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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 19th Jun 2006, 9:59 pm   #1
Station X
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Default Trio R-1000 Communications Receiver.

This receiver came from Ipswich Freecycle. Normally all the good stuff gets snapped up quickly by people like myself who are able to keep an almost constant watch for incoming Freecycle emails. However this item had been posted for almost four hours before I saw it, so there obviously wasn't much interest. A quick call to the donor and it was mine. I collected it the next day. It was complete with Owner's and Service Manuals. There were two aerials with it. A professionally made dipole cut for the 31 metre broadcast band and fed with ladder line feeder plus a solid copper longwire. Neither seemed to have seen much, if any, use. Also included was an Antenna Tuner and an Audio Filter. I felt quite guilty about getting all this stuff for free, as I have Communications Receivers stacked three high. It would have been useful to a youngster starting out in Shortwave Listening (SWL) or Amateur Radio, but as I said no one was interested.

The Trio R-1000 Communications receiver was manufactured between 1979 and 1985:-

http://www.rigpix.com/kenwood/r1000.htm.

It differs from the Kenwood R-1000 only in the front panel badge. The Kenwood name was used in the UK to market foodmixers etc, so the electronics gear was rebadged as Trio. It's a general coverage communications receiver tuning from 200KHz to 30MHz. In actual fact it will go down to about 150KHz, so it will receive BBC Radio 4 on 198KHz longwave. It's a double conversion receiver with switchable bandwidth. There is a BFO (Beat Frequency Oscillator) for Carrier Wave (CW) (Morse) reception, but it's on a fixed frequency, so it's necessary to use the main tuning dial to get the right pitched note. There is a front panel display which can display the received frequency, act as a clock, or be used as a timer to switch an external tape recorder on and off via a relay.

I'd been after a receiver like this for a while. It's smaller than the traditional 19" rack comms receiver and the carrying handle plus ability to work from a 12 Volt supply makes it truly portable. I particularly like the large internal speaker. The receiver has plenty of AF power to drive it.

Having got the set on the bench I connected a couple of metres of wire to the antenna socket and switched on. A quick tune round the bands showed that it was functioning well as a receiver. Some crackling from the volume, attenuator and tone controls disappeared after they had been rotated a few times. Just as well, as there are no holes in the potentiometer casings into which to squirt switch cleaner. However the Frequency Display/Digital Clock was completely dark, apparently a common fault with these receivers.

A look at the circuit diagram showed that the display was of the Vacuum Flourescent Display (VFD) type. I had to read up a bit on these, but it turns out they're just directly heated triodes with glowing anodes. There is a heater supply which is common to all segments and decimal points in all digits. There is one grid per digit and one anode for each similar segment and decimal point. By applying about 25 Volts to a grid and anode a single segment can be made to light up. The heater and HT supplies are derived from the secondary of a transformer which forms part of a DC-DC convertor. The layout of the PCB made it impossible to check the heater supply which is about 2 Volts AC. However it was possible to measure the HT supply at -25 Volts DC. This may seem strange, but the -25 Volts is connected to the heater (cathode) which make it necessary to ground an anode and grid to light a segment.

The display is driven by a custom IC the MSM5524RS made by OKI. It is thoroughly obselete and as far as I know only used in the R-1000 and the Yaesu FRG-7 receivers. I checked voltages on the IC pins and it looked sick. There is a one transistor amp connected to the crystal which provides timing for the chip. The output is wired to a test point which is designed to drive a frequency counter or scope. Connecting these items of test equipment revealed no output whatsoever. Varying the crystal trimmer and connecting a known good crystal made no difference at all. There was nothing for it, but to remove the PCB and then the chip.

Removing the PCB was not difficult, but took a bit of time. There are about a dozen plug in leads, but all are well labelled. The PCB is retained by about eight screws, which is good as they prevent it flexing. Finally the front panel controls have to be removed.

I turned the PCB over and what a sight met my eyes. Some one had been there before me and judging by the charred PCB and lifted tracks it looked like they had used a 50 Watt soldering iron. Some tracks had been repaired with wire bridges, but these were made from nasty thick multi-stranded wire.

I used a small iron to carefully unsolder all 40 pins of the chip. Had I known for certain that the chip was faulty I would have cut all the pins and unsoldered them one at a time. Having removed the chip I set about cleaning up the PCB tracks. You can see the result in the photo.

I built up a minimum circuit round the chip consisting of a 5 Volt supply, crystal, capacitor and trimmer capacitor. There was no sign of oscillation, so the chip was binned.

