I have a dozen power transformers that were intended for various projects, but have been in my basement for longer than I really want to admit. The 1st ten of these are steel encased transformers that were spares for analog Government video processing equipment that was taken out of service due to obsolesce years ago. I believe that the current ratings of most of these transformers is conservatively rated because they were for equipment that was specified for very high reliability in operating conditions much harsher than in home use. I’m not likely to make use of these, and so hopefully they might find a good home. I'll be glad to provide additional photos by email.
I have provided a short list, and then a more detailed description of each transformer. I have tested them for proper operation as noted in the detailed descriptions below. All will operate fine on 120v 60 Hz input. Most of these will fit into a USPS Priority Mail medium flat rate boxes, and in many cases more than one would fit in one box and so domestic US shipping should be about $15 for what would fit in one box. Local pick-up in Northern Virginia would be welcome as well. I don’t know how to fairly price these, so if my price seems unreasonable, make me an offer.
Summarized list, with 120v 60 Hz input. Details on each transformer follow this summary.
#1 Two secondaries, 105v Center tapped @ 2A, & 55v Center tapped @ 0.2A $50
#2 Three secondaries, 52v Center tapped @ 9A, 65v @ 0.65A, & 28v @ 10ma $80
#3 & #4 Two Identical Transformers. One Secondary, 37v @ 2.7A $25 each
#5 Large &Very heavy with multiple taps on primary. Center tapped Secondary, 24v CT @ 48A, with several other taps at lower current levels (NO Shipping on this one) $60
# 6 & $7 High voltage, close to 2000v Center tapped secondary. Marked for 950v DC @ 0.5A, but this is an AC output at a much higher voltage according to my meter. Both transformers are identical. $20 each
#8 Small 1000v CT @ 50ma DC $10
#9. Filament transformer. Secondary is 6.3V Center Tapped at 1.5A. $10
#10 5.7v @ 3.0A & 5.8v @ 5.3A $20
#11. 10V Center tapped @ 3 A. $10
#12 12v @ 8A, or 24v @ 4A. $20
Transformer #1, Weight is about 13 pounds, 4 x 4.5 x 5” tall. It has 4 mounting studs at the bottom surrounding the wiring terminals for mounting onto a chassis. The 115/230v primary is rated for 50-400 Hz. The main output is marked 102v, CT @ 2 amps, with an extra 5v tap just off one side of the center tap. Using the center tap, this would also yield DC output voltages in the 75-volt range. Additionally, there is a separate 53v center tapped secondary rated @ 0.2a. I ran this for a couple of hours with 120v in, and a 100-watt light bulb across the 102v secondary, and there was no noticeable temperature rise.
Transformer #2 - Weight is about 16 pounds, 4” x 4.75” x 6” tall, not including solder terminals.
This steel encased transformer has tapped locations on the sides for mounting screws to screw into the metal case of the transformer for mounting. The threading is for the common ¼” 20 TPI screw threading.
Input is for 120v, 57-63 Hz. Output rating on the main secondary is 52V CT @ 9 A DC. I don’t know why it is marked in amps DC, because my multimeter and oscilloscope show this as an AC output at 52v RMS. Primary DC resistance is 0.32 ohms. With the use of a couple of full-wave bride rectifiers and suitable filter capacitors this could easily built into a DC power supply of + and – 75volts DC. Ideal for a high-powered Class AB Transistor Power Amplifier. There are two additional secondary windings that are not center-tapped. One is marked 28v at 10ma DC, and the other is marked at 65v at 0.65a DC. I also ran this transformer for several hours, but the 100-watt light bulb wasn’t as much of a load, but again there was no noticeable temperature rise.
Transformers # 3 and #4. There are two identical transformers, marked 120v 60 Hz input, and rated output is 37v @ 2.7a. Each of these measures 4 x 2.25” x 4” tall not including solder terminals, about they weigh about 4.5 lb. each. I also ran these for several hours, but with no load applied. Again, there was noticeable temperature rise.
Transformer # 5. This one is a Beast of a low-voltage transformer. It measures 8” x 7 ¼” x 8” high (not including terminals on the top), and it weighs more than 70 pounds. I will not attempt ship this one due to the weight. If interested you can pick it up in Falls Church, VA. The primary is for 60 Hz input, and has multiple taps to adjust for input voltages. Input taps are marked at 130v, 125v, 120v, and at 115v. There is also one just below 115v that isn’t marked, but my guess is that it’s for 110v. The secondary, with a center tap, has multiple output taps, with varying current ratings on the taps. Taps are marked with Voltage from the CT to each tap, and I confirmed with my multimeter that this is correct.
