Welcome to my RU-vid channel. I spent 25 years working as a Program Manager at Microsoft on the Visual Studio, Windows Internet of Things and Windows teams. Now I run my own company doing IoT consulting. This channel hosts videos of my personal projects in the IoT space.
The power supply capacitor (100uF) in my unit has been replaced and the meter lives again! Thanks!! I found the service manual on the Internet, but it doesn't have the waveforms. Do you have a link to a manual that does?
NP - Happy to help - I've dropped a copy of the waveforms here - imgur.com/a/0O9NB9t - but I really recommend getting the great scans from ArtekManuals.com - Very reasonably priced and they do a great job in getting the image quality high, way better than Keysight did.
You're absolutely correct If this was just a PC - However, I use this as a host for a HP Viper Card (basically a MC68K HP 9000 computer), and that talks directly to the motherboard/bios for the drive so that overlay software wouldn't be running or be able to intercept the IO calls so I need the base machine to recognize the drive. The actual machine has recently developed additional issues so it needs to go back onto the bench and be worked on again, unfortunately.
Thanks so much for the videos on the repair of the 432 power meter. Mine had the same symptoms as yours. I was just getting ready to check my power supply voltages just before watching your video. I found my 100 uF capacitor was bad, just as yours was! I have one on order, but I think I have a pretty good handle on it thanks to your video!!
I have one of these meters and when I turn it on, it pegs the meter in the negative direction and the Coarse Zero does not adjust it up any. Ideas anyone?
Start by checking the power rails. I did a somewhat long series on fixing one of my 432A's that might be worth a watch. If you don't already have it, grab the manuals from ArtekManuals.com, great quality scans
This is the first video - It seems to have the same problem that you were having - Take a look and let me know how it goes for you. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-oVKNVzdx3N0.htmlsi=D4Or08jMA3fESLMV&t=269
This was just a video showing the needle bouncing around due to the noise in the photo-chopper circuit - Really just a celebration of the D’Arsonval movement
@@tgsoapbox OK, I was watching your video because I recently picked up a Fluke 845AB at a hamfest for next to nothing, it appears to work to some extent but it's not very accurate and the meter is very erratic. I guess this is a common problem, I'm not sure I even know where to start attempting to repair it. It's dated May 1969, mechanically it's in good shape.
@@harrybond007 Dr Frank pointed out that he posted to this thread over on eevblog - www.eevblog.com/forum/metrology/teardown-fluke-845aabar-tweaks-and-mods-(and-repairs)/?all - about the neons and capacitor replacements that addressed the noise in his 845AB. I did a Neon update and showed that in a later video but I haven't yet looked at the caps in the unit. It'd be worth checking out that thread for insights into what might be going on with your meter.
@@tgsoapbox thanks for the link, that is a great resource, I did search online but never found that, are these units still useful?, still used today?, the used ones on eBay are listed at high prices, even if not tested?
@@harrybond007 Sort of, really depends on what you're doing. If you have an 8.5 digit meter then in most cases you can just move on from these - Though in one of the threads on EEVBlog they have a discussion about current bias and how these null meters are still better than the current 8.5 digit ones for metrology purposes. I had a chance to acquire one for a fairly inexpensive price along with a Kelvin-Varley divider so I thought I'd just go do it and see what goes - I am a noob when it comes to these units as well. Good luck.
Hi, there are still several things not right.. zero can not be "calibrated", there is probably an issue with the amplifier circuit, you need to check the waveforms and the supply voltages acc. to the manual. In my 845AR, I had to replace two electrolytics, which were dried out. The needle should be much more stable in the 10µV range, even in 1µV, my unit shows much less noise (ok, the damping time constant is much higher there). I just checked: in the 10µV range, the needled slowly wanders +/- 2 divisons, or +/-400nV, in the 3µV and 1µV ranges it's as well +/- 2 divisions, i.e. about +/- 50nV Have you checked the neon bulbs, whether they fire in the dark? If these new ones show the dark effect, then the noise is related to misfiring. We had a detailed discussion on eevblog, identifying possible root causes.
