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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 24th Apr 2017, 3:49 am   #1
Damien VK3RX
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Default J.I.L. SX-400 receiver/scanner

I picked up one of these with the RF-1030 MF/HF converter a while back both in great condition, and wonder if anyone here owns or is familiar with them. I have the online versions of the SX-400 user and service manuals. I note a post from someone in 2012 seeking help to repair, but that's about all.

After an alignment tweak and a couple of faults fixed the SX-400 is performing well, although the loss of memory data after 36 hours without power is a bit of a nuisance (it uses a cap to hold memory data for up to this period). I see a 2200uf cap in that part of the circuit - as anyone tried fitting a larger value or done another fix? My DC cable doesn't have the third (orange) wire for memory backup, but I have a new cable coming.

The RF-1030 did not come with a manual or schematic, and a hunt online only turned up a poor scan of a brochure @ the Universal Radio site, showing the SX-400 interconnections between modules. If anyone has the RF-1030 schematic and/or manual and indeed anything else of interest relating to the SX-400 and could scan for me that would be appreciated.

The SX-200 model was popular here and I suspect quite a few would still be in use, but given the cost of the SX-400 and the various converters I don't how many would have been sold here.
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Old 27th Apr 2017, 12:08 am   #2
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Default Re: J.I.L. SX-400 receiver/scanner

Some pix of the RF-1030 loaded to my shack pix page.
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Old 27th Apr 2017, 12:26 am   #3
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Default Re: J.I.L. SX-400 receiver/scanner

I just get a blank page.

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Old 27th Apr 2017, 12:38 am   #4
Damien VK3RX
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Default Re: J.I.L. SX-400 receiver/scanner

Try again - I was reloading pix because some earlier ones were flagged waiting mod approval.
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Old 28th Apr 2017, 11:18 am   #5
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Default Re: J.I.L. SX-400 receiver/scanner

Quote:
Originally Posted by Damien VK3RX View Post
the loss of memory data after 36 hours without power is a bit of a nuisance (it uses a cap to hold memory data for up to this period). I see a 2200uf cap in that part of the circuit - as anyone tried fitting a larger value or done another fix? My DC cable doesn't have the third (orange) wire for memory backup, but I have a new cable coming.
Hi Damiem,Ive got one of these scanners, and it came with a mod already done to the memory backup circuit.
Its simply a small rechargeable battery to hold the 5v rail live.
I can't find any published data about where it came from but I've attached the very simple circuit and a picture of where it connects. You only have to take the top panel off, no messing with the pcb, just tack the wires to a couple of convenient points.(ground and the link to pin 20 of processor)
I've left mine for a week and still had the data stored.
The 3 wire cord only works if you keep the 3rd wire (orange) live such as in a vehicle.
Hope this helps.
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Old 29th Apr 2017, 3:02 am   #6
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Default Re: J.I.L. SX-400 receiver/scanner

G'day Dave

Gee - thanks for this.

Comparing your pix to my main board there does appear to be a slight mod done. It looks like a resistor was removed and a yellow wire run from where that was to the "batt" point on the main board. Sounds fair enough, to incorporate a low voltage battery backup.

I shall do some investigating

A no-so-elegant way would be to use a plugpack powered up to supply 12v via that orange wire, but the battery backup option would be far better.
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Old 29th Apr 2017, 8:35 am   #7
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Default Re: J.I.L. SX-400 receiver/scanner

Thats interesting Damien, I've never had cause to probe any further, but when I get 5 minutes I'll whip the top off again and have another look.
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Old 29th Apr 2017, 9:17 am   #8
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Default Re: J.I.L. SX-400 receiver/scanner

These days, rather than using batteries for memory backup (with all the self-discharge/leakage issues) the industry approach (where they're not using non-volatile Flash memory) is to use a "Supercapacitor".

It's quite easy to get tens/hundreds of Farads of charge-storage in little wire-ended packages that look just like ordinary electrolytics.
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Old 29th Apr 2017, 11:13 am   #9
Damien VK3RX
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Default Re: J.I.L. SX-400 receiver/scanner

Actually a closer look indicates a resistor wasn't removed, just a yellow wire seems to have been run between two points "f" indicated in my pix attached of this board area (unless there is another circuit change somewhere).

Re a supercapacitor. I have wondered if the 2200uf cap was the one holding the charge to maintain memories.
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Old 29th Apr 2017, 11:41 am   #10
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Default Re: J.I.L. SX-400 receiver/scanner

The super cap is SP301 0.1Farad. Unless I am mistaken my SX400 has a second 0.1F capacitor attached to the same place circuit wise.

I can understand why the supercap was replaced with a nicad. It is not just the memories that are lost when the cap discharges. The set will only work if the recessed reset button is depressed before switching on. That one caught me out when I first got mine.

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Old 9th May 2017, 3:47 am   #11
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Default Re: J.I.L. SX-400 receiver/scanner

I have an NRD515 HF receiver that reverted to *.000.0 khz on turn-on and a memory unit with amnesia - both had 4xAA NiCads that had leaked badly with the usual corrosion problems before I got it. I replaced both sets of cells with 4.7F (yes F!) 5v supercaps and they have worked very well - the radio keeps it's memory for well over a month, the memory unit does get amnesia after about three weeks but it only fails to read the data, not the data itself, so it just needs some time turned on to recharge the cap.
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Old 13th May 2017, 2:26 am   #12
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Default Re: J.I.L. SX-400 receiver/scanner

That may be a simple option i.e. replace the current supercap with a higher value, though a battery would give long term memory storage.
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