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Unread 08-13-20, 08:39 AM
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Jhogan0101 Jhogan0101 is offline
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Rheostat Source?

Looking to replace my instrument lighting rheostats (6)
A quick google search on the part numbers was not fruitful.
Is there a source for these or is it feasible to rebuild?
They are very difficult to adjust currently.
Philadelphia PA
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Unread 08-13-20, 09:23 AM
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hharney hharney is offline
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Herb R Harney
1968 337C

Flying the same Skymaster for 45 years
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Unread 08-21-20, 09:16 AM
frank.oconnor19 frank.oconnor19 is offline
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If we use these rheostats to replace the current ones, does that eliminate the need for the transistor based lighting controls found in the avionics bay?
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Unread 08-21-20, 06:09 PM
DrDave DrDave is offline
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Call Joe at Max Dim. I use their pulse width modulation dimmers. Max Pulse/Max Dim is located in Spokane. Joe is in Georgia? PWM is the best way to control EL lighting. Oops, that last comment was meant for Frank.

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Unread 08-29-20, 11:10 AM
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n86121 n86121 is offline
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Potentiometers vs rheostats

The potentiometers ('pots') provide a reference voltage from 0-24 at low current, to the BASE input high of the high current 2N3055 (powe4r supply type) NPN transistors that actually take the load.

If the transistors have fried, any 'ol big juicy NPN transistors will do, as their role is merely amplifying current.

If the pots are jumpy, try spraying corrosion X into the body. Their internal wiper arms and carbon track may be slimed after decades.

If you want to go with rheostats direct to the lighting, check the current. At 24 volts supply, the highest power will be at 12 volts (half way on/off). At 1 amp that is 12 watts heat dissipation, so you would want something rated for 150-200% of that power requirement.

Transistors are easier.
David Wartofsky
Potomac Airfield
10300 Glen Way
Fort Washington, MD 20744
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Unread 08-30-20, 01:50 PM
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Learjetter Learjetter is offline
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Seton Engineering

Apparently, max pulse max dim is now Seton. Tech docs, STC, AML, AMOC, etc here:

Aircraft spruce is one dealer.
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