SGibson

My Feedback: (2)

I bought an old Micro Avionics with the green anodized case and airborne equipment. The transmitter looks like new and absolutely no corrosion inside the case. The battery looks like it did new. It is actually taking a charge from the original charger The airborne charger is working. The tiny bulb in the charger appears to be burnt out. Where can I buy a replacement bulb. I would love to see if this radio will still work on the ground. I would never try to fly a plane with it. Can I jump the connections for the bulb or does the bulb do something to the electricity to allow the battery to charge?
S Gibson
Houston TX

HighPlains

My Feedback: (1)

I think that the neon bulb did part of the voltage drop and is a necessary part of the circuit. Does the charger have an isolation transformer, or does it connect directly to the line? Because if your house wiring happens to be incorrect, it is possible to get quite a shock from some of the old circuits used in early RC equipment.

grotto2

My Feedback: (2)

The radio schematic doesn't seem to include the charger, but the bulb is likely a current limiter. You'd best replace it with the same type.
-Ron

SGibson

My Feedback: (2)

There arent any numbers that i can read on the bulb. Any recommendatios for a replacement? The out side wires come into the charger. One wire goes into a small square white object and the othe wire has a small cylinder that looks like a resistor conected to one side of the bulb holder. I will try to post a clear photo and post here

SGibson

My Feedback: (2)

With magnification, I see it is a GE #47 bulb, available at Grainger. Before I run off to Grainger, I will check to see if the transmitter charger uses the same bulb. If so I'll switch them out to see if the airborne battery will take a charge.

SGibson

My Feedback: (2)

I switched out the bulb and the new one didn't light up. Took the airborne battery case apart and the third wire in the middle of the pack was disconnected. The airborne battery has some corrosion so I will probable quit messing with this unless somebody here can tell me how to make a three wire battery pack.

Michaelj2k

Run a third (white) wire to the other side of the pack to get 2.4V.

sidgates

My Feedback: (2)

I owned a Micro radio in approx. 1967 and sold it when I started Royal Electronics and built our own radios for 16 yrs. Call me if you want help on the phone. 303-757-7019

jaymen

Hello.
If the servos are 3 wire, then leave the white wire alone as it's not needed. If the servos have 4 wires, then the white wire goes to the middle of the 4 batteries.

The reason the bulb is not lighting is probably because the battery pack is bad, and so it will not draw any current, and that current is what lights the bulb. The GE-47 acts as a charge indicator, and fuse to protect the charging system.

I have several real old radios with nice looking batteries in them that have not corroded, and some actually will charge up, but they don't hold very much of a charge, and die in a few days.

HighPlains

My Feedback: (1)

This is what, a 1966 or '67 era radio? At that time many radio sets had 7 cell airborne packs with two or three taps for different voltages. The 4 cell pack with a center tap was a breakthrough in weight reduction and reliability. The three wire servo was several years later when EK introduced it.