HP 8711A/B stuck keys?

[wd5jfr]

Just acquired one with 8711A on panel but after booting it shows 8711B so I guess it's been upgraded.  The first problem was that several of the rubber keypads were stuck under the panel and I was able to get them to pop out, ( I wonder if this was abuse by a disgruntled employee?).  The second problem is that it doesn't always respond to button pushes more so with the soft keys.  The AVG, CAL, and FORMAT key pads not seem to be protruding as much as the rest. Haven't had a chance to open it up but I wonder what kind of membrane matrix iOS under the panel and if it's fixable or replacements are available.?  Is it a big job to get under the front panel for a look see?  I also see there's a DIN plug on the back for an IBM PC keyboard and if I can find one can I control the unit with the keyboard before I have to tear into it?
Thanks
Hank WD5JFR Green Valley AZ

[TheSteve]

The front comes off very easily if the screws on the front edges are removed. There is one ribbon cable that connects it to the chassis. Someone likely kept pushing harder and harder on the keys as they stopped responding. Once the front panel is removed you can easily remove the PCB, clean the board and the push buttons with alcohol and reassemble. Chances are it will work a million times better. I have done that with a few VNA in the series now all with excellent results. The disassembly diagram is usually on a sticker on the bottom of the unit.

[wd5jfr]

 Well I took it apart last night and could see that the keys were pressed so hard that several of the snap retaining clips were disengaged and one broken, so the keyboard pcb was not correctly in place.  So I pushed the board back in position and it worked a bit better but not right.  So I disassembled again and separated the keyboard circuit board totally and found that the silicon button substrate was torn between the middle softkeys.  One of those buttons was hit so hard that the snap retainer was broken and the stress on the silicon button substrate caused it to tear.  I taped  across the tear with some scotch tape, cleaned the pads with a qtip and alcohol and after assembly it worked a lot better but several buttons require real hard pressure or multiple attempts.  So I guess I can live with that till I find a good used keyboard or total front panel.  Any tips on a surplus panel  appreciated.  Now to try to learn how to use it and  see if I can figure out a way to use it for 50 ohms because it's 75.   I live in an HOA with antenna restrictions so this 8711b should help me especially if I can get meaningful use with 50 to 75 adapters and then get the eprom upgraded so I can do Smith chart plots.
Hank WD5JFR