Thanks Dr. Frank - I believe the neons are working but I have not confirmed - They are certainly working more than the previous ones I had in there. I know you can't calibrate the zero but I was planning on doing that as a step before I started looking at further issues with the noise. Will review the EEVBlog thread.
Thanks Scott - I did watch your vids, you never replied to my question you bastard :) - As for the battery I replaced mine with some Tenergy NICADs to try and keep it original (though I suspect I'll need to move to the non-photochopper mod at some point and so I'll probably go your path then) - The noise dropped quite a bit between what I had before and now with the new neons - I'm hoping to ressurect it to working with old school components.
I think I have an older one than yours (at least your knobs from memory as white where mine are darker - Did yours have the Neons or the newer chopper circuit?
@@tgsoapbox keeping it original would certainly be nice. I don’t remember seeing your comment, sometimes I have found comments on videos that don’t show up in my notifications of comments list… (or filtered comments) it’s a bit odd.
Don’t take the 155 degrees “rating” at the face value! What it tells is the INTERNAL hot spot temperature. There is a big difference between the internal and measurable - outside -- temperature. Depending on the heat sinking, it can be several tens of degrees.
Thanks for the comment - I think from memory, and it's been a while ago, the failure case here had a lot of current draw and thus heat dumping which drove it over the value. I think I'm commenting on the fact that the power dissipation in the working unit is well under that value. Will have to go back and watch the whole series to make sure - There are I believe several posts over on HPAK groups.io right now I think that reference swapping these with LEDs instead of the CCFL like I did. Anyway, thanks for commenting - Appreciate it,
I could not locate these fluorescent tubes since these contain Hg and are not longer in production. What I did is purchase a 15 inch LED strip and driver for LCD TV repair from Amazon. I used the +12V input pins on the High Voltage board to power the LED Driver. To hold the LED strip in a 3-D printer was used to make a part which held the LEDs in place inside the metal rail. The LED strips can be trimmed to lenght.The result was a brighter LCD screen on my LA.
good video! I have many of these relics running in several labs that are used for FPGA emulation. These LA frames now cost a fortune and have fewer I/Os to boot!
Leakage probe is just a 135K ohm resistor (1%), with a shorting bypass pushbutton switch. Can be easily built by almost anyone. Two 270K resistors make 135K. Use the carbon film types, to make sure they are good for 200+volt breakdown. Some chip resistors are not rated for high voltages. PassItOn.
Thanks, Dr. Frank - I see over on EEVBlog that people have used Barthelme 82305 neons as direct replacements (I'd like to try and keep the unit as original as possible) but I can't seem to find any - Suggestions on a source or other replacement?
My 432a is acting similarly...your lecture has shown me that the power rails are key to making sense of the issue..not a guess.. I will start there and follow your path...Thanks KA3TXR
Might want to check the memory backup batteries in these units. Consist of 2 AA Nicads if I remember. I have two for these units myself. Also have had tag tantalums go s/c.
Hello, I have an HP 8901B modulation analyzer, it works well up to 600 MHz and up there it doesn't work anymore, as if it were the doubler. Have you seen any failure like this. thank you
Yes I had a similar problem in an 8902A - It was the doubler but the part was a HP only part that was unavailable as a replacement - I was lucky enough to get a spare board from a member of the HPAK forum (over on Groups.io) - The internals of the 8902A and the 8901B are almost identical so the same documentation should help in the troubleshooting - Service Sheet 17 in both cases. I did a video on my experience here - ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-21nozchgOag.html Happy to send you the PDFs I have if you don't have them
Good to know - Thanks for the post - I ended up getting another 4406 as part of an auction bid so I didn't go further trying to address this - I still have the broken unit here so I'll add it to the long list of things to work on - Thanks again.
I mean... thnx for the vid... and the work... but, to me.... an IMO... this seems like to most convoluted way to determine the max power of the S.G., over it's range. Well... maybe, I could think of a harder way.
If you are just looking for a close measurement of what a signal generator outputs then you can absolutely use an SA for that. I didn't want to take the chance that the sig gen of unknown providence wouldn't do something rogue on the output but clearly, in hindsight, I could just have used the SA (I have many sensors but only one SA) However, a power sensor is going to get you a power measurement that is around an order of magnitude better than the SA and might be even more depending on the SA that you use. This is why most of the calibration processes for sig gens use a power sensor rather than an SA for their adjustment steps.
