Did you take a picture showing where the thermal fuse is located? I've never opened a 10811.Sounds like a crude device as you described it. I've used thermal fuses as a safety feature for fast-recharge medical NiCd battery packs but those looked like big diodes.LarrySent via the Samsung Galaxy S20 -------- Original message --------From: Jared Cabot via time-nuts <time-nuts@lists.febo.com> Date: 11/30/21 9:35 AM (GMT-08:00) To: Discussion of precise time and frequency measurement <time-nuts@lists.febo.com> Cc: Jared Cabot <jaredcabot@protonmail.com> Subject: [time-nuts] Re: HP 5065A, no 2nd harmonic. I was reading in a past thread on the time-nuts mailing list that the thermal fuses can occasionally spontaneously go open circuit with age, far more often than going open due to a real thermal fault.(I wonder how many have been discarded over the years due to this issue?)They appear to be constructed from two spring contacts held closed by wax. As the fuse heats up, the wax melts allowing the contacts to permanently open.It would appear that age can cause the contacts to open too... A common fix is a wire jumper (The fuse is conveniently socketed, so a resistor leg offcut makes a nice jumper).I plan to source a replacement thermal fuse, just to keep things a bit safer.Also, I did get the pictures, thanks for that! I replied directly just now.Jared.‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐On Wednesday, December 1st, 2021 at 02:05, Larry McDavid <lmcdavid@lmceng.com> wrote:> Do these thermal fuses fail spontaneously or is there a common cause?> > If the "heater" transistor mounting screws were quite loose, those> > transistors themselves might have overheated and failed. But, a thermal> > fuse should fail by high temperature...> > Sounds like progress, though. Cold OCXO means low frequency.> > Jared, I sent you a private email with some pictures; did you get that?> > Larry> > On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote:> > > Well, I found it, the thermal fuse is open circuit.> > > > If I briefly bypass it with a jumper wire, the oven pulls the expected current.> > > > Looks like I need something that will trip at roughly around 115C, rated to 1.0A> > > > (HP Part number 10811-80008)> > > > Hopefully I can find something in Akihabara to make it easier to get my hands on ASAP...> > > > Jared> > ...> ---> > Best wishes,> > Larry McDavid W6FUB> > Anaheim, California (SE of Los Angeles, near Disneyland)> > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com> > To unsubscribe, go to and follow the instructions there._______________________________________________time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.comTo unsubscribe, go to and follow the instructions there.

On 1/12/21 5:03 am, Jared Cabot via time-nuts wrote: > Hopefully I can find something in Akihabara Yeah yeah, don't rub it in! :^)

Hi, Just a little warning. Included are some pictures of a 10811 where thermal fuse protection have not functioned. I do not know why, if the fuse did not work, or somebody replaced it with a wire, as this was in a HP 8663A that I found in a recycling bin, and I do not know the history. Regards, Askild On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq <kb8tq@n1k.org> wrote: > Hi > > The thermal fuses die on their own far more often than they die protecting > anything. The fuse is there to provide safety is certain odd situations. > The > simple answer these days is to replace it with a piece of wire. > > Bob > > > On Nov 30, 2021, at 12:05 PM, Larry McDavid <lmcdavid@lmceng.com> wrote: > > > > Do these thermal fuses fail spontaneously or is there a common cause? > > > > If the "heater" transistor mounting screws were quite loose, those > transistors themselves might have overheated and failed. But, a thermal > fuse should fail by high temperature... > > > > Sounds like progress, though. Cold OCXO means low frequency. > > > > Jared, I sent you a private email with some pictures; did you get that? > > > > Larry > > > > > > On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote: > >> Well, I found it, the thermal fuse is open circuit. > >> If I briefly bypass it with a jumper wire, the oven pulls the expected > current. > >> Looks like I need something that will trip at roughly around 115C, > rated to 1.0A > >> (HP Part number 10811-80008) > >> Hopefully I can find something in Akihabara to make it easier to get my > hands on ASAP... > >> Jared > > ... > > -- > > Best wishes, > > > > Larry McDavid W6FUB > > Anaheim, California (SE of Los Angeles, near Disneyland) > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send an email to time-nuts-leave@lists.febo.com > > To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there. >

