On 10/10/2015 12:27 PM, 'Peter' bunge@... [hp_agilent_equipment] wrote:
> New clues:
>
> I started through the Section 5 adjustments and got to 5.2 step 7 with
> minor adjustments. Entering 13.5 GHz freezes the displays. They start to
> flicker at 13.370 GHz. I can no longer select any frequency above this.
>
> The second observation is that the A9 reference resistor heat sink is
> too hot to touch. It shows Q1 and Q3 power TO3 devices on the schematic
> but has 3 on the heat sink and shows 3 on the component diagram, fig
> 8-70 in my manual (83592-90079). Q2 & Q3 are identical but not directly
> connected together. Q3 is supposed to be a voltage regulator. Q1 is
> supposed to be the coil current driver. It is difficult to tell which
> device is making the heat. The parts list does not show any of the
> “transistors/regulators”. Q1 is marked 1820-0430, Q2 & Q3 are marked “
> RCA 4-0080 HYP8432”.

To me this further suggests a power supply problem. As you increase
the YIG coil current by calling for higher frequencies, one or more of
Q1/Q2/Q3 is heating up too much, and probably dragging one of the power
supplies down. How do the rails look when you go up into that frequency
range?

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA