HP 4952A Protocol Analyzer - Service Manual - Page 1
Forum section: electronics / testgear

author: sdscotto
author_rank: Contributor
timestamp: January 12, 2014, 11:30:19 pm
content: Any recommendations on where to find a service manual for this?I've tried google and the manual sources I'm aware of, but so far, haven't been able to locate one.Any advice is welcomed.Thanks in advance.

author: dfmischler
author_rank: Frequent Contributor
timestamp: January 13, 2014, 04:10:49 pm
content: I'm not sure there ever was a published service manual for the 4952a (or the 4951x). There was one for the 4955a, but it is a bigger case and older series. There are references to service bulletins for the 4952a in the HP Bench Briefs archives, but I haven't been able to locate the bulletins themselves.

author: sdscotto
author_rank: Contributor
timestamp: June 05, 2014, 10:30:55 pm
content: I was able to secure a service manual for the 4951C, which also included the service information for the 18147A, 18177A, 18179A, 18180A and 18160A interface pods.It appears that the changes between the 4951C and the 4952A are minor enough that this will serve my purpose. At first glance, it appears that power supply, video (CRT), and disc controller are nearly identical.Part number of the service manual is 04951-90703 and microfiche part is 04951-90759 on the off chance it may help someone else.

author: RetroSwim
author_rank: Contributor
timestamp: August 09, 2014, 02:59:23 pm
content: Hi there, I have obtained a 4953A, and I'm trying to repair it.I've narrowed down the issue to either the CRT2 board, or the CRT itself. The trouble is that the CRT's HT doesn't start up, and I don't know if it's because something's actually wrong with the CRT, or if the CRT2 board just isn't sending the right signals. I have seen the behaviour in other early TTL monitors, where HT doesn't run unless there's a H and V sync within range.Since you have the service manual for a similar model, could I trouble you to have a look and tell me what the horizontal and vertical refresh should be, and also see if pinout is available for the connection between the backplane (or I think they call it the "motherboard"?) and the secondary display board.Thanks in advance for any assistance!

author: dfmischler
author_rank: Frequent Contributor
timestamp: August 09, 2014, 06:56:23 pm
content: I used a 4953a at one point and IIRC it is not in the same protocol analyzer family as the 4951x/4952a (different case, different keyboard, much bigger CRT, etc.), so don't get your hopes up too much on the similarity.

author: KK
author_rank: Regular Contributor
timestamp: August 09, 2014, 08:00:15 pm
content: Do you have the several hundred page operator manual with technical adjustment section-http://www.hpmuseum.net/document.php?hwfile=5973I bought a 4957A that was broken. One cap on the power supply board at the feedback control chip and that's all it was. I never did find the service manual for it.I remember reading some discussion on HP using proprietary parts for the CRT HV section.

author: TerraHertz
author_rank: Super Contributor
timestamp: August 10, 2014, 01:25:50 am
content: Also I'll ask here - I want a service manual for the HP 4972A LAN Protocol Analyzer.Have Op manuals & software, but can't find the service manual. Annoying.The 4972A has only 10 Mb/s interfaces, but otoh, one can probably trust it to not be doing any data hiding rubbish.

author: RetroSwim
author_rank: Contributor
timestamp: August 10, 2014, 10:17:03 am
content: Quote from: KK on August 09, 2014, 08:00:15 pmYeah, this one needed 5 caps on the PSU replaced (all 4 poly caps, and one electro).Unfortunately, this unit also had some pretty catastrophic battery leakage on the "OPT" board, which was more or less destroyed, and caused some damage to the backplane. I discarded the OPT board, and cleaned up the backplane as best I could, but it still wouldn't work initially. Then on a closer inspection, I noticed that the contacts were missing for a few pins on the PROC and MEM boards (probably corroded through, and fell out at some stage). I circumvented the missing connections with some wire jumpers, and now it sorta works, but it's still a bit sad.It won't boot "normally". You have to enable one of the diagnostic modes on the CPU card's DIP switches (doesn't matter which) then set the DIP switches back to "normal" and hit reset. I'm not sure what the cause of this is, all of the diagnostic tests show 0 errors. Also the tape drive is screwed, the motor has completely seized up. I don't think it's useful as a protocol analyser any more, but I'm now thinking about how I could create something new and cool out of it, now that I know the screen and keyboard work nicely.So I probed around with my oscilloscope, and found that the while the Vsync is a common 60Hz, the Hsync is a more exotic 25kHz. Apart from the Hsync figure, it seems to act as a normalish TTL monochrome monitor. I wonder if there is some way to drive this display with a Raspberry Pi or similar... Hmm.Here are some pictures, in case anyone's interested:

author: SeanB
author_rank: Super Contributor
timestamp: August 10, 2014, 10:43:09 am
content: I will guess the monitor will work with standard VGA as an input. Likely it is being switched into a higher resolution VESA mode, but it likely does run fine at 640 by 480. You probably could put a mini ATX or similar motherboard in the place occupied by the card frame and get a luggable computer with insane performance, like an insanely upgraded Osborne 1 portable.

author: RetroSwim
author_rank: Contributor
timestamp: August 10, 2014, 02:09:00 pm
content: Bearing in mind the horizontal refresh of 25kHz, and the fact this thing is from 1984, I'm certain it doesn't even know what VGA is, let alone VESA.EGA is a lot closer (23kHz), but I don't know how accommodating the monitor's circuitry is, or how well protected it is against non-native modes.

author: KK
author_rank: Regular Contributor
timestamp: August 10, 2014, 05:41:53 pm
content: That one is a beast!The 4957A is quite a bit smaller. The screen is 3-4" tops. It is about a foot wide and two feet deep.Same kind of UI though.