Solartron 7150 input impedance

[wn1fju]

I just got a Solartron 7150W.  Even though the front panel says 7150, the nameplate on the back has the "W."  I don't know what that means. 

Here's the puzzlement:  I was under the assumption that the input impedance on VDC is supposed to be >10G on the 0.2V and 2V ranges, and 10M on the 20V, 200V, ... ranges (maybe this is my mistake!).  But my input impedance is 10M on ALL ranges.  I verified this by putting 1V through a 10M resistor into the unit and got a 0.5V reading.  So naturally I suspected the relay that switches in the attenuator was stuck.  But the relay checked out OK, so I suspected the ULN2003 driver.  But that also checked out OK.  The ULN2003 is driven directly by the HD68P01 microprocessor and so I suspected a stuck line.  But the voltage on the line goes from TTL high to low when I switch the 7150 away from DCV mode.  So the line isn't stuck.  The meter is simply being directed to leave the attenuator in at all times (so on low ranges, it is in parallel with another closed relay directly putting the input into the FET amplifier).

I cannot believe that the program is corrupted, since everything including the cal procedures, work fine.  It's almost like it's supposed to work this way.  Is this what the "W" in 7150W might mean?  Does a normal 7150 have 10M input impedance on all DCV ranges?

[wn1fju]

Oops, never mind.  The >10G input impedance on the 0.2V and 2V ranges is for the 7150plus version.  The straight 7150 says 10M for VDC without distinction as to the ranges.  So it's supposed to work that way.  Pretty lame.