AnalogPackrat
Well-known member
I made a trek to visit the legendary "Andy" and his garage with CJ recently and got, among other goodies, two Freed transformers marked: "P/N 39811" on one side (presumably the part number) and ""52 8-69" on another which looks like a date code for August 1969. I can't find anything about them anywhere on the web.
These are in fully sealed metal cans about the size of the UTC A series--square cross section, but a little taller--maybe 3.25" (8cm). There are four mounting studs at the corners and eight eye-loop terminals. I forgot to take a photo--will post one later. I had a few minutes to spare last night so I did make some measurements. Here's what I found:
There are four independent windings. Apparently there is no internal shield connection brought out to a terminal and the can is isolated from all the terminals.
DCR:
1-3 8.6 ohm
2-4 10.8 ohm
5-7 32.7 ohm
6-8 32.4 ohm
Leakage C (all connections open):
1-2 170pF
1-5 211pF
1-6 208pF
2-5 420pF
2-6 580pF
5-6 320pF
Inductance (using cheap BelMerit digital LC meter)
1-3 0.633H
2-4 0.631H
5-7 1.96H
6-8 1.96H
1-4 with 2&3 strapped 2.4H
5-8 with 6&7 strapped 7.3H
I put 600 ohms in series with my generator and ran a sine into 1-3 with all other connections open (it was late and now I realize I should have used a lower series resistance ). Turns ratio relative to 1-3:
2-4 1
5-7 1.7
6-8 1.7
Did a quick sweep with a 10K load and it was fine up past 30kHz, but got a little grungy and lossy down at the low end. Then again, my input resistance was probably wrong and who knows about the load.
So it looks like two split coils with a 1:1.7 (or 1.7:1) ratio. Using PRR's rule of thumb about impedance and DCR it looks something like a ~100ohm Z for 1-3 and 2-4 and ~300ohm Z for 5-7 and 6-8. So, what is it? Input? Output? Repeat Coil? Any other measurements I should do to suss it out?
Thanks,
A P
These are in fully sealed metal cans about the size of the UTC A series--square cross section, but a little taller--maybe 3.25" (8cm). There are four mounting studs at the corners and eight eye-loop terminals. I forgot to take a photo--will post one later. I had a few minutes to spare last night so I did make some measurements. Here's what I found:
There are four independent windings. Apparently there is no internal shield connection brought out to a terminal and the can is isolated from all the terminals.
DCR:
1-3 8.6 ohm
2-4 10.8 ohm
5-7 32.7 ohm
6-8 32.4 ohm
Leakage C (all connections open):
1-2 170pF
1-5 211pF
1-6 208pF
2-5 420pF
2-6 580pF
5-6 320pF
Inductance (using cheap BelMerit digital LC meter)
1-3 0.633H
2-4 0.631H
5-7 1.96H
6-8 1.96H
1-4 with 2&3 strapped 2.4H
5-8 with 6&7 strapped 7.3H
I put 600 ohms in series with my generator and ran a sine into 1-3 with all other connections open (it was late and now I realize I should have used a lower series resistance ). Turns ratio relative to 1-3:
2-4 1
5-7 1.7
6-8 1.7
Did a quick sweep with a 10K load and it was fine up past 30kHz, but got a little grungy and lossy down at the low end. Then again, my input resistance was probably wrong and who knows about the load.
So it looks like two split coils with a 1:1.7 (or 1.7:1) ratio. Using PRR's rule of thumb about impedance and DCR it looks something like a ~100ohm Z for 1-3 and 2-4 and ~300ohm Z for 5-7 and 6-8. So, what is it? Input? Output? Repeat Coil? Any other measurements I should do to suss it out?
Thanks,
A P