Oh jeeZ. I have one that has been sitting here n my bench "dead" for almost ten years. It was dumped on me by the local ham club because they didn't want to store it any longer. When I first got it I spent a few hours probing around checking voltages & clocks with barely a schematic. And no videos for it really existed then. I know it WAS working before they dropped it off to me. I'm guessing this might be the issue. Thanks for posting the video! Steve in Ann Arbor Michigan N8LBV
Very clever idea with the LED as a quick sub for the battery - Excellent. I have a 4195A that I just took out of storage and had this same problem. I had basically figured the problem out (at least as far as the reset circuit). I also had measured the battery (not under power) but had decided the battery was probably OK - your video relieved me of the task of figuring out the battery failure circuit - THANKS for an EXCELLENT video. Did you loose the calibration data when you cut the battery of - I plan to replace the battery under power.
Thanks ! As I understand the RAM-backed data is only user programs, configurations, and custom O/S/L calibrations, so nothing irreplaceable. Mine's data was long gone of course so I didn't bother doing a powered replacement. Besides, I haven't touched that machine since the video until I took it out again recently - I still have to decide on a replacement battery ! I don't suppose you have the "adjustment program" floppy disk by any chance ?
Hi, I recently got this useful lab device. I have the following problema. When I try to start it, the screen is black (nothing can be seen) and an alarm is on. Any idea? I would like to repair
Not sure... you will need to refer to the service manual. I would probably start with an inspection of the power supplies and look for corrosion near the battery.
@@carlosdominguez-palacios9392 I don't recognize the symptoms you're seeing, and uUnfortunately I cannot provide individual support. I suggest you start a thread either on the EEVblog forums or the more specialized Groups.io mailing list : groups.io/g/HP-Agilent-Keysight-equipment/topics
Great video; thanks for sharing! It's always nice to see that sometimes what seems like a major problem can be quite simple if you use basic troubleshooting steps to diagnose :-)
Nice repair, looking forward to a follow up demo video. I envy you guys that make repair vids, I also repair HP gear, but I don’t have enough spare brain processing power left to troubleshoot and speak at the same time 😉😉
@@fenugrec5697 your video was / is extremely helpful. Measuring that voltage on battery was good nugget of info. Before I just had blank screen on power on button push I sent request to Keysight (support page, lets' see what they come back with._.) Thank you again for your work on this.
Hi, not much - I did some boring tests like T to S, T to R, etc just to verify channel matching and attenuator range; I don't have the proper instruments (power meter, external signal generator) to really verify the 4195's accuracy. I'm also lacking key pieces of gear for the more interesting measurements: a directional coupler and power splitter.
@@fenugrec5697 Thanks for the video BTW. After I was away from my 4195A for 4 years (we missed each other so much.. LOL) we are back together. SO, now I think I will check the battery. I hope that it hasn't leaked all over the place. If I place a big capacitor across it and let it charge, then I quickly add a new battery do you think it will work and I won't lose my settings ? Or is it a crazy idea ?
@@linuxaos depends on your tolerance to risk. You could also power the memory-backup section (refer to schems) directly with a current-limited source while you replace the battery. Capacitor, maybe, no idea what the backup memory current draw is.
@@fenugrec5697 yeah, that makes sense. So, first things first, measure the current draw from the battery. I'll just buy a ammeter attachment for my multimeter. I'll keep you updated. However, you and others have mentioned that the settings are not important and can be re-created by performing a new calibration (open, short, load). Is this correct ?
Oh jeeZ.
I have one that has been sitting here n my bench "dead" for almost ten years.
It was dumped on me by the local ham club because they didn't want to store it any longer.
When I first got it I spent a few hours probing around checking voltages & clocks with barely a schematic.
And no videos for it really existed then.
I know it WAS working before they dropped it off to me.
I'm guessing this might be the issue.
Thanks for posting the video!
Steve in Ann Arbor Michigan
N8LBV
Very clever idea with the LED as a quick sub for the battery - Excellent. I have a 4195A that I just took out of storage and had this same problem. I had basically figured the problem out (at least as far as the reset circuit). I also had measured the battery (not under power) but had decided the battery was probably OK - your video relieved me of the task of figuring out the battery failure circuit - THANKS for an EXCELLENT video. Did you loose the calibration data when you cut the battery of - I plan to replace the battery under power.
Thanks ! As I understand the RAM-backed data is only user programs, configurations, and custom O/S/L calibrations, so nothing irreplaceable. Mine's data was long gone of course so I didn't bother doing a powered replacement. Besides, I haven't touched that machine since the video until I took it out again recently - I still have to decide on a replacement battery ! I don't suppose you have the "adjustment program" floppy disk by any chance ?
Hi,
I recently got this useful lab device. I have the following problema. When I try to start it, the screen is black (nothing can be seen) and an alarm is on. Any idea? I would like to repair
Not sure... you will need to refer to the service manual. I would probably start with an inspection of the power supplies and look for corrosion near the battery.
@@fenugrec5697 thanks. How could I message you more frequently? I think you could help me a little.
@@fenugrec5697 I did the same as you (your video) and no luck. Any idea?
@@carlosdominguez-palacios9392 I don't recognize the symptoms you're seeing, and uUnfortunately I cannot provide individual support. I suggest you start a thread either on the EEVblog forums or the more specialized Groups.io mailing list : groups.io/g/HP-Agilent-Keysight-equipment/topics
Great video; thanks for sharing! It's always nice to see that sometimes what seems like a major problem can be quite simple if you use basic troubleshooting steps to diagnose :-)
actually I presently think of buying one, so I might need some advice in the future...
I measure 1.4 v with board out of unit on the battery
Nice repair, looking forward to a follow up demo video. I envy you guys that make repair vids, I also repair HP gear, but I don’t have enough spare brain processing power left to troubleshoot and speak at the same time 😉😉
Thanks ! I can assure you, it took more than one take to do the right things while also not sounding completely dumb !
Did you ever locate floppy disk? I installed new battery. Now get message : memory test in progress
No... I suspect there are not many copies of that disk left in the world
@@fenugrec5697 your video was / is extremely helpful. Measuring that voltage on battery was good nugget of info. Before I just had blank screen on power on button push I sent request to Keysight (support page, lets' see what they come back with._.) Thank you again for your work on this.
It works!! noob move... the boards weren't seated. It works! Thanks!
Did you replace the battery?
It took a long time, but yes - see part 2 ! (link in description)
Hello, any update on this unit ?
Hi, not much - I did some boring tests like T to S, T to R, etc just to verify channel matching and attenuator range; I don't have the proper instruments (power meter, external signal generator) to really verify the 4195's accuracy. I'm also lacking key pieces of gear for the more interesting measurements: a directional coupler and power splitter.
@@fenugrec5697 Thanks for the video BTW. After I was away from my 4195A for 4 years (we missed each other so much.. LOL) we are back together. SO, now I think I will check the battery. I hope that it hasn't leaked all over the place. If I place a big capacitor across it and let it charge, then I quickly add a new battery do you think it will work and I won't lose my settings ? Or is it a crazy idea ?
@@linuxaos depends on your tolerance to risk. You could also power the memory-backup section (refer to schems) directly with a current-limited source while you replace the battery. Capacitor, maybe, no idea what the backup memory current draw is.
@@fenugrec5697 yeah, that makes sense. So, first things first, measure the current draw from the battery. I'll just buy a ammeter attachment for my multimeter. I'll keep you updated.
However, you and others have mentioned that the settings are not important and can be re-created by performing a new calibration (open, short, load). Is this correct ?