HP 4952A Protocol Analyzer questions - Page 1
Forum section: electronics / repair

author: TerraHertz
author_rank: Super Contributor
timestamp: February 29, 2020, 10:56:58 am
content: I bought one of these recently, and it arrived on Friday, undamaged.Runs fine, though the screen geometry is a bit off. Common with 'transported CRTs'.One surprise: to run the COPY DISK utility requires a memory extension Opt 002, which this unit lacks.Wondering about battery condition, whether the memory can be expanded just by adding chips, etc, I opened it up.Nope. It's apparently a rider board. See the spare ribbon connector.Oh, RIFA mains filter caps, nicely crazed. They've got to go.There was one of the little CRT geometry magnets loose inside, and the bottom three spikes on the yoke don't have magnets. Hmm, did they all fall off? No hotmelt glue on them, because hard to access? Maybe the other two fell out of the case via the fan?The CRT separated. No sign there was ever hotmelt on these bottom yoke spikes. Maybe the loose magnet was just dropped in during initial CRT adjustment?Anway, continuing disassembly:Top board, floppy disk controller mostly.Middle board, incl printer port, CMOS config RAM and a NiCd battery. Surprisingly it isn't flat and leaking. Measures 3.1V. The pins have been soldered sometime since the unit was manufactured, so maybe it's relatively recent? No notation visible of when it was changed though. Those three green rotary switches are all set to zero; what are they for?Bottom main board, with power supply, CRT driver, pod interface, etc.There's a total of 7 EPROMs. I read and saved their contents.RIFA be gone!The NiCd battery. Does anyone have any experience with this brand? Do they have a tendency to destroy all electronics within several inches around, like most NiCds when they inevitably leak, or can they be trusted?Continued in next post...

author: TerraHertz
author_rank: Super Contributor
timestamp: February 29, 2020, 11:53:04 am
content: Taking it apart changed the screen geometry a bit. Previously the bottom-left corner was much more curved in. Maybe it was the loose magnet lying near the tube? Anyway it's still off. Annoyingly since the soft keys don't line up with the screen.After some fiddling with the loose magnet, then also the ones fitted, I found it was much better to just remove all the geometry magnets.Also re-centered using the CRT neck rings. (What are they called?)But to get it to fill the screen I had to increase both the width (a coil with slug mounted on the yoke) and height (pot on the main board.) This makes me suspect the EHT is too high (which makes the image smaller.)But since I can't find a service manual for the 4952A, either paper or PDF, I don't know what the EHT is supposed to be.Anyone know?I'd hoped maybe I could find specs for the CRT, and that would tell me the correct EHT voltage. But no, can't find anything.What came with this one:* Manual: Data Communications Test Library - User's Guide* Manual: HP 4952A protocol analyzer - Getting started* Cable to interface pod. (But no pod.)* A yellow manual update, for the Operating Manual. Ha! Whoever removed/lost the manual from this kit, forgot to keep the related change notes with it.* Sleeve with four 3.5" disks.- Utility disk 04952-16003 Rev A.00.00 (But not the Data Communications Test Library floppy.)- 2 blank unformatted disks (I stuck on the HP labels and formated.)- 1 disk with a couple of user data saves. No label.Interesting to see the original unused HP disks, that hadn't even been formatted. Together with the unit being incredibly clean inside, would suggest it was almost never used.Found:* Software: Data communications test library. 5062-2119http://www.bitsavers.org/bits/HP/4952A/In the post:* HP 4951C with a 18179A Interface. (It was the quickest way to get an 18179A pod!)* HP 4952A Operating Manual 264252394805 $30Want:* Extended memory, opt 002 (It's an add-on board) Needed for COPY DISK util to work.* Service manual. Seems to be unobtainium these days.Relevant threads:https://www.eevblog.com/forum/testgear/hp-4952a-protocol-analyzer-service-manual/https://www.eevblog.com/forum/testgear/hp4952a-protocol-analyzer-software/https://www.eevblog.com/forum/repair/new-dave-repair-project/https://www.eevblog.com/forum/beginners/decoding-rs232rs485-on-a-cheap-scope/It's weird to find no service manual available for a machine that was quite common back in the 80s. Does anyone have a paper original they'd sell?

author: TerraHertz
author_rank: Super Contributor
timestamp: February 29, 2020, 12:45:38 pm
content: Here are the EPROM images for the HP 4952A.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 02, 2020, 10:35:31 pm
content: The CRT EHT measured: 9.1 KV.I wish I knew what it was supposed to be. Doesn't anyone have any experience with one of these?To me it seems in the right range for a small CRT like this, but that's not based on much experience.Anyway I can't see any adjustment for the EHT voltage.Going to close it up now.It sucks so much that still no service manual/CLIP for the HP 4952A can be found. Curse the closure of all the old archivesof real manuals, like Manuals Plus.http://everist.org/NobLog/20190223_full_spectrum.htm#alexSuch a terrible loss.Akk! I just noticed I typo'd the thread title. Should be 4952A not 4852A. Hopefully, fixable.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 25, 2021, 04:45:04 am
content: Are you making any progress on this? I just picked up two HP 4951Cs and they both appear to work but I don't have software for them.FWIW there are two HP 4952s presently on FleaBay that have option 002 (added memory) installed but between the purchase price and shipping (even within the US) either one would cost over $100.The HP 4951s didn't even have an option for added memory so I wonder how you were supposed to be able to run the Disk Copy utility?

author: Kryten 2X4B
author_rank: Contributor
timestamp: February 02, 2022, 08:32:21 am
content: I also recently bought an HP 4951C on evil ebay. A disk image of the extra software used by both the 4951C and 4952 can be found at the HP Computer Museum website.My 4951C worked for 10 minutes while I was running the self-test routines. Then I heard a fizzt from inside and the buzzer started beeping, I grabbed the line cord and yanked it out of the wall. My guess was that the main electrolytic on the primary side of the switching supply had vented. No, it was one of the across the line caps in the line input filter which vented some goop. While it looks as though Schaffner who made the original filter/fuse/switch combo don't make the exact part anymore, their FN380 series is close electrically and will fit to the rear panel.As far as the battery is concerned the 4951C uses the same one which is in the 4952, currently mine reads 2.5V without the unit running and when I first powered the system it did tell me that default values would be used as any previous configuration had been lost, so a new battery is required.I'll also be testing all the electrolytics in the system and the two RIFA caps on the main board are for the chop, at least one has large cracks in the outer case and I've had these fail in the past.

author: Renate
author_rank: Super Contributor
timestamp: February 04, 2022, 12:21:37 pm
content: The OP has a nice, clean unit.If I had one I'd just use it as a retro-laptop.Walk into a meeting, "Where do I plug in my laptop?"

author: m k
author_rank: Super Contributor
timestamp: February 05, 2022, 08:14:06 pm
content: One must wonder if #1 reply has a regular CRT bed.BTW,https://www.antiqueradios.com/forums/viewtopic.php?t=1443Users browsing this forum: bob91343 and 6 guests