|
Hello everyone,
about a year ago, turning on my HP8563E spectrum analyzer, several errors appeared, including the ravenous error 334.
From research on the net, and a direct inspection, I found that the YTO model 5086-7906 was broken.
Pin 1, corresponding to 4 of connector J3, of the 5 VDC power supply, appears to be shorted to ground.
About a month ago, I bought an HP8560E Spectrum Analyzer at a good price with the intention of using its YTO for my HP8563E.
In fact, the analyzer cost me as much as a used YTO!
Before mounting it, I checked that the voltages of +5V, +15V and -15V were present.
Then I mounted the YIG oscillator, checking several times that the connectors were mounted correctly. Which I always do when I reassemble an electronic instrument.
When I turned the spectrum analyzer back on, I found that the new YTO was also broken !! A check of the same confirmed this.
What could I have done wrong? Has anything like this ever happened to anyone? Is there anyone in the group who has experience with these damn YTOs?
Given that I'm not really fasting with electronic instruments, such a thing had never happened to me.
I contacted a local company that repairs the YTO at a price of around 800 euros but I'm afraid that if I don't find out the reason for the break, this too could break ...
|
Picol,
It has been a while since I tried (with partial success) to repair on of these YTOs.? If I recall correctly, the output of the NPN oscillator is buffered by a FET amplifier with the drain fed from the +5v supply.? If that FET is a GaAs type, it probably requires a negative bias to turn off.? It might appear as a (near) short to ground with no negative bias available.
--John Gord
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On Sun, Aug 28, 2022 at 11:18 AM, @Picol wrote:
Hello everyone,
about a year ago, turning on my HP8563E spectrum analyzer, several errors appeared, including the ravenous error 334.
From research on the net, and a direct inspection, I found that the YTO model 5086-7906 was broken.
Pin 1, corresponding to 4 of connector J3, of the 5 VDC power supply, appears to be shorted to ground.
About a month ago, I bought an HP8560E Spectrum Analyzer at a good price with the intention of using its YTO for my HP8563E.
In fact, the analyzer cost me as much as a used YTO!
Before mounting it, I checked that the voltages of +5V, +15V and -15V were present.
Then I mounted the YIG oscillator, checking several times that the connectors were mounted correctly. Which I always do when I reassemble an electronic instrument.
When I turned the spectrum analyzer back on, I found that the new YTO was also broken !! A check of the same confirmed this.
What could I have done wrong? Has anything like this ever happened to anyone? Is there anyone in the group who has experience with these damn YTOs?
Given that I'm not really fasting with electronic instruments, such a thing had never happened to me.
I contacted a local company that repairs the YTO at a price of around 800 euros but I'm afraid that if I don't find out the reason for the break, this too could break ...
|
John, thanks for your answer!
It is true what they say, but I forgot to write in the previous message that I tried the two YIG oscillators on both SAs connected to a power meter and they show no signs of life.
The thing that drives me crazy is knowing what I did wrong. Murphy has struck again!
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Today I tried to power the YTO 5086-7906, that of the 8563E, externally to the analyzer.
Granted that I have checked all the components of the small PCB on the oscillator, I noticed that the current absorbed values are:
+5 VDC, 98 mA
+15 VDC, 28 mA
-15VDC, 1mA
I also powered the main coil (pins 5 and 6) with a current from 50 to 100 mA, not knowing the exact operating value.
By adjusting the latter, the value read on the power meter does not change: about -28 dBm. Instead of the expected +10 dBm!
Now I'm sure the YTO is broken.
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What style of output connection is on this YTO? Not whether it's SMA, but how it's mounted to the body. If it's a barrel type screwed into a threaded hole and locked with a nut, you can as a last resort try rotating it, a little at a time. I have an old HP YTO that had way low output because of intermittent connection inside right at the connector. When this happens, you have a tiny capacitance in series with the output, so only a tiny bit of signal gets through, even though the guts are working. Sometimes you can restore operation by changing stress at that joint - maybe temporary, but doable. If the YTO is of a type of construction that can be opened up, it may be possible to actually fix it with soldering or silver DAG.
If you manage to "fix" it by adjusting the rotation, the trick is to make sure that whatever final outside connection is made, can't stress it back to non-working while tightening it up, so it takes careful assembly. Keep in mind that every time one of these YTO connections is undone and redone, for diagnosis or experimenting, it adds to the wear and tear. This is why simply swapping out YTOs can succeed or fail, depending on what happens with marginal connectors.
