Help wanted with CVR(T) night sight.

#1
Is there anything serviceable inside a CVR(T) gunners night sight?

The sight on my Scorpion makes clicking noises but no sign of an image or any glow.

I am assuming I just have to find a working tube?

I know there is 2700 volts floating about so I will be careful!
 
#2
All knackered sights get sent back to the factory to be fixed. The only unit level maintenance is a wipe with a soft cloth.
 
#6
The clicking could be one of a couple of things - if it s an old L3A1, and its not fitted with a dummy inverter, then the high voltage may be shorting out on the body. The High voltage is delivered via to coax. Secondly, it may be the flash shutter operating (strange enough designed to safeguard the IIT when the gun fires). If the flash shutter is continually closed, you will not see an image.
 
#7
Thanks for that wfb. I read that being exposed to direct daylight fecks the tube too?

The shutter sounds like its moving back and forth. Not sure how I can test the HV safely.
 
#11
HMVF Might be able to provide more enthusiast appropriate answers.
 
#12
Being exposed to ANY daylight will burn out the tube, especially if it is the high voltage type. To check if it is high voltage, find the output on the control box |(where the coax is connected) and WITH THE POWER SWITCHED OFF remove the round inverter housing (if I remember correctly, by turning the large round knurled cap). Inside the housing you will find either a silver inverter, a silver dummy inverter or what looks like a wooden dummy. If it is the silver dummy, it should have the word 'dummy' on it - however this is not always the case. Remove the inverter/dummy and check continuity between the top and bottom contacts. If it is a dummy you will get no resistance. If it is a dummy then reassemble and check that you are getting a voltage from the centre pin of the coax socket output - I can't remember what the voltage should be but it will be significantly less than 12 volts. If you are getting an output then reconnect the coax at the control box and disconnect the coax on the L3 housing (it should be just above the optical hinge and check again for this voltage). If you are getting supply along the cable the chances are the IIT is kaput, if not the coax cable is suspect and can easily be repaired. If the IIT is kaput, and if you can find an Instrument tech that remembers the L3 he may be willing to confirm this if you offer enough beer etc
 
#13
Thanks WFB, that's a very useful reply!

I have read about the dummy inverter version and seen that some control boxes have a label on the front to indicate that they are the lower voltage version.

I'll take a look at the control box.

I have also posted the question on HMVF, my first place of call, but I thought it would be worth a shot here too, and it was!
 
#14
Don't trust the label on the control box - when the mod was initially issued, the labels were made of aluminium and would be perm fixed - however later issues were sticky backed shite which had a habit of falling off after a couple of weeks (if the tech actually bothered attempting in the first place)
 
#15
Don't trust the label on the control box - when the mod was initially issued, the labels were made of aluminium and would be perm fixed - however later issues were sticky backed shite which had a habit of falling off after a couple of weeks (if the tech actually bothered attempting in the first place)
Hi WFB,

It has a silver dummy inverter marked as such and there is 7 volts at the output.

I'll check the other end of the coax when I can find it!

Incidentally, do you know where the bulb is to illuminate the graticule? Do I take the side cover off where the revolving joint is or the smaller plate on the side of one of the eye pieces?

Cheers,

Richard.
 
#16
If you are getting 7v from the control box, then the supply is ok - check the other end of the coax for the same 7v. The grat illum bulb is under a small cover plate on the main objective assy (the front end) where the ballistic grat adjusters are.
 
#17
Hi WFB,

Just spent a day and a half getting the bulb cover off the cowl (those dumb slotted head bolts are not really the best design for applying torque) only to find the bulb is fine!

I assume if the tube is fecked, I wouldn't see the graticule anyway.

So next question is, do I take the cowl off to get the sight out, or does it come out backwards into the turret?

(New tube ordered off ebay for 35 quid!)
 
#18
L3 is removed via the front - make sure you remove the cowl release cable from inside the vehicle. When you get that far, and have the IIT in your mits let me know an I will take you a stage further
 
#19
Cowl is off now...

Do I undo the four smaller cap heads around the sight or the two big counter sunk bolts going into the mantlet?

I have undone the bolt that goes under the viewing end.
 

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