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Counting on the HP 5328B

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jrharley:
Greetings fellow test equipment junkies!

Recently picked up an HP5328B Universal Counter. Serial Number: 2450A00594. Options 010 and 031are present. Pretty clean unit overall. As is often the case when buying used gear, this one arrived a little worse for the journey. The seller packed it reasonably well, but not well enough. Even though the box showed no signs of it, it obviously took a vicious tumble at some point.

One of the cast aluminum rack handles was broken clean off and the unit no longer had a display. Checking the rails on power up showed a missing
-5.2V rail. All boards were subsequently removed and examined. All card edge connectors were scrubbed with a fiberglass brush, cleaned with IPO and treated with a light brushing of D-100. They were re-seated into card sockets cleaned with CRC and treated with D-100. The missing negative 5V rail cleared after lifting a few likely components on the motherboard and re-installing them.

Upon re-assembly things started coming back to life. Display reads a solid 10.00 MHZ in the check position and the unit is responding to switch manipulations. Still lots of work left to do to run it through the maintenance checks etc., as well as some cosmetic items. The most troubling of those are the Function and Freq. Resolution knobs. Some genius decided to seat the grub screws into what appears to be some JB Weld, and so those guys are not coming out without a drill bit. Pondering that situation for a bit.

So, I’m calling out for any options folks can suggest for knob sources, as well as feet for this unit. Looks like standard HP feet will work on it. As always, any thoughts, advice, etc. are appreciated on this guy. A photo is attached for reference. I’ll report back on functionality after I get into it for awhile. Thanks in advance for any help!- JRH

Stray Electron:
   It's too bad that the Chinese or someone like them haven't started reproducing the HP feet.  Used TE always seems to be missing at least one of them.

   The knobs on much of the HP gear are surprisingly unique to each model!  I've collected a pile of them and even though some of them look very similar, when you compare them closely you'll find differences. 

    My strong advice regarding the knobs on yours is to buy a set of left hand drill bits and use on of them to drill out the JB-welded set screws. LH bits will frequency unscrew broken or stripped bolts but I don't know if it will get out the JB-welded ones.

    The best way to handle set screws that have tendency to loosen up is to simply install a 2nd setscrew on top of the first one.

    One other thing, some of the HP knobs use 1/16" set screws (0.0625") and some use 0.050" set screws so be sure that you're using the correct size wrench.  With either of those sizes it's very easy to strip the both the Allen wrenches and the screws!  Buy a good set of small Allen wrenches and put them somewhere safe and take good care of them.  Check the corners before you use them, especially when dealing with tight screws.  If the corners of the wrench start to get rounded, the wrenches can slip inside the set screw and round out the hole in it and make them very difficult to remove.  I grind the tips of my wrenches down when they start to get rounded so that my wrenches always have a good sharp corner at the end.

   FYI, you called them grub screws but we refer to them as set screws. 

tautech:
3dp models of HP feet are here:
https://www.eevblog.com/forum/testgear/replacement-knobs-feet-and-fittings-for-test-equipment/msg2255118/#msg2255118

jrharley:
Thanks for weighing in Stray! Good to know you’re on it.

All good points. Yeah, I’ve laid into one with a left hand bit, but there’s no backing these puppies out. They are seriously bonded. Since these cool “Thumb Paddle” knobs are composed of 99% Unobtanium, it seems to me that preserving them, even if the, ahem……SET screw core, is sacrificed, should be the prime directive. Bottom line in this situation is that I need to sleep on this one for a bit. These set screws are the .05 versions. Tiny little Grubs! 😊 Looks like I may need a source for those too. You’re right about Allen wrenches, thanks for the tips! I’ve got more Allen wrenches than Allen himself, but haven’t thought much about the details. I keep one brand new set in the lab for precision use only.

Thanks for the links tautech! Looks like some browsing is in my future.

Really appreciate you guys chiming in!  :-+ -JRH

factory:
It shouldn't be hard to find grub screws in UNC sizes where you are, you have places such as McMaster-Carr;
https://www.mcmaster.com/products/screws/fastener-head-type~headless/set-screws~/thread-type~unc/

In the UK I've used Accu, choice isn't as good of course;
https://www.accu.co.uk/shop/precision-components/precision-screws/grub-screws/socket-head-set-screws/imperial-cup-point-setgrub-screws?page=1

The common sizes of grub screw & allen keys used for HP TE, the #8-32 is usually found on much older HP TE;
#8-32, 5/64"
#6-32, 1/16"
#4-40, 0.05" (50 thou)
#2-56, 0.035" (35 thou)

For removing the grub screws I usually tighten them first to break the corrosion, it works for me most of the time, if it's too far gone drilling is probably the only option. Tek stuff seems worse with steel grub screws into aluminium.

David

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