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Thread: Bassman build finally completed!

  1. #1
    Supporting Member Randall's Avatar
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    Bassman build finally completed!

    I started on this almost two years ago. As the story goes, a young man without a clue was trying to sell around town a badly abused 68 Bassman head, and a music store he tried to hawk it to gave him my number. He wanted $200 for it, but it was badly rusted, heavily and poorlly modded, and the head cab was chock full of carpenter ants. I told him I'd give him $100, and that was a risk, not knowing if the transformers were good or bad. He declined and left. About a week later, he changed his mind and I bought it for $100, although I immediately wished I had offered less.

    Turns out all the trannies tested good, so I proceded to tear it down. I stripped the chassis and tranny covers to bare metal and painted. I cleaned as much rust as I dared from the laminates, and sealed with lacquer. I made new boards from grey fiber (which after time does have some conductiveness, but without any real symptoms), and used what blue mallory caps I could. I used F&T filter caps, Sprague cathode caps, Mallory 150 and silver mica tone caps, and 1 watt carbon film resistors on the board, and 2 watt metal film in the PS. I put in new sockets, jacks, pots and switches. Cleaned up the brass plate real good, put in mid controls at the back where two jacks had been added, installed a Hi/Lo power switch where the ground switch was located, and a push/pull on one of the volume controls as a channel jumper switch. I wired it as a AB165, but with AB763 style bias circuit, and the first channel having a 5F6-A tone stack, no deep switch, and bright switches on both sides.

    It has a Fender branded Eminence 4 ohm 100 watt speaker, and GT branded Russian 5881WXT power tubes. This was my first tolex and grille cloth jobs as well.

    I did not do the cabinetry, I supervised a friend. He used 3/4" finger jointed pine for the cabinet, and 5/8" cabinet grade baltic birch ply for the baffle.

    In the end, I am quite pleased with it. This amp does not sound like any Fender I have ever played, it barks like a dog, very crunchy, but with nice articulation. It is a nice size and weight, and it's LOUD. Thanks fellows for the advice on the tweed tone stack (nice touch), and the channel jumpering. I got the switch idea from Rob Robinette's site.

    Here are some photos of the process:

    Click image for larger version. 

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    17 Not allowed! Not allowed!
    Last edited by Randall; 06-09-2019 at 07:25 AM.
    It's weird, because it WAS working fine.....

  2. #2
    Master Destroyer nosaj's Avatar
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    Awesome Job Randall.!!!!

    nosaj

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    Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

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    Nice work!

    Man that was bad!

    I love seeing projects like this.

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    The world is full of people that are right.

  4. #4
    Bent Member Chuck H's Avatar
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    SWEET!!! Do us all a solid and find the best guitar player you have at your disposal to play for a video clip Would love to hear it. It sounds like it would be simultaneously unique and familiar. A player that knows how to get the most out of an amp could really exploit it's character. I want to hear it. Hell of an effort and I'm sure well worth it. Nice job.

    2 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  5. #5
    Supporting Member Randall's Avatar
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    Thanks Chuck, I'll see what I can do about the video. Kind of a politically sensitive area with my guitar player friends, but I'll try. How do you even make a loud video that doesn't sound crappy anyway?

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    It's weird, because it WAS working fine.....

  6. #6
    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Randall View Post
    How do you even make a loud video that doesn't sound crappy anyway?
    One mic set about 1/2" inside of the speaker edge angled toward the center just as close as you can get without distorting the mic. Another mic set at the furthest point in the room. Blend them, or don't But between the two one, both or a blend will work.

    0 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  7. #7
    Old Timer olddawg's Avatar
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    You can get a pretty accurate recording (within reason) with an iPhone 10ft away.

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  8. #8
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    If you still have it wired as an AB165 topology with that 3rd "gain" stage w. negative local feedback, that might explain the bark. That's something no other Fender before or since came with besides the AB165 & later 50W Bassman heads. The AB165 has some "wonky" stuff that didn't last, & that might be why so many people trash them as sounding bad... But if you put a gun to my head & said I could only choose one amp of mine to keep- it'd be my AB165.

    Excellent work, & I'm glad someone else out there likes the AB165.

    Edit: question! Is that the original spec OT? Is there any indication it came with a different one? It looks huge compared to the PT. Reason I ask is, mine is the same way. I looked into the Fender part numbers & found out mine crosses to a Twin Reverb OT; I then found a couple of the mounting holes on mine are off a fraction of an inch. Sure enough, I've got a matching loose TR OT at home with the same Fender part number. If so, that might also explain some of rhat bark.

    Justin

    4 Not allowed! Not allowed!
    "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  9. #9
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    Excellent piece man! Very nicely done!

    Is there a thread that I can read to get up to speed on the build details (ideas that might have been tossed around etc) that helped this come to fruition?
    (Love the documentary pictorial BTW!)

    0 Not allowed! Not allowed!
    Start simple...then go deep!

    "EL84's are the bitches of guitar amp design." Chuck H

    "How could they know back in 1980-whatever that there'd come a time when it was easier to find the wreck of the Titanic than find another SAD1024?" -Mark Hammer

  10. #10
    Supporting Member Randall's Avatar
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    "Is there a thread that I can read to get up to speed on the build details (ideas that might have been tossed around etc) that helped this come to fruition?"

    This is how it started: https://music-electronics-forum.com/...hlight=bassman

    1 Not allowed! Not allowed!
    It's weird, because it WAS working fine.....

  11. #11
    Supporting Member The Dude's Avatar
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    Awesome job, Randall! I'd love to hear it, too.