I'm guessing that you may have two good YTOs if you can restore their connections.
Ed
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Hi Ed, unfortunately the RF signal output connection is via a female SMA connector. The YTO 5086-7906 is built very well, as per HP tradition, and it is also easy to open it, having a little foresight and in a non-dusty environment.
I opened one of the two, broken, that I have, to check if inside there were any burn marks or gold wires, welded with the wire bonding technique, interrupted. Unfortunately, even with the microscope I did not find anything abnormal.
Opening the YTO is very easy: just remove the locked rear cover and unscrew the rear spacers.
The oscillator thus opens in two parts, the rear contains the two windings of the MAIN COIL and the FM COIL and the front contains all the electronic circuitry I believe on a sapphire substrate, including the ball in yttrium iron garnet.
Much of what I know I learned from reading the Keysight forum thread at: https://community.keysight.com/forums/s/question/0D52L00005IdorQSAR/hp-8560e-spectrum-analyzer-yig-yto- a11-questionproblem
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A lot of them tune at 20 MHz/mA, so 100 mA may not have been enough.? I'd crank the main coil current up to 200 mA and see if that makes a difference. ? -- john, KE5FX ?
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From: [email protected] [mailto:[email protected]] On Behalf Of piecolav via groups.io
Sent: Monday, August 29, 2022 10:09 AM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 5086-7906 YTO? Today I tried to power the YTO 5086-7906, that of the 8563E, externally to the analyzer.
Granted that I have checked all the components of the small PCB on the oscillator, I noticed that the current absorbed values are:
+5 VDC, 98 mA
+15 VDC, 28 mA
-15VDC, 1mA
I also powered the main coil (pins 5 and 6) with a current from 50 to 100 mA, not knowing the exact operating value.
By adjusting the latter, the value read on the power meter does not change: about -28 dBm. Instead of the expected +10 dBm!
Now I'm sure the YTO is broken.
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Below is a high level YIG tuning coil freq v current graph. 50 mA is to low, 125mA is about mid range 3-7GHz based on a similar HP YIG from a HP-8594E. 
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Thank you for the information, John! I tried to increase the tuning coil current up to 200 mA but to no avail.
Then, I also wanted to look at the second YTO under the microscope, the one extracted from the HP8560E and I discovered to my surprise that the wire connected to the PIN of the 5 VDC power supply was interrupted.
With a lot of patience and using the finest soldering iron tip I had, I pre-wetted the PIN. Then using a thinned toothpick I bent the wire until it touched the PIN. And I lightly rested the tip of the soldering iron on it for a moment.
I checked and the soldering was successful. I did well? I used as little tin as possible to avoid tin bubbles that could out-scale the YTO.
Unfortunately my microscope has a maximum magnification of 57X. It would take one with at least double the magnification.
I connected the YTO to the power supplies by crossing my fingers and to my surprise I found that it worked!
The peak power, about 13.5 dBm, I get it with a tune current of 90 mA.
Instead I noticed that the absorbed currents, with the YTO running, have varied a lot, that is:
+5 VDC, 73 mA
+15 VDC, 20 mA
-15 VDC, 7 mA
I reinstalled the YTO in its SA and checked it was working properly. I kept it running for several hours doing all the tests possible, all passed positively.
At this point the hypotheses for the breakdown of the second YTO have narrowed down to only two:
1- internally the YTO of the HP8560E, although similar in structure, differed slightly from that of the HP8563E. Question: Were there different versions made? Or is the YTO mounted on the HP8560E not the 5086-7906? So why did it break?
I also found that this YTO has been repaired. Internally there are several scratches ...
2- The +5 VDC voltage of the HP8563E has some problems. I checked it and it is stable and precise but, I doubted that some tantalum capacitor (there are several on that line) is interrupted and the power on extra current, not absorbed by the capacitor, may have caused it to burn the two YTOs.
Could mine be a valid hypothesis?
Sorry if I'm insisting on the subject, but I just want to try to understand and learn and thank you all for your cooperation!
