EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: VK5RC on March 24, 2015, 11:01:08 am
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Hi
Posted as a bit of documentation if this fault occurs to another Agilent 53230 frequency Counter owner.
Channel 1 was becoming 'intermittent' and the fault seemed to be related to position of the BNC connector/cable, with no force applied no signal was registered, when a little pressure toward the machine was applied to the male BNC, the signal was acquired. Multiple cables would demonstrate exactly the same intermittent fault, and none of these cables would demonstrate this issue with other known good equipment.
A look at the PCB (with the case off and from below) did not reveal any visible faults and the signal could not be found beyond the centre connector.
Reworking the joint (desoldering and resoldering using lead based solder) only served to stop any signal getting through at all!
Tracing the signal in CH2 finds the centre signal goes to an unused (thanks Agilent) resistor PCB pad.
A quick bypass from the centre pin to the PCB pad (as show in photo below) has it working again.
Hope this is a one-off issue.
Ch1 on left side of photo below.
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I had exactly the same problem on my Agilent counter.
After fixing the loose solder connection, I also noticed that one of the reasons for this problem is the slightly larger hole in the front cover, which allows the BNC post to slightly move around and wiggles. So, before I re-assemble the unit, I used a small piece of thin shrink tubing around the BNC post and then there was no longer a play between the post and the cover and it feels really tight. I think this was an oversight during the design.
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Thanks for the suggestion, I will look into how loose the BNC socket is. I must admit I 'cheated' and did the soldering with the board in the chassis.
Robert
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Under normal circumstances, when you take the BNC connector in the front with tow fingers, you can easily move it up and down and you know right way that this will eventually fail.
You have to use a very thin wall shrink tubing. The "normal" shrink tubing I had was too thick and did not fit correctly and I did not want to enlarge the holes.
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We've had to repair this on two 53230A's already. Always the left input when viewed from inside the case (like in the pictures)
http://www.anderswallin.net/2014/11/53230a-counter-input-channel-fix/ (http://www.anderswallin.net/2014/11/53230a-counter-input-channel-fix/)
Anders
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You have to use a very thin wall shrink tubing. The "normal" shrink tubing I had was too thick and did not fit correctly and I did not want to enlarge the holes.
Try (plumbers) PTFE thread tape, wrap as many turns as you need
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I might start using Ch 2 a bit more for single channel activity as it seems more robust.