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    “Yeah, well, you know, that’s just, like, your opinion, man.”

  12. #12
    Supporting Member nevetslab's Avatar
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    Quote Originally Posted by Randall View Post
    Click image for larger version. 

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    What does the Low/Hi Mode Switch do?

    EXCELLENT RE-BUILD JOB!!

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    Logic is an organized way of going wrong with confidence

  13. #13
    Bent Member Chuck H's Avatar
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    Quote Originally Posted by nevetslab View Post
    What does the Low/Hi Mode Switch do?

    EXCELLENT RE-BUILD JOB!!
    You set it according to your mood. The lo mode sounds better for minor chords.

    1 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  14. #14
    Supporting Member The Dude's Avatar
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    I was guessing it's a pentode/triode switch.

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  15. #15
    Supporting Member eschertron's Avatar
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    Quote Originally Posted by The Dude View Post
    I was guessing it's a pentode/triode switch.
    +1. Removing the death cap provides a hole in just the right spot to jump the screens. And the switch can be re-purposed, so no parts to buy!

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    If it still won't get loud enough, it's probably broken. - Steve Conner
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  16. #16
    Don't forget the joker g1's Avatar
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    Quote Originally Posted by Chuck H View Post
    You set it according to your mood. The lo mode sounds better for minor chords.
    Wait, it's a mode switch or a mood switch?
    Consult your mood ring for best results.

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  17. #17
    Supporting Member Randall's Avatar
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    "And the switch can be re-purposed, so no parts to buy!"

    Actually the ground switch was a SPDT, I needed a DPDT for the pentode/triode switch, but I had a bunch on hand so the end result is the same.

    And I will post some audio of it, I just don't know when that will be. I can no longer play.

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    It's weird, because it WAS working fine.....

  18. #18
    Supporting Member eschertron's Avatar
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    Quote Originally Posted by Randall View Post
    I can no longer play.
    Whoa. Sorry to hear that. Care to elaborate?

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    If it still won't get loud enough, it's probably broken. - Steve Conner
    If the thing works, stop fixing it. - Enzo
    We need more chaos in music, in art... I'm here to make it. - Justin Thomas
    MANY things in human experience can be easily differentiated, yet *impossible* to express as a measurement. - Juan Fahey


  19. #19
    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Randall View Post
    "And the switch can be re-purposed, so no parts to buy!"

    Actually the ground switch was a SPDT, I needed a DPDT for the pentode/triode switch, but I had a bunch on hand so the end result is the same.

    And I will post some audio of it, I just don't know when that will be. I can no longer play.
    I hope that's an exaggeration and what you mean mean is that you can no longer play as well as you'd like if you're going to show it to other musicians. Because I empathize with that entirely. But I hope, as esher clearly does, that you haven't been maimed in some way that prevents you from playing at all.?.

    1 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  20. #20
    Supporting Member Randall's Avatar
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    My left hand is toast. I played professionally since about 20 years old. Now I can barely make a few chords to test out an amp. I have a contracture syndrome in the fascia that impedes and mis-routes my tendons, and doesn't allow me fully open my hand. I also have a real bad arthritis in my wrist that doesn't allow me to bend it much, and it hurts quite a bit. Also, I was attacked by a pit bull a while back which caused some nerve damage in that thumb, which makes it dumber than it was and sometimes move on it's own. Someday, I fear I will not be dexterous enough to use tools, but I will jump off that bridge when I come to it.

    2 Not allowed! Not allowed!
    It's weird, because it WAS working fine.....

  21. #21
    Supporting Member Randall's Avatar
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    "Edit: question! Is that the original spec OT? Is there any indication it came with a different one? It looks huge compared to the PT. Reason I ask is, mine is the same way. I looked into the Fender part numbers & found out mine crosses to a Twin Reverb OT; I then found a couple of the mounting holes on mine are off a fraction of an inch. Sure enough, I've got a matching loose TR OT at home with the same Fender part number. If so, that might also explain some of rhat bark."

    Justin, the no. is 022871, believe it is a stock Bassman OT.

    1 Not allowed! Not allowed!
    It's weird, because it WAS working fine.....

  22. #22
    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Randall View Post
    My left hand is toast. I played professionally since about 20 years old. Now I can barely make a few chords to test out an amp. I have a contracture syndrome in the fascia that impedes and mis-routes my tendons, and doesn't allow me fully open my hand. I also have a real bad arthritis in my wrist that doesn't allow me to bend it much, and it hurts quite a bit. Also, I was attacked by a pit bull a while back which caused some nerve damage in that thumb, which makes it dumber than it was and sometimes move on it's own. Someday, I fear I will not be dexterous enough to use tools, but I will jump off that bridge when I come to it.
    I can sympathize with tendon and arthritis trouble. Not to the degree you describe though. Also a couple of injuries and breaks here. Also some trouble manipulating tools in my day job due to pain and mobility issues. Really sorry to hear about it. But hey, we still have the creation of the tools used by players to have fun with for now The woods are lovely, dark and deep... But we don't get to be done until our destinies are fulfilled and we don't know what they are, so...

    1 Not allowed! Not allowed!
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

  23. #23
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    Fantastic work Randall. Wish I had 10% of your skills.

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    The only good solid state amp is a dead solid state amp. Unless it sounds really good, then its OK.

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