Fender Blues Jnr Repair – Ghost Notes

Fender Blues Jnr repair

This Fender Blues Jnr repair was another urgent job completed quickly for a customer who needed it for a gig in Lincoln on the evening it was dropped off.

He brought it to me reporting that something ‘wasn’t right’ with the sound. Upon listening to the amp I could tell what he meant – under certain notes there was an odd ‘subharmonic’ type sound, ghost notes appearing underneath the played notes.

I’ve done other Fender Blues Jnr repair work in the past – but unfortunately someone else had already been working on this amp. They’d make a bit of a mess of the power amp

Fender Blues Jnr repair

Unfortunately the previous attempt at repair, though well meant, caused problems – you can see in the first two images there are lifted pads (possibly the original problem or caused by excessive heat when soldering), no solder between pin and pad on the cathode and some burning on the PCB through excess heat (this is actually on pin 3 of the EL84 which isn’t used so not a big issue).
Fender Blues Jnr repair - PA rewire
The third image is how it should look – Fender’s original soldering on the preamp valves is intact. The preamp valves have the screws closer, they’re shorter so there’s less force exerted and they’re not near the place where you’d put the mains cable.

The power valve section of the PCB was beyond sensible repair and the best way to proceed was to take out the PCB, and saw it in half, re-fit the preamp part of the PCB and wire the power stage point to point. I used chassis mount valve sockets to prevent this happening to the power stage in the future.
Fender Blues Jnr Repair 2
There were also some hairline cracks observed under the microscope which I resoldered.
Having fixed these sources of issues I was finally able to address the problem with the ghost notes. This is caused by a common problem with modern fenders – lousy filter capacitors. I was able to replace the filter caps with parts that I had in stock in order to meet the 24h deadline.

The ghost notes were visible on the oscilloscope – and so it was easy to see on the bench when these horrible sounds disappeared. You can also hear the difference in the video:

If you need a Fender BLues Jnr Repair, please get in touch.

Fender Blues Jnr Ghost Notes

Fender Blues Jnr Ghost Notes

Fender Blues Junior Repair – Urgent Repair

Fender Blues Junior Repair

This Fender Blues Junior Repair was an urgent repair job for a London based guitarist. I got the amp at 23:30 on the Saturday after a gig in Southwell near Newark and had it diagnosed by 11:15 the next morning before he returned to the ‘big smoke’.

Actually, big smoke was obviously a problem that this amp had experienced in the past as can be seen in the image. A power valve had blown and seriously damaged the PCB. Unfortunately the amp had been taken to a Nottingham music shop for repair and I’m afraid they didn’t know what they were doing!

Whoever fixed it has did something weird and wired up a valve pin that doesn’t connect to anything – it should have been going to the cathode, although they have then wired up the cathode separately. There’s no actual harm with this, it just suggests they didn’t know what they were doing!
They also not secured the valve base very well, so it rocks and lifts the pins when you remove or move a valve. This has started to pull up a PCB track on one of the power valves. This will almost certainly cause problems in the future.

I’ve performed a temporary fix on the problem pin 7 by shaving the solder mask off the copper and adding more solder to give the pin an extra connection.

I recommended rewiring the whole power stage at some point in the not too distant future because the amp is a bit of an accident waiting to happen. Unfortunately there wasn’t time to perform the full repair before the customer left for London.

However all this was a chance discovery. I was actually asked to look at a faulty spring reverb on this blues Junior repair. The problem turned out to be with the tank itself. I checked continuity and ground on the cables and observed signal getting to the tank and nothing coming out.

I’ve got a short Accutronics reverb tank kicking around from an amp I gutted so I thought I’d try it, The impedances didn’t match and it sounded terrible with the Blues Junior! But it proved that this was the only problem with the reverb.

The good news is that the customer could buy a spring reverb unit and fit it himself – you only need a screwdriver.

The customer was kind enough to leave a review on my Facebook page.

If you have a Fender blues junior repair, please get in touch.