"Old Reliable" : A Princeton Reverb Builderino

Discussion in 'Shock Brother's DIY Amps' started by kleydejong, Jun 10, 2021.

  1. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    I have been commissioned to build a friend a Princeton Reverb. I can't for the life of me come to building any amp bone stock, so I am sure I will deviate from Fender's tried and true design - but not by much.

    My friend wishes that the amp be built into a Tweed 5E3 type 1x12 combo. I ordered one from Guitar Cabinets Direct for $286. It looks quite nice!

    [​IMG]

    Next I raid my stash of transformers. I have one with masking tape labeled "Deluxe Reverb". It carries the marker 40-16519. Seems like a Classictone? I found some info on it here:

    https://www.tubesandmore.com/products/transformer-fender-replacement-power-330-0-330-v-120-ma

    https://www.tubesandmore.com/sites/default/files/associated_files/p-tf41316_wiring.gif

    It appears a Deluxe Reverb PT is 10v hotter than a Princeton Reverb. It has higher current potential on the B+ and the 6.3 filament winding. I reckon it should work just fine, especially with JJ 6V6's that I tend to use.

    I selected this OT: https://www.amplifiedparts.com/products/transformer-hammond-output-replacement-fender | A Hammond P-T1750E.

    I bought an undrilled 5E3 aluminum chassis.

    I'll be working from Rob's fantastic PR schematic and layout: https://robrobinette.com/AA1164_Princeton_Reverb.htm

    I imagine I will have switchable NFB and possibly a tone stack lift. Other than that pretty standard.

    Away we go!
     
  2. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    37
    Posts:
    3,678
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Is it going to all fit? The PR is 3-4" longer than a 5e3 I think, and they are pretty dang full once it's all done.
     
    Paul G. and Greg70 like this.
  3. zeppelinofled69

    zeppelinofled69 Tele-Meister

    Posts:
    415
    Joined:
    Feb 10, 2011
    Location:
    Buffalo, NY
    Don't forget to pay very close attention to your transformer and tube placement... 5E3 cabs can make speaker choices slim if you put these things in spots that will interfere with the speaker basket or magnet.
     
    Greg70 likes this.
  4. Greg70

    Greg70 Tele-Meister

    Age:
    50
    Posts:
    341
    Joined:
    Feb 21, 2021
    Location:
    St Louis, MO
    Another consideration is the proximity of the PT to the reverb tank. Princetons have a tendency to induce hum into the reverb circuit if the PT is too close to the return side of the tank.

    Rob's schematic is definitely fantastic and I incorporated several of his suggestions into my build. I would also suggest adding 1 Ohm resistors between the power tube cathode and ground for easy bias testing.
     
  5. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    Thanks for the input guys. We're going to find out whether it will fit or not!

    I did a lot of work on the chassis. Holes drilled. Hardware mounted.

    [​IMG]

    [​IMG]

    I'm testing an experiment for a faceplate. I'm using a sheet of aluminum and using letter stamps to engrave indicators for each control. Then I paint fill with black acrylic paint. Let it set for 3 minutes. Then wipe it off with a kleenex and some fingernail polish remover. It leaves paint in the letter stamp, but the base around the letter is clean. I want something simple, minimal, and hand made. If I don't like it I can easily remove it and try something else. I'm not sold yet, but I think I'm more positive than negative.

    [​IMG]

    The rest of the hardware mounted.

    [​IMG]

    Still need a pilot light...

    [​IMG]

    I got to work on the eyelet board. A stock PR board is about 11" long. I have about 8". So I decided to stagger some of the eyelet locations.

    [​IMG]

    [​IMG]
     
    trancedental and sds1 like this.
  6. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    I have never done eyelets from scratch before. I bought this staking tool - https://www.amplifiedparts.com/products/staking-tool-eyelets-and-turrets. I also have a bunch of brass eyelets - https://www.amplifiedparts.com/products/eyelets-brass-121-x-125-x-200-mt-0095-package-10.

    It is a simple enough concept. 1/8" drill bit to drill the hole. Insert eyelet. Flip it over so the 'top' of the eyelet (the side with the rim) goes face down on an anvil. Place staking tool so the pointy tip is in the eyelet. Hit it with a hammer. This compresses and pushes the eyelet to conform to the board pressing it in place. I definitely struggled a bit with hitting it too many times / too hard. Once I got rolling it is a fairly simple process.

