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Cubic CDR-3250 Display Replacement

Posted on January 9th, by Shaun Merrigan in Electronics, Radio. Comments Off on Cubic CDR-3250 Display Replacement

The Cubic 3250 VLF-HF receiver is a 10kHz – 30 MHz DSP based radio receiver with 51 IF bandwidths and 7 receive modes. It falls into the category of professional/military grade equipment and the build quality certainly reflects this. According to Fred Osterman’s book, “Shortwave Receivers Past and Present, 3rd Ed.”, it was manufactured from the mid 1990s until at least 1998 (possibly later). I have found that the audio recovery and readability of this receiver is outstanding.

These receivers have a VFD (vacuum fluorescent display) as part of the front panel/human interface. The VFD in one of my units must have had many, many hours on it because it was quite fuzzy and dim, to the point of being blurry:

Aged, dim, blurry VFD

The old display on the CDR 3250 showed considerable burn in when viewed using UV light:

Burn in of old VFD with UV illumination.

BTW, you can use the UV light trick on older instrument CRT’s to reveal burn in.

Using the radio while looking at this display gave me eye fatigue and was downright unpleasant. I had been searching for a reasonably priced VFD replacement for quite some time but without success. The part number of the display/driver assembly is GU256X64-312 or GU256X64-312A. As with most VFD modules, this comprises the raw display, the power supply/driver/interface board and the mechanical and electrical interfaces. This configuration is not easy to find and quite pricey when you can find it. The going price on eBay is over $350 USD. However, I did finally find one on Aliexpress for just over $200 USD including shipping. It was clearly used, but in very good condition.

Replacement (top) vs original (bottom)

I installed the new display board by removing the front panel as described in the CDR3250/80 Technical Manual. This is a relatively simple process; taking care not to stress the interconnect wiring is the most important thing to remember. The replacement display looks like this:

Cubic CDR 3250 with replacement VFD

The replacement display is easy to look at and I have it dimmed down to the lowest level that gives good viewing. I have done a 72 hour burn in test on the display followed by the appropriate on board display diagnostics and found no problems. I expect this VFD will last for the life of the receiver.

Thanks for reading.

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