[Ron Ramirez]

Here's a drawing of the front view of Philco's Automatic Tuning dial:

[Image: http://i326.photobucket.com/albums/k420/...g~original]

Light has to pass through the dial screen holder assembly (26), which includes one sheet of amber plastic with a slot in the middle and the glass rod in the center; through another sheet of amber plastic (11), the mask assembly; and finally, onto the dial scale (12).

All of these parts have to be clean. You have to be careful with the dial scale, of course; usually, careful wiping with mineral spirits (never water, never glass cleaners such as Windex or any other brand - only mineral spirits) will clean the dial and prevent the numbers from washing off. As always, test in an inconspicuous area first; such as a part number that may be printed away from the scale itself. If these numbers do not wash off, you should be good to go.

The mask assembly and dial screen holder assembly can be cleaned more aggressively, since there are no numbers printed on these. Clean, clean, clean. You can't make the old plastic lighter, so you have to be sure the pieces are clean so you can get as much light through the individual elements of the puzzle as you can.

Not long ago, the 37-690 I used to own went to its new home in the great collection of y2k Bruce. Before it left here, I was experiencing a similar issue in that the lamp behind the dial was barely effective. A 4-chip LED lamp made a big difference in the illumination of the 37-690 dial. YMMV.

I used this LED bulb from Pinball Life:
http://www.pinballlife.com/index.php?p=product&id=2561

I also have one of these in my 610T (630 chassis), and I am having excellent results with them. Again, YMMV.