Date set for next Sphere Stuff Day/Radio Amateur Swap Meet
Mike,
Ouch!
Not opening before they say OK seems like a good strategy.
I just wanted to share that little story even if it doesn't help you.
It was worse when I got a BVA with crushed thermo-flask. I was
actually given a replacement thermo-flask within a few days from OSA.
Cheers,
Magnus
On 03/06/2016 02:15 AM, timenut@metachaos.net wrote:
Magnus,
In this case, the rattle is not of light weight pieces, but of a heavy object.
So, I am guessing that the outer oven broke off somehow. Won't really know
until and unless I open it up. The vendor probably won't want it back, but
they might, so I won't touch it until I hear from them.
Mike
Hi,
On 03/05/2016 10:45 PM, timenut@metachaos.net wrote:
I got the replacement MTI 260-0624-D OCXO today.
It rattles!
I've seen that on one oscillator. I did a RMA and complained about the
maracas mode, which I had demonstrated to the rep. When it arrived they
wondered what that mean and the rep just smiled and ask them to pick it
up... and it rattle. Turns out that the way they soldered their ovens,
drops of solder could form and get loose, so they changed the process.
Unfortunatly, it is also the failure mode of rough shipping/handling for
some oscillators.
Cheers,
Magnus
I didn't even bother trying to power it up. Not much point. I have not taken
it apart, but have notified the seller. I may disassemble this one as well,
depending on what the seller says.
Mike
I just received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After testing it,
it is clear that it is defective.
1. It never heats up.
2. The reference voltage is zero.
3. Only noise is seen on the output pin.
I tested with a 12.54V, 2A supply voltage with around 30mV noise. That should
be sufficient to test.
All I was looking for was a 5Mhz signal whose frequency changed when the
adjustment pin was either tied to ground or the reference voltage. Never got
that far because I never go a signal at all.
The seller packed it well and shipped it promptly. I will see how he handles
it.
Mike
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Hi
Anything electrical (duty cycle/ harmonics / output level / etc)
is designed in on a modern part done in high volume.
The only candidates for a pot on top of the oven are:
Inner oven temperature
Outer oven temperature
EFC
You have already ruled out EFC (it would be a coarse set so
visible on a normal counter).
That leaves inner oven and outer oven.
Why inner oven - to adjust for the data from your temperature run. The parts
are at best coarse set based on crystal temperature.
Why outer oven - same as above or to set for inner / outer separation
and clearance after the thermal stabilization in the sealed can.
If there is no apparent change in frequency (and from the location of
the pot) that suggests the outer oven. Regardless of which oven is being set, the
adjustment is likely a “move it 1.25 turns" sort of thing. You then
re-run the temperature test to see if it is in spec yet.
Bob
Bob,
In a separate communication, Angus has stated...
On the two that I tested, it appeared to adjust the temperature of
both of the ovens.
One was a 5 MHz 260-0545-B. The outer oven was at 78.2 degC and at
least around that point the temp changed at about 1 degC per turn. The
EFC adjustment on this one was not quite enough to bring the frequency
to exactly 5 MHz, but the oven temp did look to be close to correct.
The other was a 16.384 MHz 260-0546-G which was unused old stock, but
had overall poor stability. It turned out that the oven temp on it was
1-3/8 turns from the turnover point, but when or how that happened I
don't know.
It would be interesting to hear from somebody who knows how this type
of thing is actually adjusted in production.
I finally got my 260 (sort of) repaired and have done some measurements.
Generally, I can confirm what Angus was saying, to the limits of my ability to
measure. One of the things that I can measure is the source voltage. I have a
hacked together 12v supply. When hooked up to the 260, it initially reads just
over 9v. As it warms up, it eventually tops out just under 10v. There appears
to be roughly four different points, around 9.1v, 9.35v, 9.8v and 10v. The 260
starts at around 9.1v, quickly moves up to 9.35v and after a while to 9.8v. It
will then sometimes move briefly up to 10v and back down to 9.8v.
I interpret this as different heating stages - probably both ovens on, one
oven on, some sort of maintenance heating point and no heaters on.
