[Amps] 4K Ultra Restoration

[HAROLD B MANDEL]

Bob,

Go for the D7 tube right away.

You're going to have to completely strip the chassis anyway, right?

I'm working on an old Alpha 76a for my hotel room station. The first
thing was to strip everything right out of the chassis.

The variable caps are going into the sink to soak the tar off the plates
as nicotine is a dielectric.

In restoring or refurbishing an old amp you will derive that much
more pleasure in knowing you gutted it completely, and
held every assembly in your hands, inspecting, cleaning,
repairing, replacing as necessary.

An old 8877 is still big bucks. You never know what's going to 
happen if you don't send it to Zonem Industries out there for
a load test.

For that money, you can budget in the cost of a socket and
appurtenances for the D7. The filament tranny will be a bruiser,
but the first time she makes output power and them needles climb the
scales
you will feel it in your bones.

It's like taking a Harley down the road after you've held the motor
parts,
gauging thicknesses of thrust washers and cross-hatching the cylinder
walls. You won't know if it's going to run or blow up if you don't
twist the throttle.

Hal
W4HBM


On Sun, 4 Dec 2005 00:34:08 -0500 "Bob Maser" <bmaser at tampabay.rr.com>
writes:
> Well, I found a 4K Ultra, brought it home, and started to clean up 
> the years 
> of cigarette tar that this amp had been subjected to.  Not a pretty 
> sight 
> but fixable.  My first surprise was finding that some previous owner 
> had 
> replaced the original 240VAC blower with a pair of 115VAC muffin 
> fans 
> connected in series.  Does anyone out there have a blower that will 
> fit? 
> Can someone tell me what was the original blower used in the 4KU?  
> Looking 
> at the Grainger catalog, it looks like the only one they sell that 
> could 
> possibly work is the Dayton 4C869, which is 230VAC @ 1600 RPM but 
> I'm not 
> sure of the opening size match.
> 
> Also, I pulled out the 8877 and I believe it is the original.  It 
> has what I 
> think is a date code printed on the top of the anode cap "7707" and 
> I assume 
> that this is from the 7th week of 1977.  It may be older than the 
> amp 
> because the amp uses a ceramic 2000pf Jennings cap in C2, which I 
> understand 
> was glass when the amp was first introduced in 1971 and later on 
> they 
> started using the more modern ceramic cap.  My amp does not have a 
> serial 
> number label so I don't know how old it really is.  I haven't gotten 
> the RF 
> deck off the cabinet yet so I don't know how many surprises are 
> under there. 
> The amp was operational when I first saw it about a month ago 
> although it 
> took about 100W to get 1500W out of it so I am going to have to 
> replace the 
> 8877.  Anyone have one for sale at a reasonable price?  Ultimately I 
> am 
> planning on installing the new Eimac 3CX1500D7 but for now I just 
> want to 
> clean it up let it make RF.
> 
> Help is appreciated,
> Bob Maser  W6TR
> Valrico, FL
> 
> 
> 
> 
> Bob 
> 
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Harold Mandel
Superintendent of Construction
Baran Telecom Inc.
606 - 205 - 0172
hmandel at barantelecom.com