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Hi and welcome to this listing for my Alnicomagnet “Blackface” Mod Kit for the Fender Blues Junior II or III amplifier.
Introduction
I find all Blues Juniors a bit of a compromise. They’re not super clean in the traditionalFender “Blackface mid scoop clean” sense. Neither do they make a really good “dirty juston the edge of breakup” amp. (For that you need to look elsewhere – Orange or Marshall).Talking to quite a few guitarists, I found that most preferred to use their Blues Junior as a”clean platform” (with the “master” up high and the “volume” down), and use pedals forwhen more gainy sounds were required, and almost all said they would prefer the amp tobe cleaner and less “boxy” sounding, like a mini Twin Reverb if possible.
So I’ve developed this mod kit which addresses these issues, reduces noise, adds somefeatures, and sets the amplifier to run the output valves cooler, leading to less valve wearand a much sweeter tone.
The output valves are set to run very hot, leading to premature valve wear and a harshtone. With new valves fitted, anode dissipations were calculated at 15 watts per valve atidle in the UK supplied stock amp, this is way too high as EL84 valves are only rated at 12watts absolute maximum anode dissipation. (With old valves fitted, the anode dissipationswere calculated at around 10 watts in the stock amp, showing that they were worn out).The modified amplifier anode dissipations with new valves fitted were calculated at just over10 watts per valve at idle. (Based on new JJ Electronic EL84 output valves running with ameasured 241V UK mains input voltage).
Mod details:
1. (UK only) the amp is reset to run on our 240 volts mains supply voltage.2. Additional HT filter stage and bleeder resistor fitted to lower the ripple and anyresulting background hum, this also ensures that the HT filter capacitors dischargeslowly and safely.3. Screen voltage supply resistors are “beefed up” for better reliability.4. EL84 bias circuit is changed from fixed bias to cathode bias (also known as “selfbias” or “auto bias” – this ensures correct valve operation whatever valves you fit.5. AC heater supply is changed from AC to DC to remove the “buzz saw” heater buzz.6. Tone circuit is changed to Fender Twin Reverb spec for more bass and a better midscoop sound.7. All relevant capacitors in the signal path are upgraded to Sprague Orange Drops andsilver mica for the cleanest possible tone. Coupling capacitors are increased in valuewhere necessary to increase bass.8. The negative feedback loop is now switchable for when a looser, less brittle, moreorganic tone is required.9. The rubbish plastic input jack is changed to a proper genuine Switchcraft USA metaltype.10. V.2 Blues Junior PCBs are converted to V.3 spec, (the so-called “sparkle mod”).
Note: I also offer as a separate mod kit a Carling 3-position off/standby/on switch. Itreplaces the stock power switch, requires no extra drilling, and preserves the stockappearance. Using it will put less stress on the HT filter capacitors and valves. Check out my other listings.
Tools needed
Installation of the modifications requires only basic soldering tools and a few items availablefrom your local hardware or electronics store. You will need: A good quality general purpose soldering iron with stand (rated at about 25W) Solder and a good desoldering pump Safety glasses or goggles A multimeter, preferably with a digital screen, and a couple of alligator clips to attach the probes to component leads Various screwdrivers, including a set of small jewellers screwdrivers Small side-cutters Wire stripper Sharp craft knife Small needle-nosed (radio) pliers Large pair of pliers Masking tape or sticky tape A desk-mounted light or illuminated magnifying glass (useful but not essential) A or 3/8 drive metric socket set and/or a set of small metric spanners (wrenches) up to and including 14mm An electric drill with a good selection of HSS bits including 1mm up to 6.5mm A flat file A round file An old toothbrush and/or a small stiff paintbrush Paper, pencil, ruler
Instructions and pictures are kept in a folder. The folder is stored on a download site (dropbox). You will receive a download link via email which will be sent to you at the same time as you receive confirmation from eBay that the kit has been shipped. I will use your PayPal registered email address unless you inform me of an alternative preferred email address.
Important! Dropbox has recently changed and now requires you to open an account with them before you can access the files.You will need a pdf reader to access the instructions. You will need a picture viewer to view the pictures.
