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Old 2nd September 2007, 11:21 PM   #1
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Default Transformer - mystery VA

I bought a pair of surplus transformers custom manufactured by Toroid for a local company. The (custom)part number does not jive with the standard part numbering/ID scheme which would normally indicate primary/secondary configuration, secondary voltage and VA rating.
Hand-written labels on tape identified the units as 20V, 100VA and as they are equipped with single secondaries, I used a pair for my first IGC. Quite impressed with the performance and having a few more chips to play with, I returned to my "dealer" and carried 10 more units home @ $10 ea.
I don't seem to have adequate power resistors on hand to properly test these things, but based on size/weight, I'm guessing that the units are indeed ~200VA.
Weight- ~5 lb
Dims- 1 3/8" x 5"

Does this sound about right to those in the know?

thanks
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Old 2nd September 2007, 11:30 PM   #2
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My rough rule of thumb for toroidals is 1 kilo per 100VA, so that looks about right to me. Good deal.
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Old 3rd September 2007, 12:30 AM   #3
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Thanks for confirming Pinkmouse!
I weighed them @ 4.5 lbs ea
Having twice the power that I had counted on may well effect my project list...


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Old 4th September 2007, 12:14 PM   #4
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Quote:
Hand-written labels on tape identified the units as 20V, 100VA
Contradictory situation.
The label says 100VA, yet you want it to be 200VA.
I guess you won't know for sure until the fat lady sings.
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Old 4th September 2007, 06:20 PM   #5
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Yeah, the fat lady is warming up...
The garage sale style labels and the physical dimensions appear to tell two separate stories. No worries though as my next two quickie projects are two channel GainClones which run happily on these trafos. I'll run a load test BEFORE I make any plans requiring more power


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Old 5th September 2007, 04:50 AM   #6
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The rule of thumb i've heard is 20VA per pound for EI. Toroid is likely a bit higher, so that jives with the labels.

dave
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Old 5th September 2007, 04:23 PM   #7
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I found a size/weight chart on toroids site...
toroid
... seems to jive with PinkMouse's observations.


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Old 5th September 2007, 04:38 PM   #8
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Hi,
if they got the VA wrong, could they also have got the voltage wrong?

Measure the voltage before you connect smoothing caps and/or rectifiers.

Measure the assembled PSU before connecting the amplifiers.
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Old 5th September 2007, 04:58 PM   #9
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Quote:
Originally posted by planet10
The rule of thumb i've heard is 20VA per pound for EI. Toroid is likely a bit higher, so that jives with the labels.

dave

I've got a 300VA EI, it's certainly not 15 Lbs. More like 5 lBs. I've got 50VA EI's that that are less than a pound.
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Old 5th September 2007, 05:20 PM   #10
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Thanks guys...
I called Toroid but the girl I spoke to couldn't find the specs for this custom part number as it is at least 3 years old. Testing to come.
Andrew,
126 Volt mains yield 23.6VAC(no-load), 30.6 VDC after rectifier/smoothing caps. I've had a pair of these running a 3875 Inverted GC for about 2 weeks. Cool and quiet.


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