HP 8644A Signal Generator - Problem with step attenuator on 5 DB scale.

[aa7ae]

I received an HP 8644A from E*BAY today and everything seemed to be in order.  I ran a complete diagnostic routine with code SPCL 320 and it came back with +0 as in all is good.  However, when I started looking at the output of the signal generator on my spectrum analyzer, I notice that when I  move the knob for DBM the signal drops completely out on the 5's of the DBM scale. It works fine on even 10's, but in between on the 5's it's gone. I can hear a click, so I think the relay is fine, but the pad must be faulty for this range. Does anyone know what the part number of this is and how hard it might be to repair the bad 5 DB pad?

Thanks

[wn1fju]

Google "HP step attenuator repair."  There are some articles, YouTube videos and eevBlog posts that might help you.  I don't know the part numbers of the individual pads, and even if Keysight has any for sale, so you might be forced to buy a similar old HP attenuator (on eBay) and salvage the parts.  But I would start with a gentle cleaning and inspection of the plunger's O-rings (if the attenuator is the kind that has them).  I doubt there is a way for an average user to "fix" an individual pad.

Fortunately, my unit has the electronic attenuator, not the mechanical one, so I am spared this ordeal.  Good luck.

[aa7ae]

My attempts to repair this signal generator has taken a bit of a turn for the worse 
I was able to revamp all the o-rings in the step attenuators with new ones and clean up the contacts. However, when I put everything back together again, there was no RF output.
In my attempts to troubleshoot why there was no RF output, taking the boards in and out, etc. now the I/O board seems to be having problems as I'm getting a fault 15,022,110 
In addition, the hardline coax that goes to the input of the step attenuator suffered damage to the SMC connector, now I have to find a way to replace it.