I picked up a $20 Dovetron MPC-1000CR-II at the Shelby
hamfest.
It has the BBP-100 rev A board and a TSR-300D SELCAL/REGEN
board.
Unfortunately I can't find a TSR-300D schematic.
I aligned the RY generator for 45 baud and calibrated the
VFO and AFSK OUT for Mark and Space.
It seemed to be working fine on 170 and 850 shift signals -
regen was OK, autostart was OK (I did not test SELCAL), RY was
OK, ITTY was OK. Then just before I went to put the covers
back on I turned it on for one last check.
Uh-oh it is stuck in Mark-Hold. The cross-LED shows the M-S
detectors are still working fine. SIGNAL LOSS LED is always
lit, output is always MARK.
REGEN ON-OFF makes no difference.
SEND-RCV makes no difference
THRESHOLD makes no difference.
Any suggestions? I tried pulling off the TSR-300D board so
I could scope the BPP board, but then things are stuck in
SPACE, even with the REGEN switch OFF. Next stop is attempting
to trace the BPP in/out on the bottom of the MPC main board I
guess, And maybe trying to trace the leads to the TSR-300D
board to figure out what it might be doing.
Has anyone run into a stuck Mark-Hold before?
I confess that I have a hard time figuring out logic made
out of interconnected 741 op amps instead of straightforward
TTL or CMOS logic chips.
And just trying to figure out how the BPP interacts with
the MPC board is a royal pain. FWIW I marked up a schematic
with some of the mods made to the MPC board when installing
the BPP.
Does anyone have a better copy of the BPP Rev A schematic
75195?
The one I have is hard to read -
Other Dovetron schematics and manuals are at
Cheers,
