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WJ-9205 Signal Monitor

The WJ-9205 Signal Monitor can display up to three traces simultaneously from up to three different receivers with each trace at a different sweep width. A 21.4 MHz unit with -100 dBm sensitivity. Sweep widths available are 50, 100, 200 & 500 kHz and 1, 2 & 5 MHz. Standard resolution is 10 kHz. Options include 2 kHz resolution and a IEEE-488 interface.

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The inside is tight but cleanly laid out.

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The back has blank plates for options. The three DB-15s labeled J2, J3 & J4 only have two wires connected to each, presumably to interface with WJ-8615P receivers, for which this unit was originally designed. J1 provides for X-Y outputs or X-Y inputs, which can be selected from the front panel.

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The sad story

The replacement tube for these SMs is listed as the Thomas 4E35P31, a very rare CRT. The original tube is a Magnavox D1062P31 (General Atronix Division). Replacements are all but impossible to find.

Google draws a blank on the Magnavox tube. The Thomas tube pops up a few references. Thomas will rebuild your tube, for $1000. The US Defense Supply Center placed a request for pricing on this CRT with an NSN of 5960-01-350-2925, so there may be some floating around the system.

The X-Y signals are available on the rear panel in J1, if you happen to get one with a dead CRT. It will drive a Tektronix 604 display nicely with some minor adjustments to the X and Y amplitudes. The pinout of J1 is:

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