What I find as I adjust the pot (after letting the 260 warm up) is that
turning the pot counter clockwise the supply voltage will go up to 10v and
turning it clockwise it will drop to 9.35v or 9.1v. So, from that it would
appear that you are right in that the temperature set points are being
adjusted by the pot. Whether only one is adjusted or both are changed as Angus
says isn't clear.
I also noticed that the 260 consistently has an adjustment range of +/-2e-7,
regardless of where the frequency is set, with 0v applied to the adjustment
pin giving a frequency 4Hz higher than when the 5.65v reference voltage is
applied to the adjustment pin. It will adjust further if the reference pin is
hooked up to the supply voltage.
So, I decided to get as much information as I could. I turned the pot
clockwise until it "ticked" once each turn. That dropped the temperature to
the minimum. I then turned it counter clockwise 1/2 turn at a time and
recorded each temperature / frequency reading. I did this until it "ticked"
once each turn. That took nearly three days. To obtain the temperature, I
used Kapton tape to tape a temperature sensor for my multimeter to the casing
of the outer oven. This is not necessarily the hottest spot, nor does it
actually measure the temperature in either the inner or outer oven. Further,
the multimeter's precision is only around 1 degree C. The accuracy is unknown,
but it should be repeatable and roughly linear. I used my (uncalibrated)
2465BCT to measure the frequency. This is limited to 7 digits without a
calibrated frequency standard and is probably slightly off. Still, that gave
me a good bit of data. Here is the raw data.
60 5.000001
61 5.000002
61 5.000003
62 5.000003
62 5.000004
63 5.000005
63 5.000006
64 5.000006
65 5.000007
65 5.000008
66 5.000008
66 5.000009
67 5.000009
67 5.000010
68 5.000010
69 5.000010
70 5.000011
71 5.000011
72 5.000012
73 5.000012
74 5.000012
75 5.000012
76 5.000012
76 5.000013
77 5.000013
78 5.000012
79 5.000012
80 5.000012
81 5.000012
Here is a rough graph. It shows the expected SC temperature / frequency type
of curve. However, what is interesting is the range over which adjusting the
temperature affects the frequency. This is a total of 12Hz! Also, it should be
noted that the outer case was not in place, so the outer oven is exposed to
ambient temperature. That probably limited the maximum reachable temperature.
I could noticeably change the both the temperature and frequency by simply
blowing on the 260.
5.000013 * *
5.000012 * * * * * * * * *
5.000011 * *
5.000010 * * *
5.000009 * *
5.000008 * *
5.000007 *
5.000006 * *
5.000005 *
5.000004 *
5.000003 * *
5.000002 *
5.000001 *
60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81
The vendor has refunded my money for the 260 (the one that rattles), so as
soon as I get a chance I will try a new opening technique and see if it is
possible to repair it. Having learning a lot about the construction from the
first one, I think it is at least a possibility.
I will let everyone know what happens - with pictures - once I have done that.
That may take me until next week. I am attending the Charlotte hamfest
Saturday.
Mike
Hi
Judging from your data, the pot takes the oven from at or above the inflection temperature of the crystal down to a point well below the crystal’s lower turn temperature. That’s about all it needs to do.
Bob
On Mar 11, 2016, at 11:19 PM, timenut@metachaos.net wrote:
Hi
Anything electrical (duty cycle/ harmonics / output level / etc)
is designed in on a modern part done in high volume.
The only candidates for a pot on top of the oven are:
Inner oven temperature
Outer oven temperature
EFC
You have already ruled out EFC (it would be a coarse set so
visible on a normal counter).
That leaves inner oven and outer oven.
Why inner oven - to adjust for the data from your temperature run. The parts
are at best coarse set based on crystal temperature.
Why outer oven - same as above or to set for inner / outer separation
and clearance after the thermal stabilization in the sealed can.
If there is no apparent change in frequency (and from the location of
the pot) that suggests the outer oven. Regardless of which oven is being set, the
adjustment is likely a “move it 1.25 turns" sort of thing. You then
re-run the temperature test to see if it is in spec yet.
Bob
Bob,
In a separate communication, Angus has stated...
On the two that I tested, it appeared to adjust the temperature of
both of the ovens.
