https://www.ebay.com/itm/323310255105
Is there maybe some generic programmable atten (like this one, but probably not THIS one) that uses the same or similar module? Do you at least have specs for the attenuation steps so you might be able to search for a generic substitute?
[EDIT] NM... I just realized it's a 2 stage atten. Not likely gonna find a generic one of THAT. [/EDIT]
mnem
moo.
Yeah ... If only it was that simple.
HP used something unique. It is a hybrid approach, using (I imagine) a voltage controlled amplifier to give 0.1dB increments over a 10dB range which is then fed into the step attenutator stages.
The first stage has two inputs - a low band (0.1 - 123.5 MHz) and a high band (123.5 - 990 MHz) - with two 30dB pads ... and a couple of extras.
The second stage has 10dB, 20dB and 30dB pads ... and a couple of extras.
The pads are controlled by the application of either 0V or 15V to the relevant terminal. When 15V is applied, you can hear a click - so we have some relays inside. With 15V voltage applied to both control pins on the first stage, measurement between the low band input and the output show effectively no resistance. The logic appears to be 0V - pad in, 15V pad out.
I mapped out the voltages on the pad control terminals against the attenuation display and by simply using the pad values noted on the schematic and the above logic, this table fell out very naturally.
With this, one would expect a zero loss path through the second stage, with the three relevant control inputs supplied with 15V - but nothing was getting through.
Open heart surgery is next on the list.