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Hello
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I've just joined this group and have a mint FRG-7...it came with its box and other bits.?
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A friend gave me an old digital display unit which turns out to be a Timestep Electronics DFC-7 from 1981. It uses an OKI MSM5525RS LSI chip and a couple of others, one being an unmarked round can.
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Does anyone, by any chance, have some information on the kit please?
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Thanks
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Simon, M5POO, UK
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Hi Simon,
Have attached a data sheet on the MSM5525 plus a couple of pics re the DFC-7.
Enjoy
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Don’t fit the digital display gents, it looks terrible and completely ruins the whole feel visually of the radio. The whole beauty of this radio is its retro appeal and I urge you to not be tempted to fit the aftermarket hideous digital display unit… It really does not do the radio any favours whatsoever. Thank you 73
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On 21 Jan 2025, at 02:16, Steve Quigg (VK2TUM) via groups.io <stevequigg@...> wrote:
? Hi Simon,
Have attached a data sheet on the MSM5525 plus a couple of pics re the DFC-7.
Enjoy
<MSM5525_6.pdf> <time_step-04.jpg> <time_step-03.jpg>
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Thanks Steve, that’s exactly what I need. Sadly the circuit diagram is a bit low res to read clearly. Would you mind scanning the DFC-7 pages for me, or if you don’t have a scanner, could you take a photo of the diagram which fills the frame please? Cheers, Simon.?
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Hi Mark
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I would never spoil the radio. This kit sits in a box on top of the radio.?
cheers
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simon
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Hi Simon,
Unfortunately I don't have the originals; the attachments are as I found (somewhere; too long ago to remember) the on the web.
Re the schematic,? it is readable, albeit with some difficulty. IC2 appears to be strapped for direct reading, i.e no IF offset. Crystal X1 (DS(?)C7 in the pic) would be , I'm surmising, 3.455 MHz, mixed with the input from the FRG-7 to give a 0-1MHz signal which is input to the MSM5525. Can't make out the mixer part number, but appears to be a Texas Instruments part.
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Cheers,
Steve.
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Yes, thats exactly how it was done, the input signal was mixed with a 3.455 MHz oscillator, a low pass filter used to remove the higher mixing product, the counter chip then? read the difference.
Other Wadley loop receivers of that era used a similar arrangement, the Century 21 being one example. This method was a very simple and elegant way to get an offset? using analog? mixing, rather than digital divisors, and, being in a seperate box with its own power supply removed the dangers of any birdies and interference being introduced into the radio..
The display chip itself is simply the manufacturers data sheet implementation of that chip, so a schematic really is not required to get this working once again.
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Simon
I have fiddled with the background colour - do these help?
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Andy  
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Thanks everyone for your help on this...I've put Steve's diagram and instructions through PaintShop Pro and uploaded the results into the 'files' section on the group.
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Pentagrid - I've spent most of my life working on equipment without diagrams. Data sheets are of course a great help, but it's much easier if someone has the original manufacturer's diagrams and PCB layout, as I'm sure you will agree. The metal round IC, a mixer chip, isn't identified on the diagram...and the numbers have been removed from the physical part. I thought it might be a 'Birkett Special' Plessey SL640, but the connections don't match. I don't recognise the pinout and connections; is it familiar to you?
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The original owner had used an 18-0-18 volt transformer, with a separate 3v winding to feed the filament of the display. I'm fairly sure the counter chip is faulty, but believe I have a spare one 'somewhere safe'.
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I would never dream of installing it in my receiver, but will re-box it and sit it on the top.
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Cheers
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Simon M5POO
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Enjoy it stock. Not worth the effort.
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On Jan 21, 2025, at 1:13?AM, Mark Feltham via groups.io <dodacarem@...> wrote:
? Don’t fit the digital display gents, it looks terrible and completely ruins the whole feel visually of the radio. The whole beauty of this radio is its retro appeal and I urge you to not be tempted to fit the aftermarket hideous digital display unit… It really does not do the radio any favours whatsoever. Thank you 73 On 21 Jan 2025, at 02:16, Steve Quigg (VK2TUM) via groups.io <stevequigg@...> wrote:
? Hi Simon,
Have attached a data sheet on the MSM5525 plus a couple of pics re the DFC-7.