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I was looking for info on this YTO, and stumbled upon this ebay listing, which I found to be very informative, and disturbing:
https://www.ebay.com/itm/HP-AGILENT-YTO-YIG-REPAIR-5086-7903-8593E-8594e-8595e-8596e-8592L-8593em/252216883196
This has a bunch of info on these YTOs. What I find disturbing is that it appears that a whole family (856X and 859X) of HP portable SAs may have a serious reliability issue - big enough to support a cottage industry repairing their YTOs. Maybe the the actual failure percentage is tiny, and there are just a lots and lots of units out there, so no big deal, but it seems like an awful lot of failures to me. I don't have any of these models, so it doesn't affect me, but I wonder what the deal is. My experience with lots of old-school YIG devices is that they last virtually forever, unless abused.
Ed
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Ed, you're absolutely right. It's the same thing I thought when I started getting interested in buying one of these YTOs.
Especially the 856X series SAs are still today pretty good tools. They have a low noise floor, wide dynamics, low phase noise and digital resolution up to 1Hz. And surelythere are tens of thousands of instruments still in operation around the world. But, nevertheless, the number of YIG oscillators still seems to be too large.
But the biggest problem, I believe, is the high price required to repair them.
Even Keysight, whom I contacted, hasn't sold any in a while, but continues to repair these YTOs by shipping the complete instrument. Sum required? About 3000 euros!
They are probably shipped to the US for repair, I read in another forum that they would be built by the Microsource of Santa Rosa, and realigned on the instrument, but still it seems like an overpriced.
I understand that they are professional instruments, and I don't even want to think about how much a new instrument of similar characteristics costs today, but still they look like giants with feet of clay ...
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The Ebay listing is from Testcalinstruments.? I have done business with him in the past and can say that he knows what he is doing, has reasonable prices, and is good to deal with.
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I have 2 HP8563E both bought with dead YTO. and both YTO has aged BJT that has insufficient gain to keep the oscillation happen. The new original YTO is not obtainable, so I modified the YTO driver loops and installed two different type YTO (omini / advantek)? and both of them works without problem.
?
Also check the power supply. HP YTO (EYO) in 85xx has output level control loop. The loop will over voltage the BJT and finally destroy it if 5V (for output FET) is not present for some extend period.
?
I¡¯m also work on the new oscillator board for the EYO. With some modern tiny SMD device the rebuild YTO performance can even better than the old thin film circuits.?
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Yue, thanks for the information Yue. As I had already written, I had checked the power supplies of the YTO and they were correct, including that of the 5V.
Is't possible to have more information on the modifications you made to install other YIG oscillators? Thanks.
I hope you will soon be able to design a modern oscillator to replace HP's fragile YTO. You would have me as your first buyer!
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I am a hobbyist from Milan - Italy and I am trying to bring my 8595E back to its former glory
I have been following the HP-Agilent group for years and I have appreciated your frequent and intelligent contributions among which the expertise regarding the HP analyzer series stands out
I was wondering if I can ask you for some advice that can help me get my analyzer back on track
thanks in advance
adri
?
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----- Messaggio originale -----
Inviato: 29/08/2022 00:33:35
Oggetto: Re: [HP-Agilent-Keysight-equipment] HP 5086-7906 YTO
Picol, It has been a while since I tried (with partial success) to repair on of these YTOs.? If I recall correctly, the output of the NPN oscillator is buffered by a FET amplifier with the drain fed from the +5v supply.? If that FET is a GaAs type, it probably requires a negative bias to turn off.? It might appear as a (near) short to ground with no negative bias available. --John Gord On Sun, Aug 28, 2022 at 11:18 AM, @Picol wrote:
Hello everyone,
about a year ago, turning on my HP8563E spectrum analyzer, several errors appeared, including the ravenous error 334.
From research on the net, and a direct inspection, I found that the YTO model 5086-7906 was broken.
Pin 1, corresponding to 4 of connector J3, of the 5 VDC power supply, appears to be shorted to ground.
About a month ago, I bought an HP8560E Spectrum Analyzer at a good price with the intention of using its YTO for my HP8563E.
In fact, the analyzer cost me as much as a used YTO!
Before mounting it, I checked that the voltages of +5V, +15V and -15V were present.
Then I mounted the YIG oscillator, checking several times that the connectors were mounted correctly. Which I always do when I reassemble an electronic instrument.
When I turned the spectrum analyzer back on, I found that the new YTO was also broken !! A check of the same confirmed this.
What could I have done wrong? Has anything like this ever happened to anyone? Is there anyone in the group who has experience with these damn YTOs?
