Re: [time-nuts] Looking for Z3801 OCXO
You may have seen this before, but there is a nice writeup on how to disassemble the whole thing, with pictures and all. http://www.realhamradio.com/GPS-oven-journey.htm I had to take mine apart quite a few years ago to replace the opamp in the inner oven temperature regulator circuit. If your problem is just adjustment, you don't even have to open the inner oven. BTW as I recall, the ovens are sequenced, to reduce power at turn-on. I forget the order, but one (probably inner) has to be up and running close to setpoint, before the other is activated. Ed ___ 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.
Re: [time-nuts] Looking for Z3801 OCXO
Thanks, Warren. That's a very nice solution! I have a unit on the way from another time-nut, so I should be set. I'm pretty sure the problem with the old unit is just aging as I watched the EFC creep for months toward the limit. I bought two units at the same time (long, long ago) and though they had similar running time, this one always had EFC values far higher than the other one, which is still running fine. > On Feb 5, 2016, at 1:39 AM, ws at Yahoo wrote: > > > John > If it is off very far the first thing I'd suspect is the inner oven. > > Assuming the freq is still stable and low noise, one option is to rewire it, > and make the freq adjustment accessible. > Removing the original inner wiring wrap also provides many other advantages, > and no down side that I've found. > After modifying several, it now takes me about an hour to do. > From the outside you can not tell that it has been modified, unless I change > the crappy little blue shielded RF and EFC cables that it originally comes > with, which I now always do. > It takes about five minutes on a correctly modified unit to readjust the > frequency. The adjuster nut and hole is accessible after temporarily removing > the bottom outer cover, thru a 3/8 inch access hole drilled in the bottom of > the outer oven that is placed *under* the bottom heater flap. > It is easy to adjust thru the bottom of the unit and can be done without > powering down or disturbing the oscillator or either oven's power. > > Picture attached of modified inside cabling, before the two shielded cables > are added. > No mess. Any goo gets cleaned up with alcohol or thrown away. > > ws > > > > John Posted: > "Looking for Z3801 OCXO" > > I have a Z3801A whose oscillator has aged out of correction range, and > thus throws an EFC alarm. > > Anyone have a still-in-range double-oven HP10811 from a unit that died > for another reason? If so, I'd be happy to acquire it. > > (I tried disassembling one of the double-oven 10811s years ago and found > that extracting the oscillator can from the outer oven, heater, and > gooey insulation made such a mess that it would be impossible to > reassemble.) > > Thanks! > > John > > > ___ 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.
Re: [time-nuts] Looking for Z3801 OCXO
John If it is off very far the first thing I'd suspect is the inner oven. Assuming the freq is still stable and low noise, one option is to rewire it, and make the freq adjustment accessible. Removing the original inner wiring wrap also provides many other advantages, and no down side that I've found. After modifying several, it now takes me about an hour to do. >From the outside you can not tell that it has been modified, unless I change the crappy little blue shielded RF and EFC cables that it originally comes with, which I now always do. It takes about five minutes on a correctly modified unit to readjust the frequency. The adjuster nut and hole is accessible after temporarily removing the bottom outer cover, thru a 3/8 inch access hole drilled in the bottom of the outer oven that is placed *under* the bottom heater flap. It is easy to adjust thru the bottom of the unit and can be done without powering down or disturbing the oscillator or either oven's power. Picture attached of modified inside cabling, before the two shielded cables are added. No mess. Any goo gets cleaned up with alcohol or thrown away. ws John Posted: "Looking for Z3801 OCXO" I have a Z3801A whose oscillator has aged out of correction range, and thus throws an EFC alarm. Anyone have a still-in-range double-oven HP10811 from a unit that died for another reason? If so, I'd be happy to acquire it. (I tried disassembling one of the double-oven 10811s years ago and found that extracting the oscillator can from the outer oven, heater, and gooey insulation made such a mess that it would be impossible to reassemble.) Thanks! John ___ 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.
Re: [time-nuts] Looking for Z3801 OCXO
John, Like you I have a bad oscillator and I also pulled the thing apart to find "The goo" Nasty stuff. Also re-wrapping the outer oven wire would be a big pain. Since that 3801 had further issues I set it aside. Regards Paul WB8TSL On Thu, Feb 4, 2016 at 1:20 PM, John Ackermann N8UR wrote: > I have a Z3801A whose oscillator has aged out of correction range, and > thus throws an EFC alarm. > > Anyone have a still-in-range double-oven HP10811 from a unit that died for > another reason? If so, I'd be happy to acquire it. > > (I tried disassembling one of the double-oven 10811s years ago and found > that extracting the oscillator can from the outer oven, heater, and gooey > insulation made such a mess that it would be impossible to reassemble.) > > Thanks! > > John > ___ > 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. > ___ 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.
