repair shop that is authorized by Fender but I would push to have the amp swapped out for a new one.
Keep us posted on this

Keith
aka GnLguy

Hey JoLa, that’s a bummer. I also had a noise issue with my Blackstar HT5 tube amp when I bought it 1 year ago, but my local shop exchanged it. They said noise is a common issue with tube amps🤨. But that noise on your amp is really bad.
I hope you will get an exchange by Fender soon, you have the right to.
Denise

I’d return it to the store. I know that Sam Ash is going out of business, but that’s BS. Make a bit of noise, I’m sure they’ll take it back If they don’t have another one, I’d get my money back. There are plenty of Blues Jr. 4s out there. Good luck.

PS. Worse comes to worse you can play the intro to Magic Man by Heart every time you turn the amp on!!! 😉
Good luck

What a bummer JoLa. 😞 I assume it didn’t make this noise when you demo’d it at the store. I’m no amp expert but I might suspect one of the tubes got loosened a little on the ride home.

If it were me I would try removing the back and making sure the tubes are fully seated properly and even try removing them, cleaning them with a little electronics cleaner, and re-installing them. There are plenty YT videos to show you how to do it.

Be careful you don’t bend any of the prongs on the tube. And be careful not to touch any capacitors which are likely still holding a charge. I’ve done it with my Fender Super Champ X2 amp and it sounds more difficult than it really is.

Good Luck! If Sam Ash doesn’t help, and you decide not to try this yourself, hopefully you have an authorized Fender technician nearby. 🤞

JoLa
You are not alone here. I wouldn’t say it is common with tube amps but it does happen. Having owned mostly Fender tube amps over the years, this has happened to me. I would trust GnLguy’s thinking, but you need to take it in and have it checked. It’s probably and easy fix for a Fender amp tech. It’s the price we pay for pure Fender tube tone. Honestly, it could be jut one bad tube. Congrats and welcome to the Fender pure tube tone club!!

John

Assuming Sam Ash is not helpful, you would think Fender could direct you to a Fender authorized dealer. During the pandemic I discovered that many retailers would only service equipment bought directly from them. It’s getting harder and harder to find amplifier repair people and, if you do, it can be very expensive. That’s one reason I ended up buying a digital Katana for everyday use.
John

JoLa wrote:

My newly purchased Fender Pro Jr IV has a very predictable high pitch noise that starts at about 2-3 minutes after being turned on. It lasts about 20 seconds and then stops and does not happen again. Is that normal???

The amp was purchased as new with a warranty from Sam Ash store but I assume it has spent 2 years as their floor model because the sticker inside shows 2022.

I have attached the recording of the noise. The amp’s volume was set at 0 and the input cable was NOT connected.

JoLa
I linked your post on another forum that I take part in from time to time. One of the members does a lot of guitar amp repair, I think that he may be an engineer not for certain. Whatever his title, I trust what he tells me.
He agreed that its likely an oscillation being passed into the power section of your amp. His response is at the end of this post

What is an oscillation?? it is stray unwanted signals that are randomly generated within a circuit that will keep growing until either the circuit is destroyed or until the limits of the components in that circuit is reached.
These signals can be caused either by components that are damaged or – personal opinion here – bad solder joints. The printed circuit boards (PCB) in amps are run thru a machine that has a “pool” of molten solder and in theory, it will automatically make good solder connections as the PCB is passed thru it. Doesn’t always work out like it should

If swapping the tubes doesn’t fix the problem, Fender will likely swap out any PCBs in that amp

Keep after them and don’t let them stick you with a lemon

Keith
aka GnLguy

————
By all means get it fixed under warranty.

With tube amps, always suspect the tubes. It doesn’t always fix it, but it’s the easiest thing to test, provided you have extra tubes to use. Even if you borrow from another amp.

It does sound like an oscillation. I put a standby switch in a Blues Jr, and when you switched it out of standby it would start at around 100 hz and slowly increase the frequency until it was above audible range. But it kept oscillating at 50 kHz. You couldn’t hear it but it was wasting power and probably headroom. The fix was to put a small cap across the phase inverter signals going to the power amp.

A lot of advice says to re-arrange the ribbon cables between the main and tube pcbs. But that didn’t help on the BJr.

JoLa wrote:

A lot to learn here! I wish I had liked the physics lessons back in high school a bit more 😬🥴😵‍💫

I dropped the amp off at the authorized Fender repair shop on Wednesday, see what happens…

This is useful info, Keith – thank you! “Always suspect the tubes” 👍
At least I can sound like I know what I’m talking about when I ask them questions 😁

JoLa
You are on your way to becoming great at electronic troubleshooting!!!

First rule for electronic repair, check the easiest which many times is cables. With a tube amp, it’s the tubes. Fortunately, I have a tube tester which probably dates back to the 1960s but if a person can come up with some extra tubes to swap out, that’s good route.

Feel free to ask me if anything comes up in the future. I have sources on the internet that I can use if I can’t answer the question

Keith
aka GnLguy

JoLa wrote:

UPDATE!