Very nice! Right out of high school, I took a summer grunt job before college. The owner of the company brought his new dual-floppy IBM 5150 and HP 7475 plotter in to see if I could make it do something useful. Thus began my career! Eventually, he got me a 7550A. A lot of what those plotters did was driven by software I wrote. I like to think that my work with those machines and other things that followed were a not-insignificant contribution to the company's rapid growth and eventual domination of the industry (from a small father/son operation). I never did make it to college! 7550A (and also 7475) are very near and dear to me. I wish I had room for one now.
Definitely - Seems much faster than my 7090A - Need to get some heavier-weight paper to try out if that addresses the slight misalignment in auto-feeding - It has multiple inputs as well, hmmm, maybe a Serial to Network adapter to use it from my PCs...
got the same beast a few months ago, sadly only have the A4 paper tray, but it's feeding fine. missing the catch tray too so it flings the finished plot across the room :)
I'm going to have to make a custom catch tray myself to get it to fit in the place I have it aimed for - I only have one tray but mine had screws in the guides so I could convert it from US Letter to A4. Seems a lot fast than the 7090A I had already.
@@tgsoapbox Thank you for responding. The problem I have is on the 8902A. Specifically, the machine 8902A measured at 10 MHz frequency; 20 MHz; 1.3 GHz. But at 125.6 MHz, 700 MHz the machine shows 4 dashes. Can you please advise me? Thank you very much
@@user-kk2ij1pv3m I replied to your other comment on this - I would start by testing the front-end amp (U1) to ensure that it is working correctly - If it is then you'll need to follow the signal path through to see if you can find the issue - The numbers your mentioning don't ring a bell with me as key points in the frequency range unfortunately.
That isn't a problem that I have seen before so I'm not sure where it would be happening (especially if the instrument is working correctly outside that range). I'd probably start by putting something like 95MHz into the instrument and then checking the signal path to see where it stops being what the service manual expects.
Actually, the connectors on the digital I/O boards are not custom parts. They are standard DIN41612 connectors. In this case the 96 pin ABC variant (rows A, B and C are populated with pins). All sorts of variants exist, like 64 pin AC in the same plastic shroud, but also shorter ones with less pins, as this HP has on its backplane. Really nice and reliable connectors. Often found in (mostly European I suppose) industrial control systems, T&M stuff. And in VMEbus computers. cheers, Wilko
Interesting - Thanks for the info - I've never seen the connectors outside of the bits hanging off the back of these units - I'm still fairly sure I won't use the boards for anything though :)
@@tgsoapbox Yeah, these are not the most useful cards for the average home user. The aforementioned DIN41612 connectors also come with coax contacts. I just stumbled on pictures of those. They are found inside my Efratom modular Rubidium frequency reference, More than happy to send you a copy (just need to figure out how 😀). best , Wilko
The thumbscrews on the coax-based cards screw into the switch controller in the same way that the other cards' (the "non-coax" ones, so to speak) wiring harnesses screw into the unit. IOW, all the cards eventually have something that screws into the back of the 3499 (or 3488).
I was really just wondering why the VHF card had screws and the Microwave card had thumbscrews - I can understand them both having either screws or thumbscrews but the difference seemed strange.
@@pa1wbu Could absolutely be but I think both these boards were earlier vintage I just find it interesting that they have different mounting hardware - It'd be great to know if it was just a "release date" thing or if there was a real design decision behind it.
it's the membrane keypad and the only solution is to replace it. been there done that several times. was never successful in repairing that keypad membrane.
Thanks - I wouldn't have thought that this would make a difference as the button should be in parallel to the short but it certainly appears to. Looks like I'll need to disassemble the front panel - Did you have any success in cleaning the keypad?
I just checked eBay and they have replacement membrane keypads for around US$25 - I've never had much luck cleaning them but it'll be interesting to see if it is possible.
Aaaahh.... The 'ol exploding flux pen trick! Who knew tgsoapbox was a comedy channel :) Never seen that happen before but you gotta' admit it was funny. Nice methodical troubleshooting work TG, looking forward to your next one.