One was a 5 MHz 260-0545-B. The outer oven was at 78.2 degC and at
least around that point the temp changed at about 1 degC per turn. The
EFC adjustment on this one was not quite enough to bring the frequency
to exactly 5 MHz, but the oven temp did look to be close to correct.
The other was a 16.384 MHz 260-0546-G which was unused old stock, but
had overall poor stability. It turned out that the oven temp on it was
1-3/8 turns from the turnover point, but when or how that happened I
don't know.
It would be interesting to hear from somebody who knows how this type
of thing is actually adjusted in production.
I finally got my 260 (sort of) repaired and have done some measurements.
Generally, I can confirm what Angus was saying, to the limits of my ability to
measure. One of the things that I can measure is the source voltage. I have a
hacked together 12v supply. When hooked up to the 260, it initially reads just
over 9v. As it warms up, it eventually tops out just under 10v. There appears
to be roughly four different points, around 9.1v, 9.35v, 9.8v and 10v. The 260
starts at around 9.1v, quickly moves up to 9.35v and after a while to 9.8v. It
will then sometimes move briefly up to 10v and back down to 9.8v.
I interpret this as different heating stages - probably both ovens on, one
oven on, some sort of maintenance heating point and no heaters on.
What I find as I adjust the pot (after letting the 260 warm up) is that
turning the pot counter clockwise the supply voltage will go up to 10v and
turning it clockwise it will drop to 9.35v or 9.1v. So, from that it would
appear that you are right in that the temperature set points are being
adjusted by the pot. Whether only one is adjusted or both are changed as Angus
says isn't clear.
I also noticed that the 260 consistently has an adjustment range of +/-2e-7,
regardless of where the frequency is set, with 0v applied to the adjustment
pin giving a frequency 4Hz higher than when the 5.65v reference voltage is
applied to the adjustment pin. It will adjust further if the reference pin is
hooked up to the supply voltage.
So, I decided to get as much information as I could. I turned the pot
clockwise until it "ticked" once each turn. That dropped the temperature to
the minimum. I then turned it counter clockwise 1/2 turn at a time and
recorded each temperature / frequency reading. I did this until it "ticked"
once each turn. That took nearly three days. To obtain the temperature, I
used Kapton tape to tape a temperature sensor for my multimeter to the casing
of the outer oven. This is not necessarily the hottest spot, nor does it
actually measure the temperature in either the inner or outer oven. Further,
the multimeter's precision is only around 1 degree C. The accuracy is unknown,
but it should be repeatable and roughly linear. I used my (uncalibrated)
2465BCT to measure the frequency. This is limited to 7 digits without a
calibrated frequency standard and is probably slightly off. Still, that gave
me a good bit of data. Here is the raw data.
60 5.000001
61 5.000002
61 5.000003
62 5.000003
62 5.000004
63 5.000005
63 5.000006
64 5.000006
65 5.000007
65 5.000008
66 5.000008
66 5.000009
67 5.000009
67 5.000010
68 5.000010
69 5.000010
70 5.000011
71 5.000011
72 5.000012
73 5.000012
74 5.000012
75 5.000012
76 5.000012
76 5.000013
77 5.000013
78 5.000012
79 5.000012
80 5.000012
81 5.000012
Here is a rough graph. It shows the expected SC temperature / frequency type
of curve. However, what is interesting is the range over which adjusting the
temperature affects the frequency. This is a total of 12Hz! Also, it should be
noted that the outer case was not in place, so the outer oven is exposed to
ambient temperature. That probably limited the maximum reachable temperature.
I could noticeably change the both the temperature and frequency by simply
blowing on the 260.
5.000013 * *
5.000012 * * * * * * * * *
5.000011 * *
5.000010 * * *
5.000009 * *
5.000008 * *
5.000007 *
5.000006 * *
5.000005 *
5.000004 *
5.000003 * *
5.000002 *
5.000001 *
60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81
The vendor has refunded my money for the 260 (the one that rattles), so as
soon as I get a chance I will try a new opening technique and see if it is
possible to repair it. Having learning a lot about the construction from the
first one, I think it is at least a possibility.
I will let everyone know what happens - with pictures - once I have done that.
That may take me until next week. I am attending the Charlotte hamfest
Saturday.
Mike
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