Post some pictures of the PCB.
OR: Does anyone already HAVE the 33521B/33522B unit - or a similar model, with the OCXO
and knows what part they have used? Keysight has no info on this
obviously.
Hello,
I just replaced the original TCXO on my 33521A with the same part suggested in
https://www.eevblog.com/forum/testgear/updating-agilent-counter-53220a-to-option-010-ultra-high-stability-ocxo-timebase/ and it works just fine.
Very simple procedure, remove original one and put this in place. 10 minutes if done carefully. Nothing else needs to be done.
The firmware does not notice the change and the
About screen does not say anything about High Stability Option, but even the calibration routine does it's job trimming the frequency of the TCXO. I am not even sure this upgrade is actually announced on the
About screen on a properly factory-upgraded unit. I haven't found any suspicious hardware mod to tell the CPU about the change, it might be a firmware tweak.
Warmup time is obviously longer now but stability is a lot better, once stable that is
Regards,
Roberto EB4EQA
The official upgrade is noted in the about screen.
It also says "installed" instead of "licensed" so I am sure there are some jumpers somewhere to indicate it is installed.
Thanks for the confirmation Steve
Well, not so fast... I just noticed my unit raises "PLL ERROR" instead of "EXT LOCK" when connecting an external reference. Even if it seemed to work OK, the simple replacement of the oscillator is not so OK as I thought.
If the rest of the required operations on the generator are purely hardware (I haven't found anything obvious) or include FW tweaks too, that would be great to know.
Thanks,
Roberto EB4EQA
The only way to make progress is for people to post high-res pictures of the main board so that a board with the ocxo and without can be compared.
Bought a broken 33521B not too long ago. It had a couple issues but should be 100% very soon.
I would like to upgrade it to an OCXO, I m quite sure it is just a jumper or two that need to be moved. Here are some pictures of the PCB top and bottom in the OCXO area. You can see one or two unpopulated 0603 sized jumpers but nothing jumps out or is labeled like the 532x0 series of counters.
Does anyone happen to have a 335xx series AWG with the OCXO factory installed that could slide the cover off and take some pictures of the top/bottom OCXO area for us?
I have a few of these Generators and I am pretty sure, that one of them has the OCXO officially installed. Right now I am traveling but when I am back next week I can take a few pictures for you.
Ok, the first one open up, a 33522B with all software licenses installed but unfortunately NO OCXO.
Next one to follow.
Here are the pictures.
There is a 0 Ohm resistor near U904 and an empty position near it. The empty position goes to U1005, I think it controls U904 (either gain or enable/disable).
There is a 0 Ohm resistor near U904 and an empty position near it. The empty position goes to U1005, I think it controls U904 (either gain or enable/disable).
That is on the RF output so I don't think it will change any detect details.
The original firmware did tell you if you had the ocxo installed in the about screen.
Spent some time comparing my 53230A counter to my 33521B last night. The PLL/clock systems aren't that similar between the two but I was able to find enough in common to make an educated guess on how we might get the AWG's to recognize they have an OCXO installed and to also operate properly. After some experimentation I believe I have figured it out.
It is nice and simple - remove the stock osc, install the OCXO and then remove resistor network R901. Removing R901 enables the OCXO in firmware and hardware at the same time.
You can then power it up and wait for things to settle down to perform a reference calibration. The calibration is easy and are the first steps in the calibration routine, you can exit when the reference calibration is done so as not to mess up any other settings.
The OCXO I used is a Vectron C4550A1-0213 - it was a whopping $13.99 shipped for a surplus one out of China.
Keep in mind this mod is only as good as the OCXO that is used. The original Keysight one is a Vectron C4550A2-xxxx I believe. The "A2" is a taller package with more insulation vs the "A1" I used. The last 4 digits on the end detail the specific options ordered but most aren't covered in the datasheet. Vectron makes all kinds of variations of this model, AT and SC cut, different stabilities etc. I am quite sure Keysight uses a very good SC cut model. So just because we add the OCXO doesn't mean it will meet the same specifications listed in the Keysight datasheet.
So far mine is working well. When I connect an external reference I do see a brief "PLLERR" before it locks to the external reference. I am quite sure this is normal. This isn't an error that is logged in the official error queue which is why I think it is normal warning, and it is quite common for things to take a few seconds to synchronize to an external clock. We can only verify everything if we eventually find a factory OCXO model to compare to.
Here are a few pictures to assist:
VERY good work! I am travelling but I will try this in mine as soon as I get back home. Thanks!
Roberto EB4EQA
Great, TheSteve !
I will test this as soon as I have a fitting OCXO
I just performed the upgrade, both OCXO and firmware. Everything went smoothly as expected.
Thank you Steven!
Merry Christmas!
Roberto EB4EQA
Glad to hear it is working for you. So far my cheapie surplus OCXO has drifted more then I'd like. In the first 24 hours it drifted about 200 mHz. It has been slowing each day and is behaving better now. The one in my counter is only 20mHz off from when I cal'd it 1.5 years ago - pretty hard to complain about that!
Be careful, you could cross the line to the time-nuts side and never consider anything in frequency again, ever
Roberto EB4EQA
The OCXO from China (Vectron C4550A1-0213) arrived and is installed in my 33510B generator.
It seems to work perfectly.
I need to get my counter warmed up to measure the new OCOX.
Even the original plastic cover fits over the upgraded OCXO.
Thanks again for a great hack!
Very nice! With success for two other people I guess we can confirm that my analysis on how to perform the mod was correct.
I've noticed the AWG will also tell you when an external ref is present but not selected - a nice touch.
P.S. the output 10Mhz from OCXO needs to be Square Wave for all options of OCXO
I modded my 33512B
the whole operation took 10 minutes
all you need is a desoldering pump (solder sucker)
one OCXO (Vectron C4550A1-0213 bought from AliExpress for 8$ shipping included, delivered in 1 week)
and it works just perfectly !!!
I can clearly see the difference on square wave.
Nice mod !
