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Posted: 7/14/2012 9:39:34 AM EDT
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I recently traded for a well used Gen 3, non-autogated D300. During the trade I tried the unit for about 2 minutes and it worked great. I then took it home and played with it for 20-30 minutes and it still worked great. During this time I turned it off/on/IR at least 30 times with no problems. About 2 hours later I tried it again and there was no image. The IR worked (could see the faint red light) and the yellow "on" light indicator was lit but no image at all. My thought was "Oh crap, what have I done?". I changed to brand new batteries with no change in results. I wiggled, turned, turned it on/off countless times, all without any luck. Since it was late I decided I would try to trouble-shoot it the following day.
About 20 hours later once it was night-time again I picked up the unit and it again worked flawlessly. I played with it for 15-20 minutes, turned it on/off/IR dozens of time, all with zero issues. It worked perfectly. A few hours later I decided to do some testing with an IR flashlight and again the image was completely black. I fiddled with it a little but could already see a trend here. I put the unit back in its bag and waited until this morning. This morning in a pitch-black closet it again worked perfectly. What could be causing this? Definitely not a battery issue and doesn't seem to be a switch issue. Is there a capacitor or something that when it reaches a certain threshold after 1-2 hours has to fully discharge before the unit will turn on again? Some type of tube thermal protection? I am completely stumped. I have been a lurker on this forum for several years and can't say that I remember seeing this issue. Any thoughts appreciated. Thanks. RockHoundTX |
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it might be a tube problem, but what you describe doesn't sounds like a tube problem. The thing most likely to be affected by temperature is the battery. Also, don't discount mechanical problems in the power supply line - from misaligned contacts to a bad wire - Even one that is temperature sensitive. Regards
David |
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Agree with David. Sounds like a issue in the power supply to the tube. You could check this by removing the tube and applying 3 volts directly to the tube contacts. If it lights green after several tests you know the issue is in the contacts, switch or wiring. Sometimes even a cracked solder joint can make you pull your hair out. From the naked eye all looked fine on a scope I owned. I used a loupe and found the issue. Cracked solder joint. Depending on how I held the scope the joint may or may not make contact.
Had me stumped for a good hour before I found the problem. Every time I had it taken apart it worked fine. When the tension of the screws were used to put it together it would spread the crack and cause intermittent operation. You really got to dig in and find the problem. Some are obvious and others make you work for it. |
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