[MrFixr55]

+1. Definitely change the cap. If not shorted, it is open and could lower the Voltage across the meter. There is not many caps and resistors in this set, the big thing are the switches and all the connections, so replace the caps, ohm out the resistors and pots, including that funky wirewound with the lever.

Do you have the instructions, including the dial settings? (Roll built into the unit with the settings?) Most tube testers have what amounts to a gain pot (The Plate pot on your unit?). Not really gain, but using that term, you get the picture. If this pot is not set correctly, tubes that are not power tubes could read "bad" when they are good. Maybe that funky open frame rheostat is a calibration pot. I don't know if this was done on only Transconductance testers or also with emission testers, but there was usually a tube that was "calibrated" that could be used to calibrate the tester.

Note that right at the "bad-good junction" is a line marked "Line". There should be a switch setting and a pot to adjust for line voltage.