[time-nuts] Rapco (Pendulum) 2804B - Troubleshooting . . .

[Ulf Kylenfall]

Regarding the Pendulum (Rapco) 2804B from a flea market...

I spend some time trying to fix it after downloading the manual
kindly provided by Lisa Perdue.

First, I resoldered the main PCB as I could clearly see a number
of poorly soldered thru-hole components. This solved an initial problem
where the display and LED-panel randomly got black. (Not the
units screen saver.) 

Scrolling down the pages and trying different settings for the OSC2
("OSC" - Depending on various options), in this unit a 10MHz unit
with a de-facto standard footprint) I recognized that the locking procedure
seems to be pretty static. No "adaptive" algorithm whatsoever.
Two settings available, short and long for re-synchronization, the
short being some 8 minutes (Default).

After having placed the antenna outdoors and the unit sees a large number
of satellites, it starts acquiring a lock, a procedure that takes several
hours during which thew OCXO control voltage slowly adjusts the control
voltage.

When at last the unit stabilizes, the OCXO is about +0.5 Hz wrong.
What then happens is that the unit seems to realize that something
is wrong. The two LED's "GPS" and "CONTROL" goes out. An alarm is set
and this situation persists for a few minutes after which the operation
returns to normal. The Control voltage (low resolution) seems
to be unchanged.

In one of the test menu pages "LOOP Page", a parameter "Control Index" is listed.
My unit reaches 2, a number not listed in the manual. It should be between
4 and 8.

At the same time, the number of satellites remains high and with
fine S/N values.

The manual was of great help in using the menus but the lack of
service documentation (CLIP) makes further troubleshooting difficult.

Right now, I am inclined to beleive that the problem could be the
OCXO that is malfunctioning, being unstable. It also gets a bit to hot 
compared to what I have felt from other similar units. 
Having a few compatibles, I will try to replace itand see if there is any improvement.
Ulf KylenfallSM6GXV