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

Hello Ulf, It may be the SAT orbital table is quite old and it will take quite a few SAT passes before the new table can be rebuilt.  Also, regarding the OCXO, it also may not be working and as it warms up and approaches a near on frequency point it will appear to be locking on until the system see it is not and alarms the operator. I would give it a week of on time before doing anything rash. good luck, Bill    WB6BNQ On 6/13/2023 1:36 AM, Ulf Kylenfall via time-nuts wrote: > 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 > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com