teletech Posted March 4, 2023 Share Posted March 4, 2023 I have one I've never used but was supposedly "like new". I'm wondering what the power cable input wiring is? There are three pins, I assume one in ground and the other is 24V, but I don't know if the third pin is used and I don't know which pin goes where and I naturally don't want to hurt anything. A manual would be amazing, but the pinout of the power cable would be a good start. I have what I suspect is the correct cable (the ends are correct) but don't quite trust it. I'm also curious about the difference between the L18A1 and the L5A1, which I gather is also a fit for the CVR(T)? Quote Link to comment Share on other sites More sharing options...
andym Posted March 4, 2023 Share Posted March 4, 2023 In my experience, AFV three pin power connectors are always Pin A 24V, Pin B 0V and Pin C N/C. Andy Quote Link to comment Share on other sites More sharing options...
G8RPI Posted March 4, 2023 Share Posted March 4, 2023 I can confirm that Pin A is + 24V pin B 0V (ground) is correct for these periscopes. I don't have a note of the model numbers, but generally the different models refer to different age / performance of tube used. Early ones needed external infrared light sources. The late ones (narrow body and single tube) used high perfomance microchannel plate "Generation II+" tubes like the XX1332. Robert Quote Link to comment Share on other sites More sharing options...
teletech Posted March 5, 2023 Author Share Posted March 5, 2023 Well, the good news is my cable seems correct: A=24V, B=GND, C is actually a short wire that looks like it could be intended as a local RFI ground to chassis. The bad news is my sight does nothing at all when I hook it up and power it on. Fuses are present and have continuity. No HV whine, no eyepiece illumination, and also no indicator lamp (I don't know if that's for the heater or NV). I'm a little reluctant to take it apart without knowing which bits will disturb the iris, does anyone have some guidance on this? Quote Link to comment Share on other sites More sharing options...
G8RPI Posted March 5, 2023 Share Posted March 5, 2023 Do you have continuity between pin A and the fuse holders? Are you sure of the model number? I can't find a reference to a L18 A1. I have L5 A1 and A7L1 units. Any photos ? Quote Link to comment Share on other sites More sharing options...
teletech Posted March 9, 2023 Author Share Posted March 9, 2023 (edited) On 3/5/2023 at 10:32 AM, G8RPI said: Do you have continuity between pin A and the fuse holders? Are you sure of the model number? I can't find a reference to a L18 A1. I have L5 A1 and A7L1 units. Any photos ? Interesting! Pin A has continuity to the fuse holder near the plug, Pin B has continuity to the fuse holder farther from the plug. This suggests that this NV sight might need pin B after all. Edited March 9, 2023 by teletech Typo Quote Link to comment Share on other sites More sharing options...
G8RPI Posted March 9, 2023 Share Posted March 9, 2023 OK that is a new model to me. It is basically the L7A1 sight design adaptoed to fit in the L5A1 mount. Earlier versions used just an adaptor plate between the two. I have a couple of those adaptors. It is unlikey to need positive on two pins, particuarly if you are seeing no countinuity on pin C. You mention pin B twice, can you correct? I'll check the L7A1 body I have later. Quote Link to comment Share on other sites More sharing options...
teletech Posted March 9, 2023 Author Share Posted March 9, 2023 (edited) 43 minutes ago, G8RPI said: OK that is a new model to me. It is basically the L7A1 sight design adaptoed to fit in the L5A1 mount. Earlier versions used just an adaptor plate between the two. I have a couple of those adaptors. It is unlikey to need positive on two pins, particuarly if you are seeing no countinuity on pin C. You mention pin B twice, can you correct? I'll check the L7A1 body I have later. I corrected the typo, one fuse holder is connected to A, the other sees B. II didn't see continuity on pin C, but it was the end of the day and I neglected to check it on the higher ranges and with reversed polarity to see if there was any path from a or B to C with the heater or illumination switches on. The reason I haven't just started pulling it apart is partly the condition of the paint is so nice, I hate to mess it up by removing screws. Thanks for identifying it as likely L7A1-derived, this suggests that going in from the flat plate just about the viewing section is likely to give me the best view with the least disturbance to the unit. Edited March 9, 2023 by teletech Quote Link to comment Share on other sites More sharing options...