In general it is a very bad idea to defeat safety provisions that a manufacturer put in their product. They are there for a reason, any manufacturer would omit them, if only to save on cost. I would think no-one on this list would replace a blown fuse in their house fuse box with a nail. Or? Wilko > On 1 Dec 2021, at 12:13, Askild <megafluffy@gmail.com> wrote: > > Hi, > > Just a little warning. > Included are some pictures of a 10811 where thermal fuse protection have > not functioned. > I do not know why, if the fuse did not work, or somebody replaced it with a > wire, as this was in a HP 8663A that I found in a recycling bin, and I do > not know the history. > > > Regards, > Askild > > > >> On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq <kb8tq@n1k.org> wrote: >> >> Hi >> >> The thermal fuses die on their own far more often than they die protecting >> anything. The fuse is there to provide safety is certain odd situations. >> The >> simple answer these days is to replace it with a piece of wire. >> >> Bob >> >>>> On Nov 30, 2021, at 12:05 PM, Larry McDavid <lmcdavid@lmceng.com> wrote: >>> >>> Do these thermal fuses fail spontaneously or is there a common cause? >>> >>> If the "heater" transistor mounting screws were quite loose, those >> transistors themselves might have overheated and failed. But, a thermal >> fuse should fail by high temperature... >>> >>> Sounds like progress, though. Cold OCXO means low frequency. >>> >>> Jared, I sent you a private email with some pictures; did you get that? >>> >>> Larry >>> >>> >>> On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote: >>>> Well, I found it, the thermal fuse is open circuit. >>>> If I briefly bypass it with a jumper wire, the oven pulls the expected >> current. >>>> Looks like I need something that will trip at roughly around 115C, >> rated to 1.0A >>>> (HP Part number 10811-80008) >>>> Hopefully I can find something in Akihabara to make it easier to get my >> hands on ASAP... >>>> Jared >>> ... >>> -- >>> Best wishes, >>> >>> Larry McDavid W6FUB >>> Anaheim, California (SE of Los Angeles, near Disneyland) >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe >> send an email to time-nuts-leave@lists.febo.com >>> To unsubscribe, go to and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send >> an email to time-nuts-leave@lists.febo.com >> To unsubscribe, go to and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there.

And I will bet the smell is as bad as the larger 0106 oven. As I say its in a sealed bag and not sure how I will recover it. Need the windows open. The suggestion of buying a replacement is the best even if you do need to buy 2-3 to locate a good one. Regards Paul On Wed, Dec 1, 2021 at 6:13 AM Askild <megafluffy@gmail.com> wrote: > Hi, > > Just a little warning. > Included are some pictures of a 10811 where thermal fuse protection have > not functioned. > I do not know why, if the fuse did not work, or somebody replaced it with a > wire, as this was in a HP 8663A that I found in a recycling bin, and I do > not know the history. > > > Regards, > Askild > > > > On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq <kb8tq@n1k.org> wrote: > > > Hi > > > > The thermal fuses die on their own far more often than they die > protecting > > anything. The fuse is there to provide safety is certain odd situations. > > The > > simple answer these days is to replace it with a piece of wire. > > > > Bob > > > > > On Nov 30, 2021, at 12:05 PM, Larry McDavid <lmcdavid@lmceng.com> > wrote: > > > > > > Do these thermal fuses fail spontaneously or is there a common cause? > > > > > > If the "heater" transistor mounting screws were quite loose, those > > transistors themselves might have overheated and failed. But, a thermal > > fuse should fail by high temperature... > > > > > > Sounds like progress, though. Cold OCXO means low frequency. > > > > > > Jared, I sent you a private email with some pictures; did you get that? > > > > > > Larry > > > > > > > > > On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote: > > >> Well, I found it, the thermal fuse is open circuit. > > >> If I briefly bypass it with a jumper wire, the oven pulls the expected > > current. > > >> Looks like I need something that will trip at roughly around 115C, > > rated to 1.0A > > >> (HP Part number 10811-80008) > > >> Hopefully I can find something in Akihabara to make it easier to get > my > > hands on ASAP... > > >> Jared > > > ... > > > -- > > > Best wishes, > > > > > > Larry McDavid W6FUB > > > Anaheim, California (SE of Los Angeles, near Disneyland) > > > _______________________________________________ > > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > > send an email to time-nuts-leave@lists.febo.com > > > To unsubscribe, go to and follow the instructions there. > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send > > an email to time-nuts-leave@lists.febo.com > > To unsubscribe, go to and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there.

