Need help with my new Silver Jubilee Reissue!

[Reapy]

Hey,

I have been more of a reader until now, but I have some little problem with a new 2555X which I hoped you could help me with!

As far as my person goes, I am 28, live in Germany, currently working on my master's degree in electrical engineering and am enjoying those old school metal tones I can get with Marshall amps. I own a 2203 (seems to be an early reissue, it is dated to '94 and has horizontal inputs), a 2100 SL-X and a JVM410H. As much as I like my 2203, the JVM is one of the best amps I ever played. A lot of people seem to hate it, but in my opinion this is a monster of an amp and a very strong contrast to the other two single channel amps.

I was always looking for a Silver Jubilee but before the reissue was out I couldn't afford one used (they were, and maybe still are, crazy expensive). Then I was pretty hyped when they announced the reissue and planned to save for one. But my life was kind of complicated and other things got in the way, so I forgot about it. In March this year I stumbled across the amp again and the price at Thomann was so good (around 1100€) that I went for it. Unfortunately, my amp had some defect (I know a lot about electronics and would have been probably able to fix it myself after some time, but the amp was new and I didn't want to mess with the warranty) so I had to send it back. The problem was that I couldn't run it in pentode mode, there was a very loud screaming noise coming out of the cabinet as soon as I turned it on. In triode mode everything was fine and the amp sounded amazing. After it arrived at Thomann again, they told me that it would probably take them 2 to 3 months to fix it and they don't have another one in stock, which led me to ask for a refund, because I didn't want to wait this long. In the meantime, the amp was sold out everywhere else too. So I had to wait until now to get one again.

The funny thing is, the amp I got yesterday also has a problem. The amp is working and sounds very, very good, but it has a very noisy mains transformer. I tried the amp in different rooms and even at my parent's house to make sure it is not due to the wiring in this house, but the problem seems to come from the amps mains transformer. It really sounds like 50Hz hum and I can feel that this is mechanical hum, it doesn't come from the speakers.

I am not sure what I should do now (I will contact the retailer tomorrow and look what they have to say). If that is an easy fixable problem I would like to keep it, since it is sold out everywhere again and I think that I would have to wait another few months. It could be that the transformer screws are not tightened enough, but I would have to open the case and I don't want to mess with an amp I potentially have to send back. Could it also come from one of the power tubes (unfortunately I am not that familiar with tube amp circuits...yet)?

Well, what would you do? Mess with the amp and potentially void the warranty or send it back and potentially wait another few months again (which is just off putting to me...)?

Edit: Oh, I forgot: The humming starts as soon as I turn the amp on, regardless of standby and dialed in volume. It also is not affected by different cabinets.

 

[anitoli]

Could be the laminations in the transformer are vibrating at the AC's frequency.

 

[PelliX]

I generally recommend people don't mess with their warranty, but you can remove the back panel and check the AC transformer screws and/or replace/re-seat all the valves. This does not void warranty as it's considered standard maintenance. To be honest, any amp that went through shipping gets a re-seat before it sees mains here.

 

[Reapy]

Thank you so far for your replies.

The screws are very tight, so I guess the transformer mounting is not the problem.

I will re-seat the tubes tomorrow morning. Can they actually be the source of the power transformer humming? I thought that the transformer draws dc current which could be the problem, but all my other amps are working fine on the same power outlet...

 

[Reapy]

As it turns out, re-seating all the tubes (power- and preamp) didn't change anything. Honestly, I think this is only related to the power transformer itself.

I don't know if I should ask for a refund, since the amp sounds amazing (and even better than the first one I had in March). It sounds in fact so good that I fear a replacement would sound worse. But the humming is bugging me...I don't know if it will get better over time

What would you do? Refund the amp and wait potentially another few months for a possibly subpar replacement or just keep it and wait until your brain ignores the hum? When playing at bedroom volume, you can clearly hear it. I doubt that it will matter much in the rehearsal room, but that will take time until I can test that (corona...).

 

[Sir Don]

Maybe if you could upload a video of the sound? I know the 900 series trannys make a bit of noise which is, of course, un-noticable when playing at volume.

 

[DonP]

As it turns out, re-seating all the tubes (power- and preamp) didn't change anything. Honestly, I think this is only related to the power transformer itself.

I don't know if I should ask for a refund, since the amp sounds amazing (and even better than the first one I had in March). It sounds in fact so good that I fear a replacement would sound worse. But the humming is bugging me...I don't know if it will get better over time

What would you do? Refund the amp and wait potentially another few months for a possibly subpar replacement or just keep it and wait until your brain ignores the hum? When playing at bedroom volume, you can clearly hear it. I doubt that it will matter much in the rehearsal room, but that will take time until I can test that (corona...).

Is the amp set for the correct voltage in your area?

 

[El Gringo]

Greetings and Welcome ! I have 2 -2555X reissues and I love them so much . If you like how the 2nd amp sounds better , why not have this 2nd one sent back for warranty service ? Thru Thomann who you purchased this from ? That is what I would do . Best Wishes as this is a most awesome amp and I know once everything is sorted out it will be awesome for you !

 

[PelliX]

I think @El Gringo has a point here. After all, if the first one you had didn't buzz like this then obviously there's something fishy with this one. Thomann should be pretty decent when it comes to service, too. That being said, I've often voided the warranty on kit to fix it, because I accept that it will be my problem after 6/12/24 months anyway. Transformers are not cheap, though, so unless you feel comfortable spending the extra money and doing the work, the returns route might be the best one.

 

[Reapy]

I think I will ask them for fixing it I guess. I honestly would have liked to avoid sending it back, but waiting a little longer is not as bad as trying to live with a faulty transformer or spending the extra money to change one (if a transformer would be in the range of 30€ or so, that would be totally fine. But from what I have seen I would need around 150€ and that is just too much).

