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53132A bad display

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BarsMonster:
Many of remaining 5313* displays will die... I hope I will get one that will survive.
To prolong it's lifetime - I am thinking about adding a switch to disable display when doing long measurements with logging. Did anyone ever did that and is there any hints?

artag:
I have a number of instruments with VFDs. None of them seem to have degraded further while I've owned them, but some were quite faded when I acquired them. The oldest instruments are not necessarily those with the dimmest displays.

My assumption is that, if powered up only when used, they will last a very long time but if powered on all the time because they're part of a production or test bench, they will fade in a few years. I doubt that dimming the display during a long measurement will help much unless you do that all day, every day.

Robaroni:

--- Quote from: BarsMonster on October 16, 2022, 11:35:45 pm ---Many of remaining 5313* displays will die... I hope I will get one that will survive.
To prolong it's lifetime - I am thinking about adding a switch to disable display when doing long measurements with logging. Did anyone ever did that and is there any hints?

--- End quote ---

I remember that counter, I switched mine out for a Tektronix FCA3000. Doesn’t help you but from other Agilent/HP stuff I’ve had those displays last a pretty long time, My 34401A had a bad display and I changed it out, the new one lasted till I sold it. I replaced it with a NOS 34401A that does all the basic measurements on my bench now. You can leave it on doing testing but they go bad if you leave them on all day everyday for years. Usually when I have to leave a meter on for extended time I have the luxury of a Keysight 34465A which is a better measuring device.

pqass:

--- Quote from: BarsMonster on October 16, 2022, 11:35:45 pm ---Many of remaining 5313* displays will die... I hope I will get one that will survive.
To prolong it's lifetime - I am thinking about adding a switch to disable display when doing long measurements with logging. Did anyone ever did that and is there any hints?

--- End quote ---

I suppose you can add a pair* of low value resistors (5R or so) in-line with each filament lead (with DPDT switch shorting the resistors for full brightness). That should dim the display down; prolonging the phosphor.  I didn't see a "DISPLAY OFF" GPIB command like in the 34401A.

* it needs to be a pair (for symmetry) since the filament is driven by 5.5VAC whose center-tap is 6.2V above ground (via VR2 zener).

Service manual: http://www.ko4bb.com/getsimple/index.php?id=download&file=HP_Agilent/HP_53131A_53132A_53181A_Universal_Counter/HP_53131A_Universal_Counter_Service_Manual.pdf
DC/DC+AC converter used (HP:0950-2325 = ERG:E2577VF): http://static6.arrow.com/aropdfconversion/21bc2cafea0620cdaf462a249c08dfffcf094564/e2577vf.pdf  FYI: HP manual pinout seems to be off by one.

ALTERNATIVELY, if possible,
you can break the connection between U2 (SN75518FN) pin 21 and pin 24 (VFDSEN remains connected to pin 24), and instead connect pin 21 to the common pin of a SPDT switch. Then pin 24 is connected to the NC switch pin and a 10K resistor to +5V is connected to the NO switch pin.

Pin 21 is the STROBE and as per the datasheet: "When STROBE is low, all Q outputs are enabled. When STROBE is high, all Q outputs are low."  So, when "...all Q outputs are low" all segments and grids won't attract electrons from the filament; ie. blanking the display.  This shouldn't interfere with any ongoing pin 24 activity (latching data) and once pin 21 and pin 24 are reconnected via the switch, whatever the state of the latch will be visible.

SN75518FN datasheet: https://pdf1.alldatasheet.com/datasheet-pdf/view/546161/TI/SN75518FN.html

BarsMonster:

--- Quote from: pqass on October 17, 2022, 02:16:11 am ---I suppose you can add a pair* of low value resistors (5R or so) in-line with each filament lead (with DPDT switch shorting the resistors for full brightness). That should dim the display down; prolonging the phosphor.  I didn't see a "DISPLAY OFF" GPIB command like in the 34401A.

* it needs to be a pair (for symmetry) since the filament is driven by 5.5VAC whose center-tap is 6.2V above ground (via VR2 zener).
--- End quote ---

Thanks for detailed answer, this will definitely help!

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