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Dead 54720D
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One day my beloved 54720 just won't power up. It turned out the SMPS auxiliary voltage flyback switcher (always on when the back power switch is on) went dead with charred PCB around. Not a shred of documentation about this SMPS (it's Yokogawa) but I took the time to retrieve the schematic, a standard self oscillating flyback converter, with some quirks on base control (some unmarked devices which I allege one is a zener, the other one is a diac device. No attempt to fix it yet, since I was able to get a replacement power supply, plugged in, and it shuts down after 10-15 seconds. Ok, probably another bad power supply, but during those 15 seconds I was able to note the "mainframe calibration lost" message and a "self test failure" message. Got to run the Self Test and it came up with Failure "Hybrid ID Test" but that's as far the power supply will hold...
I wonder if I should keep attempting repairing this unit (fix the power supply, or get another working one, then pick from there for the rest, although a 54717 for calibrating the mainframe is practically unobtanium) or just save some grief, write it off as a part mule, and just get another working mainframe, replace the NVRAM? battery and happily live after (I have plenty of plugins and probes for this old dog). Anybody knows if this "Hybrid ID Test" failure is somehow related to the lost NVRAM content? |
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On Nov 13, 2019, at 5:10 PM, Ovidiu Popa [Business] <ovidiu.popa@...> wrote:
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Ok, so I fixed the power supply (one dead mosfet) and now my dear 54720D is like a Schroedinger cat, dead and alive at the same time. It works, I configured everything that can be done manually (serial number, model, date/time, etc...) but without recalibration it only makes a nice door stop.
Really, anybody has a 54717A calibrator I could borrow for a ten minutes calibration job? I¡¯m willing to pay back and forth shipping plus a realistic compensation for the trouble. If not, this amazing scope is ready to go for target practice, fortunately with pellets only, here in Canada. I¡¯d like to do the same with those designing this amazing scope around a $5 battery, without the possibility of self calibration. |
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I just cracked up laughing at your comment. Those stupid batteries. But at least most quality equipment has either defaults or internal self cal. Or maybe its just older equipment has those behaviors. Then someone discovered they could make lots of money by enforcing calibration. I have some very nice DVMs that want to be Cal'ed every year. Not going to happen. But at least in general there is a way around it. I actually do cal some of them have much of the gear. Its such a pain to step through all of the ranges. Great to do one time but not every year. Regards Paul |
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A quick Google search turns up a couple of places that ostensibly rent these out. Here's one?, and there's another?. Yet one more?. I have no affiliation and have never tried any of those places, but $170/month seems reasonable? ? On Wed, Dec 11, 2019 at 9:00 PM Ovidiu Popa [Business] <ovidiu.popa@...> wrote: Ok, so I fixed the power supply (one dead mosfet) and now my dear 54720D is like a Schroedinger cat, dead and alive at the same time. It works, I configured everything that can be done manually (serial number, model, date/time, etc...) but without recalibration it only makes a nice door stop. |
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Thanks, I'll contact these companies, but I'm not setting my hopes too high; they are all distributors that eye the corporate big bucks and don't care about the small fish in the pond. $170 for a month plus back and forth shipping plus Canadian taxes is about what a 54720D frame is worth, but I'd take it if available.
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Sorry you missed out on that one... On Fri, Dec 13, 2019 at 17:59 Ovidiu Popa [Business] <ovidiu.popa@...> wrote: And to add insult to injury, while I was struggling to fix the power supply, a 54717A was sold on EBay :( I cannot hope the buyer is a member here... |
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Ok, so if everything fails, I will try building a 54717A calibration plugin.
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I found in the 54720A service manual the 54717A schematic. The signal path... doesn't exist! It's only two coax cables (obviously equal in length) between the front input and trigger N connectors, and the back coax connectors. There is a limiter on each cable, which I'm confident it can be skipped for now.
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The whole shtick is to have the plugin report "54717A" to the mainframe, otherwise the mainframe cal routine won't start. I have a couple of 54712A pluging that I am barely using, and I'm willing to temporary hack one for this project.?
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So the whole id and other information is on a HN58C65 EEPROM in SOP-28. I need a SOP-28 to DIP adapter, then read the content with a standard Willem programmer. Hack the content (I can't imagine the model string is encrypted). Re-solder the chip on the 54712A board, disconnect the internal signal path and replace with two cables as described and with a bit of luck I'll have a clone of the unobtanium 54717A. Calibrate, restore the EEPROM from a backup, wire back the 54712A signal path and everything is back, but with a now calibrated 54720D. |
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On 12/13/19 7:14 PM, Ovidiu Popa [Business] wrote:
Ok, so if everything fails, I will try building a 54717A calibration plugin.Good plan. Please document that EEPROM format, if it's convenient to do so. -Dave -- Dave McGuire, AK4HZ New Kensington, PA |
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So far, no cigar. Simply changing the string from 54712A to 54717A leads to an "Unknown" module detection. There's some checksum involved, I need to look close to that binary. I've uploaded the 54712A_EEPROM.bin in the file area /g/HP-Agilent-Keysight-equipment/files/54712A_EEPROM.bin in case somebody else wants to take a look.
