--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:
For the price they charge for the suckers, they out to gold plate
them too!
Don't be blinded by all the Dahl-Hipersil hoopla, there's a few
other very good companies who make some gem dandy transformers, and
for a way better price. I'll dig up a couple of address for you
later today.
### someone listed on 'amp's.. think it was Johm Lyles... about
15 x diff xfmr makers in the USA. Someone got a cheap quote
from 'magcapengineering' xfmrs.... about $100.00 less than the
Dahl.... then we he got it.... found that the DC secondary
resistance was 65 ohms !! [ 5-10 ohms is more like it.] Use
a large C input filter... and the V reg sucked... the high peak
currents will cook the cheaper xfmr's. Rich claims the Dahl's
will do about 4 x their rating on ssb.
One in Canada who makes the ones for Ten-Tec.
### Hope it's not Hammond. Hammond makes superb stuff....
however.. they don't have a clue as to how to build Hypersil
anything... just standard EI stuff. Hammomnd thinks the way to
build a plate xfmr is to center tap it. All their plate xfmrs were
known as 'high reactance types'... all had center taps... and all
were made for tube rectifiers... and choke input.
## Hammond does make superb EI custom fil xfmrs. Also their
7.5v-21 A and 5v-30A are dirt cheap. [$40.00 US funds]... run
barely luke warm... but only come with 115 V primarys.
There's one in Kentucky, that does a really good job, but I can't
remember the name without looking it up. Another is Galaxy
Transformer who makes some big ones for a builder down in Florida.
If you get a chance, ask Hal Mandel about a dealing he has with
Dahl on a custom transformer. It made me wonder who they had there
designing them.
### Dahl and some engineers do it themselves. IF u just take his
standard 45-65-127-253-440 lb cores.... and specify the sec taps u
want... they always turn out great. The primarys are all wound
the same with the +10 0 -10.... 208....240 set up.
### Primary KVA = DC input x 1.22 That allows 11% for power
factor... and 10% for core losses. His CCS ratings are based
on a 50 deg C temp rise over ambient. I have seen several...
almost all vault transformers where the temp rise spec is sky
high... typ as much as 155 deg C.[over ambient] Why they run
em so hot is beyond me. Power co's do the same thing with
pole pigs... they run em hot. Ever wonder how a 50 KVA xfmr
can run 16 x homes...all with "200 A" service ?? There is
hardly any oil in em either.... the oil is just to transfer heat
to the outside case [I suspect the cases are aluminium..never
seen rust on em]... and keep moisture out during storage.
If things work out, I'll be doing a few C-cores up to 3 kVA output
(1.5 kVA input) for a few friends. I just got an e-mail back from
the core supplier today.
### How do u propose to get 3 kva output.... with only 1.5 kva
input ??? U need loads of square/rectangular wire to wind
em.... no round wire is used in any dahl's...other wise u end up
with too many air gaps between turns....and more chance of
corona.
### Back in the 'old days' pumping dahl's with silicone
varnish glop was an option.... and several of the ones that didn't
pay for the option....and stored em in damp locations... had em
short out, etc. Corona is bad news.
I'd be interested in these other xfmr builder's specs.
Later......Jim VE7RF
