[Amps] AL-1500 pi-network capabilities

[Rob Atkinson, K5UJ]

Hi Will,

thanks very much for these observations.  I apologize for not giving more 
information.  I naively thought the photos would be enough.  interesting 
what you said about the low frequency coil, as I have heard that having it 
wound on a solid cylinder form may be a problem (heat buildup?).
I wish I had one of the original h.v. transformers.  I would be glad to send 
it to you but I guess the shop kept it.  your comments about coil tube 
thickness and plating very interesting also.
Why don't these amp manufacturers just bite the bullet and make us an amp 
with the needed monster coils?  I don't care about having a compact amp.  I 
want an amp that works well.  If it is the size of a chest of drawers so be 
it.  Where did this mania for having everything smashed into a tiny cabinet 
come from anyway?  Some of these 1.5 kw amps being made today (i won't name 
names) are incredibly small for the p.e.p.  okay, end of rant.  The 
relationship between Q and tarnishing I did not know about.  I guess 
aluminum tube coils are not an option for some reason or surely they would 
be used.

73,
Rob/K5UJ


<<<Rob,
It's hard to tell the exact rating of the transformer. He gives a weight
of 32 pounds, but that's total weight including the coil. I just figured
a core for an op the other day to fit an Alpha 76 he was overhauling.
The core weight came to 24 pounds for a rating of 2400 Vdc under load at
800 milliamperes. The total weight would have been more than this. This
would have had about a 2800 Vdc OCV value. This was to run a pair of
3CPX800A7's.

In order to determine what they done, I would need to know the physical
core size so I could figure the area of the central core itself. In this
design, it is known as a "shell core" using two C-cores to make it up.
This is the preferred way to emulate an EI core. Now it said it would
produce 3200 Vdc which would probably sag to about 2800 Vdc under load.
On 10 meters, it look like it was running 800 milliamperes of plate
current. 800 mA would require a wire size of 22 gauge wire in the HV
secondary and about 12 gauge wire in the 240 Vac primary. The problem
is, even though the core could be sized right, or even over-sized, they
could have skimped on the wire size. In amateur service, running ICAS, I
recommend running the wire size at 750 circular mils per amp. However, I
have seen some running it from 300 to 500.

If I had a transformer to autopsy, and find out all these details, I
could tell how many watts it was good for. Or, if somebody could take
these measurements, it can be reverse engineered easily. Weight can tell
you something, but not everything.

The tank capacitors has to be rated by their air gap. I can't see any
part numbers to convert into a size. The capacitors usually have their
air gap in the part number someway. These capacitors look like Oren
Elliot M-73 capacitors. The part number would be stamped on the back end
bell of the cap itself. The 10 meter tank coil looks like it's made with
either 3/16" or 1/4" plated copper tubing. The lower freq. coil looks to
be either 12-14 gauge plated wire. It also looked like it had been hot
in one of the pictures up torward the top of the coil.;

http://www.hamradiomarket.com/Articles/Ten%20Tec%20Centurion%20Images/422010.jpg

If I had the air gap on those caps, I could tell you in about 5 seconds
what their rating was.

Will Matney


Not to digress (too much), but the comments on the SB220 tank and power 
handling and the AL-1500 tank being similar but for over 2 kw caused be to 
go back and take a look at some on-line photos of the Centurion innards:

http://www.hamradiomarket.com/Articles/Ten%20Tec%20Centurion%20Images/422010.jpg

here's one that gives some scale:

http://www.hamradiomarket.com/Articles/Ten%20Tec%20Centurion%20Images/422020.jpg

Any comments as to their power handling capability?


also,
stock fan arrangement:
http://www.hamradiomarket.com/Articles/Ten%20Tec%20Centurion%20Images/42207.jpg

stock h.v. xformer:
http://www.hamradiomarket.com/Articles/Ten%20Tec%20Centurion%20Images/42209.jpg


tnx
rob/k5uj>>>

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