Hi:
I have a pair of UTC transformers marked FH-757 and North Atlantic 202348.
I found an expired auction on eBay for UTC LH-519 transformers that also displayed North Atlantic 202348 so I know they're equivalent.
They are marked 10k ct: 5k ct, 50 cps - 20 kc, 0.13W
I'm curious if these might be usable as tube/valve interstage transformers, and if so, what kind of DC current would be reasonable.
I found a schematic for the North Atlantic Instrument they were used in and they were used in a (solid-state) phase angle voltmeter, so I cannot infer what kind of DC current they might tolerate, or make too many analogies to tube circuits.
P=E^2/R for 10k and 130 mW = 36 v...not too encouraging, but I don't know what the power rating context was.
Thanks for your thoughts.
Murray
I have a pair of UTC transformers marked FH-757 and North Atlantic 202348.
I found an expired auction on eBay for UTC LH-519 transformers that also displayed North Atlantic 202348 so I know they're equivalent.
They are marked 10k ct: 5k ct, 50 cps - 20 kc, 0.13W
I'm curious if these might be usable as tube/valve interstage transformers, and if so, what kind of DC current would be reasonable.
I found a schematic for the North Atlantic Instrument they were used in and they were used in a (solid-state) phase angle voltmeter, so I cannot infer what kind of DC current they might tolerate, or make too many analogies to tube circuits.
P=E^2/R for 10k and 130 mW = 36 v...not too encouraging, but I don't know what the power rating context was.
Thanks for your thoughts.
Murray
I'm trying a pair of these as I/V converters in a CS4397 DAC project. So far they are pretty good - no measurements yet but the system is built and I'm comparing them against a few others I have onhand: Hammond 850G, 804, etc.
The DAC is based on a CS4397 evaluation board I had on my parts shelf, and loosely modeled on the digital input section of Andrea Ciuffoli's project here:
Hi-End Transformer-Coupled Tube Headphone Amplifier With Digital Input by Andrea Ciuffoli
Anyway, so far so good with the UTC FH-757 tx units in this application. They're in and working at least. I seem to like them turned around backwards wired with secondaries as primaries and primaries as secondaries. I need to do some measurements on them still as part of the comparison project.
PM me if you want to discuss more?
The DAC is based on a CS4397 evaluation board I had on my parts shelf, and loosely modeled on the digital input section of Andrea Ciuffoli's project here:
Hi-End Transformer-Coupled Tube Headphone Amplifier With Digital Input by Andrea Ciuffoli
Anyway, so far so good with the UTC FH-757 tx units in this application. They're in and working at least. I seem to like them turned around backwards wired with secondaries as primaries and primaries as secondaries. I need to do some measurements on them still as part of the comparison project.
PM me if you want to discuss more?
Not enough to PM you...
I think I got rid of them, but just found another pair. I did the same math again, and was unimpressed again.
The only part I am fuzzy on is that I calculated a voltage based on the power rating. This ignores frequency, which of course cannot be ignored in a transformer...so maybe that's at the 50 Hz 130 mW limit, and goes up with higher frequency.
Trying to use common sense, I think something is wrong with my assumptions...but no signal source I can think of using myself, would have 130 mW available...probably because the signal voltage would be a mere fraction as an input transformer. Interstage would be a different situation.
I think I got rid of them, but just found another pair. I did the same math again, and was unimpressed again.
The only part I am fuzzy on is that I calculated a voltage based on the power rating. This ignores frequency, which of course cannot be ignored in a transformer...so maybe that's at the 50 Hz 130 mW limit, and goes up with higher frequency.
Trying to use common sense, I think something is wrong with my assumptions...but no signal source I can think of using myself, would have 130 mW available...probably because the signal voltage would be a mere fraction as an input transformer. Interstage would be a different situation.
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