UPD:
I've played with settings some more and here's what i have discovered. When i set (sensitivity) ASA dial at 50 or below, and shutter speed at 1/1000 underexposure indicator lights up (with mamiya/sekor 55/1.4 wide open), when i change the shutter speed to 1/500, overexposure indicator lights up and stays lit all the way through F16, and even with lens cap on. Now, i know these both readings are incorrect, there is no way 1/500 indoors at ASA 50 should trigger the overexposure indicator. But the fact that, i am able to trigger both over and under lamps - shows that they are working and aren't burnt. (phew).... I also have found
service manual online, and discovered pretty interesting stuff under "Malfunction of the exposure readout circuit". So according to service manual, my tl electro x seems to be suffering from following:
4.2.5 Adjustment of the exposure readout circuit.
Adjustment of the exposure readout circuit consists of either one of the following two methods:
One method consists of loosening the two screws on top of the slide resistor assembly and turning to offset resistor ring to alter its position in relation with the brush. This method (providing a balanced shifting of the offset resistor characteristics) enables precise regulation of the 'light turn-off point' without altering the 'light turn-off range'. The other consists of adjustment of the 30K semi-fixed resistor incorporated in the amplifier unit. This provides effective regulation of the 'light turn-off point' of the "OVER" indicator lamp.
4.2.5.1 Improper adjustment of the 'light turn-off' position.
The 'light turn-off' position generally tends to shift toward a direction providing under-exposure at all light levels.
This malfunction is caused when the resistance of the offset resistor (VR-1) rises to a level beyond the standard reading. To repair, turn the offset resistor ring in a left motion to effect a balanced shifting of the resistor characteristics.
The 'light turn-off' position generally tends to shift toward a direction providing over-exposure at all light levels.
This malfunction is caused when the resistance of the BALANCING resistor (VR-1) declines below the standard level. To make adjustment, turn the offset resistor ring in a right motion.
4.2.5.2 The 'light turn-off' range is either excessive or too limited. The factory standard calls for a 'light turn-off' range of 1/3 to 1-2/3 EV and, therefore, the following adjustment must be made in case the range is determined to be excessive or too limited. Because this range is adjusted on the basis of the function of the "OVER" indicator lamp, the VR-1 must be properly regulated in case it is determined after adjustment of the 'light turn-off range' that the 'light turn-off point' has shifted from the normal position. (Refer to pertinent details given later.)
Excessively wide 'light turn-off range'.
This can be attributed to adjustment of the 'light turn-off range' adjustment resistor (30K ohm VR) to a resistance reading below the normal level. To repair, turn the resistor in a left motion with the aid of a screw-driver to a setting that provides higher resistance.
The 'light turn-off' position generally tends to shift toward a direction providing over-exposure at all light levels.
This malfunction is caused when the resistance of the BALANCING resistor (VR-1) declines below the standard level. To make adjustment, turn the offset resistor ring in a right motion.
4.2.5.3 In case both the 'light turn-off range' and 'light turn-off position' are determined to be not up to standard. First of all, adjust the 'light turn-off' adjustment resistor (30K ohm) and set the 'light turn-off range' to normal level. Then, adjust the BALANCING resistor ring (VR-1) and set the 'light turn-off point' to the required position.
Looks like, i have to pop it open...