JRC repair tips and tricks

We don't have a forum area for discussing repairs to late(r) model gear so I'll park this thread here until such time as we create one.

JRC gear has to be used to be appreciated. I was peripherally aware of the stuff until around this time a couple of years ago, at which time I got hold of a DOA NRD-515. None of the equipment can be considered boat-anchor, hybrid, etc. as it's all solid-state. Even the earliest amateur and commercial (marine) gear used some pretty sophisticated concepts and techniques in the equipment lines, particularly at the RF end of things. The results are some of the quietest receivers and the cleanest transmitters I've ever played with. If you can sound better than an FT-102, you're doing something right - and I can A/B the JRC and Yaesu rigs at will.

My current inventory of the gear includes NRD/NSD-515s, the NDH-51x memory units, several NRD-525s, a couple of NRD-535s, a JST-135 and a Raytheon RAY-152. The latter is actually a re-badged JRC JSB-176, which is a stripped-down JST-135 with a marine-style display/front panel unit and a mission-specific firmware set.

The -525, 535, -135, -152/ -176 all share some common DNA in their various circuits - especially where the plug-in cards are concerned. Some are re-usable across models; others aren't. As I walk through various repair procedures and configuration options I'll try to present a road map of what's what.

Note that I won't be covering the NRD-545 or the JST-145/245 series of equipment. Those are the last amateur/hobby models which JRC produced before they pulled out of the amateur market altogether, and use different architectures than their predecessors.

Tip 1 - ALWAYS check the rig prior to power-up

I got a decent deal on a complete RAY-152 setup which had a couple noted problems. Distortion on SSB; dim back light. After the rig was unpacked and visually inspected I put it in the lineup with an antenna connected and proceeded to test it out. The radio is spec'd at 150w PEP and whomever was using it prior had the power control (internal adjustment) set to almost DOUBLE this value. Yeah, that'll distort. Remove covers, start servicing procedure. Eventually I discovered the balanced modulator was allowing some BFO leakage, resulting in ~200mW carrier in SSB TX. Definitely noticeable to my area 10M buddies. Studying the schematics, I saw a SN16913 DBM used as a balanced modulator, similar to what Yaesu did in the FT-817. Unlike Yaesu, there is no Carrier Null pot included in said JRC circuit. I decided to inspect the board to see if it had simply been omitted, but my JST-135 doesn't have one either - and it's very clean (in proper tune).

Hmmph.

Removing the board suddenly revealed the nemesis of JRC - their choice of mechanical SSB/CW filters. These were packed with a foam substance which turns to a gooey mess and greatly affects the passband of the filters.

https://people.zeelandnet.nl/wgeeraert/koku/koku.htm

I've repaired at least ten of these things since acquiring my first JRC receiver so in I went. Better...but still some BFO leakage present. The radio went on my test bench, where extender cards were used to elevate the Filter Unit (CFH-38A) out of the card cage for inspection. Application of power resulted in Factory Smoke^(TM) being emitted from somewhere behind the front panel.

:wall:

See the "Phones" jack in the pic below (not my rig)? Somehow in a previous life it had been snapped off internally - and as luck would have it, the jack's Ground lug hit just the right place (the +9V rail for the front panel) to cause a filter choke to burn up and render the radio inoperative. Mind you, this rig passed the Rattle Test before I put it on the bench the first time.

When I disassembled the front of the unit to inspect things I found a couple more potential time bombs...but we'll address those as soon as the parts to fix this mess arrive. Also need replacement EL panels - and looks like I'll be making (trimming) my own.

Attachment 17821

Look on the bridge of any large ship and you’ll likely see two brands of radio: Icom and JRC. Both are big in the maritime sector.

Quote:

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Originally Posted by K6BSO

Look on the bridge of any large ship and you’ll likely see two brands of radio: Icom and JRC. Both are big in the maritime sector.

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And this is why JRC stuff rarely appears on the used market - though DSC and GMDSS requires might change that. People love the radios from what I've gathered.

Tip 2 - Don't over-pay for power connectors

JRC transceivers and transmitters use an Amp/Tyco Mate-N-Lok connector setup for their DC power feed. A number of online sellers I've encountered will provide a complete package involving connector body, pins and strain relief for a non-trivial amount of money. The problem with these is that the pins provided are only usable with 14-16ga wire. JRC's manuals state that 2x #10 per polarity (total of four conductors) is to be used for runs of up to 3 meters. I can verify (through tests at max power out) that a pair of 14ga conductors for each side of the supply run is marginal - if simply not up to the task at all.

Doing a little shopping at Digikey, we find the following:

• 1-480704-0 (A1456-ND) - Conn, plug, 6POS 94V-2
• 1-640721-0 (A14353-ND) - Conn, strain relief, enclosed, 6POS
• 350922-6 (A25386CT-ND) - Conn, pin, 10-12AWG gold (male)
• 350923-6 (A25387CT-ND) - Conn, pin, 10-12AWG gold (female)

I listed both types of pins. All of my JRC gear (and the Raytheon "clone") uses male in the chassis socket and female in the power cable plug; thus, most people building their own cables will only need the female pins.

A complete plug assembly can be sourced here for roughly $5 and is suited to the 30A DC requirements of these transceivers.

Tip 3 - There's a bug in the machine

When I began tracing suspected BFO leakage problem with my RAY-152, I threw the symptom out on various mailing lists to see if anyone else observed the condition.

Surprise...they ALL do it. With the display backlight turned on. It's not BFO leakage. It's an audio tone from the DC-DC converter circuit used in the backlight, for generating voltage required for the EL panels. Somehow this is getting coupled into the Mic Amp circuit.

I tried all the usual fixes (electrolytic cap replacement, bypassing, filtering) and didn't make much headway. Someone from the PNW had a friend who knew how to fix this problem but unfortunately the gent went SK before passing on the knowledge. I may try contacting Raymarine for any Service Bulletins they may be aware of, -but for now, turning the backlight off addresses it.

Tip 4 - Boards Bounce

Got a fully optioned NRD-525 from overseas. While the rig was packed fairly well, a month and a half of being jostled around resulted in almost every board in the unit walking off its connector set.

FYI, the NRD-525/535, JST-135, JSB-176 (and re-branded RAY-152) plus a number of other marine receivers used motherboard/card-cage construction techniques. There are guide tracks for each board, and while these usually are a snug fit they'll sometimes let the various circuit boards slip out of their edge connectors. This resulted in an inoperative receiver - no audio, erratic S-meter/AGC operation, etc.

Re-seating all the boards fixed it. I'll usually look at the various loop lock lights on the Ref DDS and Loop 1 boards as a start point when troubleshooting one of these rigs, but this particular problem was evident at first glance.