Hoffman Plexi 6V6 project

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Hoffman Plexi 6V6 project
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 is my Plexi 6V6 in a nice Poplar finger jointed cabinet. A Hoffman forum member made this cabinet for me. I cut the fancy slots and oval on my CNC machine I made the face panel on my CNC machine. Note that I don't make face plates or cabinets here for sale I am not set up to do face plates or cabinet work
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I added a faceplate to my Plexi 6V6 It looks pretty sharp now
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Here's is the finished Plexi 6V6 chassis without the face plate I have not installed the pilot lamp yet in the picture above Start at the bottom of the page and go up to see the build sequence The parts list for this amp is on this page The Schematic, Layout diagram, BOM and sound clips are on this page I am using the Hoffman Stout Chassis found on this page - Page Link The transformer set the Heyboer 18 watt PT and OT, plus a 125C3A choke The tubes are EH 12AX7's, Sovtek 6V6's Some detail about the chassis The chassis is pre punched with all the holes you see plus a few extra pot holes There are 3 x 9 pin sized holes and 2 x 8 pin sized holes I used a 9 pin block off plate on one of the 8 pin holes - Page Link
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The last thing I install is the wires that go from the board to the pots I do this because I fly them overhead above the parts The pot wires are soldered inside the turret lug hole on top They are not wrapped around the turret lug I make a nice small bend in the wires to give them some strain relief and then head straight for the pot It's a small chassis and makes for a nice compact build
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Now is when I add the parts to the board Look how clean the board looks This is why I add the parts after the board wires have been added All the leads are straight and the board does not have any big solder flux blobs on it It's beautiful :)
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I mounted all the pots and added the buss wire to the back of the pots I Dremel clean a small area on the pot where I want to solder the buss wire and tin that spot with soolder The pots are mounted in the chassis using two of my Alpha washers for each pot I also mounted a trimmed down terminal strip on the back of the Bright channel volume pot This is where I mounted the 470k mixing resistors and a 500p bright cap You can see in the picture above that the 68k resistors on the input jack reach down to pins 2 and 7 on the first pre amp tube And the two 470k mixing resistors have a wire down to pin two on the second preamp tube Some folks like to run all the board wires under the board and come up through a hole Do that if you like to do it that way I like to see exactly where all the wires go when I look at the top of the board
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The wires that go from the board to the tube sockets have been installed People always ask me why I do it this way Why not put all the parts on the board and then add the wires? Because it very difficult to wrap wires around the lugs when parts are ion your way You can see how nice and neat my board construction looks in the images up above The main filter cap comes out of the bracket easily so you can get to the tube socket under the filter cap Or you could add all the wires shown above fist and then wire up the filter cap
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The turret board has been mounted in the chassis using 1/2 inch hex standoffs The main filter cap has been mounted and wired up to the board Mount the board so that it is not too close to the rear panel parts
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Back panel view
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Topside view
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Topside view The transformer set is the 18 Watt Heyboer PT and OT The choke is a small Fender style 125C3A
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The heater wires have been run and the items on the back panel have been wired up I added the resistors that go on the tube sockets All the transformer wires have been hooked up to their proper locations The yellow and white wires on the PT are not used because this amp uses rectifier diodes Notice the main ground screw between the power tube sockets and the PT All the major grounds go to this screw, except the one that goes to the input jack
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This is the same picture as the one above, just a different angle
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Transformers and tube sockets mounted to chassis
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The back side of the board showing the two jumper wires
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The turret lugs have been laced together and soldered
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The bare board with turret lugs installed
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