Markings on transformer:
70.0 volts @ 1.3 A
30.1 volts @ 2.1 A
20.5 volts @ 3.3 A
12.0 volts @ 48.0 A (this is not a mis-type)
6.2 volts @ 4.1 A
CT
6.2 volts @ 4.1 A
12.0 volts @ 48.0 A (again)
20.5 volts @ 3.3 A
30.1 volts @ 2.1 A
70 volts @ 1.3 A
I would interpret this as:
140v CT @ 1.3A
60.2v CT @ 2.1A
41v CT @ 3.3A
24v CT @ 48.0A
12.4v CT @ 4.1A
This is how the transformer is marked. I don’t know how the rating might be affected if you were simultaneously attempting to draw 1.3 A from the 70v taps and 48 A from the 12 v taps at the same time. I have used it to supply 12v to a string of 12 bulbs around my rear deck lighting, but am converting that to LED lighting soon and that won’t need anywhere near as much current.
Transformers # 6 and 7. These weight about 13 pounds each, and measure 4” x 4 ¼’ and are 5 ¼” tall not including the wiring terminals. These supply high voltage, that might? be useful for a tube amplifier. They are marked for 115/230v input at 50-60 C.P.S. Since they are marked CPS instead of Hz, they are obviously older, but appear in fine condition. They are also marked intermittent duty, so some derating of the output drawn might be necessary in actual usage. The center tapped secondary rating is strangely marked as: 950vDC – 0.200a, and 900v DC 0.500a. I connected the input to a variable input transformer to attempt to measure the output voltage, since I didn’t want to damage my meter. It appears that the voltage from the Center tap to each end of the secondary is above 1000v with no load applied. I connected the two primary windings in serial (as if I were using it for 230v input), and I measure just over 600 volts from the center tap to each end of the secondary winding.
Transformer #8. This is a small steel encased transformer for 115v input at 60 CPS. Output is marked as 1100 V CT, at 50ma DC. I haven’t checked or measured the AC output voltage yet, but if anyone is interested in this one, I will check it out further.
Transformer #9. This is a small steel encased filament transformer. Primary if for 115/230 v 50-60 CPS. Secondary is 6.3V Center Tapped at 1.5A.
Transformer #10. Small filament transformer. This measures 3 x 3 ½” and is 3 1/8” tall not counting terminals. Weight is 3 ¾ pounds. Primary is for 50-60 ~, Multiple input voltage taps @ 107.5v, 112.5v, 117.5v, 112.5v, 215v, 225v,235v, and 245v. Outputs are 5.7v @ 3A and 5.8v @ 5.3A.
Transformer # 11 A more conventional open frame transformer, 10V Center tapped @ 3 A. Primary is marked for 117v 50-60 CY.
Transformer #12. Another conventional open frame transformer. 12v @ 8A, or 24v @ 4A. Primary is marked for 115/230 v 50-60 CPS.
I have provided a short list, and then a more detailed description of each transformer. I have tested them for proper operation as noted in the detailed descriptions below. All will operate fine on 120v 60 Hz input. Most of these will fit into a USPS Priority Mail medium flat rate boxes, and in many cases more than one would fit in one box and so domestic US shipping should be about $15 for what would fit in one box. Local pick-up in Northern Virginia would be welcome as well. I don’t know how to fairly price these, so if my price seems unreasonable, make me an offer.
Summarized list, with 120v 60 Hz input. Details on each transformer follow this summary.
#1 Two secondaries, 105v Center tapped @ 2A, & 55v Center tapped @ 0.2A $50
#2 Three secondaries, 52v Center tapped @ 9A, 65v @ 0.65A, & 28v @ 10ma $80
#3 & #4 Two Identical Transformers. One Secondary, 37v @ 2.7A $25 each
#5 Large &Very heavy with multiple taps on primary. Center tapped Secondary, 24v CT @ 48A, with several other taps at lower current levels (NO Shipping on this one) $60
# 6 & $7 High voltage, close to 2000v Center tapped secondary. Marked for 950v DC @ 0.5A, but this is an AC output at a much higher voltage according to my meter. Both transformers are identical. $20 each
#8 Small 1000v CT @ 50ma DC $10
#9. Filament transformer. Secondary is 6.3V Center Tapped at 1.5A. $10
#10 5.7v @ 3.0A & 5.8v @ 5.3A $20
#11. 10V Center tapped @ 3 A. $10
#12 12v @ 8A, or 24v @ 4A. $20
Transformer #1, Weight is about 13 pounds, 4 x 4.5 x 5” tall. It has 4 mounting studs at the bottom surrounding the wiring terminals for mounting onto a chassis. The 115/230v primary is rated for 50-400 Hz. The main output is marked 102v, CT @ 2 amps, with an extra 5v tap just off one side of the center tap. Using the center tap, this would also yield DC output voltages in the 75-volt range. Additionally, there is a separate 53v center tapped secondary rated @ 0.2a. I ran this for a couple of hours with 120v in, and a 100-watt light bulb across the 102v secondary, and there was no noticeable temperature rise.
Transformer #2 - Weight is about 16 pounds, 4” x 4.75” x 6” tall, not including solder terminals.