Hi The last time I went 10811 shopping, I found a seller with a lot of them. His price was right ($40 each) if you bought a batch at a time. I tested them all for ADEV / phase noise and the other basic bench stuff. I did not run any of them over temperature ( but neither did HP …. ). Net result was about 5% that had some significant issue ( = you could not use them in a counter). Maybe another 20% had phase noise or ADEV that was in spec, but not that great. The balance ranged from pretty good down a few with high parts in 10^-13 for ADEV. The real issue is finding a group that has not already been sorted. There are folks who run through and do the same sort of testing. The worst 1/3 of the group then goes back on eBay …. (including the ones with significant issues). Bob > On Dec 1, 2021, at 9:11 AM, paul swed <paulswedb@gmail.com> wrote: > > And I will bet the smell is as bad as the larger 0106 oven. As I say its in > a sealed bag and not sure how I will recover it. Need the windows open. > The suggestion of buying a replacement is the best even if you do need to > buy 2-3 to locate a good one. > Regards > Paul > > On Wed, Dec 1, 2021 at 6:13 AM Askild <megafluffy@gmail.com> wrote: > >> Hi, >> >> Just a little warning. >> Included are some pictures of a 10811 where thermal fuse protection have >> not functioned. >> I do not know why, if the fuse did not work, or somebody replaced it with a >> wire, as this was in a HP 8663A that I found in a recycling bin, and I do >> not know the history. >> >> >> Regards, >> Askild >> >> >> >> On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq <kb8tq@n1k.org> wrote: >> >>> Hi >>> >>> The thermal fuses die on their own far more often than they die >> protecting >>> anything. The fuse is there to provide safety is certain odd situations. >>> The >>> simple answer these days is to replace it with a piece of wire. >>> >>> Bob >>> >>>> On Nov 30, 2021, at 12:05 PM, Larry McDavid <lmcdavid@lmceng.com> >> wrote: >>>> >>>> Do these thermal fuses fail spontaneously or is there a common cause? >>>> >>>> If the "heater" transistor mounting screws were quite loose, those >>> transistors themselves might have overheated and failed. But, a thermal >>> fuse should fail by high temperature... >>>> >>>> Sounds like progress, though. Cold OCXO means low frequency. >>>> >>>> Jared, I sent you a private email with some pictures; did you get that? >>>> >>>> Larry >>>> >>>> >>>> On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote: >>>>> Well, I found it, the thermal fuse is open circuit. >>>>> If I briefly bypass it with a jumper wire, the oven pulls the expected >>> current. >>>>> Looks like I need something that will trip at roughly around 115C, >>> rated to 1.0A >>>>> (HP Part number 10811-80008) >>>>> Hopefully I can find something in Akihabara to make it easier to get >> my >>> hands on ASAP... >>>>> Jared >>>> ... >>>> -- >>>> Best wishes, >>>> >>>> Larry McDavid W6FUB >>>> Anaheim, California (SE of Los Angeles, near Disneyland) >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe >>> send an email to time-nuts-leave@lists.febo.com >>>> To unsubscribe, go to and follow the instructions there. >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe >> send >>> an email to time-nuts-leave@lists.febo.com >>> To unsubscribe, go to and follow the instructions there. >>> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send >> an email to time-nuts-leave@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there.

