The view from inside HP when I worked with the people who designed and built the 10811 some 35-40 years ago was that:
1. 10811 ovens rarely fail. 2. When they do fail, it is rarely because the oven runs away. I know I have never encountered a runaway. No one at HP had a "trophy" on their desk of a runaway 10811. People tend to collect stuff like that. One engineer did have a 10811 with a 45 caliber bullet fired through it (long story). 3. From a business perspective, a failure is a failure and so there is no business reason to have a fuse. 4. Because the fuse could not be soldered in, it had to be socketed, and the socket failures exceeded any oven runaways by a good margin. Therefore, it made the "failure rate" worse. That is all that matters to the bean counters. 5. The one and only reason it was in there at all was the concern about toxic gases being released from the foam. Even without a runaway, foams tend to have a "slow burn" and outgas "stuff" all the time. Various foams were evaluated to balance that issue with thermal resistance and with the big issue with foam which is mechanical fatigue. This is similar to the wear out of foam mattresses. What should have been done with the thermal fuse would have been to put crimp lugs on the leads and attach the crimp lugs with screws. However, there was no space for all that stuff. Rick N6RK On 5/10/2017 4:43 PM, Dan Rae wrote:
As I reported the last time this subject came up, or maybe the time before, the only time I had an open thermal fuse was in a 10811 that had an open thermistor. I was able to replace that and get the OCXO working, but if the fuse had been replaced with a wire link I'm sure the entire oven would have been toast. There have been two types of fuse fitted, all I those have are the type that can be fitted with the plug in axial panasonic type, less than a dollar from Digikey. The older ovens had a different type but I imagine it's similarly easy to replace. All my 10811s have the higher temperature Panasonic fuse fitted and I sleep well at night... Dan _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
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