Agilent 4287 Hard drive failure and HP 6848C Func. Gen failure. - Page 1
Forum section: electronics / repair

author: TK0130
author_rank: Contributor
timestamp: February 28, 2020, 02:02:29 am
content: I recently scored a decent load on a "Dumpster Dive" including a Rubidium frequency standard, VNA (3ghz) as well as a bunch of blown equipment (2 spectrum analyzers, 2 old analog scopes, RF Power Meter, RF Noise analyzer, and a HP 8648 sig-gen that I plan to repair) All in all this was an awesome score for a sophomore EE student.First up on the repair list is an Agilent 4287 RF LCR meter. It appears to be fully functional other than a hard drive that has failed. I have had trouble finding the required firmware and while I might be able to find an old win-98 install disk, the device firmware itself might be troublesome. I was wondering if anyone here knew where I could find it. I skimmed the service manual as well as both Agilent and Keysight's sites but can only find firmware updates. Can anyone give me a dump of the drive?Second, I have an HP 6848C function gen that doesn't boot. Power supply is shot, seems to be a simple switched mode Will work on repairing it. The service manual only includes a theory of operation and pinouts of main connectors.

author: MadTux
author_rank: Frequent Contributor
timestamp: February 28, 2020, 02:06:10 am
content: Damn, that dumpster seems even better than the one in Dave's basement

author: coromonadalix
author_rank: Super Contributor
timestamp: February 28, 2020, 03:33:58 pm
content: Post a search thread for an drive dump, image, cloneyou may get lucky ??Ask Keysight for a drive recovery procedure ??

author: TK0130
author_rank: Contributor
timestamp: February 28, 2020, 04:29:03 pm
content: So I did some more testing of the function generator, I gave it the 5v, 15v, -15v, and 38v required to power up and the screen backlight lights up but nothing appears. I checked the data lines to the LCD and there is nothing on any of them. Checked CPU (MC68HC000) and it has a clock signal but it looks rather... messy to me.5V rail is 4.9v and has no noise on it at all.Any input on what to check next? I am going to trace the LCD wiring back to the cpu.I believe it is doing stuff as the RF power on/off switches a relay internally. As it has no beeper I can't tell if anything else is being processed.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: February 28, 2020, 05:48:31 pm
content: That clock looks ok. The CPU has a Schmitt-Trigger at the Clock-Input, if I'm not mistaken.On my PM3320A (Using a 68000 Processor) Scope the clock, if I remember correctly, was pretty much a sine-wave coming directly from an oscillator and the clock-signal then snaked across the board. Data-Signals and other stuff also looked quite "rounded" when I looked at it with a 100MHz Rigol Scope.I would also assume that many signals on equipment of this age are basically open drain-signals with pull-ups to help the PMOS transistors of the chips to improve rise-times. So rouded edges on data and clock-lines are more or less normal.Instead I would put my money on the software-side and/or ROMs that have forgotten a few bits. Unreliable DRAM-Chips (if the device uses DRAM instead of SRAM) might also be a culprit.

author: TK0130
author_rank: Contributor
timestamp: February 28, 2020, 08:38:09 pm
content: Quote from: SaabFAN on February 28, 2020, 05:48:31 pmAs shown below, the riser board seems to have a bunch of TMS27PC010 chips. They have stickers on them showing (I assume) SW revision. They are UV erasable. Do you think they have lost the data? Any idea how to salvage this?This seems to be the only PROM devices in this thing. I just see some FPGA/CPLD stuff and ram.

author: TK0130
author_rank: Contributor
timestamp: March 02, 2020, 09:35:55 pm
content: Update:Failed 5v voltage regulator. Fixed it, LCD still didn't work. Spent a good two days chasing rabbit trails until I finally figured out that the LCD contrast pot failed and had the contrast turned the entire way to one end. Working perfectly now off external power supplies.Now to just fix the internal power supply. Once I am done I will post a schematic of the power supply (Primary side) for future reference as it isn't available online anywhere I can find.