Agilent 54624A oscilloscope not starting - Page 1
Forum section: electronics / repair

author: MaxFrister
author_rank: Regular Contributor
timestamp: September 07, 2021, 03:55:51 pm
content: I have a 54624A oscilloscope that isn’t starting. When powered on the fan starts, the floppy spins, it flashes all keys, flashes the pulse-width key, lights the pattern key and stops. The display remains blank and it is unresponsive to all keys. I believe it should flash pulse-width, flash pattern, flash the more key and start.All the power rails seem okay. The cmos battery is okay. The supervisor IC is causing a reset and the 68020 seems to be running (it continues to generate watch-dog resets and memory activity). I’ve tried holding down a soft-key on power-up (nvram reset) with no change.I’ve ordered and will install new SRAM but I’m not optimistic that that is the problem.Another possibility is that the firmware is corrupt but the IC’s are of such fine pitch I'd rather not remove them unless I am pretty certain that that is the problem.I’m running out of ideas to figure out what the processor is waiting on. Anyone know what is supposed to be happening while the “pattern” key is lit? Is there a way to get a boot status log? Anyone have a schematic/CLIP? Anything else I can check?Thanks.

author: MaxFrister
author_rank: Regular Contributor
timestamp: September 17, 2021, 12:15:13 am
content: As I feared, replacing the SRAM did not change the symptom (booting halted with unresponsive keys).After checking the subsystems as best I could, I repeated something I had done at the start and looked for text on the 4 obvious rs232 lines. This time, I found activity on one of them. After some very neat and professional work to make sure it didn't blow up my "logic analyzer" [scare quotes are intentional] I was able to read the text.Eureka, it finally told me what was wrong. After a few phone calls and an hours drive, I located a computer that could still write a 3-1/4 floppy. I copied the latest SYS6462X.JZP onto a blank diskette and tried the scope with the following result.Quote[jedi muskrat???].After reinstalling the case for cooling the scope was operational. It failed self-test until a user cal was complete. It now passes all tests and seems to be working nominally.It still requires a few things:

author: Runco990
author_rank: Frequent Contributor
timestamp: September 17, 2021, 02:18:40 am
content: Congratulations!Sounds like someone botched a system update. Happened to me once and I thought I bricked the scope. Fortunately this scope can be recovered by trying a floppy again, even after "bricking" it. In my case I wrote another disk and it worked.I love these scopes. I use 2 of them.

author: MaxFrister
author_rank: Regular Contributor
timestamp: September 17, 2021, 01:52:43 pm
content: Hints for Non Starting Agilent 54621A, 54621D, 54622A, 54622D and 54624A oscilloscopes. [Porbabably also relevant to the 54641A/D and 54642A/D]In trying to diagnose this problem, I’ve learned a bit about these scopes. I thought I would record some notes on the off chance it might help someone in the future.Service manual.There is a limited service manual (https://literature.cdn.keysight.com/litweb/pdf/54622-97037.pdf) available for these scopes. It has some minimally useful information and things to check but no schematics. I have not been able to locate a schematic. There is a component level service manual including schematics for the earlier generation of these scopes but they are pretty different.Light code.A correctly functioning scope flashes all lights and then the sequence “pulse-width”, “pattern”, “more”, and then displays a trace.Simple things.If you have a scope that doesn’t start, there are some simple things to check:That the cmos battery is 3.0V.That the power supply voltage are correct without excessive ripple. Test points are located on the bottom of the scope and shown in the “service” manual.Try resetting the nvram by holding down a soft-key and power cycling (but see the next note).Soft Keys.These scopes are notorious for failing soft-keys. To check open up the front panel and put an ohm-meter on the soft-key traces and try each key. Resistance should be less than about 100 ohms. If not clean the board with IPA but NOT the carbon on the rubber key. Those can be made temporarily better with a soft carbon pencil.Boot log.When the scope fails to boot, it prints out diagnostic info on the serial rs-232 port on the back of the scope. The default (which can be changed) is 8 bits, no parity and 9600 baud. Beware that rs-232 is a +/-15V (or more) protocol with active low. In order to read it using my cheap logic analyzer I need to clamp it and invert it.Firmware recovery.If the firmware is missing or corrupted, the scope will attempt to recover it by loading it from a floppy or over GPIB.IC inventory.I’ve attached an inventory of the major ICs that I created in trying to reverse engineer the main board. Note that in this document the “front” of the board is the part you see when you turn the scope upside down. I was able to identify all but a few of the important ICs. There are many assumptions and guesses in this list, so take it with a grain of salt.

author: MaxFrister
author_rank: Regular Contributor
timestamp: March 14, 2023, 02:53:46 pm
content: I received this question via message but I thought I'd reply in public in case others have better ideas:QuoteI also really liked this scope. I've replaced it with something more modern that takes longer to boot and I'm not sure I like as well.Certainly sounds like a similar problem. What equipment do you have available to you? Another scope (you know you're not allowed to own just one old scope)?I think the fact that it lights the panel lights means that the processor is starting the boot process. It is just failing earlier than mine.I think that the firmware is meant to be programmed via either the floppy or GPIB. I don't know where the boot-loader resides....perhaps in the processor? Unfortunately I gave the machine away so I can't check. The only firmware I have is the code that is intended to be loaded via floppy/GPIB.I assume you checked the power supplies for ripple. I'd suspect other things around the processor. The processor itself (check address and data lines). SRAM - U314/U315 in particular. Supervisor U340. RTC U350. Failing anything obvious, I might just change the SRAM.Best of luck and please let us know what you find.

author: jsgytqq
author_rank: Newbie
timestamp: October 18, 2025 03:00:33 am
content: Hello, I also have an Agilent 54622D. It was working fine before. I haven't used it for a long time. Now the indicator lights keep flickering randomly and I can hear the sound of relays. I tried your method, but the floppy disk doesn't start. The power supply is fine. Could you please advise if there are any other solutions? Thank you! E-mail 346892738@qq.com