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Post subject: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 1:34 pm
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I recently bought a 1967 Blackface Bassman head and cabinet with a pair of JBL D120F speakers.

When I got it home, I noticed a buzzing sound from the cabinet. At first I thought one or both of the JBLs may need re-coning, but after putting weight on the cabinet (by sitting on it while playing) the buzzing immediately stopped and the cab sounded great.

My friend and I looked at the speaker cones with a strong flashlight and found nothing wrong with them.

We then opened the back of the cab and noticed that the speakers were not tightly screwed to the baffles and the center baffle (separating the speakers) was lose as well.

We plan to take the speakers out and tighten all the baffles to the cabinet and re-install the speakers to the baffles. Since everything will be out of the cab, we're planning to rewire the speakers as well.

My question: Is there any Fender or other source material that tells us how the whole cabinet is put together at the factory? We want to make sure we do it to factory specs to avoid having to do it again any time soon.

Needless to say, any help, advice, or information is greatly appreciated.

Thanks...


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 2:59 pm
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The cabinet case is assembled via interlocking finger joints at the corners. The interior cleats are glued to the inner surfaces. The baffle board is secured to the front interior cleats with 1.75" #9 jackson-head philips screws and finishing washers. The interior partition is screwed to the baffle board at the front and held in position at the rear by the back panel screws.

Be sure to check that all of the cleats are still securely affixed to the inner walls of the case (re-glue and clamp until dry as necessary). Baffle screws should be torqued to 30 ft/lbs. Do not over-tighten the kep nuts holding the speakers to the baffle, and do not tighten them sequentially. Do one, skip four, do that one, then repeat until all fasteners are snug -- around 25 in/lbs (a quarter-turn more than finger tight) is sufficient. Use a minimum of AWG#18 for your speaker wire.

Best of luck, HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 3:28 pm
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Arjay,

Thank you for your detailed instructions.

We will confirm that the exterior case, including the interlocking finger joints, are secured.

We will then check all the interior cleats to make sure they are properly glued and secured and will proceed from there in the order you suggest.

With regards to the interior partition and the screws that secure it in front and back, are there glued guides on top and bottom of the case to prevent lateral movement?

And great advice regarding the order by which to screw the speakers to the baffle.

I will be sure to report our progress by early next week after we tackle this interesting project over the weekend.

Thanks again!!! :D


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 3:47 pm
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fendaholic wrote:
With regards to the interior partition and the screws that secure it in front and back, are there glued guides on top and bottom of the case to prevent lateral movement?


No. At the rear, the partition simply "floats" once the cab's back cover is removed. This is a design deficiency IMO and I correct it in my custom cab builds by attaching a stamped sheet-metal "T" bracket on the inside of the rear cleats, then screwing the tab to the brace affixed to the rear of the partitian. It's totally concealed once installed and adds some overall structural integrity to the enclosure.

Arjay

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Post subject: Re: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 4:23 pm
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Retroverbial wrote:
No. At the rear, the partition simply "floats" once the cab's back cover is removed. This is a design deficiency IMO


I agree with your opinion. When I saw the partition almost floating after removing the rear panel, I assumed there must have been a missing piece somewhere to give it more structural rigidity.

I'm trying to mentally picture how your sheet metal "T" bracket looks once installed, but am having a tough time with it.

Regardless, I agree with you that it's needed.

Thanks again...


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 5:11 pm
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Unfortunately, that seems to be one of the details that I overlooked when documenting my work. This crudely-modified pic should explain all......

Image

The blue "T" brackets are screwed to the reverse sides of the cleats and the center brace, thus rendering them invisible except under extremely close scrutiny. Note also that I use 1/2" MDF for the partition rather than the factory's choice of 1/4" plywood.

HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 10:20 pm
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That's some nice work there RJ.


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Wed Feb 16, 2011 11:02 pm
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Thanks for the kind words, RS.

Arjay

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Post subject: Re: My 1967 Bassman Cabinet
Posted: Thu Feb 17, 2011 10:59 am
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Arjay,

Thanks for the photograph. It gives me a much more clear view of what I need to do.

I'm not with my cab right now, but I'm pretty sure the partition in my cab is more like 1/2 to 3/4" plywood. I'll be sure to take photos when we work on it this weekend.

You've been terrific with your advice...Thank You!


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Thu Feb 17, 2011 11:48 am
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Indeed, 1/2" ply was a relatively common material for partitions as this pic of my '65 Dual Showman cab demonstrates......

Image

As the miserly CBS era wore ever on, this partition would later be reduced to 1/4" ply, then finally a microscopic piece of MDF.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Thu Feb 17, 2011 12:18 pm
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WOW! If I could make my cab look that good, I would be tempted to leave the back cover off just to show off!

YOU'RE GOOD!!!


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Post subject: Re: My 1967 Bassman Cabinet
Posted: Thu Feb 17, 2011 12:32 pm
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I didn't build this one, Carlos. It's an original, dated to July of '65. I did do a full cosmetic restoration on it though, then installed a pair of vintage (circa 1967) JBL D130Fs.

Here's how the entire set turned out......

Image

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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