[Premium-Rx] CUBIC-CDR-3250-LF-HF-DSP-COMMUNICATION-RECEIVER

[Peter Hamilton]

I had two PSU failures out of four. Symptoms not identical to yours, the
restarting was intermittent. I didn't need to trace out the schematic as
the worst one had failed dramatically and I just had to follow my eyes /
nose.

(NB, this was the 31xx - but probably similar / identical to the 32xx)


One of the electrolytic capacitors, C10 (220uF, 35V) has a top-side track
running close to it. There is no solder resist on the top side. The C had
been fixed to the PCB with blobs of glue, big enough to cover the nearby
track and soak under the C. The glue in the failed PSUs had decayed with
heat/age and was brown and slightly sticky. Decayed glue can be conductive,
but to make matters worse the Cs had leaked some electrolyte which had
seeped under the glue to the adjacent track. In the worst PSU this had
clearly cooked for a long time, leaving the board charred to about half its
depth.

The second PSU in that unit had the same decayed glue and capacitor
leakage, but there was no charring.

Both PSUs worked some of the time (until the worst one died in a puff of
smoke), but would intermittently shut down and restart.

The second, more recent, 3130 used different glue, possibly cyanoacrylate,
which was still clear and brittle.

To be safe I updated all four PSUs by removing all glue, replacing all the
electrolytics with 105deg long-life ones, and removing the offending track
and replacing it with an insulated wire link. They've now been on soak at
260V for a couple of weeks without problems.

If anyone's interested I have a "shopping list" of >=105deg, >=5000Hrs
electrolytics with Farnell/Newark order codes.

Not sure whether the list supports attachments, but I also have some pics.


--

Peter (G4VLC)


On 31 December 2015 at 22:15, VK3XYZ <VK3XYZ at wia.org.au> wrote:

> Hi all,
> Given it looks like there's a few of these receivers about ...... would
> anyone have reversed engineered the schematic for the power supply (would
> save me some effort)? I have a couple that continuously cycle between
> startup and shutdown. I suspect the obsolete ML4811 switch mode IC is dead
> but if anyone else has come across this before and found a solution I'd be
> very interested.
>
> If it is the controller IC, again to save some effort, would anyone have
> already designed a form fit replacement?
>
> Thanks
> Greg
>
> -----Original Message-----
>
>
> Today's Topics:
>
>    1. Re: CUBIC-CDR-3250-LF-HF-DSP-COMMUNICATION-RECEIVER
>       (Peter Hamilton)
>    2. Re: CUBIC-CDR-3250-LF-HF-DSP-COMMUNICATION-RECEIVER (Rick Vesny)
>    3. Re: CUBIC-CDR-3250-LF-HF-DSP-COMMUNICATION-RECEIVER
>       (Peter Hamilton)
>    4. Re: CUBIC-CDR-3250-LF-HF-DSP-COMMUNICATION-RECEIVER (W4NJ)
>    5. Re: Cubic CDR-3250 (Tisha Hayes)
>    6. Re: CUBIC-CDR-3250-LF-HF-DSP-COMMUNICATION-RECEIVER (Ed)
>
>
> ----------------------------------------------------------------------
> End of Premium-Rx Digest, Vol 109, Issue 9
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