[time-nuts] HP5334A Option 010 replacement connector J8

Hendrik Dietrich don_hendi at gmx.de
Wed May 21 16:18:08 EDT 2014


Dear group,

as I just yesterdays implanted a non-original OCXO (C-MAC STP2390C) into 
a recently ebayed counter, I wanted to share my experience:

Swapping C8 to C100 position as per 5334B Service Manual (the B) is 
fine. J8, the connector for Option 010, is not in the 10811 layout as in 
the B.
As I cannot find a A service manual, I had to poke and trace.

This table will give you the pinout of the connector J8, with the lowest 
row representing the pins that are closer to the front, seen from 
component side top and the left column closer to the right edge of the PCB:

OFF State
--------------------
+30V  I  +30V
--------------------
GND    I   GND
--------------------
           I
--------------------
           I
--------------------
+15V I +15V
--------------------
I  10 MHz out


ON State
--------------------
+29V  I  +29V
--------------------
GND    I   GND
--------------------
           I
--------------------
-5V   I   -5V
--------------------
+15V I +15V
--------------------
I  10 MHz out

A 10 turn pot was mounted on the hole on the backside of the unit, 
connected to the EFC input of the Osc. as a voltage divider of course.
All wires are twisted pairs (or twisted triple talking about the EFC.) 
even the 10 MHz is not a coax - yet.

Having the rig open, I discovered burnt resistors at the 50 Ohm 
Termination of Channel A (only used B terminated so far), where the 
previous owner even stacked new resistors right on top of the original 
ones. (both pairs burned). A 619 Ohm Resistor in the ARM Path was also 
burned but Diodes OK, so I replaced it with a 620 Ohm Resistor, as 
expected without adverse effects.

Counter and OCXO cost me about the price of a single 10811.

Greetings

Hendrik






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