Enjoy
<MSM5525_6.pdf> <time_step-04.jpg> <time_step-03.jpg>
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By memory I think you will find the mixer is a CA3028 transistor array or similar. Look in any 1970s? American? radio constructor books for details of these chips, they were used often before the days of LSI.? Three transistors, long tail differential pair in a round case with 7 legs
Basically, the oscillator into the? base of the long tail, signal into one base of the differential pair. The two products are available at the output. The LPF will remove the high product 3.455 +2.455? to? 3.455 + 3.455 = 5910 to 6910, leaving the low product 3.455 - 2.455 to 3.455 - 3.455 = 1 to 0 megs, this product passes to the counter module. This is a very elegant way to do this, as it also automatically reverses the count.....? the FRG7 actually tunes backwards. The second IF is below the first IF, and the first IF is above the signal frequency, that is the basis of drift cancelling...... both first and second signal mixers using? the same VFO....?
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Hi All,
When I looked carefully (pic time_step-01.jpg in files/DFC-7), the mixer is definitely Texas Instruments, and I thought I could make out "SN7651?". Did a search and came up? with a data sheet for a SN76514 balanced mixer. Function and pin-outs match the schematic for the DFC-7, and part was around when the FRG-7 was produced, so I'm calling this as THE part number for IC1.
Have put the datasheet in files/DFC-7.
Cheers,
Steve
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Thanks Pentagrid…I thought it might be one of those myself, but the pin out doesn’t match. As previously mentioned, it looks like a TI logo on on of the images, and SN something or other for the part number. Sadly, the image is just to low resolution to make it out.
It is indeed an elegant solution. A friend and I used a similar method with Deltahet and G3PDM receivers.
Regards, Simon.
Sent from my Interocitor
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For what it's worth I've got a Communications Concepts Inc. (CCI) digital display for my FRG-7. It sits on top. No longer available of course but if you can find one I can highly recommend it. It's easy to program for the FRG-7 and it works very well. DXing with the FRG-7 and this display is a lot of "old school" fun.
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Cheers,
John
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If only Dxing existed anymore John The broadcast bands are high powered China or Romania now Everyone’s gone over to internet… Its a shame My radio is a beauty but sadly nothing to listen to any longer The tropical bands are dead too It’s sad that? We knew it was coming with the WWW… The king is dead, Long live the king..
73 M
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On 25 Jan 2025, at 21:37, John Hudak via groups.io <hudakjm@...> wrote:
? For what it's worth I've got a Communications Concepts Inc. (CCI) digital display for my FRG-7. It sits on top. No longer available of course but if you can find one I can highly recommend it. It's easy to program for the FRG-7 and it works very well. DXing with the FRG-7 and this display is a lot of "old school" fun.
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Cheers,
John
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So painfully true. I was thinking of Kat on Deutsche Welle today.
Reg
On Saturday, January 25, 2025 at 06:39:03 PM CST, Mark Feltham via groups.io <dodacarem@...> wrote:
If only Dxing existed anymore John The broadcast bands are high powered China or Romania now Everyone’s gone over to internet… Its a shame My radio is a beauty but sadly nothing to listen to any longer The tropical bands are dead too It’s sad that? We knew it was coming with the WWW… The king is dead, Long live the king..
73 M
On 25 Jan 2025, at 21:37, John Hudak via groups.io <hudakjm@...> wrote:
? For what it's worth I've got a Communications Concepts Inc. (CCI) digital display for my FRG-7. It sits on top. No longer available of course but if you can find one I can highly recommend it. It's easy to program for the FRG-7 and it works very well. DXing with the FRG-7 and this display is a lot of "old school" fun. ? Cheers, John
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Hi Steve
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Thanks for doing that...I just couldn't make the numbers out. I spent ages trawling data books I have and looking for TI mixers on-line, but nothing came up.
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According to Google, it became the TL442.
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I'll check it out though...hopefully the one I have is okay.
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It appears the previous owner did what Pentagrid suggested and referred to the MSM5525 data sheet when connecting it up; at least in part! The DFC-7 uses a 9-0-9 volt transformer, and gets the 3v for the display filament, by using a resistor from the supply. Said previous owner used an 18-0-18 volt transformer for some reason, and used its 3v AC winding for the display filament.
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Somewhere I have a spare counter chip...probably not a mixer, but you never know. The counter chip will go in a socket and I'll see what happens.
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Thanks very much for all your help Steve, and I appreciate everyone else's input too.
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Regards
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Simon
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Simon Robinson