Hi Just wanted to say I installed your blackface mod to my blues junior about 4 months ago and it is extremely good. The clean tone with rich valve harmonics sounds like a boutique amp now. The BJ is a perfect portable rehearsal small venue amp that with your mods is much more like a vintage fender. I may switch out the speaker now too.
Thanks and great work!!!Hi NigelAll the Blackface mods done and seemsto be working with no smoke or buzzing noises. I carried out all your stepsincluding the test ones at the end and all are coming out about 3 volts adriftfrom your readings so I am really pleased that it looks like its been asuccess. First thing I did notice on switching it on for the first time is thatthe valves didnt start up bright and drop down to their orange glow which iswhat was happening prior to your mod, its like your circuit wizardry is workingand balancing things out and everything will be controlled properly by yourmod.
I bottled out of doing the standby switch mod at the same time as I just wantedto get it all back up and running first. I generally only play at home now andalthough I will probably go back and do that mod too, I didnt feel it was a priorityat the moment; Im just so pleased that it all started up with no issues.
Once again Nigel your expertise, knowledge and presentation of the walk through,both in photo and in step by step guide to help the likes of me do this modhave been absolutely outstanding. You are a very clever, helpful and talentedguy. I have been playing through the amp for about 30 minutes and all is wellso I am going to get the back cover back on and tidy up the mess I have made inboth the living room and kitchen. Although I dont fancy ever doing it again,lol.. (my eyes were struggling to cope) Im so pleased I have managed to get itdone.I have never beforeseen such a detailed and structured walk through like this before both on thetext and photos for each stage down to the test results and what and where tomeasure and the expected result, what you have supplied is perfect.
There are mod kits and then there are yours, I would certainly put yours upthere as one of the best. Not forgetting you include absolutely all that isneeded in quality components.
Thank you for all the effort you have gone to, to make such acomprehensive and thorough project, its brilliant and now I feel my amp isbeing looked after way better too…. perfect.
Kind regards
Dave Scott
Hi Nigel
Loving my ‘new’ amp.
Yesterday after fitting the mod I was basically just playing around with my custom shop strat fitted with dual mag pickups and I got the amp dialled in really good after the mod. As the strat has the grease bucket and blender controls fitted its already really flexible to set up a tone wise but I never really appreciated just how good the mod has changed the amp’s tone until I plugged in my 335 today…. all I can say is WOW… I now fully appreciate the exquisite tones now available all because of your mod…. my 335 has never sounded better its absolutely gorgeous now and Im totally blown away and so happy.
I originally looked at getting the mod purely to help treat and look after the new valves I was putting in and treat them in a more controlled and friendlier way along with the other good features of the mod. To be honest, I wasn’t really too bothered about the tone mods as I was generally happy with the sound. as long as it was still clean and everything worked after me attacking it with a soldering iron.
Well…I hadnt expected was just how much change to the tone this mod has made, its absolutely gorgeous and my 335 is now so velvety smooth yet crystal clear its astounding. Never noticed it so much yesterday with the strat because of all the blend and greasebucket circuitry i could dial in basically anything I wanted anyway but the new lease of life in my amp hit home today after plugging in my 335. You have made this great little amp a phenomenal one with the Blackface sound restructuring.
Worth every penny Nigel and your kit is second to none and with no having to find additional components, you supplied the lot right down to the last bit of sleeving. and all with instructions and photos anyone could follow… lol… apart from me with pin 3 on the valve :)) silly me.
So thankful to you Nigel.
Kind Regards
Dave Scott
Dear Nigel,
Just wanted to thank you again for supplying your Switch and Blackface Mod.I upgraded the Amp yesterday.I really did this to fix the Voltage and preserve my valves. I expected minor improvements to Bass, Mid and Treble and a reduction in some hum.I supposed I was more concerned that I might make an error somewhere and the hope of just wanting the Amp to work, had dominated my thoughts.When I switched it on, I was amazed by the result, I hadn’t attached any pedals, the sound and control was fantastic, I just didn’t want to turn it off.I got a row from my wife for being late home for tea!! My brother in law, had been telling me how much better I could make it, but I guess it just hadn’t sunk in. If you need a customer reference any time I can recommend your service Thanks again,
Regards Bill Somervail
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Category: Musical Instruments:Pro Audio Equipment:Amplifiers
Location: Rochdale, Lancashire