A manual for the HP 416A, this test setup shouldn't be too difficult.
http://ftb.ko4bb.com/manuals/86.173.155.242/HP_416A_Ratio_Meter_Operation_Manual.pdf
David
Thanks for that !
Of course the A and B are bound to be very similar, so will be of great help.... <a few hours later> hell, I finally got a manual for the 416B after all !
.... No PDF online, but strangely on Ebay I found no less than 4 original paper manuals for it !
3 in the US for a fair price but obviously expensive shipping but.... the 4th and last one was in Europe, yeah !
Not in the EU though, sadly... in the UK. But only 5 quid or so ! And only 5 quid for shipping.
https://www.ebay.fr/itm/115081598875So for 10 quid I will receive that manual.. I can afford that...
Of course I may have to pay customs and shit, but calculated on a 10 quid basis, it can't amount to much can it....
Thanks for that, nice drawing... in " 3D ", looks so artistic and cute, love it !
OK, some news... worked on the thing last evening, but was so exhausted I could not post about it, went straight to bed.
So here goes...
Got lucky, found a new plug in my electrical junk box... so I replaced the old plug. Cleaned the horribly crusty cord while I was at it... it's clean now, great, but it's still a bit sticky ! I guess the material has degraded... same that happens on some plastic trim in car interiors, cheap steering wheels etc. It's nasty.
So I could plug it at last, good, an earthed as well, great... feeling safe now.
Powered the thing up via the Dim bulb tester... which lit brightly at first, then dimmed a bit.
I could see the heater in most tubes, glow faintly, good. I let it cook this way for a few minutes, to give the old filter caps a bit of time to wake up, after decades of sleep. Thing didn't go haywire, no flickering of the DBT light, no short... looked good to me so I took my chances and plugged it straight to mains, crossing fingers.... no smoke, no explosion, good....
So I then played with the thing for a bit. There is life left in this thing for sure, but it's a bit ill, I think...
I made a video clip summarizing my findings. I fed both inputs with the same signal so that it shoudl read 100% on the scale, FSD. 1kHz sine wave, amplitude a few mV (switched on the max 60dB attenuation on my sig gen). Here is what I do, in order :
1) Instrument powered off : the needle on the meter is at Zéro, spot on.
2) I flick the power switch, come sto life : pilot light, magic eye working and open.
3) Close-up on the scale : the needle has been pushed below zero, now hitting the mechanical stop... when it ought to be full swing to the right
instead.. not good
4) Now something else : I pan to the upper right part of the front panel. Next to the magic eye, there is a pot labeled " Reference Adjust ", and next to it there an attenuator switch, for the reflected input. So I guess adding attenuation of should lower the reading on the scale, from 100% (if it worked that is...) to lower and lower values. That had no effect on the needle, it' still stuck on the left mechanical stop. However the magic eye does react : if I operate the pot, I have a varying degreee of control on the eye : the more attenuation I select, the more I can close the eye.
First I start at 0dB : pot has bugger all effet.
Then I switch to -10dB : pot now allows to close the eye a little bit, enough to be easily noticed.
Then switching to -20dB : I can almost close the eye.
Then switching to -30dB : I can close the eye fully and even beyond : the two bars meet at the center and then I can even make them overlap a bit.
5) Now moving on to a toggle switch in the center of the panel, labelled "Excess Incident Attenuation ", where you can select between 0dB and 10dB... 10dB not minus 10... so looks more like 10 dB BOOST rather attenuation, and the block diagram of the 416A confirms that... there is a 10dB AMPlified in there, and the toggle switch inserts a resistive divider between the input and that amp. So overall the label is misleading...
Anyway, the point is : when I flick this switch, for a split second while it's transitioning from one state to the other, I can see the needle jumping up ! Yeah, it's not dead ! ... except it's camera shy it seems, and when I made the video somehow it refused to move, bastard ! :blah
HOWEVER.... you can see that the magic eye, DOES react : it briefly closes then opens up again. So hopefully it will convince you I did not lie about the needle jumping as well...
6) Ok almost done. Now I power off the instrument, and get closer to the scale to show you a strange little dance that the needled does, 100% repeatable, like clock work...
- Needle violently jumps up a bit, then just as soon and just as violently, moves back to where it was, at the mechanical stop.
- Then the needle rises fast to maybe 40% FSD
- Then immediately does the reverse trip, ending again at the mechanical stop.
- Then the needle is "freed" : it slowly moves up to the Zero mark on the scale, where it was at the power up.
I am now waiting for the service manual. I am willing to do a bit of troubleshooting to see if I can get it working, but nothing major of course, and certainly won't spend considerable money neither. I had a peek under the chassis with a torch light, I can see a decent number of electrolytic axial caps that I can replace as a no brainer.. the Sprague black beauties also found in my old Tek scopes, and also some Mallory ones in paper tubes... Then some contact cleaner here and there.. then reassess ... check voltage rails... The basic stuff. Any TE deserves at least that much...
I won't bother listing them for sale, waste of time... can't be shipped, and if I can't get them working, worth nothing at all.
So I am thinking of a plan to save them... I can't use them, I can't sell them... and I can't get myself to take them apart and scrap the case.. because they look just so gorgeous and sexy in the flesh, I love them. And this magic eye is the icing on the cake...
So I am thinking :
1) I could put one of them as a decoration in my living room, once the house is in a state that the living room actually looks like a living room and not like a dump.
2) The other one.. as MK said, would make a nice project box. I am thinking I could repurpose the thing to do whatever.. a power supply, my big electronic load project, whatever... I could get a hobby CNC milling machine to engrave an aluminium plate to make a custom face plate, using the same font and overall looks as HP used, reusing HP knobs and controls, same paint, to make it look like a genuine HP, but repurposed for whatever project I may have. Of course I would save the original 416B face plate and guts...
Wadyathink ?!
I am trying hard to find ways to save these lovely puppies...