Fender Blues Juniors
At Surrey Audio Works, we see a lot of Fender Blues Juniors.
It's a very popular amp, and for very good reason - it packs a lot of features into a (relatively) light and portable cabinet, and has plenty of volume for a gigging amp suitable for most genres.
It's not without its problems though, which at some stage, every owner who wants to keep their Blues Junior, will need to address.
At the same time as this work is undertaken, it's sensible to carry out some upgrades as preventative maintenance. There are also some modifications which can be carried out to influence the tone of the amp, and the way the tone controls operate, which further enhance this already solid performer.
Below are many of the jobs we regularly complete on Blues Juniors.
Filter Capacitors
The Blue components (sometimes grey) are the "electrolytic" filter capacitors, which filter out the AC "ripple" from the DC supply which provides the power to the plates of your valves. These ones are notorious for failing before their time, and when they do, they can cause multiple problems, such as increased mains hum from the speaker, reduced power, and even oscillation (squeals, overtones etc.)
At Surrey Audio Works, we prefer to replace these with very high quality German F&T brand capacitors.
To do it properly is a "board-out" job, so the other electrolytic capacitors are replaced at the same time.
Valve Operating Conditions
From the factory, all Blues Juniors have the output valve bias current (the current which flows through the valve irrespective of input signal) set very high indeed. Often exceeding 130% of the valve specification. This causes the valves to run very hot indeed, which shortens their lifespan, and can damage the valve socket PCB board, which in severe cases can require replacement. It's not just bias current either, the screen current is also far too high. At Surrey Audio Works, we can address the screen current issue, and install an adjustable bias control, to cool things down and bring it back under proper control.
Valve Socket Boards
If the overheating of your Blues Junior's valve socket board has gone too far, and it has become conductive, or the terminal pads and traces are literally coming away, then fear not! Surrey Audio Works has high quality replacement boards in stock, fitted with the best "Belton" sockets. Extra-thick and with the traces printed on both sides for double the current-carrying capacity. A marked improvement on the original.
Adjustable Bias Boards
There are a number of ways of addressing the bias on Blues Juniors. This little add-on PCB is by far the best method we have seen.
Designed and manufactured in the UK by a very competent tech. They are inexpensive and we keep these in stock and fit them whenever the customer agrees. It avoids hassle in the future, and is really the way Fender should have designed it in the first place.
Input Socket & Speaker Plug
The standard PCB-mounted input jack is quite vulnerable, and often requires replacement. We prefer not to do a like-for-like swap here, and instead install a top quality genuine "Switchcraft" socket - ultra reliable since the 50's and thankfully still available. It just won't let you down - ever!
Likewise with the stock plastic moulded speaker jack. They have a rivetted tip connection (which you can't see because it's moulded) which vibrates loose and eventually fails altogether. We replace them with a genuine Neutrik angled plug, The bit you solder to is the same piece of metal which forms the tip of the connector, so there's nothing to vibrate loose.
Tone Modifications
On the Blues Junior, for some reason, Fender chose some quite "un-Fenderish" component values in some parts of the circuit which are critical to the tone "signature" of the amplifier. Some of these deviations from standard Fender practice, align closely with many of the gripes that owners often have about the shortcomings of the sound of the amp. Surrey Audio Works have compiled a short list of some of the most popular modifications, which bring the tone circuit back to a more "Princeton-like" spec. They're not expensive to achieve whilst the PCB is out of the chassis, so why not give the amp it's best chance. We always have excellent feedback from customers about their upgraded amps, which is very rewarding to hear.
Is It Worth It? Yes it is!
We understand all this sounds like a substantial piece of work, and it is, especially if your amp requires a replacement socket PCB. The Blues Junior could be considered a mid-priced amplifier. They're not cheap to buy new, and when they work well, they punch well above their weight. Lots and lots of professional players use Blues Juniors. Reliability is key though, and nobody, whether they're a pro or not, wants to have an amplifier behind them that they cannot 100% rely on. Surrey Audio Works have completed many Blues Juniors for all kinds of players, who have fallen back in love with their amplifiers, especially after the tone mods have been completed too.
So yes, it's a bit of work to get them to pro-standard, but it's a fraction of the cost of a new replacement amplifier, which may come out of the box with many of the problems addressed above.
So if there's an iffy Blues Junior that stares back at you every time you open the cupboard - get it out and get it to Surrey Audio Works for a service / refurbishment / revitalisation - we bet you won't regret it!