    I got into PTP wiring a while back thinking it was cheaper than eyelet or turret boards. Now I don't think that's necessarily true... I also think eyelets have potential for a cleaner looking build. My PTP designs get a little rats nesty. I do think PTP would work great in a tight chassis like this though.
     
  7. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    37
    Posts:
    3,678
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    How are you doing your filter caps? Cap can, inside, or doghouse?
     
  8. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    I finished the eyelets. It may get a little tight, but I feel I can get the components on this board.

    [​IMG]

    I'm thinking I might require a doghouse. I have installed two terminal strips on the PT bolts. I need to do the filter caps and the bias circuit off board. I believe I could squeeze it in, but I need to draw a layout.

    [​IMG]
     
    Last edited: Jun 11, 2021
    jsnwhite619 likes this.
  9. D'tar

    D'tar Friend of Leo's

    Posts:
    3,394
    Joined:
    Jan 11, 2013
    Location:
    WNY
    Kley! I think you should use a really small cake pan for the dog house! Lol!!!

    Cool build!
     
    King Fan and kleydejong like this.
  10. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    The board is a bit tight. Some of the 1.5k cathode bias resistors are getting stuffed under the 25uf bypass cap. Future servicing of that component likely would require pulling the cap too. I'm willing to live with that.

    I'm also trying to keep some semblance of color code. Red for plate. Green for cathode. Yellow for grid.

    [​IMG]

    I haven't built from a layout in a while, just schematics and mostly PTP. It feels odd to go to a more simplified building style. It is nice though, and makes things feel more relaxed.
     
    trancedental likes this.
  11. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    Hmmm, I dun goofed.

    [​IMG]

    My chassis and circuit board are backwards...

    [​IMG]

    All the wires on the top of the board run to the tube sockets on the bottom. Derp...

    As I see it I can:

    1) Make a new component board. This would produce the cleanest looking result and remove some concerns about weird signal runs potentially adding noise or instability. It would also waste my efforts thus far.

    2) Run the wires criss cross over top. This would result in a messy looking amp. It would also make it a bit of a pain to service.

    I'm leaning towards #2. I need to sleep on it, I'm befuddled.
     
  12. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,933
    Joined:
    Dec 30, 2019
    Location:
    california
    If you choose the number 2 option... the amp will always be a *number 2* if you know what I mean.

    Edit: I reread the original post... "commissioned to build a friend a Princeton Reverb"...

    Suck it up and use option 1 for your friend.:cool:
     
  13. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    37
    Posts:
    3,678
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    The one I built was the most sensitive amp I've done in regards to lead dress, wires crossing...the NFB and tremolo leads were insanely sensitive as to there location and surrounding wires. I think option #2 is an invitation to a nightmare of noise, ticking, and other problems when you fire it up.

    This was the one I built, and it was not fun getting it to the level of noise I wanted.
     

    Attached Files:

    Bellacaster and sds1 like this.
  14. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    37
    Posts:
    3,678
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Any updates on this one?
     
  15. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    Per usual you guys steer me in the right direction. I am in the process of redoing the component board. It will definitely be worthwhile, especially given how cramped things are going to get.

    I'm currently taking the components out. I think I may attempt to flip the bare board upside down. The eyelets have a little more surface area on the top, but I think it should work fine having the current bottom side upright. But if I have issues I will redo that as well.
     
    sds1 likes this.
  16. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    37
    Posts:
    3,678
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    For the cost of eyelets and fiberboard, I would suggest starting over. PR has at least one cluster of 4 or 5 leads in one eyelet. It's a "son of a motherless goat" to make that work with a good connection as is. The board isn't going to "hold" solder, it's just going to float on top or have a paper fiber connection at best. Personally, I would punch a new one to match - I've tried and it's a bear getting properly set eyelets out of a fiberboard. I would drill a new one and set it, then start over if that is where you are now. I would have a major concern about solder pooling on fiberboard, then lifting at some point and the entire joint lifting off the board.
     
