[Premium-Rx] Cubic R-3030/80 Power Supply

[Terry O']

Todd,
I ran into a similar problem with a power supply not matching the 
schematic and it was all discrete transistors.  No way I was going to 
spend hours reverse engineering that one.

I used a bench supply for the +/- 15 VDC and a Chinese switching supply 
that had an adjustable output for the 25 VDC I needed.  I powered it up 
and measured the currents.  Then I built new supplies with LT1085 and 
LT1033 switching regulators.  The new circuit board (actually perf 
board) was much smaller than the old PCB and generated far less heat.  
Each of the LT regulator circuits was just 4 parts and the IC.  I used a 
trim pot in the circuits to set the volts and tacked them down with my 
old standby, Sally Hansen "Hard as Nails" clear nail polish.  It's still 
going strong.

Terry O'


On 6/16/2020 8:47 AM, Todd K. Rodgers wrote:
> Hello group
>
> I've got a Cubic R-3080 (half width) receiver. It's been working fine 
> for 10 years now. On the last power up attempt, nothing. Removing 
> covers, the power supply has faulted. I warm up the soldering iron, 
> pull out the VOM and know to look for bad electrolytics, blown 
> thermistors, etc. I pull out the manual, start comparing the power 
> supply schematic to what I have and it just doesn't look the same.
>
> I then notice that the power supply part number on the exterior of the 
> module is ASSY NO. 2871-1104, then that the diagonal stripe on the 
> module top face actually "slopes" in the opposite direction from all 
> other modules (no straight "line" here) and isn't in the last module, 
> right most (viewing from front of chassis, top side) position. Opening 
> up the power supply module (not ever done before) reveals some 
> evidence of modification, and some gunky stuff around the large filter 
> caps (perhaps original glue to affix the device better to the board, 
> perhaps leakage). The internal board layout doesn't match any of the 
> drawings/schematics I've been able to get my hands on.
>
> Anyway, the repair operation can take two routes:
>
>  * Trace out everything, make sense of this "new" circuit", and
>    judiciously replace parts and restore this odd power supply to
>    working order
>  * Or, attempt to replace all innards with modern switching power
>    supplies for +-16VDC and 8VDC (either mounted in the original power
>    supply casing or externally). I'm guessing heat generation might be
>    an issue (so perhaps best to avoid linear supplies) so don't want to
>    go overboard.
>
> The second option begs the question what current level outputs are 
> required for the 3 voltages? Does anyone on the list have any ideas?
>
> Any thoughts/suggestions, most appreciated. Any source of original and 
> appropriate power supply modules (ASSY NO. 2140-1124) also of interest.
>
> thanks!
>
> Todd, KC1SQ
>
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