So the lamps are trying to start? (that's what the glowing at the ends is all about).
This sounds like an end of life situation. Lamps have reached the end of their useful life, requiring a replacement.
The glowing ends would indicate:
[*]Both pins on one end of a lamp are in contact with the lamp holder,
[*]The wiring from the Ballast to that lamp holder is continuous,
[*]The Cathode (fillament) at that end of the lamp has continuity,
[*]The Secondary winding of the Ballast is (most likely) continous,
[*]The heater winding(s) on the Primary side are (most likely) continuous.
This would be accurate if BOTH Cathodes are glowing (both ends of the lamp). If only one end of the lamp is glowing, there are more things to consider.
If both Cathodes are glowing, try replacing a lamp with a known good / operational equivalent lamp. This lamp should strike and operate normal. If not, verify the obvious conditions, which include:
[*]Both lamp holders are connecting to lamp pins solidly,
[*]Both lamp holders have solid lead connections,
[*]Ballast is operational (not over heated or visible signs of damage or failure).
Voltage between both lamp holders should be no less than 200 VAC, and voltage across terminals of a lamp holder should be no less than 3 VAC. Any values lower than what's shown here would indicate Ballast failure, requiring Ballast replacement.
If only one end of a lamp is glowing, this indicates several things:
[*]The Cathode on the lamp end which is not glowing has no continuity - therefore it has failed,
[*]The lamp holder to the side which is not glowing is not connecting to both pins of the lamp,
[*]The circuitry to the lamp holder on the non glowing side does not have continuity,
[*]Heater winding on Primary side has failed, or the Secondary winding has failed.
Overall, simply check the obvious stuff first - such as broken lamps and lamp holders, loose lamps, very darkened lamp ends, and not to forget about correct lamp-to-Ballast matching! Trying to use an HO or VHO lamp on a 430ma Ballast will result in starting failure. If 430ma lamps are driven from HO or VHO Ballasts, the lamps' life will be drammatically reduced.
After verifying the obvious, then check voltage readings - first at the Line Input, then for Open-Circuit values across lamp holders and lamp holder terminals.
Sorry to not include enough information, but this should do fine for you.
Let us all know the results, plus feel free to ask further questions if you need to.
p.s. to assist in lamp/Ballast circuitry voltage measurement points, check out this schematic: F40 T12 2 lamp Ballast Schematic
btw, are the "U" tubes T12 type or something different? If they are T8 compact U lamps, or T5 "Biax" or "PL" types, these would be much different than the above.
Describing the Rapid Start Hot Cathode lamp operation. Click on the above hyperlink, or go to the Technical Reference section and select it from the list of items.
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