It works!

[majoco]

Many months after the memory unit of my JRC NRD 515 finally succumbed to the rot caused by leaking dry cells eating the traces of the printed circuit board, I have finally ironed out the self-made faults of it's replacement. Now all I have to do is dial in on the thumbwheel switches the frequency I want, but a button-push goes back to the knob-twiddling. I had to have a guide to tell me the memory number for a specific station, now the guide just tells me the frequency! Easy!

The old board...



Memory unit in use.

 

[K4EET]

That is splendid news there mate! Jolly good show! Cheers! Dave K4EET

 

[commscanaus]

Really like your NRD-515 Martin.
Very pleased you were able to repair the damage to the memory unit.
Just goes to show that any equipment fitted with batteries needs to be periodically checked to ensure that there is no deterioration and subsequent leakage.
Same goes for older equipment with electrolytic capacitors which can also leak and destroy circuit boards.

The circuit board in that JRC memory unit would just about be irreplaceable.

Commscanaus.

 

[majoco]

I didn't actually "repair" the damaged (ruined?) original memory board - it's been entirely replaced! Previously it had only 24 memory locations (but with a bit of fiddling I got that up to 48) but the memory IC's that were eaten by the battery acid are unobtainable. The outputs of the IC;s are now replaced by the thumbwheel switches which feed 6 4-way line drivers and then out to the receiver. It's a bit like a bowl of coloured spaghetti but it works! The 'preset-manual' pushbutton tells the receiver to listen to either the remote or it's internal tuning switch and knob.

 

[ratboy]

I learned the hard way to never leave batteries in equipment more than a year. I had the 96 Channel NRD-515 memory box and caught it just as one of the batteries started to leak. I had a calendar program that I set to remind me on the anniversary date, and later on did it with a cell phone's calendar app. Now, I change them all on my birthday, except for the stuff I use all the time.

I miss my 515, but selling it, the memory box, and speaker paid 2 months of my mortgage when I was short on cash. Now I'm about to sell all my HF stuff. Not because I need money, because I live in RF hell, where I can barely listen to anything below FM Broadcast.

 

[majoco]

After I cleaned up the board and got the memory unit going, almost 14 years ago now, I fitted a 4.7F (yes, Farad) 6v capacitor in their place which I charged from the 5volt rail - it would last for over 6 weeks before getting discharged. You can see it in the pic of the board at the top right corner- the white blob. I also use another capacitor to keep the kHz digits alive in the radio - that one does not last as long but not such a loss as the memory unit.

 

[ratboy]

Did you ever have any problem with the interconnect cables inside your 515? Mine were an endless hassle until I soldered the center leads and put DeOxit on all the plugs and sockets.

 

[majoco]

I knew when I bought the 515 that it had not been used for a while given the dust all over it so as soon as I got it home I completely stripped it down and gave it a good clean and a re-alignment - the receiver itself has been as good as new performance-wise. The memory unit has always been a hassle due to the battery problems eating the pc board.

 

[ratboy]

Mine had some issues early on, an IC blew right after I got it, and the back up battery had blown up and had that weird inner goo all over the chassis, but none of it got on any PC board. I put a AA battery holder in to replace it and changed the batteries every year. Other than the one IC, almost all the other problems it had in the 1986 to 2009 period I had it were interconnect related. Mine was a Gilfer modded one and had less noise than a stock one, but it didn't sound any better.

 

[majoco]

I've heard about the Gilfer mods but never found any documentation about them. I did replace the "Delta-F" (RIT?) potentiometer with a 10-turn without the annoying centre detent but the shaft was not long enough to get the turns counter fitted unfortunately. Mine came with the genuine speaker which sounded pretty awful and tinny but much better after I fitted sound deadening linings and filled the cabinet with BAF - but now every audio goes through a 8 channel mixer to a pair of nice speakers so it's redundant.

 

[ratboy]

The Gilfer mod was changing an FET to quiet the receiver, and some caps to slow down the fast AGC a little. Compared to stock unit, mine was a little bit less noisy and was more sensitive. I had Universal add the Bournes? knobpot which was a huge help when I used to decode FDM, or whatever the term is now. That detent for the delta tune was an insane design choice, IMO. Only thing I could see it good for was the detent allowed you to put it back on center freq without looking at it. I'm not bragging, but nobody was as good as I was at getting my M-6000/7000's to print legible stuff on the monitor. I even went down to Universal once and showed a couple of the guys who had real problems tuning it in. I got to the point I could tune it without a scope, just by ear.

The stock speaker was a joke. About 10 years after I got it, the speaker began to make buzzing noises. Inside, I think it was just a cheap Mitsubishi speaker, and instead of buying one (I found some place that had like a hundred in stock for 9 bucks each), I started looking around and called up one of the places that sells Hifi speakers and gambled on one that cost about 12 bucks and was very happy with it. I stuffed the cabinet with foam and it sounded great. I eventually put the same speaker inside my NRD-525's speaker, and added a high cut filter that I found in an old magazine.

The 515 was a tough tank of a radio, mine survived without any real problems a power surge that took out two of my VCRs one day when I was gone and had forgotten to unplug it. Only thing killed on it was the meter light, which gave me an excuse to replace the bulb with an LED that came from a friend's model train parts bin. It was a little on the orange shade, but worked great and never died again.

Posting about it has me thinking about buying another one, but with the insanely bad RFI my place has, there's no point, and I still have my 525, a mint Kenwood R-1000, a mint FRG-7, an Allied SX-190, and a couple more, gathering dust. They will soon be going on Ebay. I can spend that cash very easily on other stuff.