[Amps] Fw: building amps.

[Jim Thomson]

Cecil Acuff wrote:
>>
>>  Of course the pole pigs are big and heavy, but there's no rule the
 transformer and PS has to be in the same cabinet.

##  Put the HV supply on the floor, where it belongs, or the bottom
of a small 19" rack.  If you do buy a new dahl/harbach xfmr, get LOTS
of taps. BTW, you can grab ANY 2 x sec taps.  My dahl is tapped for
0-2300-3900-4800-5200   I  was upset, cuz I forgot the 2900 tap. 
Well 5200-2300= 2900 !  Knowing that info.. I would carefully spec taps
Also, having a 220/240  or  230/240  pri is a great asset.   Then, between
pri and sec,  you have literally loads of combo's.  Buy one big xfmr, then you
can use it on ANY amp, with voltages  from A-Z.  A  46 lb hypersil  runs $400.00
which is what`s used in the alpha 77dx/sx.  Now  $400-$600  may seem like
a lot of $$,  but it's the most important part of the amp !  power starts  with the
xfmr.  $400-$600 is cheap.. compared to the $8-9K   alpha wants  for the same thing.

##  you can always get all your money back on a dahl xfmr, and then some... or
just pass it on from father to son. 

##  I paid $75.00  for  my 10 kva  4160/4800  hypersil pole pig, 120 lbs, just
under 1 cubic foot.  You just can't blow it up.

## arnold howell, from howell tube sales has access to a LOT of pole pigs.
Smallest ones are 5 kva.  He also has 2 x doz  YC-156's [ youngstown ohio]  



>
> -----------------
>> But lets say you have access to one of those ultra linear 3CX or
>> 3CPX5000 pulls with fantastic IM in the minus 50 db range,  that can
>> comfortably run the legal limit using all of the drive from your 100
>> watt exciter.

## Roger.  with 100 w of drive... you will send a YC-156 way over 1.5 kw
maybe 25-40w max. 



> ----------------------------
>
> Can someone provide sourcing info on reliable, reasonably priced pulls 
> for home builders to build with?

##  www.ctrsurplus.com   YC-156's   $125.00   [419] 683-3535
if u dilly dawdle, you will lose out.. and probably have by now. 




> Would love to buy a couple Triodes that don't require sockets.  Would 
> even consider tetrodes.

  Another place 
would be http://www.wa8wzg.net/forsale.htm which has been posted before. 

## he's good too. 


>
>> Winding the tank coils is easy, but may require sacrificing some copper
>> tubing while learning, or you can find some one who is good at winding
>> coils.  Given the plate impedance, you should be able to find a design
>> to copy which makes placing the taps on the coils much easier.  Also
>> good hefty toroids for the 160 and 75 meter bands is now the way to go.

##  I'd dump any notion of using torroids on a HB amp.  They  run way too hot
and u have plenty of room.   I have not wrecked a tubing coil..yet.  Tubing comes in
15-25-50' rolls.   They are very easy to wind.. and silver plate  with cool-amp. 

## Most of us use GM3SEK's  PI  spead sheet.  Then u can design the entire
amp in abt 1/2 hr flat.   I use a B+k  875-B  [ mouser]  to dial in the taps..
dead on the 1st time around.  u want 2.6 uh.... well the meter reads down to .1uh
Toss the GDO, it's useless for taps.  


>
> > What about no band switch and no tapped tank....just a large edge 
> wound roller inductor? 

##  I use a new RI-40  from SSON.  $245.00  on my  3CX-3000A7
0-40 uh, tapered pitch at one end, and uses 3/8" edge wound silver
plated ribbon, .072" thick.  4 x gold plated contacts, [2 x per side]
pinch the ribbon.  It's  built like  a tank, no torroids required. 
Handles  5kw+.   Just elevate it off the chassis by 2-4" 



 and at least one of them is 
almost sure to hit one of the resonances for the plate choke.

## Use the rf parts/ameritron choke, or the alpha choke.



> bit more expensive but time and loss of materials to trial and error 
> are expensive too.
##say what ? 




When you take into account the cost of a custom band switch and the time 
to get the taps correct

##  It takes literally 5 mins to get all the taps correct.. and that's if ur
slow.  The lcr meter makes short work of taps.  It's ur #1 tool !!!! 
You are dead with out it.   The 875-B and other's  will read down to
.1 pf.... and  .1uh 

>
> > I have been inspired by the posts of the last several weeks...
Now that I'm really glad to hear.
> to the point where I started looking for suitable cabinetry for 
> building.  Purchased two 19" rack mounted chassis that had contained 
> 900Mhz radio transceiver systems from work.  Should make excellent 
> cabinets for home amp projects.  All aluminum, probably 18" tall and 
> 24" deep.  Will require some work to add and remove some internal 
> compartments but good starts for $25.00.

##  Good.  perfect size. 


Remember too, that with an amp look carefully at how the commercial amps 
are constructed. Most are of a modular construction with a single bottom 
plate instead of building on the old 14" X 18" X 3" chassis like we used 
to do.

## IMO, don't even try copying the no chassis  route.  I'll take a 
hb  17"  x 18" deep  x 4-5"  tall  chassis  any day.  Input and
tuned input  below chassis.. all output kw stuff above chassis.
Put the B+ supply in a separate box.. on casters... on the floor,
where it belongs.  Or use a 4'  tall rack.. with Rf deck at top,
HV supply at the bottom, use casters.  


You might even want to build some metal working tools such as a metal 
brake.
##  I make all the chassis  from flat panels.. all joined with 1" x 1"
angle AL.  Any panel can be removed, or replaced,[ if u wreck one]
.... and put into the drill press, and drilled  from either inside or outside
 etc, then re-installed.   You can even use an old chassis and put a
 clean new AL plate on top,covering all the old holes.
I get all the al flat plates  chopped to my specs.. at local sheet
metal shop. both the plates and the 1"  x 1" are all  1/8" thick 6061-T6.
Easy to drill, cut, etc.  Greenlee now makes combo drill+tap... super fast
to now tap a hole.. all in one motion.   Use SS hardware.  

##  stick the $125.00 YC-156 in there.[ + mating pole pig]
... and a  smile  will come across your face when you realize you just
beat alpha, etc.. at their own game.
The  YC-156  will make the $9K  alpha  look like a sick puppy.  It will
make 4 of em look like sick puppies.  

Jim   VE7RF