Given that I'm not really fasting with electronic instruments, such a thing had never happened to me.
I contacted a local company that repairs the YTO at a price of around 800 euros but I'm afraid that if I don't find out the reason for the break, this too could break ...
_._,_._,_
|
Hi Adri, ? I have owned a 8595E for a few years, but it recently broke down and I had to repair it, what is your problem exactly? I can see that the RF part is disassembled, but please give more details. ? Yves ? I am a hobbyist from Milan - Italy and I am trying to bring my 8595E back to its former glory
I have been following the HP-Agilent group for years and I have appreciated your frequent and intelligent contributions among which the expertise regarding the HP analyzer series stands out
I was wondering if I can ask you for some advice that can help me get my analyzer back on track
thanks in advance
adri
|
I have a fully working (AFAIK) 8595E,
if you need anything I can read from the screen or via IEEE-488.
Swamped with work for the next few weeks, so any disassembly is
out of the question.
Steve Hendrix
On 2024-08-25 3:50 PM, Yves Tardif
wrote:
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Hi Adri,
?
I have owned a 8595E for a few years, but it
recently broke down and I had to repair it, what is your
problem exactly?
I can see that the RF part is disassembled, but
please give more details.
?
Yves
?
I
am a hobbyist from Milan - Italy and I am trying to bring
my 8595E back to its former glory
I have been following the HP-Agilent group for years and I
have appreciated your frequent and intelligent
contributions among which the expertise regarding the HP
analyzer series stands out
I was wondering if I can ask you for some advice that can
help me get my analyzer back on track
thanks in advance
adri
|
Yves, Steve, thank you very much for the offer of help
I'll try to make it short:
A few years ago my 8595E had shown signs of "deafness" in band 1 and given the prices of a SYTF I decided to keep it as it was
?
Unfortunately, some time later the main oscillator (YTO) also stopped working
?
This component also had prices out of my reach and, with a lot of patience and little hope, I purchased a YTO at a reduced price and, months later, a SYTF both sold "as is"
?
Not having in my hobbyist laboratory everything I needed to test them (for example another working 8595E) I left the project pending until a tiny instrument (TinySA Ultra) appeared on the market that is allowing me to address the problem, at least at a diagnostic level
?
And so I started to test the measured YTO on the bench, verifying that it covers continuously from 3.06 to 7.52GHz at 23mA/GHz with an output (excluding the extremes) between 7 and 10 dBm with peaks of 13.4dBm (FM coil not tested)
?
It would therefore seem to work well
?
I then tested the SYTF: the switch section seems to work well and also the filter section seems to work well as a bandpass with an insertion loss on the tested frequencies (5 - 6GHz) up to 11 dBm
?
And so I installed the two components in my 8595E and first I tried to do the calibration but the sequence soon stops with "Cal signal not found"
?
Now, the calibration signal is present (and in specification) both on the BNC connector, and after the attenuator, and after the SYTF filter, and after the low-pass filter at 2.9GHz
?
And for now I have come this far The next step will be to proceed to verify the Dual Mixer, (but first I have to understand what to expect to see on each of its 5 ports)
?
Thanks for any suggestions
Adri
?
?
?
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----- Messaggio originale -----
Inviato: 26/08/2024 03:28:52
Oggetto: Re: [HP-Agilent-Keysight-equipment] HP 5086-7906 YTO
I have a fully working (AFAIK) 8595E, if you need anything I can read from the screen or via IEEE-488. Swamped with work for the next few weeks, so any disassembly is out of the question.
Steve Hendrix
On 2024-08-25 3:50 PM, Yves Tardif wrote:
Hi Adri,
?
I have owned a 8595E for a few years, but it recently broke down and I had to repair it, what is your problem exactly?
I can see that the RF part is disassembled, but please give more details.
?
Yves
?
