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My DIY HK Citation II Cage

bryans12v

bryans12v

Marantz / Altec Junkie
Subscriber
Posted some images in another thread in the tube forum but figured I'd start my own with some recent pics of a semi finished product. Still waiting on the post clips which should be here Monday.

Story is.. I picked up a really nice II sometime last year. Since then I've been able to get all the Jim Mcshane mods done and find myself using it a lot more since doing them. It's dead quiet and really packs a punch now. Anywho.. My main listening area is the family room (for now as I'm finishing my basement finally) and i have 2 kids; a very wild 8 year old boy and an 18 month old curious girl. I'd always come home to find fingerprints on my tubes, the 12BY7A tubes bent in every direction, etc. I new I needed a cage and soon and finding one is tougher than biting through steel.

Well, I decided to pickup a pan brake and make one myself. Surprised really on how it easy it is to physically make one. Just a couple bends really. Here are some pics of the progress.

The brake and perf both arrived last Friday. Perfect timing!
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Did a quick doodle to get some metal cut up.
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Couple bends later..
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Test fitting side panels..
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Side panels tacked on..
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Test fitting was a success!
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At this point I knew had to do something with the spot weld dimples. My original plan was to pop in some short welds to fill them and then file and sand but unwanted to take a more delicate approach and didnt want to heat the side panels anymore that I did with the spot welder as its 22 guage and prone to warping when not head uniformly.

I tried a something for the first time in my 40 years alive. Bondo. Yes, I know this stuff is frowned upon. This particular 3M product has steel powder in it and was a pleasure to work with. Easy to apply/sand and is very forgiving. The applied layer is very thin. I seriously doubt any heat from the tubes (which mostly rises) will have any bearing on this product whatsoever.

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Got the cage primed yesterday.

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Shot in gloss black last night
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Looks great so far!
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Now the real fun begins. I'm going to make another. This first one came out good but can definately be improved upon. I plan in making the bends tighter on the sides so the steel side can sit in a bit closer. Where the front panel bends in, I can get the tolerances a little tighter by using the band saw and not the shears.

This is the area I'm referring to.
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I'd also like to use a perf with an open area more similar to the original. The originals use a 6x6 mesh, 0.063mm wire diameter with an open area of around 39%. The perf I used is a 4x4 mesh with an open area of 64%. While this will aid in convection around the KT88s, it's not like the original.

I wasnt planning on making another and originally just wanted anything worthy to protect my tubes, I now see how easy it is to make and feel more at ease giving it another go. I'm also considering making one that has a step in it about the driver tubes!
 
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Now THAT is a good look!

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It's a little hard to see from the angle, but if the step is closer to the front of the amp, there would be a little more room around the 6550's
 
s-petersen said:
It's a little hard to see from the angle, but if the step is closer to the front of the amp, there would be a little more room around the 6550's
Click to expand...

Thanks for the tip. I did consider that as well but with the open area of this perf, I dont see it being an issue. The reason I started with the bends here were because they are split up evenly. 2 5/8" rises and 3" flats so its symmetrical. At this point though, it's all still experimental.
 
Made some more progress in between other projects going on at the moment. Was able to get the side panels cut, bent and tacked on. This one is much more time consuming than the first one.

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BillWojo said:
I don't know where you get your perf from but McNichols is the go to place. Nice work by the way!

BillWojo
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That's where I get it! Great service too. About a week after my first order arrived, they sent me a catalog that has a lot more stuff in it that I couldn't find on thier site.
 
Great! I was hoping you didn't overpay and get it from some other supplier. I'm sure even McMaster Carr gets it there. I work in the metal service industry and several company's I service supply McMaster as well.

BillWojo
 
s-petersen said:
It's a little hard to see from the angle, but if the step is closer to the front of the amp, there would be a little more room around the 6550's
Click to expand...

Did a test fit and seems we've got plenty-o-room around the output tubes. I really like this stepped cage. I'm thinking of maybe painting this one brown to match the chassis. :dunno:20200517_181316.jpg 20200517_181255.jpg 20200517_181303.jpg 20200517_181223.jpg 20200517_181132.jpg
 
bryans12v said:
My main listening area is the family room (for now as I'm finishing my basement finally) and i have 2 kids; a very wild 8 year old boy and an 18 month old curious girl. I'd always come home to find fingerprints on my tubes, the 12BY7A tubes bent in every direction, etc.
Click to expand...
Nice job. I think you took the right approach with this project. The alternative - making a cage for the kids - might have been frowned upon :rflmao:
 
bryans12v said:
Cheap little harbor freight job. As long as you keep the tips aligned and clean on them they do well with small guage stuff for the price.
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Well,I don't know if you can find them in that style or size,but there are "tip-caps" available for spot-welding tips that will give you a flat,larger diameter tip surface on one tip to allow you to do the type of work you are doing without leaving a dimple on the visible or cosmetic side of the part. In manufacturing, these even saved us the effort of finish sanding before paint.

I'm used to having access to industrial machines with an entire cabinet full of every tip imaginable,so I'm kinda spoiled rotten when it comes to spotwelding,haha. That,and my ex ran the spotwelding dept:rolleyes:

EDIT: I have a pair of McIntosh MC-240s and a first edition MC-275. Methinks I may do some mock-ups to see how your design would look on these.....
 
If you are inclined to make a few more I too have a HK CII that's missing the Tube Cage; would gladly pay to have the standard square repro cage made for it.
 
Looks awesome. What perforated steel are you using? Have you compared it to an original? I am in need of a cage as well and could easily make one but haven't seen a real one up close.
 
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