Ok, I got the amp back and it was “repaired” under warranty with no charge. The tech told me that he took the tubes out to check them with a tube meter and they tested fine. He put the same tubes back in and could not replicate the noise anymore. He kept testing the amp for the next few days and the noise did not come back. So the issue is resolved. Apparently, it may happen with brand new amp because the tube sockets have a coating on them and sometimes tiny impurities get in the way of a good contact. Phew! Who knew….? 😅

That’s great news JoLa!!! Glad to hear it.

I don’t know if those amps are made in China or Mexico but regardless, they are subject to humidity that causes a type of corrosion to build up and removing & reinstalling the tubes was evidently enough to remove it.
I’ll post a type of cleaner that can be used periodically to help keep that flushed out; some people use it once a year as type of PM and it helps keep your amp running problem free.

Next – hope you’ll give us a demo of the amp. I’ve heard good things about them…you could even demo that Music Man if you wanted to 🙂

Thanks for letting us know

Keith
aka GnLguy

JoLa wrote:

Keith,

These amps are made in Mexico. A cleaner is a good idea, thanks!
I used this amp in my latest (May 2024) challenge submission but there will be more recordings of my playing it, for sure. The amp tech, who btw is THE amp tech to go to in Las Vegas and all musicians in town know him, told me that many players prefer these to Fender Blues Jr’s. (He used to tour with Red Hot Chili Peppers).

As for the Music Man amp, I sold it! I decided that it was just too much for me, I won’t even crank the 15 Watts full of power let alone 50W. But what happened after I sold it is even more fascinating because I still get to play it sometimes AND have the option of getting it back if I get sentimental or something… how crazy is that???

JoLa

I recently picked up a Marshall Origin 20 for the same reason – I can run it at the full 20 watts, 10 watts or it will go as low as 3 watts; and on that lowest setting it is still really loud.

Doesn’t surprise me that some like that amp better than the Blues Jr – I think its the simplicity of it all. Your challenge submission sounds really good.
Speaking of amp simplicity, Eric Clapton used a 50s era Fender Champ with no pedals to record the Layla album, Duane Allman used a early model Princeton with no pedals – that album is one of the finest blues rock albums ever recorded and the tone that both players had was great.
The Pro Jr is in the same genre of amps with great tone so it will serve you well

Keith
aka GnLguy

JoLa

This is the most widely used & trusted contact cleaner that can be used to clean pins on tubes, tubes sockets, volume/tone controls on guitars & amps. Link below; you can buy it from this company in AZ, eBay and probably Amazon. It’s not cheap but a can of it will last a long time. If you are fortunate enough to have an electronic supply in your area, you can likely find it locally

Caig DeoxIT

I say that it’s trusted because it’s like the industry standard for techs. Contact cleaners can be purchased at auto parts stores; maybe those would be OK but I won’t use them simply because some cleaners are destructive to potentiometers (variable resistors used for volume & tone controls on guitars & amps). Those cleaners will literally destroy the internal parts of pots to the point that they have to be replaced – I will spare you the unfortunate turn of events that I experienced last year but trust me when I say – don’t use anything except this cleaner.

Cleaning is simple
1) Unplug the amp and let it sit for an hour or so
2) Pull the tubes from the amp and spray the pins; doesn’t take much, just a spritz or two
3) Do one tube socket at a time, Spray down into the tube sockets and carefully plug the tube in, remove it again and then plug it back in. One time is enough, this will suffice as a scrubbing action to remove any tarnish. (Again, it doesn’t take very much of this cleaner so no need to soak the tube socket)
4) The pins on the pre-amp tubes (12AX7’s) are really small and it’s easy to bend them. Tubes will only go into a socket one way, they dummy proofed them so people like me won’t mess things up 🙂
5) This cleaner evaporates quickly but I would let the amp sit for an hour or so just to be sure that its dried. You could take a can of compressed air used for dusting off PC keyboards and spray around the sockets to help speed the drying
6) Do this once a year as a preventive maintenance routine

https://www.tubesandmore.com/products/deoxit-caig-d5-spray-low-medium-high-spray

JoLa wrote:

Oh, that’s a great information, Keith – thank you for the detailed instructions as well! 🙏🙏🙏

The bad news is that I had to take the amp back to the shop, it turned out the issue was still there 😫
The tech was very nice and promised to get to the bottom of it as he suspected the oscillator now. He said he never encountered such odd issue before… Just my luck!

Ugghhh! I hate intermittent problems, they can be hard to track down. Nice thing about your amp – its under warranty and they can swap out some of the printed circuit boards if they run into too much of an issue

If you remember, I thought that it was an oscillation in the amp and the guy on the other forum that I questioned said the same thing. My thoughts are that it’s in the power supply, the other guy thought that was deeper in the amp so we’ll see.

it won’t surprise me if the tech finds some bad solder joints that is causing it. Those occur all of the time – I would think that the factory workers that are assembling these amps would take a few minutes to do a better visual inspection of the new circuit boards but they may be under a rush schedule that doesn’t allow them to

I hope that the tech will be specific as to what he finds wrong with it.

As far as detailed explanations – if you run into any other issues with amps, let me know. I think that I mentioned that I knew several people that I can ask if I can’t give you an answer

Keith
aka GnLguy