JRC NRD525 Modification

[CoolAM Radio]

Digital hash reduction in display board JRC NRD-525
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Another annoyance with the NRD525 is
the high level of background hash eminating
from the front panel display, much of this
caused by the push pull inverter required
to supply voltage to that very nice vacuum
flourescent display, the rest of this unwanted
noise being from the keyboard scanning function.

The former can be reduced at certain frequencies
at least by the addition of a .1 Microfarad capacitor
in parallel with C14.
Use a disk ceramic type here with short leads,
this reduces the ESR of C14 at RF frequencies.
Another disk ceramic of .01 microfarad can also
be placed acoss pins 9/10 of inverter transformer T1,
the filament supply to the VFD.

The VFD filament is  run across the total width of
the display and acts as a very good transmitting
aerial at the harmonics of the inverter frequency.
.01 ceramics can also be paralleled across  C12/C22
to further reduce radiated noise.... all above caps can
be surface mount types directly soldered across the
existing electros on the copper side of the front panel PCB.


André
CoolAM Radio - Shortwave
the Netherlands

[CoolAM Radio]

JRC NRD525/535 Mod2
 
(click image)

[sat_dxer]

JRC NRD525/535 Mod2
 
(click image)

All fine and good if whoever wrote this, had bother to mention that diode CD10 is located on the CAE-182 IF-AF AMP unit.

[Josh]

If you can find the Fine Tunings issues, one of the members did a writeeup on the 525 called something along the lines of "waste gunner on a 525" with his mods to make life more enjoyable with said rig. One thing Icom did for the same issue in the R71 was to include a metallic yet insulated flexible sheet that one deployed betwixt the front panel and the rest of the chassis just kinda fitting it in there, and that reduced hash from the front panel. Mebbe that can be done to a 525, dunno as I've never had one.

[Teotwaki]

I have a 525 that I acquired eons ago and love the old thing. I'll have to look into these mods later as I am busy resurrecting a few R-7000's for mil-air monitoring.