Products > Test Equipment
Fool for the 8656A Sig Gen
Tony_G:
Replying to my own post to make sure you see this (not sure if you get re-notified if I modify the post after you've been notified originally).
I created a searchable version of the 8657B service manual for you (the one on the Keysight website isn't searchable) - You can grab it here:
https://1drv.ms/b/s!Amqar8_XQ9Uzk48LDIJuGPej5NWrWA?e=RXh0me
TonyG
cncjerry:
where are you located? I have a signature meter. I don't know the 8656 but here's my quick scan of the thread:
1) does it have option 1, 01, 001 listed on a badge in the back? That is usually the high stability time base, basically an HP ovenized oscillator on a board you plug in. Without it, you usually need the bnc strap between the posts on the rear that would be labeled like 'ref out' to 'ref in". Sometimes you need to strap them if you have the oscillator. Many pieces of gear are scavenged for the oscillators. I pulled them out of selective level generators that were shot.
2) if it is halting on post, it could be a rom chip if it has them or something hanging the signal lines.
3) Your symptoms look like they are related to a power problem though. I've had a few generators that when your probe the power near the PS board, they look great but you need to check at some of the chips. sometimes the cables running from the power supply go bad, I have a couple of older generators that need cabling.
4) someone else mentioned about the shafts and I agree, that is the least of you worriers. I have a 3d printer and CNC gear but do you have the complete parts to copy? They would have to be drawn as I doubt scanning would give you what you want dimensionally.
I would go back and probe the power pins around some of the ICs. If the display is getting anything on it then it looks like it is running but hanging on code someplace, possibly from a bad rom chip? I don't know if I would purchase a signature meter to fix one piece of equipment. I got mine cheap and I think I've used it twice in 10yrs or so.
Jerry
jrharley:
Wow guys, thanks for posting up on this!
The effort continues. I'm starting to learn the language for navigating the HP manual schematics and info. Lot's of study going on. Not any soldering. :)
TonyG- Thanks for the link! Good to have. Not sure if there's a test switch in the system as you describe, but I'll keep an eye out. "Thou shalt test voltages" right? So yeah, I'm probing wherever I can and pouring all over this thing. Some interesting results and on going discovery. I'm starting to learn how to run things down in the info efficiently so, stand by for more updates.
cncjerry - Appreciate you weighing in! I'm in Florida, Tampa Bay area. Also appreciate the thought on loaning the test gear, but I'm realistically a ways away from any signature analysis level troubleshooting. I tend to share your instinct that this is a power related issue and so I'm covering the basics first. I'm currently in the "thorough visual inspection" phase of this project, along with basic probing. The manual has a pretty simple series of tests using a scope to evaluate the signals from the keyboard to the rest of the circuitry. I'm focusing on that thread for the moment.
Thanks again all, I'll keep posting anything relevant.
Best,
JRH
Tony_G:
Just thoughts I'd check in and see if you've had the chance to get any more data etc
jrharley:
Hey tony G, thanks for reaching out.
Not much data yet, I've taken a sidetrack to clean keyboard switches and get to know that section. Repaired a missing stand-off assembly on the keyboard stack that was allowing too much flex when some keys were pressed, but I got that stabilized. The more I look, the more evidence of rough handling I discover. It's hard to understand why equipment like this gets abused, but it does.
I've attached a photo of a connector that I found disconnected when I opened it up initially. I've been studying the circuit associated with it and have started doing some simple tests on the keyboard per the manual procedure. The good news is that I do get a 5V DC offset when I press any key. So far though, I'm not getting any evidence of data packets coming out of the keyboard, but I'm still working that, I could have my triggering set incorrectly on the scope. Anyway, comments are always appreciated and I'll keep posting any relevant discoveries.
Thanks for the interest!
JRH
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version