I am a hobbyist from Milan - Italy and I am trying to bring my 8595E back to its former glory
I have been following the HP-Agilent group for years and I have appreciated your frequent and intelligent contributions among which the expertise regarding the HP analyzer series stands out
I was wondering if I can ask you for some advice that can help me get my analyzer back on track
thanks in advance
adri
|
having received no feedback, I continue with a brief update on my attempts to bring my HP8595E back to its former glory 3
Summary and state of the art:
it all started with the failure of the main oscillator YTO (A3A7 on the block diagram); This component was replaced with the same model, purchased "as is" and installed after it was found to work and with good output across the entire range
Once installed, the analyzer returned to sweep (sometimes it gave the error LO UNLVL) but above all it revealed the problem that
no signal present in band 0 (9kHz -2.7GHz) is seen by the analyzer, (so not even the calibration signal which however turned out to be in specification and going to look for it in the analyzer I find it up to the low pass output - A3A3 on the block diagram)
I have not gone further yet
On the contrary, the signals in band 1 (2.7 - 6.5GHz) are visible and correct in frequency but attenuated
That of the attenuation of the signals in the 5- 6.5 GHz region is a fairly well-known problem with this analyzer and the diagnoses on the web have associated it with a misalignment of the yttrium spheres due to the countless thermal cycles that the SYTF undergoes over time
I opened my SYTF (particularly deaf starting from 6GHz) and I was able to see the misalignment in particular of a sphere (in the photo barely visible, under the gold mesh)
I await the arrival of a 2.5mm socket wrench after which I will try to realign
Any suggestions on how to deal with the problem of "blindness" in band 0 are welcome
adri
?
?
?
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----- Messaggio originale -----
Inviato: 26/08/2024 19:13:58
Oggetto: Re: [HP-Agilent-Keysight-equipment] HP 5086-7906 YTO
Yves, Steve, thank you very much for the offer of help
I'll try to make it short:
A few years ago my 8595E had shown signs of "deafness" in band 1 and given the prices of a SYTF I decided to keep it as it was
?
Unfortunately, some time later the main oscillator (YTO) also stopped working
?
This component also had prices out of my reach and, with a lot of patience and little hope, I purchased a YTO at a reduced price and, months later, a SYTF both sold "as is"
?
Not having in my hobbyist laboratory everything I needed to test them (for example another working 8595E) I left the project pending until a tiny instrument (TinySA Ultra) appeared on the market that is allowing me to address the problem, at least at a diagnostic level
?
And so I started to test the measured YTO on the bench, verifying that it covers continuously from 3.06 to 7.52GHz at 23mA/GHz with an output (excluding the extremes) between 7 and 10 dBm with peaks of 13.4dBm (FM coil not tested)
?
It would therefore seem to work well
?
I then tested the SYTF: the switch section seems to work well and also the filter section seems to work well as a bandpass with an insertion loss on the tested frequencies (5 - 6GHz) up to 11 dBm
?
And so I installed the two components in my 8595E and first I tried to do the calibration but the sequence soon stops with "Cal signal not found"
?
Now, the calibration signal is present (and in specification) both on the BNC connector, and after the attenuator, and after the SYTF filter, and after the low-pass filter at 2.9GHz
?
And for now I have come this far The next step will be to proceed to verify the Dual Mixer, (but first I have to understand what to expect to see on each of its 5 ports)
?
Thanks for any suggestions
Adri
?
?
?
----- Messaggio originale -----
Inviato: 26/08/2024 03:28:52
Oggetto: Re: [HP-Agilent-Keysight-equipment] HP 5086-7906 YTO
I have a fully working (AFAIK) 8595E, if you need anything I can read from the screen or via IEEE-488. Swamped with work for the next few weeks, so any disassembly is out of the question.
Steve Hendrix
On 2024-08-25 3:50 PM, Yves Tardif wrote:
Hi Adri,
?
I have owned a 8595E for a few years, but it recently broke down and I had to repair it, what is your problem exactly?
I can see that the RF part is disassembled, but please give more details.
?
Yves
?