This steel encased transformer has tapped locations on the sides for mounting screws to screw into the metal case of the transformer for mounting. The threading is for the common ¼” 20 TPI screw threading.
Input is for 120v, 57-63 Hz. Output rating on the main secondary is 52V CT @ 9 A DC. I don’t know why it is marked in amps DC, because my multimeter and oscilloscope show this as an AC output at 52v RMS. Primary DC resistance is 0.32 ohms. With the use of a couple of full-wave bride rectifiers and suitable filter capacitors this could easily built into a DC power supply of + and – 75volts DC. Ideal for a high-powered Class AB Transistor Power Amplifier. There are two additional secondary windings that are not center-tapped. One is marked 28v at 10ma DC, and the other is marked at 65v at 0.65a DC. I also ran this transformer for several hours, but the 100-watt light bulb wasn’t as much of a load, but again there was no noticeable temperature rise.
Transformers # 3 and #4. There are two identical transformers, marked 120v 60 Hz input, and rated output is 37v @ 2.7a. Each of these measures 4 x 2.25” x 4” tall not including solder terminals, about they weigh about 4.5 lb. each. I also ran these for several hours, but with no load applied. Again, there was noticeable temperature rise.
Transformer # 5. This one is a Beast of a low-voltage transformer. It measures 8” x 7 ¼” x 8” high (not including terminals on the top), and it weighs more than 70 pounds. I will not attempt ship this one due to the weight. If interested you can pick it up in Falls Church, VA. The primary is for 60 Hz input, and has multiple taps to adjust for input voltages. Input taps are marked at 130v, 125v, 120v, and at 115v. There is also one just below 115v that isn’t marked, but my guess is that it’s for 110v. The secondary, with a center tap, has multiple output taps, with varying current ratings on the taps. Taps are marked with Voltage from the CT to each tap, and I confirmed with my multimeter that this is correct.
Markings on transformer:
70.0 volts @ 1.3 A
30.1 volts @ 2.1 A
20.5 volts @ 3.3 A
12.0 volts @ 48.0 A (this is not a mis-type)
6.2 volts @ 4.1 A
CT
6.2 volts @ 4.1 A
12.0 volts @ 48.0 A (again)
20.5 volts @ 3.3 A
30.1 volts @ 2.1 A
70 volts @ 1.3 A
I would interpret this as:
140v CT @ 1.3A
60.2v CT @ 2.1A
41v CT @ 3.3A
24v CT @ 48.0A
12.4v CT @ 4.1A
This is how the transformer is marked. I don’t know how the rating might be affected if you were simultaneously attempting to draw 1.3 A from the 70v taps and 48 A from the 12 v taps at the same time. I have used it to supply 12v to a string of 12 bulbs around my rear deck lighting, but am converting that to LED lighting soon and that won’t need anywhere near as much current.
Transformers # 6 and 7. These weight about 13 pounds each, and measure 4” x 4 ¼’ and are 5 ¼” tall not including the wiring terminals. These supply high voltage, that might? be useful for a tube amplifier. They are marked for 115/230v input at 50-60 C.P.S. Since they are marked CPS instead of Hz, they are obviously older, but appear in fine condition. They are also marked intermittent duty, so some derating of the output drawn might be necessary in actual usage. The center tapped secondary rating is strangely marked as: 950vDC – 0.200a, and 900v DC 0.500a. I connected the input to a variable input transformer to attempt to measure the output voltage, since I didn’t want to damage my meter. It appears that the voltage from the Center tap to each end of the secondary is above 1000v with no load applied. I connected the two primary windings in serial (as if I were using it for 230v input), and I measure just over 600 volts from the center tap to each end of the secondary winding.
Transformer #8. This is a small steel encased transformer for 115v input at 60 CPS. Output is marked as 1100 V CT, at 50ma DC. I haven’t checked or measured the AC output voltage yet, but if anyone is interested in this one, I will check it out further.
Transformer #9. This is a small steel encased filament transformer. Primary if for 115/230 v 50-60 CPS. Secondary is 6.3V Center Tapped at 1.5A.
Transformer #10. Small filament transformer. This measures 3 x 3 ½” and is 3 1/8” tall not counting terminals. Weight is 3 ¾ pounds. Primary is for 50-60 ~, Multiple input voltage taps @ 107.5v, 112.5v, 117.5v, 112.5v, 215v, 225v,235v, and 245v. Outputs are 5.7v @ 3A and 5.8v @ 5.3A.
Transformer # 11 A more conventional open frame transformer, 10V Center tapped @ 3 A. Primary is marked for 117v 50-60 CY.
Transformer #12. Another conventional open frame transformer. 12v @ 8A, or 24v @ 4A. Primary is marked for 115/230 v 50-60 CPS.
Attachments
I want to again offer the above transformers - to US based buyers, since shipping outside the US is too much, and most of them are for 120 v input. #6 & #7 were previously sold.