teletech Posted March 9, 2023 Author Share Posted March 9, 2023 Heater OFF, NV OFF: 5.2K ohm Heater ON, NV OFF: .16K Heater OFF, NV ON: 5.19K Heater ON, NV ON: .13K Pin C is tied to the chassis, 0Ohms. I never see anything but infinity from C/chassis to A or B, so that confirms what others said. Given the various resistances, it seems a certainty the heater is working and some part of the Image intensifier electronics are at least in the circuit. I guess I'll have to open it up if I want to know more. My fear now is the HV PS is shot or even that the sight was demilled and the tube removed. Quote Link to comment Share on other sites More sharing options...
G8RPI Posted March 9, 2023 Share Posted March 9, 2023 Hi, Can you see light through the sight with the Iris open? If you can the tube has been removed. Removing the plate above the eyepiece is a safe point of entry. This unit will use a XX1330 series tube, probably a XX1332. These are very good being a 2" microchannel plate "Gen II+" tube. The tube has built-in (potted) HT supply and runs from 6.5V DC. There si a simple 24V to 6.5V regulator in the sight. If you are lucky it will be this that has failed. IT can be repaired or even replaced with a LM317T based circuit. You need to check the voltage at the tube terminals or regulator output. Not had a chance to drag my sight out yet. Robert. Quote Link to comment Share on other sites More sharing options...
teletech Posted March 9, 2023 Author Share Posted March 9, 2023 Ugh, I hated to break the paint, but here we go. Yes, I have a tube (dated from 1994). Removing the front cover also removes the down-converter and disconnects it from it's mating DB9. Pin 1=24V, Pin 2=6.8V, Pin 3-Gnd Seems to work OK. Only about .3V across the LED so I don't know if it's current-sensitive or something else, but it's part of the downconverter so at least I know it's nothing to do with the heater. Dug around for a couple DB9 connectors and hooked the downconverter up externally and the unit started working fine! put the converter back in the housing, unit still works fine, so... Oxides on the DB9 that needed breaking loose? Or, is it something else. the thing I thought of as off, on, ND filter, iris does not have a position where it actually turns off power to the tube now. SO, the switch was somehow open no matter what and in the act of disassembling the unit a bit now it's always closed? seems odd, but it's all I've got for now. Quote Link to comment Share on other sites More sharing options...
G8RPI Posted March 10, 2023 Share Posted March 10, 2023 Hi, Good news that the tube is OK. The power issue sounds more like a problem with the microswitch that controls power to the tube. You are correct. It should be OFF, ON ND, ON with iris control. No way the tube should be powered all the time. Two possibilities, the microswitch is intermittent or something is out of mechanical adjustment. Robbert. Quote Link to comment Share on other sites More sharing options...
G8RPI Posted March 10, 2023 Share Posted March 10, 2023 See photos for the details of the switch. As you can see it only moves a tiny mount due to a shallow depression in the disk. The disk is on the same shaft as the control knob. The tube is off with the roller in the depession. Slight adjustment of the switch position or bending of the lever arm may be all that is required. Looks like access on your sight is through the angled plate on the back of tthe lower section. Robert. Quote Link to comment Share on other sites More sharing options...
teletech Posted March 11, 2023 Author Share Posted March 11, 2023 The angled plate isn't removable, so I have to remove the eyepiece assembly and pull the tube spacer and the tube to gain access. Luckily it wasn't a big job at all, thanks for the pics so I knew I wasn't going to have a big pile of gears or springs or anything! Quote Link to comment Share on other sites More sharing options...
teletech Posted March 11, 2023 Author Share Posted March 11, 2023 A very slight movement of the microswitch and it will now turn off (barely), so mission accomplished! Bit of a mystery why first it didn't turn on (oxides on some contacts?), but I'm willing to call it fine now. Thanks for the support and assistance. Now, what does the stowage bracket look like so I can carry it in style? 1 Quote Link to comment Share on other sites More sharing options...
G8RPI Posted March 11, 2023 Share Posted March 11, 2023 👍 Quote Link to comment Share on other sites More sharing options...
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