I’m selling a couple of Fender Blues Junior amps that I’ve had for a little while and performed several popular mods to improve their tone and versatility.

This listing is for a Mark III Blues Junior, it has the original speaker and reverb tank with the following modifications:

‘Bill M’ Mods:

Tone stack upgrade – coupling capacitors replaced with different value and high-quality orange drops to improve the range of the High, Mid and Low tone controls. In addition, the mids control is modified to greater increase its range.

Electrolytic filter capacitors upgraded to high-quality F+T brand, with the first filter capacitor increased in value to improve bass response (a common complaint with the Blues Junior)

Input jack upgraded – the cheap, plastic stock jack was replaced by a high-quality, metal Switchcraft jack. The stock input jack is a known weak point of the amplifier, this upgrade makes it much more robust

Presence control added – a new potentiometer is added to control the negative feedback, which gives even more tonal sweep (I have marked the 'stock' position on the control panel, for easy reference)

‘Fromel’ Mods:

Some additional capacitor upgrades, replacing cheap electrolytics with high quality and higher capacity components

The full list of ‘Fromel’ mods also includes the same tone stack, input jack and filter cap upgrades described above

Others:

Bias trimpot and new power valves – a trimpot has been added, utilising a neat little PCB, to allow for adjustable bias for the power valves. The Blues Junior has fixed bias as standard and is known to consume power valves with impunity. The fixed bias is set too ‘hot’ and, while this makes an overdriven sound easier to achieve, it does wreck the valves which in turn detrimentally affects the amp’s clean sound. The adjustable bias trimpot should be used every time the power valves are replaced, as the suitable bias can change by quite a margin between sets.

Switchable ‘sparkle’ mod –a small switch on the control panel allows you to control the very high end frequencies by introducing a capacitor that removes that part of the sound. In the Mark III circuit, the popular ‘sparkle’ mod was implemented from stock, so this reintroduces a capacitor and gives an additional, in-between value with a more subtle effect. The switch can be useful in combination with the presence control.

Taming the reverb – the Blues Junior is known for having reverb you can drown in, due to excessive gain in the solid-state reverb recovery stage. I have changed a resistor value to bring this gain down and make the reverb control much more usable.

Lead dressing – In its stock condition, the leads from the power transformer are just tied together internally and there is a low-level noise problem. The AC leads have been twisted together, which helps to cancel some of that hum and bring the amp’s noise level down.

Input voltage correction – as standard, the power transformed is set for 230V input, even though the transformed has appropriate leads for 240V. This has been corrected, which together with the bias mod will help power valves last longer.

The amp is in good condition generally with no major cosmetic damage. The handle is fine and I’ve made sure all screws and nuts are tight. Power valves are new and the preamp valves were changed not so long ago and work just fine.

Collection from Hertfordshire is preferred, or I’m happy to drive a little way to meet for collection. I’d be reticent to ship the amp because I don’t have the right kind of packaging materials to be sure it was protected in transit.

Any questions, get in touch