Well, JimB, here we go then.
Maybe Kchristie is right and I just don't know how to use them!
That would be the easiest repair...
The attenuator consists of two modules containing basically 4 sets of T attenuators each. One module covers 0 to 10 dB in 1dB steps and the other covers 0 to 100 dB in 10 dB steps.
I am concerning myself here with the 10 dB step unit.
This unit contains 10, 20, 30 and 40dB attenuators which are switched by a rotary switch and either are used individually or ganged up.
So the 100 dB attenuation, for example, uses all four sections, added up.
In all the units, I own three of them, I find the 10 dB attenuation section only providing about 5dB and this error is carried thru the next few steps, I do get 15 dB instead of 20 dB of attenuation and so on.
This is peculiar since up to 40 dB each position of the rotary switch uses a different one of the 4 sections, and yet the 5dB error continues, even when switching to the the other segments of the attenuato module.
Clearly one would think that this has to do with a bad contact in the rotary switch, an error independant of the 4 different attenuators of the unit.
I opened these units, they are beautifully made. And they looked pristine inside.
While I was in there I checked as many of the resistors as I could without having to unsolder them and they all seem to be right on, no signs of any abuse.
Then I used some contact spray on the rotary switches and worked them furiously.
I also measured each of the sliding contacts of the rotary switch, thinking (hoping!) that I would find a really bad one, but no, everything looks just fine, contact resistances of a fraction of 1 Ohm by my mutlilmeter and yet they have this 5 dB or so error, all of them.
This is why I thought an HP technician, someone who has seen many of these and maintained a few, would be my best bet to find out what systemic error I am running up against???
Uwe