I was the Project Manager for the 5334B.
The A version (unlike the B version) has
a very weak power supply due to insufficient
capacitors and/or transformer. I can't
remember now after 25 years. When you
power it up with a cold 10544 or 10811, the
oven circuit looks like a 47 ohm resistor.
The 5334A can only muster 12V into this load.
This is way below the 20V minimum operating
voltage. However, the 10811 turns out to
work well enough on 12V to get the oven warmed
up. Once the oven current cuts back, the
voltage will zoom up to something like 24V,
being unregulated. This passes for "normal"
in the 5334A design. So do not be alarmed
by this behavior if you are trying to do a
sanity check.
Rick Karlquist N6RK
On 5/21/2014 1:18 PM, Hendrik Dietrich wrote:
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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