Hi The reason for the thermal fuse (which is *not* a feature of other OCXO’s) is the 10811’s deployment in a wide range of devices. There are a few that do have restrictions on them. The 5065 is not one of those devices. The protection provided is minimal. The pass transistor will fail in a runaway situation. Unless you happen to be on a submarine or something similar you are not creating a significant problem when it does. The thermal fuse significantly degrades the reliability of the device. It is by far the most likely part in the entire OCXO to fail. Putting up with this failure process (and the cost of the fuses) is not reasonable if the benefit is quite small. Indeed there was some beer involved in the discussion, but HP OCXO engineering was onboard with the above information last time we chatted about it. That would have been in the early 1990’s …. These failures have been going on for a *long* time. Bob > On Dec 1, 2021, at 7:41 AM, Wilko Bulte <wkb@xs4all.nl> wrote: > > In general it is a very bad idea to defeat safety provisions that a manufacturer put in their product. They are there for a reason, any manufacturer would omit them, if only to save on cost. > > I would think no-one on this list would replace a blown fuse in their house fuse box with a nail. Or? > > Wilko > >> On 1 Dec 2021, at 12:13, Askild <megafluffy@gmail.com> wrote: >> >> Hi, >> >> Just a little warning. >> Included are some pictures of a 10811 where thermal fuse protection have >> not functioned. >> I do not know why, if the fuse did not work, or somebody replaced it with a >> wire, as this was in a HP 8663A that I found in a recycling bin, and I do >> not know the history. >> >> >> Regards, >> Askild >> >> >> >>> On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>> >>> Hi >>> >>> The thermal fuses die on their own far more often than they die protecting >>> anything. The fuse is there to provide safety is certain odd situations. >>> The >>> simple answer these days is to replace it with a piece of wire. >>> >>> Bob >>> >>>>> On Nov 30, 2021, at 12:05 PM, Larry McDavid <lmcdavid@lmceng.com> wrote: >>>> >>>> Do these thermal fuses fail spontaneously or is there a common cause? >>>> >>>> If the "heater" transistor mounting screws were quite loose, those >>> transistors themselves might have overheated and failed. But, a thermal >>> fuse should fail by high temperature... >>>> >>>> Sounds like progress, though. Cold OCXO means low frequency. >>>> >>>> Jared, I sent you a private email with some pictures; did you get that? >>>> >>>> Larry >>>> >>>> >>>> On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote: >>>>> Well, I found it, the thermal fuse is open circuit. >>>>> If I briefly bypass it with a jumper wire, the oven pulls the expected >>> current. >>>>> Looks like I need something that will trip at roughly around 115C, >>> rated to 1.0A >>>>> (HP Part number 10811-80008) >>>>> Hopefully I can find something in Akihabara to make it easier to get my >>> hands on ASAP... >>>>> Jared >>>> ... >>>> -- >>>> Best wishes, >>>> >>>> Larry McDavid W6FUB >>>> Anaheim, California (SE of Los Angeles, near Disneyland) >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe >>> send an email to time-nuts-leave@lists.febo.com >>>> To unsubscribe, go to and follow the instructions there. >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send >>> an email to time-nuts-leave@lists.febo.com >>> To unsubscribe, go to and follow the instructions there. >>> > <P1010309_s.jpg><P1010305_s.jpg><P1010306_s.jpg> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there.

Aha! That is very interesting background information! It nicely puts your comment in perspective to "bridge the fuse with a wire and be done with it". Big grin here when reading the "beer was involved" comment. I have used a similar approach on my business visits to HP CXO (well after T&M was spun off) ;-). A bit like a certain "beer ware license" (hi Poul). Wilko > On 1 Dec 2021, at 20:20, Bob kb8tq <kb8tq@n1k.org> wrote: > > Hi > > The reason for the thermal fuse (which is *not* a feature of other OCXO’s) > is the 10811’s deployment in a wide range of devices. There are a few that > do have restrictions on them. The 5065 is not one of those devices. > > The protection provided is minimal. The pass transistor will fail in a runaway > situation. Unless you happen to be on a submarine or something similar > you are not creating a significant problem when it does. > > The thermal fuse significantly degrades the reliability of the device. It is by > far the most likely part in the entire OCXO to fail. Putting up with this failure > process (and the cost of the fuses) is not reasonable if the benefit is quite > small. > > Indeed there was some beer involved in the discussion, but HP OCXO > engineering was onboard with the above information last time we chatted > about it. That would have been in the early 1990’s …. These failures have > been going on for a *long* time. > > Bob > >> On Dec 1, 2021, at 7:41 AM, Wilko Bulte <wkb@xs4all.nl> wrote: >> >> In general it is a very bad idea to defeat safety provisions that a manufacturer put in their product. They are there for a reason, any manufacturer would omit them, if only to save on cost. >> >> I would think no-one on this list would replace a blown fuse in their house fuse box with a nail. Or? >> >> Wilko >> >>>> On 1 Dec 2021, at 12:13, Askild <megafluffy@gmail.com> wrote: >>> >>> Hi, >>> >>> Just a little warning. >>> Included are some pictures of a 10811 where thermal fuse protection have >>> not functioned. >>> I do not know why, if the fuse did not work, or somebody replaced it with a >>> wire, as this was in a HP 8663A that I found in a recycling bin, and I do >>> not know the history. >>> >>> >>> Regards, >>> Askild >>> >>> >>> >>>> On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>> >>>> Hi >>>> >>>> The thermal fuses die on their own far more often than they die protecting >>>> anything. The fuse is there to provide safety is certain odd situations. >>>> The >>>> simple answer these days is to replace it with a piece of wire. >>>> >>>> Bob >>>> >>>>>> On Nov 30, 2021, at 12:05 PM, Larry McDavid <lmcdavid@lmceng.com> wrote: >>>>> >>>>> Do these thermal fuses fail spontaneously or is there a common cause? >>>>> >>>>> If the "heater" transistor mounting screws were quite loose, those >>>> transistors themselves might have overheated and failed. But, a thermal >>>> fuse should fail by high temperature... >>>>> >>>>> Sounds like progress, though. Cold OCXO means low frequency. >>>>> >>>>> Jared, I sent you a private email with some pictures; did you get that? >>>>> >>>>> Larry >>>>> >>>>> >>>>> On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote: >>>>>> Well, I found it, the thermal fuse is open circuit. >>>>>> If I briefly bypass it with a jumper wire, the oven pulls the expected >>>> current. >>>>>> Looks like I need something that will trip at roughly around 115C, >>>> rated to 1.0A >>>>>> (HP Part number 10811-80008) >>>>>> Hopefully I can find something in Akihabara to make it easier to get my >>>> hands on ASAP... >>>>>> Jared >>>>> ... >>>>> -- >>>>> Best wishes, >>>>> >>>>> Larry McDavid W6FUB >>>>> Anaheim, California (SE of Los Angeles, near Disneyland) >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe >>>> send an email to time-nuts-leave@lists.febo.com >>>>> To unsubscribe, go to and follow the instructions there. >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send >>>> an email to time-nuts-leave@lists.febo.com >>>> To unsubscribe, go to and follow the instructions there. >>>> >> <P1010309_s.jpg><P1010305_s.jpg><P1010306_s.jpg> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com >>> To unsubscribe, go to and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there.

Well, yay... I put the OCXO back in the 5065A, and got a good 2nd Harmonic reading. So I started going through the alignment procedures and somehow I now have no 2nd harmonic again, and I can't get it back... I'm starting to lose interest in this thing, seeing as I have the Leo Bodnar GPS standard anyway that I don't have to sit for hours twiddling dials and poking things just to get it maybe sort of working. I might give this one more chance before I sell it off to someone with a little more patience, or who prefers fixing gear instead of actually using it. I think I've had this thing working for all of a couple days in the months I've owned it, whereas the GPS standard is the size of a pack of cards and has never failed in the same time. Jared. ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Thursday, December 2nd, 2021 at 04:19, Bob kb8tq <kb8tq@n1k.org> wrote: > Hi > > The reason for the thermal fuse (which is not a feature of other OCXO’s) > > is the 10811’s deployment in a wide range of devices. There are a few that > > do have restrictions on them. The 5065 is not one of those devices. > > The protection provided is minimal. The pass transistor will fail in a runaway > > situation. Unless you happen to be on a submarine or something similar > > you are not creating a significant problem when it does. > > The thermal fuse significantly degrades the reliability of the device. It is by > > far the most likely part in the entire OCXO to fail. Putting up with this failure > > process (and the cost of the fuses) is not reasonable if the benefit is quite > > small. > > Indeed there