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On the GT versions of these tubes not being able to see the tubes glow is normal for the 1A7, IN5, and 1H5 tubes. Even in a really dark room seeing them glow is unusual. Also, be careful if you measure the filaments with an ohm meter to be sure your ohm meter does not supply too much Omph for the tubes to handle. One and a half volts with filament currents as low as .05 amps is all that is required for these.
Mike
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