@Sir Don: I tried to make a video but my phone camera's noise cancellation makes it almost impossible to hear properly. But this video at about 1:15 describes pretty much what is going on and I think that is the issue with my amp too:


I don't know if I should try to fix it myself because if I am being honest I don't care much about warranty either, unless it would be something which cost me a lot. I do the maintenance of all my older amps myself too.

Thank you all for your time and help! Much appreciated.

 

[El Gringo]

Yuck that would drive me nuts . That is the best course to take advantage of the factory warranty . Best Wishes and I hope that happens sooner and gets you back to rocking on a most fine amp .

 

[Reapy]

Is the amp set for the correct voltage in your area?

Sorry, somehow I didn't read your post! But yes, it reads 230V on the backside which is the rms value in Germany.

@El Gringo Thank you and I hope so too, will report if I get it back!

 

[johnnyeggz]

I got one, sounds great (when it’s LOUD), but it’s also a bit noisier than my other amps, maybe it’s just the 2555x?

 

[Reapy]

Well, it is not just noisy, it is a clear mechanical sound which the transformer is making. The noise out of the speakers is actually really, really low (even lower than with my JVM, and that this is quiet already).

In the meantime, I got the message that they can not fix the transformer in case it is broken and I would have to wait for a replacement (I don't know if they mean amp or transformer with that). Because my patience with this amp was already low when I got it earlier this week, I decided to take a better look at the transformer to see if I am not able to do something myself. So I pulled the chassis out of the casing and tried to figure out what is going on.

On close examination, I really doubt that there are some of the laminations loose, but that may be hard to tell without unscrewing the transformer completely (which I didn't do - yet). But what I noticed was that one of the screws is missing this little "rubber pad", which indicates to me that the vibration is not coming from the transformer itself, but rather from the whole mounting structure (I hope you understand what I mean, that is hard for me to explain outside of my native language). I tried to rotate that exact screw a little bit and the vibration clearly changes up to a point where it is completely gone for a few seconds (or rather until I release the "pressure" I apply with the screwdriver).

What I will do now is to buy some of those rubber pads and maybe replace the screws and see if that is sufficient.

I played with the amp again just now. It sounds so amazing, even with the stock tubes, I don't want to send it away again
And after all, all this tinkering is always fun to me, so I don't care that much if the amp is new and has warranty or not. I am pretty certain that the replacement of these rubber pads will solve the problem.

 

[PelliX]

Well, in the ideal world a transformer would not vibrate at all, but yes - sounds like that's your problem. Strange that it would be missing. Any other signs of 'previous access' inside the chassis like worn screw heads, etc?

So just to be clear, you're missing a rubber washer/pad for a screw holding the transformer to the chassis, or the shell of the transformer to the transformer itself? I don't really see a need for them in either case, I'd probably just make sure everything is bolted up nice and tight without any rubbers.

 

[Kelia]

My tech who is an electronic engineer told me last week that those plastic
or rubber spacing are very important between the bolt and chassis, if not there , it causes something
but can't remember the term he used ,...will ask him though , should talk to him shortly.

 

[PelliX]

They can only really prevent microphonic effects caused by the vibration of the transformer itself. There is no electrical insulation there. If the transformer would shake the chassis that badly, then the washers are really a workaround...

 

[Kelia]

To @Reapy , I just came back from my tech the electronic engineer who's name is Denis Rozon,
he built amps of his own design back in the 80's and 90's but stopped when tubes were junk and couldn't make
them sound like he wanted. Later ,he invented amp switching system or multiple amp gyzmo's
for bands like ACDC , VH , KISS and the list goes on , he was designing for Radial and did some stuff for Eric Johnson also.
Anyway , to make a long strory short ,I told him about your problem and he said that probably a batch of transformers were
not vacuumed properly and this might be what is causing the issue.

He told me that when he was building amps , he was ordering from Hammond batches of 25 OT and 25 PT's at once.
One time , he was experiencing exactly what you are describing on not one but three tansformers in a row while building one of his amp , so just before calling Mr Leblanc from Hammond, the phone rang and it was Mr Leblanc telling him that a batch of trannys were not vaccuumed properly and the ones he had were from that particular batch , so below is the recipe to fix the issue and beyond your transformer will be even quietier than if it was well vacuumed.

He told me that you need to disassemble the laminations and rebuild the tranny by dipping each layer of lamination in boat varnish , when it's done and you've tightened the screws back , the varnish beeing pressed will s&it out the laminated iron , wipe the excess with a scott towel and put the tranny in the oven over night at the lowest temperature on the middle rack.
Your tranny will be the quietest one over the other Jubilee's.

So that's it , he told me an hour approximitely for the dipping part so that's not too bad versus loosing your amp for tree months
especially if your's has the magic Mojo , this might be the way to go.
And the name I was looking for on my previous post about the importance of having plastic or rubber spacings between the bolts and chassis is Eddy Current.

Good luck !

Lou

 

[PelliX]

That's what Terry outlined, too. Bare in mind that you will need to remove the PT from the chassis entirely, but if you're comfortable with this, why not.

And the name I was looking for on my previous post about the importance of having plastic or rubber spacings between the bolts and chassis is Eddy Current.

I think there's a misunderstanding here, eddy current is the phenomenon of electric currents in material induced by manipulation of magnetic fields. Simply put, at least. Rubber washers don't stop magnetic fields. I can't see those washers fulfilling any purpose except for prevention of vibration to/from the chassis.

 

[marshallmellowed]

Just send it back and wait for another, I doubt any of the new ones will sound much different from the next (tone-wise). You shouldn't be having to mess with a new amp. My 2 cents.