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Hoffman Blues Junior Conversion |
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A customer sent me his Fender Blues junior to do a total makeover with hand wired turret boards and new transformers| There is no reverb on my Turret board There are no plans to add reverb to the Blues JR conversion boards My original intent was to cut out the reverb circuit and power supply from the original PCB board This plan did not work out There is just not enough room on the turret board to add all the parts for the solid state reverb circuit The original solid state reverb with the tiny reverb tank is not all that great anyway Note: I have made some changes to the Blues junior Turret Board shown below after doing this build I added the bias circuit to the new board layout I removed the parts that had to do with the reverb circuit The reverb pot is now a meat control which is a resonance/low end control Sound clips of this amp Cranked humbucker Sound clip Single coil with the ReVibe unit clip The boards used in this build can be found on these pages Hoffman amps Turret board catalog page Blues Junior tube board Kits-parts list page |
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Note that Hoffman boards are not assembled by looking at my builds. I do test builds first and change the designs based on those builds. You assemble Hoffman boards using the documents listed below. The Layout Diagram, Schematic and BOM for this board are on this page |
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Here's the stripped out guts of a Blues Junior You do not need to remove the power transformer and the output transformer My customer sent me an Allen power transformer as an upgrade. He also wanted an upgraded output transformer and so I installed a 768 Heyboer output transformer |
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| Here's the parts I will be installing The customer sent me an Allen TP24 power transformer and a Mercury Magnetics choke The Output transformer is a Heyboer 18 watt output, which I stock The main board is a Hoffman Turret board The separate tube board assembly is shown on this page See the links at the top of this page for the catalog pages and the parts list Note: Look at the input jack hole in the photo It is larger than a 12A Switchcraft jack hole size. The fiber washer in the parts list fit perfectly in the hole so you can mount the 12A jack The fiber washer is not there to isolate the jack from the chassis |
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Here's the main board with the lugs installed and laced together Note that the newest turret board version now has the bias circuit on the board |
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The back side of the board with the jumpers |
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| This is the tube socket board that I machine on my CNC machine The newest version of the tube socket board has recessed screw head holes and eyelets for the 47 ohm resistors The separate tube board assembly is shown on this page |
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The tube socket board with the sockets installed, the heater wires run, the 47 ohm center tap resistors installed and the 1.5k input grid resistors The heater wires are not twisted and still the amp runs dead quiet. The separate tube board assembly is shown on this page |
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A side shot of the tube board with tubes installed The separate tube board assembly is shown on this page |
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| The Allen TP24 power tranny. Mercury magnetics choke and Mojo 768sp output transformer The BJ does not come with a choke, my customer wanted me to install a choke on this amp |
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Tube socket board installed. Main board installed. Jacks, pots and fuse holder installed I had to drill a 1/2 inch hole to install the Fender style fuse holder Update: I have since added a new bolt down fuse holder in my store. I realize not everyone can drill 1/2 inch holes for a Fender type fuse holder The new fuse holder looks like this and accepts standard 3AG 1.25 inch long slo-blo fuses Use a 6/32 x 3/8 inch long screw and 6/32 Keps nut to bolt it down to the chassis  |
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Tube socket board installed. Main board installed. Jacks, pots and fuse holder installed I had to drill a 1/2 inch hole to install the fender style fuse holder |
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Tube sockets wired up to main board |
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Components installed and pot wires run |
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I had to abandon the idea of using sections of the original PC board for reverb and the +15/-15/Bias supply So then I needed to make a small bias circuit board and mount it next to the main board The latest BJ Turret board version I sell has the bias parts on the board. There is no need for a separate bias board. Note that the brown wires are the bias supply wires from the power transformer. One wire goes to chassis ground and one wire goes to the 1n4007 diode. |
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| My original idea was to take the PC board and cut out the solid state reverb circuit and the +15,-15volt, bias circuit This proved to be a no go after I had installed the main turret board. There was just no where to mount the reverb board And it would make things way more complicated for others trying to add reverb to my turret board It took a very long time to cut out those two boards shown above and then add turret lug attachment points Luckily the customer that owned this amp did not want the solid state reverb and so I abandoned the whole idea The amp is without the solid state reverb and that is fine with me The original solid state reverb does not sound all that good anyway Many people use external pedals and effects for reverb and delay |
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