Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BadCatCubII on December 13, 2020, 02:30:21 pm
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Hi everyone! My name is Ben, and this is my first new topic here on the forum. I have been lurking here for about a year and learning a TON, and have commented on only a couple of posts. As a novice I haven't had much to contribute, but now that I am well into this build I wanted to share it in hopes that someone else can learn from my mistakes. :laugh:
In addition to lurking on this forum and some others, I have watched Uncle Doug a lot, read E.J. Jurich's book, Merlin Blencoe's book, and a bunch of other stuff... and I even understood some of it! :l2: A frustrated friend gave me a Fender Princeton Recording amp (I guess they are known for being lemons) that he was sick of fixing, so I decided to use the parts for my first real build, beside the 5e3 mission kit I'd done. I've also built guitars and pedals so I'm not a total greenhorn, but this is my first time building something like this from scratch, and first time doing point-to-point wiring, as well as my first time doing the "design" part of it, but I can't take credit as I have stolen from so many, even many on this forum. Thanks especially to Tubenit and Slucky, reading the threads on the Carolina Overdrive Special and the Tweed Overdrive Special were super helpful.
First I drew a schematic and a layout, then started building my chassis. I used aluminum sheet and angle for that.
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/107076488_10216981288355645_4597312259056870468_o.jpg?_nc_cat=108&ccb=2&_nc_sid=730e14&_nc_ohc=p9ICe0q-P7oAX-zjBmA&_nc_ht=scontent.fdsm1-1.fna&oh=d4190a911f48ed15c4a7a60092c18f55&oe=5FFA769F)
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Here are some shots of the chassis fabrication.
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/107370193_10216981288875658_6237241239400610748_o.jpg?_nc_cat=104&ccb=2&_nc_sid=730e14&_nc_ohc=O9vIYOYT_tkAX8S1iNj&_nc_ht=scontent.fdsm1-1.fna&oh=657b6bc31af0d918072d4d5b1bf25744&oe=5FFA2BBD)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/107593981_10216987447069609_5850565855278035369_o.jpg?_nc_cat=104&ccb=2&_nc_sid=730e14&_nc_ohc=37dXwvuezS4AX9jJAMv&_nc_ht=scontent.fdsm1-1.fna&oh=308da5e06078be6f3f84c590dbbf69d7&oe=5FFABF1F)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/106569324_10216987448629648_47168221903376337_o.jpg?_nc_cat=110&ccb=2&_nc_sid=730e14&_nc_ohc=VgQ7pZ1hesMAX-s9WLU&_nc_ht=scontent.fdsm1-1.fna&oh=907ea756ede329f1722543913b88bcac&oe=5FFE0160)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/106492669_10216987449589672_2636403311206854914_o.jpg?_nc_cat=100&ccb=2&_nc_sid=730e14&_nc_ohc=ewkjtQfcdQQAX-7NCqR&_nc_ht=scontent.fdsm1-1.fna&oh=1455687df4811e9d9431596b55dab2b3&oe=5FFD8398)
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Gonna be an interesting project. Harmonic trem may be a challenge. Can we see the schematic?
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For the faceplate I did something different. I used a heavy copper foil, and did a forced patina. I used my wife's cricut to trace out the lettering, and then the different effects of the forced patina make the lettering stand out.
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116105841_10217164899625812_1190448922776033019_o.jpg?_nc_cat=108&ccb=2&_nc_sid=da31f3&_nc_ohc=sJYdSg2UutUAX-Zx4kE&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=360619355f42dc05eff300c998233632&oe=5FFC140A)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116635840_10217164900065823_7029028472854785375_o.jpg?_nc_cat=111&ccb=2&_nc_sid=da31f3&_nc_ohc=cZhUfTObWc4AX_SvIQ5&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=2dc0d59ad9824e32bf736512a543a630&oe=5FFDA44F)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116287773_10217164900305829_523864548493033099_o.jpg?_nc_cat=107&ccb=2&_nc_sid=da31f3&_nc_ohc=mukNlIc0oN8AX8WSsHl&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=f89c1dbf5952f895c8c2af5edbb97692&oe=5FFA691D)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116212690_10217164900505834_674055194911589866_o.jpg?_nc_cat=106&ccb=2&_nc_sid=da31f3&_nc_ohc=awvotYDSYawAX9szblk&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=a056aabd4aa994ac9bdeae7133488dd3&oe=5FFCF31E)
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Thanks, Slucky! I've made some changes in the circuit that I haven't updated on the schematic, so I will make sure it is correct before post it. :icon_biggrin:
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The patina on the copper is made by covering it with baking soda and salt, then exposing it to ammonia fumes. Then I carefully painted over the lettering with clear nail polish. Finally, I heavily coated it with nitro.
