>
>
>
>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.
If there is no air space, there would be a pressure problem when a
sealed, oil-filled transformer is hot.
>>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.
agreed
>If so it MAY have a fairly large internal
>impedence which would translate to poor regulation when used with a
>capacitive only filter.
Amen. A quick test is to short the primary with a clip lead and measure
the secondary winding resistance. On my Web site, in "Amplifiers" there
are simplified approximation formulas for determining the likely under
load DC output voltage using capacitive filtering with a FWB or FWD.
Rich. Measures.,www.vcnet.com/measures, 805.386.3734
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