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Argh, doesn't appear to be a regular parity, sum complement, or CRC. Need to pull the EEPROM from the other 54712A (with a different serial number) and XOR with this one, to see where the differences appear. Hopefully, there is a checksum over the header only, up to 0x80 (that is, the calibration data in not included in the checksum). That's easy to check by modifying one bit in the calibration data area and watching if the module is still recognized (or not). The big concern is the number of solders on the 54712A board, don't want to kill the pads. I'm using hot air, but still a risk.
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Hi
Did you have any success with that eeprom hacking ? Im faceing same issue now. I have 54720A unit with lost mainframe calibration. It's crazy difficult to get this calibration plugin. I also have 54712A plugin, i will try to get programmer in next couple of days and do some comparation between those plugins binaries. Please let me know if you have any hints/ideas.? |
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Sorry, no, I gave up and wrote off the 54720D. I have too many scopes anyway, from 100MHz to 50GHz, not enough incentive to spend more time on this. Meantime, watching for a 54717A, ideally someone owning one could dump the EEPROM. I know if I'd get one, this would be the first thing I'd do, this HP money grabbing calibration abomination has to end.
If someone wants to pick up, I can forward the 54712A EEPROM binary. |
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I already found the 54712 eeprom image that you shared. Do you have any possibility, to download same firmware from the other unit ? I would like to compare. I have one 54712 unit, but still don't have programmer.?
W wtorek, 4 stycznia 2022, 16:46:54 UTC, Ovidiu Popa [Business] <ovidiu.popa@...> napisa?(-a):
Sorry, no, I gave up and wrote off the 54720D. I have too many scopes anyway, from 100MHz to 50GHz, not enough incentive to spend more time on this. Meantime, watching for a 54717A, ideally someone owning one could dump the EEPROM. I know if I'd get one, this would be the first thing I'd do, this HP money grabbing calibration abomination has to end. If someone wants to pick up, I can forward the 54712A EEPROM binary. |
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Does anyone have a copy of the 54720 or 54710 firmware disk? If I
could take a look at that, I can probably figure out how to make a 54717a eeprom image for you. On Tue, 4 Jan 2022 at 16:55, Arkadiusz Gibes via groups.io <arkadiusz.gibes@...> wrote:
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I was thinking about exactly the same. Do you want to compare to see where the check sume is stored ??
W ?roda, 5 stycznia 2022, 03:26:37 UTC, Mike Walters <mike@...> napisa?(-a):
Does anyone have a copy of the 54720 or 54710 firmware disk? If I could take a look at that, I can probably figure out how to make a 54717a eeprom image for you. On Tue, 4 Jan 2022 at 16:55, Arkadiusz Gibes via groups.io <arkadiusz.gibes=[email protected]> wrote: > > I already found the 54712 eeprom image that you shared. Do you have any possibility, to download same firmware from the other unit ? I would like to compare. I have one 54712 unit, but still don't have programmer. > > W wtorek, 4 stycznia 2022, 16:46:54 UTC, Ovidiu Popa [Business] <ovidiu.popa@...> napisa?(-a): > > > Sorry, no, I gave up and wrote off the 54720D. I have too many scopes anyway, from 100MHz to 50GHz, not enough incentive to spend more time on this. Meantime, watching for a 54717A, ideally someone owning one could dump the EEPROM. I know if I'd get one, this would be the first thing I'd do, this HP money grabbing calibration abomination has to end. > > If someone wants to pick up, I can forward the 54712A EEPROM binary. > |
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Yeah, it would be helpful to compare the EEPROM image from two units.
Though I was thinking more about the actual firmware that runs on the mainframe, I could reverse engineer that and figure it out. I do have a firmware image from my 83480A (aka 54750A) which I expect to be very similar and I've worked out the EEPROM format/checksums that it uses: The first two bytes are a (big-endian) uint16 denoting the total length of the data. The first checksum is verified by summing the first 0x7A bytes and checking that the result is zero, and the checksum byte itself is at 0x48 The second checksum is verified by summing bytes over the whole image (using the length field), and that checksum byte is at 0x7A. Both of these schemes validate correctly on the 54712A image posted above. Another thing to note is that the byte at 0x07 is a sort-of model ID and it needs to match what the firmware expects for the model string just after. Without a 54720 firmware image I can't tell what it's supposed to be, though it could be guessed in maybe 10-20 tries if someone's keen to do a bit of tedious work? :) Cheers, Mike On Wed, 5 Jan 2022 at 15:44, Arkadiusz Gibes via groups.io <arkadiusz.gibes@...> wrote:
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Dave McGuire
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