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HP 5316A Teardown and Frequency Standard

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schopi68:

--- Quote from: xrunner on April 09, 2015, 06:30:27 pm ---The distance from main board to the top is 33 mm. Distance to the side of case is 28 mm (the case is curved so this is the smallest distance.

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great to hear that, the heat sink i use for the power regulator has a height of 25 mm. So my ocxo could also be used (but would need to replace the fuse on it by a resistor to keep power on-current under control - otherwise the cap on the counters main board would charge the cap on my board with a uncontrolled high current each time the power switch is depressed - but it looks as if there is no continous power available, so maybe an ocxo isn't the best choice for this device).


--- Quote from: xrunner on April 09, 2015, 06:30:27 pm ---Have a question also. There are two main filter caps. Both of them have one negative lead and two positive leads. The 4700 uF axial has the two positive leads going to two two different traces, and the 2200 uF radial has the two positive leads going to a single trace (but on the schematic it does not indicate this). If I might want to replace these going forward, what is the designation to specify in the parts search engine of places like Mouser? I am not familiar with caps like these with two positive leads that aren't identified on the case as such. Does that means their are two complete capacitors inside them even though it does not specifically say so on the outside?

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In most cases the third pin is just for mechanical stabilization of the cap (the one placed on the metal-plated side). Without it, the cap would move during soldering or fall of during vibrational tests. Interesting to see that even this stuff had a Patent some time ago: http://www.google.com/patents/US4763227

So if you need to replace the cap with a more modern one it wouldn't be a problem to use a 2-pin cap. If this is still very big in size it could easily be glued with a small amount of hot glue to get it mechanical stable.

xrunner:

--- Quote from: schopi68 on April 10, 2015, 07:54:33 am ---In most cases the third pin is just for mechanical stabilization of the cap (the one placed on the metal-plated side). Without it, the cap would move during soldering or fall of during vibrational tests. Interesting to see that even this stuff had a Patent some time ago: http://www.google.com/patents/US4763227

--- End quote ---

Ah OK good to know that.

Was doing some testing yesterday, and found that even though the unit is spec'ed to 100 MHz it will go into the 2 meter ham bands very well, as shown in the pic (last digits were changing so they look messy). Transmitting on 144.000 MHz.

Also hooked a small antenna to the Osc. test point and was able to zero-beat the internal 10 MHz ref to WWV on same freq. using my ham/shortwave receiver, per the procedure used by W2AEW Was just a touch off but very close. If anyone wants a good freq, counter for the ranges this covers it's a very good piece of gear!



schopi68:
yes, these units are scaling up to a lot more than specified. From it's bigger brother, the 5316B i know that it scales up to 180 MHz (and more) - this is likely the same for the 5315a (input circuit is identical for both units). Only the input sensitivity may be completely out of spec. :)

cpu_bach:
amc184 kindly sent me his PCB for my HP-5316A. I had to mount OCXO slightly above the PCB surface, because original OCXO's leads were too short to directly solder on the board. I confirmed stable operation of the assembled module. I am waiting for the delivery of standoffs which are not popular in ISO standard country.
 Thanks a lot, amc184! 

Smith:
I replaced mine with a stable high quality TCXO, works like a charm! I just used a standard header, some test PCB and 2 stand-offs to create my own PCB. Next time its open I'll take some pictures (Of course I forgot to).

It's a verry nice uit to work with. Lots of options for measurements, nice display. Only thing I dislike is it's enormous length. Oh well, gues it fits my HP 8116A function generator  ^-^

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