Really great divide and conquer tactics and teaching, this time. I have always thought that I wanted to stay away from radios, particularly ham, because I don't use them and I find them complicated. Your teaching, today, lit some candles and I grokked, a bit. That spurred my interest. Kudos.
@jspencerg
11 ай бұрын
Your challenging project is our gain. Following your process is very helpful instruction. Yet again, this through-hole construction with good documentation is good fodder for a project.
@davebleamwa2bxy799
11 ай бұрын
Back in the 70's, Japanese were not very good at through hole connections on boards. IC245 among others had pop rivets that eventually became intermitent or open. And, dont trust any carbon composition resistor to be its labeled value after 20 years.
@tlrptg
11 ай бұрын
i repaired one of those one month ago. here are the drift results: the 10,7MHz carrier oscillators drift 7 hertz in the first 20 minutes after power-up, and the 133MHz PLL drifts 77 hertz. Don't worry about the displayed frequency not coinciding with the actual frequency, they always have a +/- 50Hz uncertainity. That's because the under 10KHz steps of the PLL are made with a DAC from directly the processor, and that DAC is not very precise. But otherwise, it's still a good, usable transceiver. Before aligning it, make sure that the PLL VCO initial voltage is set as in the manual. ALL the 144MHz filters depend on this voltage.
@pwrestoration
2 ай бұрын
How do you align the tx and Rx freqencnies please? Mine is off on both. If I want to listen to 144.300 I must tune it to 144.987. Trying to work out how to adjust it for LSB
@georgesampson4714
11 ай бұрын
Been there, done that. You go along and everything is working for you and then you get to a point where it no longer makes any sense and you spend hours trying to sort it out only to eventually discover that maybe you had made an assumption that wasn't true. Sometimes it is better to just walk away and let your mind unconsciously digest what you know. Quite often I find revelations occur while in the bathroom.
@Roger-pw3zz
11 ай бұрын
Very good process. And process is everything.
@Electrotech1980
11 ай бұрын
It sounds like you were almost there. It's best to probe at the output of the transistors where the signals are larger. The problem with troubleshooting radios is the few pf of the probe. It de-tunes all the circuits it connects to. Have a look at the schematic diagram for the values of the caps you connect to. I've used the brute force method of touching up all the solder joints in the radio. Anything more than 11 years old that has lead/tin solder has a problem of the metals separating. They can look like cold solder joints. Thanks for the videos. I'll keep watching
@Pixelwaster
11 ай бұрын
Check the switch D43, simple diode check in circuit. The anode should have plus voltage during TX. This also supplies the fet drain. Q43 should be checked if there is no V on D43. The gate of Q42 goes to a connector with a signal name that looks like KL or RL? I would also suggest looking at the ALC but that goes to Q44-g1, so ignore that for now. Been there, done that, and only have my insanity to show for it. 😂
@clems6989
11 ай бұрын
@15:50 Maybe problem isnt right there The 10K going down, C183 could be shorted, or anythibg in that line is shorted somewhere ? Clamping the signal to gnd ?.. You are very close !
@scottlittfin5832
Ай бұрын
Check D43. It supplies DC power to Q42 during TX.
@DirtyDog995
11 ай бұрын
Pressures on... 2 more episodes 😵💫
@mr1enrollment
11 ай бұрын
now we wait with baited breath,...
@TheElectronicDilettante
11 ай бұрын
While looking for schematic and block diagram so I can follow along at home, I came across a number of Factory Service Bulletins, a lot of which seem to address some of your issues as well as describe the steps to correct each one. I tried putting a link to where I found them, and KZitem didn’t even post my comment. If you don’t have them already, it’s like 3 clicks away in a Google search
@Soundfactory24
11 ай бұрын
Is it possible that the small coupling capacitor of 3 pF behind the LC filter significantly attenuates the SSB signal at the probe? The signal should be stronger at the drain of Q43.
@souta95
11 ай бұрын
Either that, or it might be bad. I suspect its a ceramic cap, which don't usually fail... But, "not usually" is not "never."
@Soundfactory24
11 ай бұрын
You're right, a ceramic cap usually never becomes defective. I assume that the 3pF C and the input of the oscilloscope formed a voltage divider and thus greatly attenuated the 10.7 MHz signal. But we'll probably see the secret in the next video.
@simontay4851
11 ай бұрын
18:21 Why does D43 face backwards. Its not a Zener so it doesn't make sense to me. The 10K resistor connected to the gate of the J-FET must be the biasing resistor. Check the datasheet for it. Maybe it will tell you what the biasing voltage should be.
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