The MGA With An Attitude
Instrument LAMP HOLDER Puzzle - ET-115

At 03:18 PM 11/26/05, Wray A. Lemke wrote:
>"I'm re-wiring the MGA, new harnesses from British Wiring, .... The original has the plastic light tube but the one that came on the harness from BW has the standard socket with a screw in bulb."

Bulb holder, original type Bulb holder, replacement type
Left, original type bulb holder. - Right, new replacement type bulb holder.
Back of tech and speedo with two different lamp mounts
Left, plastic tube lamp mount. - Right, steel shell lamp mount.
Bulb holder, unknown type Bulb holder, adapted
Left, bayonet bulb holder for plastic tube. - Right, original bulb holder in plastic tube.

Here's the problem. Look at the mounting for the indicator lamps on the instruments above (MGA tachometer and speedometer). The instrument on the right has what I have known and consider to be the standard mount for the indicator lamp. It is a steel cup with small hole at bottom and internal flange at top. I have seen these in two different forms, one with flat bottom which may be resistance welded or soldered to the back of the instrument case, and one with bowl shape bottom which may be crimped in place like an eyelet, but otherwise functionally similar. This design accepts the screw base bulb socket with spring finger mounting. Inside the instrument case there is a rubber-like plastic tube which guides light to the jewel mounted on the face of the instrument while shielding it from light from the illumination lamp.

The instrument on the left has an odd plastic tube style bulb mount which presses into a larger hole in the back of the instrument and incorporates the small diameter light guide tube into the single plastic part. This accepts a press fit bulb holder containing a bayonet base bulb. My first reaction is, maybe bayonet base bulbs didn't exist in the mid 50's, but I'm not sure about that. My second thought is, the plastic parts strike me as more appropriate for later production, perhaps MGB parts.

Then at 09:06 PM 11/26/05, Wray A. Lemke wrote:
".... 3 of the non-standard sockets. One came out of the tach on my 56, the other two came out of the instruments in my 55 parts car. I can't confirm that they are original, .... The brown lamp socket, I suspect, is something a PO found that would fit the plastic socket, which it does quite well. .... I will have to adapt the socket with fingers to work somehow."

Now the question(s). Does anyone recognize the plastic socket with light guide and bayonet bulb holder? Is it possible that these parts may actually have been native to the instruments in the MGA during very early production, 1955-1956, when the instruments had larger numerals on the face? (I doubt it). Otherwise, where did they come from?

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