Відео

Glad you enjoyed it

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.

Thanks - I'm using an old Canon HF R600

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.

Good to hear - Glad I could help.

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. ua-cam.com/video/oVKNVzdx3N0/v-deo.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.

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 yeah mine is newer, might be some similarities though.

@@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.

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,

我们可以很容易的提供这个驱动和灯管😂

Kerry Wong did a great backlight mod to his. I quite like the unit

That's good to hear - I wanted to try and keep the unit as close to original if I could but the LED fix is certainly a better one long term.

Thanks - Glad you enjoyed it

Thanks for the info.

Got to love the UA-cam AI - Updated....

@@tgsoapbox They nailed it! 😂

Thanks, I do think it is out of spec as that wobble is on the 10uV setting in zero and operation (with nothing plugged in).

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?

LOL

Glad I could help a little - Good luck with the repair.

Thanks - Will take a look

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 - ua-cam.com/video/21nozchgOag/v-deo.html Happy to send you the PDFs I have if you don't have them

Actually I thought I'd just post the link here - 1drv.ms/b/s!Amqar8_XQ9Uzk7pW61K_OdEpGYqjpA?e=5aGqag

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 have one of those as well - I just love the form factor that HP used on these devices.

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.

It is an 8563E - I just chickened out on blowing something seeing that I had no idea where/what/how these plug-ins I acquired worked.

I find in mildly relaxing to hear the plotter working in the background :)

Great story - It is amazing how one piece of technology can make all the difference to the path of a person's career.

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...

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.

Happy to try and help but I don't understand what the problem you're having is. Can you try explaining it again?

@@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.

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

@@pa1wbu Thanks - Maybe drop a link into the comments here - I really don't have a use for them though

Many have asked for the dumpster location, but few have received it... :) Sorry, can't share so I can protect the primarily innocent...

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.

Maybe a look at the serial number enlightens? Could very well be different production years?

@@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.

Good reminder - I should compare both units just to see how the PS is going on the 19B

Thanks - I have never been successful either but I watched FeedbackLoop's video where his magically started working so who knows :)

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.

​@@tgsoapbox I believe that they fail by developing internal shorts between layers

Yep - I completely missed the TD entry that Scott pointed out...

Well, there you go - I completely missed that... Thanks, Scott for the info.

First time for me too...