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Repair Coils on HP Attenuators

Just wanted to let you know I was able to repair and rewind the 4 damages bobbins.

I first tried using the original #35 AWG magnet wire size, but due to the physical repair I had to do on the damaged plastic bobbins I was not able to wind the same number of turns as the original coil, so the resistance was too low (about 42 Ohms instead of the original 50 Ohms).

The sink transistors in the 75468's are rated at 500mA maximum, so 42 Ohms at 24 VDC makes the current too high. It may have worked, but I did not want to risk it. I changed the wire size to #36 AWG and ended up with about 60 Ohms.

After finishing the bobbin repair and rewind, the attenuator actuators work great and I now have a working generator.

The rubber grommets that physically attach the plastic attenuator arm to the actuator are starting to dry out and will be a problem sometime in the future. Any suggestions on replacements?

Thank you again for all the information and your help with the project.


test_equipment/repair_coils_on_hp_attenuators.txt · Last modified: 2013/01/08 19:00 (external edit)
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