Technical, Techniques, Hints, and Tips > Radio Equipment
Old Micron data request...
HMS Invisible:
--- Quote from: dodgy geezer on August 10, 2025, 09:30:22 pm ---
I can see the diodes along the output rail - that rail leads into the transistor pair in the mystery electronics. A bit of smplification?
--- End quote ---
Three copper lands for each pot are adjacent to the holes.
The next task is to identify the output. I use a phone camera to read semiconductor numbers, but you can assume you have two normal signal transistors then determine npn or pnp polarity from connection or by diode testing.
If you place the pcb over a diffuse light source you should be able to sketch the encoder circuit and it should closely match the 6-channel one hosted on altervista.
I'd happily power up the encoder board but not the rf board. I'd look at the Rx components to see what band it was operating in.
dodgy geezer:
--- Quote from: HMS Invisible on August 11, 2025, 07:33:41 am ---Three copper lands for each pot are adjacent to the holes.
The next task is to identify the output. I use a phone camera to read semiconductor numbers, but you can assume you have two normal signal transistors then determine npn or pnp polarity from connection or by diode testing.
If you place the pcb over a diffuse light source you should be able to sketch the encoder circuit and it should closely match the 6-channel one hosted on altervista.
I'd happily power up the encoder board but not the rf board. I'd look at the Rx components to see what band it was operating in.
--- End quote ---
To hear is to obey!
I use a head-mounted loupe to read components - by now I need it for resistors as well as semiconductors! The encoder section looks in reasonable nick, though I cannot tell whether the component values are correct.
I enclose a schematic of the 'mystery electronics'. It looks like what I think they call a 'darlington pair' to give the signal a bit more 'oomf', but you can see that the items in red do not make sense, and may be mistakes, or partial assemblies for some added circuitry... I do not know whether the suporting resistors/caps make sense, or why there are two parallel caps on the right hand side, one an electrolytic. The rectangles are points on the copper lands which look as if they could take a connected wire..
Why not power up the RK board with a 27MHz Futaba crystal? The Rx looks like a Micron 27Mhz, but it has no crystal, and I can't tell the band from the components. I assume that the RX board has not been tuned to oscillate, but there is only one adjustable coil, and a little fiddling should get it to radiate something which can be detected using a diode/multimeter...
P.S. Just noticed that the 3906s are PNP, so the arrows on the emitters should be going the other way.... :embarrassed: :embarrassed: :embarrassed:
HMS Invisible:
That diagram makes perfect sense with the arrows changed to reflect 2N3906.
An Internet search of "capacitor frequency response" will turn up many diagram hits of impedance Vs frequency graphs. The resonace point of electrolytic caps is possibly lower than you think. At high frequency a parallel connected ceramic capacitor has lower impedance and takes over decoupling.
Testing the Rx with a working 27MHz crystal is a logical task. I didn't dabble in rf circuit design enough to recognise what I'm looking at at a finger click. All I can say is the rf board has the wrong copper layout for 459MHz vhf, ferrite & crystal socket.
I'm just overly methodical. You'll have a set that doesn't conform to the revised regulation for 27AM but you won't come to any harm!
dodgy geezer:
--- Quote from: HMS Invisible on August 11, 2025, 12:23:12 pm --- That diagram makes perfect sense with the arrows changed to reflect 2N3906.
An Internet search of "capacitor frequency response" will turn up many diagram hits of impedance Vs frequency graphs. The resonace point of electrolytic caps is possibly lower than you think. At high frequency a parallel connected ceramic capacitor has lower impedance and takes over decoupling.
Testing the Rx with a working 27MHz crystal is a logical task. I didn't dabble in rf circuit design enough to recognise what I'm looking at at a finger click. All I can say is the rf board has the wrong copper layout for 459MHz vhf, ferrite & crystal socket.
I'm just overly methodical. You'll have a set that doesn't conform to the revised regulation for 27AM but you won't come to any harm!
--- End quote ---
Thanks for that! I doubt that I'll be using it for real - 2.4Ghz is so much more convenient - but I would like to get it completed and functional after around 50 years, and perhaps add some more channels as an exercise. Learning all the time... {:-{
dodgy geezer:
Well, I attached 4 pots to the board and gave it 5v, which should have been enough to wake it up. And got nothing. No pulses at the output end and, as far as I could tell, no pulses around the multivibrator....
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