What do you mean by 'shielded jack'?  You should use a plastic type insulated jack so the bushing does not have any continuity with the chassis.
There shouldn't be any more problem with EMI than the existing speaker wires would have.  It may have to mount where the speaker wires route out of the chassis.
Not sure if the amp is capable of driving an additional speaker without disconnecting the internal speaker.

This is my first post on this site, but I have done a lot of research here on the Fender Frontman 25R. This amp was a recent purchase. This amp is from 2003 and is a Series II amp. This is the blackface-style cabinet with the "wedgie" chassis, so it does not have the speaker out.

This amp was noisy, and I wanted an external speaker jack. The speaker jack was easy to install, but an unshielded speaker jack picks up the EMI from the transformer making the amp useless. I tried a shielded jack, but was never able to get it to work properly, so I gave up on this idea.

These amps are infamous for noise issues, but I did have some success here.

- Used Deoxit on all of the pots. This helped with some of the noise. I also found that the chassis is a common ground for everything. During some testing, I noticed that the pots are extremely noisy if the washer are not fully tightened. The washer on the pot shaft must be a better ground than the ground lug on the PCB.

- There was still a higher noise floor than I would expect so I went down the rabbit hole. The noise sounds like the filter caps. Caps themselves looked good. So, I tested these with ESR meter with the caps in circuit and then removed the caps and repeated the ESR test. This showed that the caps were good. I then tested the caps with a multi-meter and they again they tested good. Soldered them back in. I was shocked to find that when I put the amp back together that the noise level was reduced. My assumption is that the act of soldering the caps fixed this problem. I guess that I could've just re-flowed the solder. I did not do this as an independent test as the solder looked good.

Thanks to the people on this forum for the information in previous posts!

I used these previous posts and there may have been others.
https://www.ssguitar.com/index.php?topic=1527.0
https://www.ssguitar.com/index.php?topic=5516.0
https://www.ssguitar.com/index.php?topic=3445.0


thanks,

Tom.

He was lucky.
Ruffling military´s feathers the wrong way isn´t healthy anywhere in the World 

Mucho gracias hermano 

All of this reminded me of my dad and two gringo (mucho barracho) buddies drove a car to Costa Rica.
I had a lot going on at the time and chose not to even try and wrap my head around it I simply told him "ok yeah well you'll never be seen again"



They completed the trip which purpose was to deliver a car 🚗 and returned.  He had hours of VHS camcorder footage including several instances of military 🎖�🪖 instructing him to put the camera away. 

Thanks A LOT.
It is VERY kind of you.
Sadly I am way too far away, 5000mi-8000km away as the crow flies.
And it would become a VERY tired crow 



But again, thanks A LOT for your kindness.

Take care Friend.

Thank you sir I can probably send you this one if you like 

I'm not a big seller on the bay but I have sold a few things lmk I will be glad to do it gratis of course.

I did skim through the content a bit one thing I noticed he likes making a voltmeter lead with a small capacitor in series

It is safer this way.

I mean, *there are* Class A SS amps, with strong idle current all the time, some Audiophiles swear by them, but then they have HUGE heatsinks and are designed to run very hot all the time.
Not our regular Guitar/Bass amps.

Not kidding: all those transistors and massive heatsinks for a puny (for us) 30+30 W RMS amplifier:

Looks very good and Sams is a very good no nonsense Tech book Company.

Maybe there is a downloadable version somewhere?

I am too far away to order a paper copy.

Quote from: g1 on April 26, 2025, 11:20:31 AMThe 'original' zener was just a defective regular diode.  Someone very smart realized it could be controlled and utilized.  Like a lot of discoveries, I guess. 
Always analyze your mistakes. 

Hey, Penicillin came out of moldy bread 

First Vaccin (smallpox) came out of a rural Doctor noticing that girls milking cows caught a "light" version of Smallpox, including (small) scars, but never ever got the "real" one.

Observation and deduction is everything.

May remember wrong, but Zeners came out of WAY overdoped regular diodes.

Thanks guys
I'm gonna use this thread to post stuff that I was surprised to learn.

Like how a dc power supply is a ground to ac.