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Old 10th May 2022, 7:09 am   #1
borjamar
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Default JRC NRD receiver experience

Hello,

New user here. I found this forum by searching for information on JRC receivers.

I got a second (or third, or N-th) hand JRC NRD 525 last week. It seemed to be flawless but it developed some strange distortion when tuning beyond 7.287.00kHz. I though it was some oddity with a filter but after several hours it became silent with the SQL indicator lit.

On this forum I saw a mention of the possible trimmer cap failure and, luckily, mine was affected by the same problem. Seems to be a standard issue on several JRC and Icom models.

https://www.qsl.net/n9ewo/nrd545.html

In my case (I don´t have an extender board although I have ordered a replacement from a guy who makes them for several radio models) it was enough to turn the VCO2 trimmer several times and leaving it roughly on the same position.

I will look for replacements anyway (the original Murata ones are discontinued). Any suggestion for similar NP0 ceramic trimmers to replace them?

Thanks!
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Old 10th May 2022, 8:16 am   #2
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Default Re: JRC NRD receiver experience

The VCO is locked-up in a phase locked loop. It is either in lock and on the right frequency or it is unlocked and wrong.

The problem is that when it's locked the frequency looks fine - there is no indication of whether it's properly adjusted and is in-lock with a good safety margin, or whether it is just on the verge of failing.

Consequently, when doing anything to one of these VCOs it is important to tune the synthesiser through the full range of that VCO while monitoring the tuning voltage. You want to find a position of the trimmer capacitor that ensures the tuning voltage stays within acceptable limits.

JRC were quite professional in their manuals, and there should be an alignment procedure for this. It is worth carrying it out and doing the other VCOs as well. Things drift over time and this allows you to get ahead of problems.

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Old 10th May 2022, 8:33 am   #3
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Default Re: JRC NRD receiver experience

Quote:
Originally Posted by borjamar View Post
In my case (I don´t have an extender board although I have ordered a replacement from a guy who makes them for several radio models)
I've owned one of these receivers for the past 30 years. Could I ask where you've ordered the extender board from please.
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Old 10th May 2022, 10:59 am   #4
borjamar
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Default Re: JRC NRD receiver experience

Quote:
Originally Posted by Station X View Post
Quote:
Originally Posted by borjamar View Post
In my case (I don´t have an extender board although I have ordered a replacement from a guy who makes them for several radio models)
I've owned one of these receivers for the past 30 years. Could I ask where you've ordered the extender board from please.
Sure!

This is the item.

https://www.ebay.co.uk/itm/224682784182

I mailed the vendor asking for NRD-525 boards and he told me this one is compatible despite not having the original connector on the bottom.

I have sent another mail asking for confirmation (I would hate to order the wrong item!). Anyway I will post a review upon arrival. It must be the most sought after JRC accessory!

I guess it will require careful placing due to the pin connectors but other than that I hope it works

Now, another question. My receiver curiously has an extra board. Half of the VHF/UHF option, CGA-118 (VHF/UFH local). Is this usual? I understood that the CGA-118 board is also optional. That would be curious, having half the option fitted.

Last edited by Station X; 10th May 2022 at 12:27 pm. Reason: Missing link added.
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Old 10th May 2022, 11:01 am   #5
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Default Re: JRC NRD receiver experience

I forgot. As for frequency accuracy, for now it is spot-on all over the place. I have been tuning knowN VOLMETs and there is no hint of drift at all.
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Old 10th May 2022, 2:10 pm   #6
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Default Re: JRC NRD receiver experience

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Originally Posted by borjamar View Post
I forgot. As for frequency accuracy, for now it is spot-on all over the place. I have been tuning knowN VOLMETs and there is no hint of drift at all.
There shouldn't be. But until you've checked the tuning voltages, you cannot know whether it is close to jumping out of lock.

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Old 11th May 2022, 9:01 am   #7
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Default Re: JRC NRD receiver experience

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Originally Posted by Radio Wrangler View Post
There shouldn't be. But until you've checked the tuning voltages, you cannot know whether it is close to jumping out of lock.
Thank you, indeed it is great advice and I will do it. But not before I receive the
riser board. I have good Fluke probes that I could squeeze but I don't want to risk a short circuit.

Besides, that trimmer is indeed flaky. It will need a replacement.
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Old 11th May 2022, 9:30 am   #8
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Default Re: JRC NRD receiver experience

I had to replace them in my IC765, including hacking them out of that vile brown anti-vibration glue.

In lieu of extender boards, I've soldered wires onto places of interest and plugged the board in. This is OK if things check out OK, but gets tedious if you have to repeatedly fit and remove the board while making fine adjustments to a trimmer.

The in-lock margin thing is like ice skating across a frozen lake. If you arrive alive at the other side, you know the ice was thick enough. What you don't know is how close you came to disaster. Knowing the ice thickness before setting out is best. So if you're doing anything in a set with PLLs, treat checking the tuning voltages as standard routine. Things drift and you have an easy opportunity to spot any impending problems ahead of time.

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Old 12th May 2022, 9:16 am   #9
borjamar
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Default Re: JRC NRD receiver experience

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Originally Posted by Radio Wrangler View Post
I had to replace them in my IC765, including hacking them out of that vile brown anti-vibration glue.
As long as it didn´t turn into conductive goo, like the stuff I found inside a failing Tannoy active monitor...

Quote:
In lieu of extender boards, I've soldered wires onto places of interest and plugged the board in. This is OK if things check out OK, but gets tedious if you have to repeatedly fit and remove the board while making fine adjustments to a trimmer.
Yes, I could do that thanks to the large test pins in place. Anyway as it's mostly working now I will wait for the board. By the way I guess a review will be useful. The seller can even make custom ones for old sets if provided with enough specifications.

Quote:
The in-lock margin thing is like ice skating across a frozen lake. If you arrive alive at the other side, you know the ice was thick enough. What you don't know is how close you came to disaster. Knowing the ice thickness before setting out is best. So if you're doing anything in a set with PLLs, treat checking the tuning voltages as standard routine. Things drift and you have an easy opportunity to spot any impending problems ahead of time.
I am sure a full check up is in order. Right now it is working (I left it tuned to Shannon Volmet on 8 MHz for several hours and there was no problem) but on Tuesday doing the same it begun to show a tell tale low frequency distortion which I interpret as the PLL beginning to unlock unfrequently for really short time periods.

Esxcept for that the old lady is performing pretty well.
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Old 26th May 2022, 7:23 am   #10
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Default Re: JRC NRD receiver experience

The riser boards arrived. No time to tinker with them (concert today, busy week!) but I'll try them and post photos this weekend.
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Old 3rd Aug 2022, 8:51 am   #11
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Default Re: JRC NRD receiver experience

Any update? I'm interested to know whether the extender boards do the job.
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Old 3rd Aug 2022, 11:11 am   #12
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Default Re: JRC NRD receiver experience

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Originally Posted by Station X View Post
Any update? I'm interested to know whether the extender boards do the job.
Would also be interested in the extender boards so as to complete service and repair of NRD 525.

Rich
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