HP 54201a scope - Page 1
Forum section: electronics / repair

author: fastpony58
author_rank: Newbie
timestamp: February 16, 2017, 03:11:33 am
content: Hello everyone,Long time lurker and I've run into a problem, and that I can't google youtube, or read my way through. Maybe someone could offer help or give me a road to go down to fix this scope I just bought.So I ran out and found a hp54201a scope from fleabay. It was supposed to be working, and of course the scope once I received it has some damage from poor packaging, and from rough handling from FedEx. So this scope once I turn it one, the screen immediately goes into "FATAL ERROR u38" So I did see that there is service manuals, and operator manuals on the net. But no where in the service manual did I see anything about fatal errors. doing the key down reset does not change things. Switching from protected and unprotected CAL doesn't change. Key down and power on doesn't change anything. Leaving it on for an hour and restarting doesn't change anything. I probed around the power supply and the voltages were in spec according to the service manual.I even did a little detective work, in that if this fatal error code relates to a chip, u38 is some kind of waveform storage SRAM. and to my surprise the battery backup still provides a voltage to the chip. I even tracked down and replaced that one sram chip, verified the conections (in that the address pins, power and ground are good, with continuity and .1 ohms of resistance.)But after replacing the chip, nothing changed, the scope still boots into "FATAL ERROR U38" My stabs in the dark aren't helping, and the service manual isn't helping with this issue. Any ideas?

author: Armadillo
author_rank: Super Contributor
timestamp: February 16, 2017, 05:55:57 am
content: Did you carried out troubleshoot page 6-21? Is the keyboard responding?

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: February 16, 2017, 12:13:45 pm
content: I have a functional 54201A and a similar vintage HP1630D logic analyser. Not had the 54201A open but did lots of logic level work repairing the logic analyser, which has an extremely detailed manual with comprehensive theory of operation and schematics. The 54201a has very little schematic detail except for the power supply. Comparing the two manuals it looks like the power supply and CPU boards are near identical in both. You might find the your CPU board sufficiently similar that the 1630D manual will help with your diagnosis. 1630D Service manual here:http://www.keysight.com/en/pd-1630D%3Aepsg%3Apro-pn-1630D/logic-analyzer-with-43-channels?pm=PL&nid=-536900196.536896359&cc=AU&lc=eng

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: February 16, 2017, 12:32:22 pm
content: Given what you have said about the way it has suffered in transit, I would look for something that needs re-seating, or a cracked PCB or track. Since it was damaged in transit due to poor packaging, unless the seller had specifically stated that postage is at your own risk, I might have been tempted to raise a refund request and just return it to the seller for a full refund.

author: fastpony58
author_rank: Newbie
timestamp: February 16, 2017, 08:11:22 pm
content: Thank you everyone for your suggestions.I'll dive into more into the keyboard diagnostic parts, and checking through to see if any chips became unseated. I hope its that easy. But as far as the seller, I was able to get a refund from them, they kicked and dragged their feet for a couple weeks...Thanks everyone once again!!!!

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: February 17, 2017, 10:17:40 am
content: Pulled the lid off my 54201A and can confirm that the power supply board at least is identical in layout to the 1630D. Photos show they're the same underlying hardware - I think the slight differences in the power supply board are just versioning details). Loathe to pull the CPU board from this old and still working machine (requires a bit more dismantling) but can do that if it will help - to confirm it's the same as the 54201A CPU board or to check signals. The CRO also has the same service port as the 1630D for mounting CPU and other boards vertically - helps greatly with debugging. The 54201A display looks to be the same setup as the 1630D with a full field graphics display area for the traces and ASCII display areas to the left and above. Given the pretty much identical layout of the CPU board in the two machines I think it's a reasonable bet that the essentials of the display drive circuitry are the same but it will use a different waveform formatter for the FF graphics writing. Reinforces idea that the 1630D manual can help you out (S8B-17 in that manual describes functioning of the formatter ROM and associated circuitry). My 1630D wouldn't write anything to the FF graphics area and I did suspect the character ROM for a while - but it turned out to be a faulty counter IC elsewhere. However, it would at least boot up - unlike yours.

author: Charles_z
author_rank: Newbie
timestamp: August 11, 2018, 03:57:37 pm
content: Hello! I got a HP54201D recently. It powered on normally, but can not read input signals. Self test found RR, RT errors, also cannot pass System Calibration step 0. Looks like this his a common problem for HP 54201A or 54201D. I think the analog board is bad, but other boards should be ok. Hate to throw it away and hope there is a way to fix it.