On Tue, 01 Dec 1998 03:59:37 GMT kf4kl@ipass.net (Doug Hall) writes:
>
>Hi all,
>Recently I started a search for a reasonably priced amp that would
>perform well in RTTY contests. During that time I've stumbled across
>enough parts that I've decided to build an amp. So far I'm having a
>good time & learning a lot. I may not end up with the ultimate RTTY
>amp, but it's cheap education & keeps me off the streets. Presently
>I'm working on the power supply.
>
>I've acquired a transformer that I'd like to use, but I'd like an
>opinion regarding it. It's an old girl, but it works, and the price
>was right (free). It was made by Union Electric & Mfg. Co. (part no.
>TF4RX02YY), has a 220v primary (0/207/220/235?) and a 2800-0-2800v
>secondary. It weighs about 60 lbs, and I'm pretty sure it's got oil
>inside it. Nothing is leaking, but when I picked it up to weigh it I
>could hear some liquid sloshing around inside it. Anyway, here's the
>sticky part - the current rating on the side of the transformer says
>530 mA DC. The amp I want to build will require about 600 mA from the
>B+ supply. My question is this: Does anyone know if the 530 mA rating
>is a CCS rating? Is it a conservative figure?
That sounds as if it may be an old clunker designed for tube rectifiers
and a choke input filter. If so it MAY have a fairly large internal
impedence which would translate to poor regulation when used with a
capacitive only filter. A dynamic load test would be the answer and I
would also warrant a guess that the ratings are a conservative CCS.
>
>I also got a 16 uF 7500vdc oil-filled capacitor. It's nearly as big as
>the transformer. Is there any reason not to use it?
None as long as its not leaking or shorted.
What problems to
>oil-filled caps suffer from?
Liberal media hype mainly. Just keep the insulator area clean to prevent
corona, etc.
I brought the PS up on a variac and
>everythig looked OK at approx. 4000vdc, but I haven't done any load
>tests yet.
Thats a good start
Partly because I have no way to do any load tests yet.
Do it
>
>I've also collected a number of parts for the RF deck (pair of
>4-400A's, yeah, I know, there are better tubes, but I got 4 of them,
>including 2 NOS Eimacs, for next to nothing.) I should be able to get
>close to a KW out of them, I'd think. I'll save the RF deck questions
>for another time.
Nothing wrong with them but at that Ep you better figure on 800ma + for
the pair fully loaded on CW. That xfmr should still be OK on RTTY if you
back the exciter drive down a bit.
Figure on around 1800W out on CW with good tubes at that Ep if the
regulation is decent...3500V under load.
73 Carl KM1H
>
>Thanks & 73,
>Doug, KF4KL
>
>
>--
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>
>
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