Hello Bill,
I have a Warrior that I refurbished and offer a few comments.
There is a reason the power transformer went south. They were too small
as was the choke. Removing both along with the 2.5V fil xfmr and the 866's
give lots of room for rework. While you are at it, pull the oil filled
filter cap as well. Now you can start from scratch and here is where you
have to make a choice; stay with 811's or go 572B's or should I say, stay
with 1500VDC or go to 2500VDC. Here are my thoughts on the subject..
The balance of the RF deck parts might (MIGHT) work ok on 2500VDC but if
not then more rework will be necessary.
If I stay with 1500VDC range of operation I can use EITHER tube and no
further tank circuit modifications will be necessary and as a bonus if I
choose to use 572B's I gain twice the plate dissipation per tube; great for
high duty modes like RTTY,SSTV,PSK31 etc. 800 watts peak out will be no
trouble for 4 572B's but pushing the max + out of 4 811A's with 65Watts of
plate dissipation each. (4 X 65 = 260 Watts + 800 = 1060 watts input. And
this assumes approx. 67% efficiency which is probably a little high. More
like 60 to 62% max. so the real PEP input is closer to 1200W.)
My recommendation is to stay with the 1500VDC range and use 572B's and
you will have a fairly conservative amp that is not as much work to get
going.
I used a transformer that I purchased on E-Bay that was rated at 750VAC
at 700ma. continuous as a voltage doubler with some new electrolytics and a
HD diode board and the no load is a bit high but put it under full tilt
boogie and it settles down nicely to the recommended range. Used a filament
transformer in reverse to provide the cut off bias and a separate filament
transformer for the tubes. Used the QSK system from Rich Measures so I have
both high speed and low switching current/voltage making the amp usable with
newer transceivers. (Real sweet using full qsk and a half gallon out during
a contest or chasing DX.) While you are at it, don't forget the glitch
resistor in the HV line and a protection diode across the meter. The best
$2.00 insurance you will ever buy especially if you blow the meter and try
to find another! (That cheep amp will start looking a lot more expensive!)
Cooling! The original fan is puny at best but remember, these tubes are
NOT forced air cooled, just circulated air cooled so yes, a good boxer type
fan is a good idea but make sure it can exit without much restriction as
those fans can't take much back pressure. Personally, I prefer to suck hot
air out rather than just stuff outside air in but you make your own
evaluation.
Money wise, here is how my amp turned out...
Original purchase price of Amp without case. $17.83 !!!
Ugly case that needs paint. $40
Paint, stripper, sandpaper etc. $20
Cooling fans $12
QSK system, suppressors, glitch parts= $60
4 New Chinese 811A tubes traded for 4 slightly used Cetron 572B $45
New plate choke, (just because) $4
New filter caps 6ea. 450MFD @ 450VDC $4ea = $24
HD diodes 8ea 1KV @ 6Amp w bleeders = $10
New power transformer and choke = $70
Misc. stuff $10
Grand total $312.83 for an amp that originally only cost me $17.83 !!!
and that does not include the human supplies like beverages/snacks necessary
for this project nor the time it took to acquire all the right parts to
finish an amp that has more invested in it than it is worth. It must be a
labor of love because it shure is not economical.
Satisfying, Yes.
Fun, Yes.
Worth it to not see a good piece of gear end up as scrap parts, Yep you bet.
Would I do it all over again if I could, Yep
Now if I could only come up with a couple of stripped out Dentron GLA-1000
or a MLA-2500B as cheeply as I got this Warrior, I would have my next
rebuild project waiting for me.
OH, BTW, anyone got a chimney for a 4-1000A cheep, they would like to see
go to a new home? Or maybe a filament transformer? ;>}
Good luck with your project Bill. Keep us posted with your results.
Best 73
Mike Baker K7DD
k7ddmjb@qwest.net
----- Original Message -----
From: "Bill Smith" <ko4nrbs@yahoo.com>
To: <amps@contesting.com>
Sent: Thursday, February 21, 2002 11:52 AM
Subject: [AMPS] HA-10 Conversion to 572B Tubes
>
> Just acquired (real cheap) a Heathkit HA-10 with a
> blown Plate transformer and no tubes. Everything else
> is in like new condition. Since the amp looks like
> new I'm thinking I should install a new Plate
> transformer of sufficient voltage and power
> capabilities to power up four new 572B tubes. This
> would increase the power out and I would gain some
> plate dissapation capibilities as well.
>
> Any thoughts?
> 73,
> bill
>
>
>
> =====
> Bill Smith KO4NR
>
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