- Unit Log -
|Power supply, audio, and metering boards reverse-engineered to produce schematic.|
|Reverse engineering to produce schematic completed.|
|74S471 and 1831 ROMs dumped from both units and compared. Match.|
|Fixed-soldered twisted-pair wiring between CPU board and RF board replaced with wiring incorporating connectors so CPU board may be removed without desoldering.|
|Wiring between rotator optical sensors and CPU board replaced with slightly longer wires so plug can be removed with CPU board in place.|
|1977 based on component dates codes.|
|1997 Aug (for JP)|
|Poor condition due to corrosion from leaking NiCd batteries.|
|Selectivity switch loose due to fractured solder joints. Resoldered.|
|Front panel backlight incandescent lamps are all burned out. Uses eight 6V tubular bulbs, or could use 16-17 grain-of-wheat bulbs.|
|Front panel removed for light polishing with Silvo to remove what appears to be slight spot corrosion on aluminum.|
|Erratic activity from microprocessor system: even channels sometimes show up while using tuning knob, call sign disappears after being entered, tuning bumps a channel or two sporadically. Pin 40 of 1802 should be connected to +5 but is O.C. Bad socket pin (cheap molex pin socket). Plastic top of socket pried off, pins retensioned. Connection restored, unit functioning. Should replace socket.|
|Loss of signal after a few minutes of operation. Tuning/display still working. 680 ohm dropping resistor in 30 V supply burned up. 10@35V tantalum cap shorted. Cap replaced with 15@50V, resistor replaced.|
|3*AAA battery holder installed. Memory line supply disconnected and diode rerouted to V+5.|
|V+15 heat sink replaced with better type. Noted that regulator receives 27V at input, and that STEREO lamp at 100mA results in significant wasted power in regulator.|
|When rotating dial the up the frequency sometimes goes a channel down, and sometimes switches to even channels. No obvious problem source.|
|Tuning direction error of Mar seems to be gone. Dial lamps still need doing. Unit returned to Jurgen.|
|1977 based on component dates codes.|
|Poor condition due to corrosion from leaking NiCd batteries. Power supply board mostly destroyed. Portion of CPU board shows corrosion.|
|One LM703 in IF stages observed to have an 8.5pF ceramic capacitor tacked on between the input and output (UIF3, pins 1 & 5).|
Setting alpha call-sign does not function properly.
Once in alpha set mode, rotating the selector knob to select a symbol changes both the symbol and the position.
Action does not seem entirely deterministic.
Address lines from UCP11 to UCP10 not going low with A0/A1 when corresponding p2K/p1K is high. Traced to faulty UCP11 not deselecting A inputs quickly enough. UCP11 replaced. Solved.
|Tuning knob rebrushed to remove corrosion.|
|Heat sink on rightmost 9368 on display board loose, reglued with crazy glue. Doesn't heat up as much as others, glue not thermally conductive?|
|L/R variable outputs observed to have been wired such that the outputs are swapped. Labels on PCB (new version of audio board) are in error. Outputs rewired to correct.|
|Resistors at output of multiplex filter cans observed to be different (L=6.8K,R=6.2K). 6.2K replaced so both are 6.8K.||Bottom shield for CPU board not reinstalled, screwed to chassis bottom plate. Will need trimming for depth, or CPU board must be raised further, if shield is to be reinstalled.||Front panel removed for light polishing with Silvo to remove what appears to be slight spot corrosion on aluminum.|
|Meters are dead, loss of signal in narrow-band IF mode, audio still present in wideband mode. On UF1 703 IC, pin 7 has 0V. Internal 100-ohm resistor between pins 6 and 7 measures open. Replaced with 110-ohm (other 703s measure 120-130).|
|Memory line supply disconnected and diode rerouted to V+5.|
|Stereo lamp not functioning. 2N3702 drive transistor BE open. Note pinout is ECB not EBC. Replaced with 2SA573. Gain is a little low but affecting lamp current by < 1mA.|