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116708709_10217164900705839_4245125701338815857_o.jpg?_nc_cat=102&ccb=2&_nc_sid=da31f3&_nc_ohc=J94vF0YHgpQAX8iZpd0&_nc_oc=AQkdRi-RIGXur3J3IrfAjOHwAe6CoISJHzeeDPnPsIixonYPcsBcaAXY9WWEH5a-r7M&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=2cdf95cc359296c6464fc744b46e84c8&oe=5FFC9905)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116151469_10217164901145850_7299351959642747572_o.jpg?_nc_cat=106&ccb=2&_nc_sid=da31f3&_nc_ohc=Z-Ietu2XkMMAX_zamdv&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=221420f7957c39d29bc42faeb67bb6cb&oe=5FFDB0D3)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116217107_10217164901425857_7160545033233648482_o.jpg?_nc_cat=107&ccb=2&_nc_sid=da31f3&_nc_ohc=dSJ_joZfFlMAX9zCcC8&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=f424be66ae59b1797b79198b32c7e63d&oe=5FFC0252)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/116263662_10217164901705864_5688540722596310793_o.jpg?_nc_cat=105&ccb=2&_nc_sid=da31f3&_nc_ohc=gNgA1J2JCIoAX8zqVjA&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=a28073f2d0290d0afec2033a1261a383&oe=5FFBD0ED)
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(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/109296303_10217094326501528_1203387890301846027_o.jpg?_nc_cat=101&ccb=2&_nc_sid=da31f3&_nc_ohc=zX8ro3rekoEAX_iDgMc&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=1d5b1ee6b7b30b81e031448c43c9a6fe&oe=5FFA71BC)
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-0/s552x414/123205116_10217759635333833_7008161163734973264_o.jpg?_nc_cat=110&ccb=2&_nc_sid=da31f3&_nc_ohc=AZryg0sIU7kAX-5cgDo&_nc_ht=scontent.fdsm1-1.fna&tp=7&oh=9bf327d112483324a5ab44b50a4b7120&oe=5FFBB20A)
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Here is my schematic, and some gut shots. This is my first time wiring point to point, so be kind with your criticisms. :)
I think that putting this much stuff in a 19x6x2 chassis was a little much, but it works! and, I think it is pretty quiet, but I do have some extra noise when the tremolo is engaged.
I used the digikey free schem-it website to make my schematic, and I didn't know how to do certain things like draw multiple secondaries on a the PT, etc. Let me know if anything doesn't make any sense.
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/131066124_10218027497470219_7023484231263768702_o.jpg?_nc_cat=108&ccb=2&_nc_sid=dbeb18&_nc_ohc=Qz4-98XCigEAX_91tFl&_nc_ht=scontent.fdsm1-1.fna&oh=57b8bc142fc9949a70d283b614235bef&oe=5FFD132C)
This is the power supply. I built it around the Princeton recording amp transformers, and I was worried because the 6.3v secondary in that amp only supplies some of the heater voltages—some of the tubes in that amp have DC heaters. That amp also has a bunch of extra solid state stuff so I used one of the other secondaries to supply DC to all the heaters for my preamp. This shows the filtering, and there are two regulated circuits.
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/131333379_10218027488950006_1258441158792677701_o.jpg?_nc_cat=107&ccb=2&_nc_sid=730e14&_nc_ohc=kU8j6wMI3QcAX-IHUGK&_nc_ht=scontent.fdsm1-1.fna&oh=f684fe1cd4590cb064e779331afb6e9a&oe=5FFD44FA)
Here is the amp part of the amp. :) The two farthest tubes to the left are pentodes, EF86 (v1) and a 5879 for the drive section. Half of the tube in the middle is used to drive the 5879, and the other half is the phase inverter for the harmonic tremolo. I haven't wired it yet, but I want to be able to switch between harmonic and standard tremolo like another cat on this forum did with his revibe project.
(https://scontent.fdsm1-1.fna.fbcdn.net/v/t1.0-9/131345546_10218027535111160_599263414121086039_o.jpg?_nc_cat=102&ccb=2&_nc_sid=dbeb18&_nc_ohc=TeViWiY6Wg0AX_k5FCL&_nc_ht=scontent.fdsm1-1.fna&oh=a1a4bf0cf529fe1134e3e1074b566d12&oe=5FFE807A)
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I love the creativity of your control faceplate. For your circuit - yikes! I have not looked to trace any details, but you are starting out with a complex circuit and point-to-point can be tricky, especially with lots of exposed leads. Pretty creative with the ground buss though.
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Thanks, bmccowen! I have a history of jumping in head first! :laugh:
My first guitar build from scratch was an arch top, and my first acoustic build had an arm bevel and a side port, so I guess going over board is my MO. :icon_biggrin:
It hasn’t bitten me in the behind YET, and the amp works! I will post some sound samples soon!
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Very cool - love to hear those clips - congrats
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I have a history of jumping in head first!
hopefully the deep end :icon_biggrin:
I like your work, I use copper foil alot, tried the chem stuff and gave up, just went with acrylic, chemicals :angel
nice chassis work also.
I chicken'd out on my last build, went with a turret board, but I still got the P-P layout to look at :laugh: