ARCHIVE: HP 54621D Mainboard Pics - Page 1
Forum section: electronics / testgear

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:37:18 am
content: Just as the title says: Hi-res pics of the mainboard from my 54621D made while doing some diag work. Archived here in case they help someone else with one of this family of scope.TOP

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:38:06 am
content: BOTTOM

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:39:07 am
content: Memory + IO Side of PCB

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:40:04 am
content: Input & Acquisition Side of PCB; Frontend & MegaZoom FCBGAs

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:40:57 am
content: FRONTEND

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:42:18 am
content: MegaZoom & MSO MegaZoom FCBGAs

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:43:59 am
content: J900, J400, J200 & J201 Mainboard Connections - J900 Bared

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:51:17 am
content: Comparison of monitor cable pinouts of 54621D vs 54645A/54600A. This is the pinout of the J900 connector ribbon cable AT THE MONITOR.This is Q960-Q961 in the video out to J900-Pin 11 on the 54621D. Q961 base goes to the Megazoom IC through a 50Ω resistor. Q960 Emitter goes to J900 pin 11. I'll update this post with more details as I continue this diag work.UPDATE:So this evening I decided to try and fake out one of my monitors to make it sync on this bastard VGA signal by building a pulse with my little PWM generator to mimic the duty cycle and amplitude of the orignal HSync from the 54621D, but at a frequency the monitor might actually try to display. Doubling that frequency got me to this point; good proof of concept but not enough granularity in the adjustment on my little $3 Chinesium generator to actually get it more legible than this.By fiddling with the symmetry on my old ProTek analog function generator, I was able to get the duty cycle low enough that the monitor almost locked onto the signal; well, close enough to get these pics and see what it is actually saying.Now that I know why this scope became a monitor PCB donor, I'm actually even more pissed off than I was before at those fucking g'rillas...mnem

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:52:32 am
content: These three pics were taken while I was investigating a replacement CDM-7SX191 monitor. I figured I'd add them here. If I have time, I may take more pics at different angles so a component list can be built.So, while I'm working on this, I dismantle both the CDM-7SX191 and CDM-7SF191 monitors; after comparing the two mainboards side by side til my eyes watered, I couldn't find any material difference between the two. While the layout appear different between the CDM-7SX191 and CDM-7SF191 mainboards, the component list appears the same.Voltages at the ribbon cable also appeared comparable aside from those I expected to be different due to the VGA analog video, but I'd literally need to draw out the entire schematic for both monitors to be sure.I didn't have time or energy for that tonight, so I took one for the team and just swapped the CRT neck board over and tried it.Franken-monitor is no joy;it is not possible to make a CDM-7SF191 serve as a CDM-7SX191 just by swapping the CRT neck PCB.I'll update here as I have time.mnem

author: mnementh
author_rank: Super Contributor
timestamp: July 20, 2022, 01:53:55 am
content: Okay, I'm done for now.mnem

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 20, 2022, 11:55:47 pm
content: Thanks for posting.This answers one of my doubts on the L.A. side of the MSO: Inputs on pin #5 on 1NB4-5036's appear unused, can be handy when one logic input is dead...Aren't you tempted to hack it up to 100MHz?

author: mnementh
author_rank: Super Contributor
timestamp: July 21, 2022, 01:18:11 pm
content: Ehhh.... my work thus far with this 54621D has been directed at trying to reverse engineer the video. This scope uses a CDM-7SX191 industrial monitor, which has been destroyed/parts robbed by gorilla abuse.I have a backup/parts mule 54600A which uses a CDM-7SF191, which is all TTL. The CDM-7SX191 is TTL Sync with a single (probably some variant of VGA) analog video signal. At this point I'm convinced that the difference between the two monitors is entirely in the CRT neck board... so I am trying to reverse engineer that.Anyotherhackage would come after that fundamental problem is resolved, though honestly, there is little motivation to go there, as I have a 54645A I'm perfectly happy with, the 54600A, and a just-acquired Teledyne/LeCroy T3DSO2102 to play with. If and when I go hacking, it will probably be to convince that scope that it is indeed a SDS2000X-series MSO.mnem

author: tautech
author_rank: Super Contributor
timestamp: July 22, 2022, 08:59:16 am
content: Quote from: mnementh on July 21, 2022, 01:18:11 pmSDS2000X!

author: mnementh
author_rank: Super Contributor
timestamp: July 22, 2022, 02:28:48 pm
content: ouchies, mr sqweek...!sorry... fixed now.mnem*whimper*

author: TCPMeta
author_rank: Newbie
timestamp: August 05, 2024, 10:38:52 pm
content: I know it's been a hot minute but any further progress been made with this?