I am a hobbyist from Milan - Italy and I am trying to bring my 8595E back to its former glory
I have been following the HP-Agilent group for years and I have appreciated your frequent and intelligent contributions among which the expertise regarding the HP analyzer series stands out
I was wondering if I can ask you for some advice that can help me get my analyzer back on track
thanks in advance
adri
|
Hi Adri, ? sorry for not giving feedback earlier, I've been very busy this week, and the days have been very long. ? For band 0, if you have a signal at A3A3 output, but nothing at A3A6 output at J2, the mixer or internal switch has a problem. Since band 1 seems to work (but needs YTM alignment), you should check that the LO frequency is correct for band 0. ? Still for band 0, with the calibrator connected, you have -20dBm at the input, but at the output of the A3A3 module, you should have -31.5dBm ¡À1.5dB. Based on a test I just did on my 8595E: after a preset, the loss from input to output A3A3 (w27, connector J2) is -10.56dB at low frequencies, -12.5dB at 2.9GHz, and finally, -11.1dB at 300MHz. Which roughly corresponds to the information on the block diagram. ? A test on the FL1 filter at 3.914GHz, gives only -0.14dB of insertion loss. ? Now, the 300 MHz calibrator at -20dBm, connected to the Spectrum input...at the mixer output, the level is -43.3dBm (specification, between -38 and -45 dBm), again, consistent with the information in the block diagram. ? To test the YTF I used an 8350B/83595A. ? Config on the 8595E: Preset center freq =3GHz ZERO span ? Config on the IF measurement Spectrum: Preset center freq =321.4MHz span 200 MHz ? For the 8350B/83595A Preset CF=3GHz Span 200MHz ? Connected to the mixer output, at the end of the w22 cable to A3A4. I did three tests: 3GHz, 5GHz and 6.5GHz. The measurement Spectrum for the 321.4MHz frequency is not manipulated during the test. It is just a matter of changing the frequency on the generator, here it is the 8350B, and on the 8595E for each of the three tests. ? By connecting to the end of the w22 cable, we can see the YTF tuned bandpass curve without any other filtering. ? The image shows: yellow curve -> test at 3GHz cyan curve -> test at 5GHz magenta curve -> test at 6.5GHz ? For a 0dBm signal at the input, I get an average close to -28dBm at the mixer output. Normally expected according to the block diagram, between -24 and -35 dBm. ? Now, if you look at the ZOOM image we find the same curves, but in a span of 5MHz, this in order to see what is the impact in a resBW of 3MHz and 5 MHz for an extended range. ? (ZOOM PRESEL PEAK), The yellow curve is the test at 3GHz with the calibrated values, named PRESEL default, and the cyan curve is after having done a PRESEL PEAK. In this case the YTF is finely adjusted to have a better centering, thus a better flatness for the IF filtering that will follow. ? PRESEL DEFAULT 3MHz -> flatness 0.3dBpp 5MHz -> flatness 0.6dBpp ? After PRESEL PEAK 3MHz -> flatness 0.04dBpp 5MHz -> flatness 0.06dBpp ? ------------------ About the problem of "blindness" in band 0: ? If you look at the image ¡°IF 3.9214GHz and LO leakage from mixer at 4.2214GHz.png¡±, we see the LO leakage through the mixer, are you able to see this signal? For the 300MHz calibrator, the LO is at 4.2214GHz ? Maybe it's a simple BIAS issue, but you may have already checked. ? Hope this information can help you. ? Yves ===================================================== ? De?: [email protected] <HP-Agilent-Keysight- [email protected]> De la part de alfa beta
·¡²Ô±¹´Ç²â¨¦?: 30 ao?t 2024 09:26
??: [email protected]
Objet?: Re: [HP-Agilent-Keysight-equipment] HP 5086-7906 YTO ? having received no feedback, I continue with a brief update on my attempts to bring my HP8595E back to its former glory 3
Summary and state of the art:
it all started with the failure of the main oscillator YTO (A3A7 on the block diagram); This component was replaced with the same model, purchased "as is" and installed after it was found to work and with good output across the entire range
Once installed, the analyzer returned to sweep (sometimes it gave the error LO UNLVL) but above all it revealed the problem that
no signal present in band 0 (9kHz -2.7GHz) is seen by the analyzer, (so not even the calibration signal which however turned out to be in specification and going to look for it in the analyzer I find it up to the low pass output - A3A3 on the block diagram)
I have not gone further yet
On the contrary, the signals in band 1 (2.7 - 6.5GHz) are visible and correct in frequency but attenuated
That of the attenuation of the signals in the 5- 6.5 GHz region is a fairly well-known problem with this analyzer and the diagnoses on the web have associated it with a misalignment of the yttrium spheres due to the countless thermal cycles that the SYTF undergoes over time
I opened my SYTF (particularly deaf starting from 6GHz) and I was able to see the misalignment in particular of a sphere (in the photo barely visible, under the gold mesh)
I await the arrival of a 2.5mm socket wrench after which I will try to realign
Any suggestions on how to deal with the problem of "blindness" in band 0 are welcome
adri
|