was some beer involved in the discussion, but HP OCXO > > engineering was onboard with the above information last time we chatted > > about it. That would have been in the early 1990’s …. These failures have > > been going on for a long time. > > Bob > > > On Dec 1, 2021, at 7:41 AM, Wilko Bulte wkb@xs4all.nl wrote: > > > > In general it is a very bad idea to defeat safety provisions that a manufacturer put in their product. They are there for a reason, any manufacturer would omit them, if only to save on cost. > > > > I would think no-one on this list would replace a blown fuse in their house fuse box with a nail. Or? > > > > Wilko > > > > > On 1 Dec 2021, at 12:13, Askild megafluffy@gmail.com wrote: > > > > > > Hi, > > > > > > Just a little warning. > > > > > > Included are some pictures of a 10811 where thermal fuse protection have > > > > > > not functioned. > > > > > > I do not know why, if the fuse did not work, or somebody replaced it with a > > > > > > wire, as this was in a HP 8663A that I found in a recycling bin, and I do > > > > > > not know the history. > > > > > > Regards, > > > > > > Askild > > > > > > > On Tue, Nov 30, 2021 at 8:34 PM Bob kb8tq kb8tq@n1k.org wrote: > > > > > > > > Hi > > > > > > > > The thermal fuses die on their own far more often than they die protecting > > > > > > > > anything. The fuse is there to provide safety is certain odd situations. > > > > > > > > The > > > > > > > > simple answer these days is to replace it with a piece of wire. > > > > > > > > Bob > > > > > > > > > > On Nov 30, 2021, at 12:05 PM, Larry McDavid lmcdavid@lmceng.com wrote: > > > > > > > > > > Do these thermal fuses fail spontaneously or is there a common cause? > > > > > > > > > > If the "heater" transistor mounting screws were quite loose, those > > > > > > > > > > transistors themselves might have overheated and failed. But, a thermal > > > > > > > > > > fuse should fail by high temperature... > > > > > > > > > > Sounds like progress, though. Cold OCXO means low frequency. > > > > > > > > > > Jared, I sent you a private email with some pictures; did you get that? > > > > > > > > > > Larry > > > > > > > > > > On 11/30/2021 8:03 AM, Jared Cabot via time-nuts wrote: > > > > > > > > > > > Well, I found it, the thermal fuse is open circuit. > > > > > > > > > > > > If I briefly bypass it with a jumper wire, the oven pulls the expected > > > > > > > > > > > > current. > > > > > > > > > > > Looks like I need something that will trip at roughly around 115C, > > > > > > > > > > > > rated to 1.0A > > > > > > > > > > > (HP Part number 10811-80008) > > > > > > > > > > > > Hopefully I can find something in Akihabara to make it easier to get my > > > > > > > > > > > > hands on ASAP... > > > > > > > > > > > Jared > > > > > > > > > > > > ... > > > > > > > > > > > > -- > > > > > > > > > > > > Best wishes, > > > > > > > > > > Larry McDavid W6FUB > > > > > > > > > > Anaheim, California (SE of Los Angeles, near Disneyland) > > > > > > > > > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > > > > > > > > > > send an email to time-nuts-leave@lists.febo.com > > > > > > > > > > To unsubscribe, go to and follow the instructions there. > > > > > > > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > > > > > > > > an email to time-nuts-leave@lists.febo.com > > > > > > > > To unsubscribe, go to and follow the instructions there. > > > > <P1010309_s.jpg><P1010305_s.jpg><P1010306_s.jpg> > > > > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > > > > > > To unsubscribe, go to and follow the instructions there. > > > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > > > > To unsubscribe, go to and follow the instructions there. > > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > > To unsubscribe, go to and follow the instructions there.

Don't give up now, Jared! You must be so close to getting that puppy running correctly. On 2/12/21 9:16 pm, Jared Cabot via time-nuts wrote: > Well, yay... > > I put the OCXO back in the 5065A, and got a good 2nd Harmonic reading. So I started going through the alignment procedures and somehow I now have no 2nd harmonic again, and I can't get it back... > > I'm starting to lose interest in this thing, seeing as I have the Leo Bodnar GPS standard anyway that I don't have to sit for hours twiddling dials and poking things just to get it maybe sort of working. > > I might give this one more chance before I sell it off to someone with a little more patience, or who prefers fixing gear instead of actually using it. I think I've had this thing working for all of a couple days in the months I've owned it, whereas the GPS standard is the size of a pack of cards and has never failed in the same time. > > > Jared. >