[AMPS] The things you see Homebrew Amplifiers

[William L. Fuqua III]

   Just bought a HB amplifier. A pair of 4-400 in GG.
It looks very nice but a few things I see need to be changed.
This one is just fine except for the following:

1. Clip on plate caps of the type usually used with 807's.
   You would think a pair of 4-400s would
   have plate caps with fins. 

2.Tubes are fan cooled on the side and I see nothing providing air 
  flow thru the bases.

3. BC-375 tuning unit band switch. This was used in a 100W transmitter.

4. No internal shielding. Just a slide on cabinet cover held with
   6 screws.

There may be a reason for #1 and #2. It may have been built for 
a pair of 3-500Zs and there is not much head room for the 4-400As.

I have seen worse. I bought a 4-400A amp  at Dayton some years ago.
It had a vacuum tuning cap grounded to the front panel, no shielding,
fuse clips on the plates and lots of bad solder joints etc.
I got it for parts. Came with 4 tubes, 2 dow-key relays, and 500pf
vacuum cap. and heavy power transformer for $100.
All the tubes were good when I checked them.

I have seen the BC-375 Band switches used in a number of homebrew
amplifiers. I would expect them to fail after a while. What do you
think?
  The absolute worst I've seen was a grounded grid 304TH not a TL. Built on
the lid
removed from an Atwater Kent receiver. Single band "75M" and no shielding,
bad solder joints. The socket was made of plexiglass with
set screws for the pens and and theres exposed HV everywhere.
 I got it for the tube for about $20. 

73
Bill wa4lav

  William L. Fuqua III  P.E.  E-mail WLFUQU00@POP.UKY.EDU  Phone (606) 257-4155
  Department of Physics and Astronomy      CP-177 Chem. Phys. Bldg.  
  University of Kentucky ,                 Lexington, Ky 40506-0055
 
  


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