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HF homebrew tube amp photo build

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  #21  
Old 10-02-2009, 01:17 PM
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looking real good! but you will only be able to see the glow from the top
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  #22  
Old 10-02-2009, 01:29 PM
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Originally Posted by linearone View Post
looking real good! but you will only be able to see the glow from the top
Got to do something about that!
The top opens like a door. I am going to cut the part out over the tubes and put mesh over it. Get that heat out and watch the glow.

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  #23  
Old 10-02-2009, 03:04 PM
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Looks like you are off to a good start. I am working nights tonight and tomorrow night with Sunday off (sleep day) and then back to work on Monday and Tuesday which is off my normal shift rotation but it enabled me to get nine days off in a row so I hope to get a few things started myself. I need to get some things done around the yard and put up an antenna but hopefully I can get some chassis work done. I have an old cabinet that was originally a frequency meter I think. It's about 17w X 9½h X 12d and needs a couple holes filled,sanded and a fresh coat of paint. The front panel has rack handles and will actually bolt to the homemade chassis allowing the entire innerds to be slid out for ease of service. I'll get some pix up early next week after I get a chance to tell night from day. On a side note,I just found out my planned 2000pf loading capacitor is about ½ inch too long to fit. Time to hit the junque box. I prefer to spell it "junque" and not "junk" because it is a higher class of junk.
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  #24  
Old 10-02-2009, 04:13 PM
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Hey I love junque!

Know what you mean about the night shift. Did that for 4 years. Been back on days for a little over 2 years now.

Cant wait to see you get started on yours. But I know how times is.

Paint
Going to paint the chassis with Walmart special. The paint is made by Rustoleum. It is called "Hammered" and leaves a great looking finish. They have it in many colors.
You you paint the inside of the tube compartment, (and I suggest you do) paint it with a flat color. This will keep the filaments from reflecting off the tube compartment and creating more heat. With 3-500's this is a must.


Transformer.
I am going through transformers to see what I can use. I have to look closer and see what the 811A and 572B likes. One transformer I have came from a Pride DX300. I believe this is 2000 volts after filter and rectifying.
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Old 10-02-2009, 06:14 PM
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Quote:
Originally Posted by QRN View Post
Looks like you are off to a good start. I am working nights tonight and tomorrow night with Sunday off (sleep day) and then back to work on Monday and Tuesday which is off my normal shift rotation but it enabled me to get nine days off in a row so I hope to get a few things started myself. I need to get some things done around the yard and put up an antenna but hopefully I can get some chassis work done. I have an old cabinet that was originally a frequency meter I think. It's about 17w X 9½h X 12d and needs a couple holes filled,sanded and a fresh coat of paint. The front panel has rack handles and will actually bolt to the homemade chassis allowing the entire innerds to be slid out for ease of service. I'll get some pix up early next week after I get a chance to tell night from day. On a side note,I just found out my planned 2000pf loading capacitor is about ½ inch too long to fit. Time to hit the junque box. I prefer to spell it "junque" and not "junk" because it is a higher class of junk.
why not just un do it and shorten it? it can be done kinda easy if you are careful. it takes loads of time though
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  #26  
Old 10-03-2009, 07:17 AM
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Originally Posted by linearone View Post
why not just un do it and shorten it? it can be done kinda easy if you are careful. it takes loads of time though
I thought of that but this one is a tough one. It has ceramic insulators running the length of it.It's actually two 1000pF caps laid end to end on a common frame.It would involve cutting two pieces of ceramic as well as three brass rods that run the length of it. I'll post some pix in a couple days,after the night shifts end and you will see what I mean.
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Old 10-03-2009, 07:24 AM
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Originally Posted by Radio Tech View Post
Paint
Going to paint the chassis with Walmart special. The paint is made by Rustoleum. It is called "Hammered" and leaves a great looking finish. They have it in many colors.
You you paint the inside of the tube compartment, (and I suggest you do) paint it with a flat color. This will keep the filaments from reflecting off the tube compartment and creating more heat. With 3-500's this is a must.

GREAT! Now you are going to make me look like a copycat! I must state that I have already painted the large 42 inch cabinet for the 3-500 amp with Walmart Hammertone black and will be doing the same on the 572B cabinet. BTW, a good paint for the inside is also available from Wally Mart.I used, and will be again, their "textured" black paint for outdoor metal furniture. It is flat black with a somewhat rough finish which is rougher than just a flat paint but not pebbled like that rocky texture stuff. I figure my amp will be hammertone black on the outside,textured flat black on the inside and the front panel will probably be gray hammertone or another shade of gray.I have a couple to choose from.
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  #28  
Old 10-03-2009, 08:57 AM
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Originally Posted by QRN View Post
GREAT! Now you are going to make me look like a copycat! I must state that I have already painted the large 42 inch cabinet for the 3-500 amp with Walmart Hammertone black and will be doing the same on the 572B cabinet. BTW, a good paint for the inside is also available from Wally Mart.I used, and will be again, their "textured" black paint for outdoor metal furniture. It is flat black with a somewhat rough finish which is rougher than just a flat paint but not pebbled like that rocky texture stuff. I figure my amp will be hammertone black on the outside,textured flat black on the inside and the front panel will probably be gray hammertone or another shade of gray.I have a couple to choose from.

Well you know what they say, great minds think alike
I love those Wal-Mart paints. Great for covering lousy prep work like grind marks and so on. Plus gives the finish character!
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  #29  
Old 10-03-2009, 02:39 PM
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Originally Posted by Radio Tech View Post
Well you know what they say, great minds think alike
I love those Wal-Mart paints. Great for covering lousy prep work like grind marks and so on. Plus gives the finish character!

That's exactlythe reason I chose the hammertone paint, to hide all the little imperfections.
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  #30  
Old 10-03-2009, 03:14 PM
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Quote:
Originally Posted by QRN View Post
That's exactlythe reason I chose the hammertone paint, to hide all the little imperfections.

That stuff works wonders and goes on al my restorations



Ok, The circuit.
If anyone wants to see a what this amplifier circuit looks like, this one will be close as you can get.
http://jlandrigan.com/files/DX-811A%...0Amplifier.pdf

This was in CQ Magazine September 1982.
Although it will differ to some extent.

I been going through transformers today.
Not having much luck. One transfomer I have came out of a Pride DX300. By the time this is rectified and filtered it will be around 2400 volts. Now that may be a proble for the 811A tubes! But this is with no load.
The 811A as I have read likes about 15 to 17 hundred volts. The transfomer under load should drop to 1800 volts @ 500ma (If I done my math right).117VAC @ 10 amps gives 1800VAC out.

Two disavantages are no CT on the secondary and no 240 input on primary.
So with 120VAC in, voltage drop across the supply, and the ground of the bridge recitifier on the TX relay, no voltage present in the stand-by mode.

I have to think about this more.
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