    Junior Little likes this.
  17. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    While I figure out my path with the component board I have moved forward with the power supply and filaments.

    I'm using an old IEC power cord that I cut the end off. Drilled a hole, installed a grommet, strung it through, tied in a knot for strain relief. Then green gets tied to the middle terminal strip that is tied to a bolt on the PT. Black goes to the switch, then fuse, then black wire on the PT primary. White goes to the white wire on the PT primary.

    Yellow is the 5 vac winding powering the cathode of the rectifier tube. Pin 8 then sends out to start the B+ step down circuit. Red has the high voltage AC tap. I added another red tap that could be used for the bias circuit as seen in a stock PR. My PT also has a blue wire which appears to be a 50 vac tap that I also could use for bias, but I'd have to use a different bias circuit. I'm leaning towards the blue tap as I think the circuit would be easier and require less resistance to dial down the voltage.

    [​IMG]

    Next I wired the heaters. I twisted the green wires and used some of the excess to wire both power tubes. Then I switched to a pair of red and blue wires for the rest of the heaters. I was mindful to keep the two wires 'in phase', meaning the same wire goes to pin 9 and the other goes to pins 4/5 on each 12AX7. Same on the 6V6's for pins 2 and 7.

    I try to run the heater wires along the bottom corner of the chassis, then keep the pair tightly twisted all the way into the socket. I also am using the gap in pins between pin 9 and pin 1. I ultimately want to keep the heater wire field away from the sensitive grid and plate connections on the tube socket.

    [​IMG]
     
  18. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    I am marching forward. I was able to get the components out of the board, flip it around, and reinstall. It is a little wonky, but it actually works just fine.

    I implemented an adjustable fixed bias circuit on a terminal strip (just under the pilot light).

    [​IMG]

    I have completed wiring on the first two preamp tubes and the tone stack as well.

    [​IMG]

    [​IMG]

    I'm going to make good use of shielded cable. I currently have some running from input jack to V1A and from the volume control to V1B. I also plan on using it a fair bit around the reverb circuit. I'm hoping to wrap this guy up quickly.
     
    Huddy likes this.
  19. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    Everything wired up. I did a once over with my layout diagram and a highlighter. I go through every connection and cross it off confirming it is correct.

    I next went into startup procedures. Light bulb current limiter comes out. Things were okay, but the voltages were a little off. The bulb soaks some voltage, but something just didn't seem quite right. I noticed after about a minute of powering on something started smoking near the power switch / bias circuit. I checked voltage on the bias supply and things were off. I reviewed the schematic and Rob's excellent Princeton Reverb layout - and I discovered that my bias capacitor was wired backwards with the negative end to ground.

    [​IMG]

    I pulled the capacitor out. It looked a little worse for wear with some bubbling on the exterior. The top also looked like it was pushing open. I replaced it with a fresh cap. That solved the smoking problem and voltages all fell right into place.

    I went forward with initial startup testing with no problems. The amp makes sound! Volume and tone controls all work as expected. Tremolo and Reverb I did not have time to check. But I'm excited to get to this point, it is always fun to hear the first noises.

     
    Last edited: Jul 16, 2021
  20. kleydejong

    kleydejong Tele-Holic

    Posts:
    833
    Joined:
    Aug 30, 2010
    Location:
    Orange City, IA
    Can anyone explain to me why a filter capacitor installed backwards would start smoking like mine did?

    I am doing research to try and answer my own question:

    As I understand it, I have a 50vac tap from the PT. It runs through a diode which chops off the positive wave form and leaves the negative. Adding a filter capacitor will smooth the ripple. Because of the half wave rectifier there is a significant gap between pulses, so the smoothing becomes somewhat 'triangular'.

    I admit at this point my understanding of why a capacitor may be polarized is lacking.

    https://www.quora.com/What-happens-if-you-put-a-capacitor-backwards

    "When hooked up “backwards” (i.e., with reversed polarity), the capacitor’s dielectric may be destroyed, a heavy DC current may then flow through the capacitor, and gases produced by electrolysis and internal heating may cause the capacitor to vent, spewing steam and nasty-smelling electrolyte everywhere. Or, the capacitor may even explode or eject flames."

    That seems to pretty accurately describe what I experienced!
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.