Before ordering a new chip I wanted to be sure that the VFD was OK, as these are unobtainable. I fitted a 40 pin DIL socket to the PCB and soldered it to four good tracks. I then set about remaking the connections to the rest of the pins. I used thin solid bare wire wrapped round the socket pins and then soldered to an intact part of the associated track. Each connection was tested for continuity in itself and high resistance to adjacent pins and tracks. The result was functional, but not pretty, so I did not photograph it! In restrospect I realise that I should have made the repairs with thin insulated wire wrapped round component pins. However as the PCB can't flex I think my repairs should be OK.

I reassembled the PCB into the radio and set about testing the VFD. I did this by grounding the IC pin connected to the same segment of each digit (anode) and then grounding the IC pin connected to each digit (grid) in turn. This was repeated for all segments. I was relieved to find that all the segments were OK and the VFD was fully functional. I was now confident enough to order a new VFD driver IC from Mark 5 Limited:-

www.mark5.com This link is now dead.

Once I had received the chip I decided not to plug it in with the PCB in situ for fear of damaging my track repairs if the PCB flexed. So I removed the PCB again and placed a piece of 1/4" thick plywood below the 40 pin DIL socket. I then pressed the IC firmly home and reassembled the PCB to the chassis. I applied power, whereupon the display lit up and displayed the received frequency. I then ran through all the display's functions and found that they all worked. Success! I connected my frequency counter to the test point and used it to trim the crystal to the correct frequency.

All that remained was to reassemble the cabinet. I am very pleased with this find and use it in the kitchen to listen on the 3.615 MHz 80 Metre AM frequency. This means that my garden now has yet another longwire antenna making four in all. The wire scape is getting a bit crowded.
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Old 19th Jun 2006, 10:54 pm   #2
Brian R Pateman
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Default Re: Trio R-1000 Communications Receiver.

I repaired several of these when I had my own business. I always fancied one but never got round to getting hold of one - a source of regret now I'm getting into SWL again.

You did well to get hold of this - congratulations!
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Old 20th Jun 2006, 12:49 pm   #3
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Default Re: Trio R-1000 Communications Receiver.

Looks like a nice straightforward piece of kit to use, front panel not too cluttered. You did well to repair the display, especially after someone had been in there first. You can never have enough receivers! My collection extends from the CR100 right through to a FRG 100, and I use them all. I had similar trouble with an MSM5525 display chip, but it cost me about £25 eventually for a replacement, because of it's rarity.

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Old 20th Jun 2006, 12:59 pm   #4
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Default Re: Trio R-1000 Communications Receiver.

The MSM5524RS driver chip cost about £30. I thought it worth spending this amount on a repair, as the set cost me nothing. No sooner had I placed the order than a chip appeared on eBay from a USA seller. There was only one bidder and it went for $10. Of course there was no certainty that it was good and there'd be all the extras like postage and currency conversion charges to add on.

Several big suppliers in the USA stock the chip, but they have large minimum order charges and won't deal with individuals. I wonder if they sell many of these chips? I can't imagine anyone needing more than one.

I hope the new chip lasts a while, as it appears they're unreliable. Of course the receiver can be used perfectly well without the display.
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Old 20th Jun 2006, 2:07 pm   #5
wireless_paul
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Default Re: Trio R-1000 Communications Receiver.

I have a number of communication receivers including Drake (3 receivers), KW (2 receivers), Eddystone (10 receivers) plus a BRT 400E and the solid AR88 etc, but must admit I probably think the Trio R-1000 is my favourite general receiver. Probably for a ham band only receiver I might have to choose the KW 202.
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Old 20th Jun 2006, 3:23 pm   #6
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Default Re: Trio R-1000 Communications Receiver.

I didn't realise you had to buy a chip for your repair. I had a similar problem sourcing the MSM5525RS in the UK. Plenty listed on the internet overseas, but, just as you say, you need to buy about 500 of them. The UK supplier originally said about £5 then they were "on back order" and when they contacted me a few weeks later they had gone up to £25! I still bought one as I had little choice and was desperate for a replacement.

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Old 20th Jun 2006, 4:51 pm   #7
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Default Re: Trio R-1000 Communications Receiver.

Whist it is nice to have the digital readout working, it must be remembered that this receiver has a good analogue display as well.
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Old 20th Jun 2006, 10:26 pm   #8
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Default Re: Trio R-1000 Communications Receiver.

I had one of these receivers some years ago but sold it when I purchased my TS940. It was a great receiver for when I went mobile on 160 metres. I remember only one mod I did to it. I added a couple of diodes ( I think from my poor memory) such that when both the wide and narrow AM buttons were pushed in together (yes it can be done) then the receiver still worked in AM mode but used the even narrower SSB filter. If you are interested in doing same, a few moments re-drawing the circuit around these switches should give you a clue as to how I did it. Gee, why does the grey matter dry up like electrolytics with age!
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