); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Highly unlikely, but, possible, especially if it was in a corrosive atmosphere. Of course then I would expect to see evidence of corrosion on other components. When we do not know the answer we can come up with so many possibilities and not have one of them correct. I have run across a lot of those defective fuses over the years as HP has been using them forever. There was no real evidence as to why they opened, and that is why before I guessed at just plain ageing and the wax eventually getting soft. I just checked the current flow within the oscillator where the fuse used to be plugged in, which was at least nice of them, and always found it to be normal. I just took a piece of buss wire and plugged it into the same two pins were the fuse used to be and never had a problem again. The situation Magnus describes of course is very unusual, and, in reality would only be found by a time nut as it is so miniscule. There is also some periodicity to it, which does suggest some control loop problem, but, I would hate to even take a guess. - Mike
Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dr Bruce Griffiths Sent: Sunday, July 22, 2007 10:32 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 5370B low frequency modulation Mike Feher wrote: > ); SAEximRunCond expanded to false > Errors-To: [EMAIL PROTECTED] .com > > I believe it is almost impossible to have an intermittent thermal fuse due > to their very clever design. Although over age they can open up. Once open, > however I do not believe they can connect again. The fuse is simply to > metallic contacts that are force to be in contact during assembly. Their > normal desired resting state would be to be not connected. When closed, the > fuse cavity is filled with wax, which mostly determines when the fuse opens > (temperature). With too much current through the fuse, the wax heats > allowing the contact to spring apart to their normal resting position. Now, > with no more current flowing, the wax hardens almost immediately, never > allowing the two contacts to meet again. - Mike > > > > Mike B. Feher, N4FS > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 > > > Mike Whilst the fuse itself may not be the problem, it is a plugin component and the contacts may be problematic. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
