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Re: Missing Q408 & T406: replacement candidate suggestions?
Hi Roger,
Thanks for the speedy reply! On closer examination, the original owner has done the ceramic resonator BFO mod and located the BFO on the underside chassis in it's own little shielded box, complete with feedthrough caps etc.? Really nice job, actually, though a lot of the original PCB trackwork around the BFO has been scratched off, which is a bit of a shame. Had me wondering there for a minute! Thanks, Jason |
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Missing Q408 & T406: replacement candidate suggestions?
Hi all,
Picked up a FRG-7 as part of an auction lot, and it's in need of a pretty heavy restoration - both cosmetically and circuit operation wise. First up will be electrolytic cap replacement and a thorough check that all supply voltages are where they're supposed to be, and I'll go from there to see what other work needs doing. But I also notice that the previous owner has pulled most of the components associated with the BFO, including Q408 & T406. Looks like Q408, a 2SK19-GR, can be replaced with a common N-ch JFET like the MPF102 (being in Australia, NTE equivalents are not common here) - hope someone might be able to confirm the MPF102 is suitable? And for T406 - guess I'll just try any donor variable inductor coil, especially if it comes from a 455kHz section of a suitable donor radio, perhaps may need to alter the value of C437 to bring it to proper resonance?? Unless someone has a suggestion for a specific, readily available equivalent? Thanks in advance, Jason |
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Re: modern digital readout
It looks like either of those cases would work. I see some interesting Hammond cases . They even have red front windows available.
I am trying to locate the source of the opportunist cases on ebay. I copied the best case picture and then removed the display and switch from the front and tried a picture match search. So far no luck but I know I have something in a case that has the same top ribs. Will take a look around. I am going to add a folder to the Files display section and add the SanJ instructions there. |
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Moderated
Re: Why would anyone want a digital frequency display on a FRG-7? Please debate!
That's true Mike! Pity there's no space on the front panel for all those cool controls we want, but if you remove the speaker you can drill the grille full of holes and add loads, starting with Treble, Mid, Bass and Stereo Balance, and then drill loads more holes in the top to relocate the speaker.
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Functionally a digital display is a nonsense: the elegant use of a single 1MHz tuning range for the main tuning dial means that it is calibrated in 10kHz increments which can be adjusted at the ends against the 1MHz spurs so the frequency can be read within at worst 2kHz, or roughly 10% of the IF Bandwidth. So, if you want to keep a watch for a transmission such as 6628kHz you can set your FRG so the full channel is within the receiver bandwidth. A nice challenge is the NCDXF International Beacon Project which has sequential transmissions on 14.100, 18.110, 21.150, 24.930, and 28.200 MHz and you can challenge yourself further to see if you can chase one of the stations up the bands, which should just be possible for 20, 17, 15 and 10 metres! As for broadcast stations, there is no problem tuning to the 5kHz channels.
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Aesthetically it seems like sacriledge to me to spoil a classic and simple design. It's like hot-rodding a classic car except you'll never get this one to go any faster: its limitations are all inherent to the technology used at the time. To do a proper job you should remove all the innards from this 70s model and graft in an 80s model with LED readout thereby ruining two different receivers! Better perhaps to get an 80s receiver to use and keep the FRG-7 on display. This will save trashing not only the appearance but also the resale value.
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?- Julian |
Jason VK7ZJA
MikeM
Julian_Hardstone