comments:
They are incredibly easy to work on. Ideally you need a PVS-14 tool kit, you can get one from Aliexpress for very cheap, I paid £30 for the set, the main one you need is the retaining ring "spanner", but a camera lens tool would suffice, $10 from Amazon. Unless you live in a high humid area, purging is not really necessary although it can protect the internal pcb from corrosion due to moisture from the air inside the housing. Living in the UK, I've never bothered and have had zero issues. If you're careful and even slightly skilled with delicate work then you should have no issues taking the tube out, inspecting the pcb and diagnosing a repair. You can test the tube outside of the housing by using a 3v CR123A to directly power it, dark room, face down on a card etc, 2 wires from battery to the connectors on the tubes side, and see if the tube powers up. If it does and does it quickly then it's likely the internal pcb and battery casing at fault. Check all contacts and solder joints are secure, no movement from the pcb, check no tiny components on the pcb are loose or missing with a magnifying glass. A common fault is the retaining ring unscrews slightly moving the tube away from the contacts on the pcb. This causes intermittent operation of the tube, especially when moving with it mounted on your helmet. Tightening that tube retaining ring might be all you need to do to fix it. Ring spanner for tube retaining ring here, https://www.amazon.com/Rierdge-Spanner-Retaining-Repairing-Cleaning/dp/B0DLK7L4QV Or get legit one from Aliexpress in a toolkit. See photo.