🔴 Cobra 25 NW ST CB Radio Repair SN9772 - No.879
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- Опубліковано 27 лип 2024
- Cobra 25 NW ST CB Radio Repair
0:00 - Intro.
0:28 - Freeing stuck channel selector of Cobra CB Radio.
4:10 - Testing for faults on Cobra 25 NW ST.
5:04 - Checking VCO adjustment of Cobra 25.
5:50 - CB/PA switch fault.
6:20 - Testing AM TX and modulation level.
7:34 - Dismantling the CB/PA switch to repair it.
9:33 - Re-testing after PA switch repair.
10:03 - Replacing the Signal Meter.
12:34 - Re-testing after signal meter replacement.
13:03 - Testing receive sensitivity of the Cobra 25 NW ST CB Radio.
17:09 - Repairing the AMC circuit.
19:52 - Adjusting the AMC after AMC circuit repair.
20:59 - Setting the AMC using an oscilloscope.
22:21 - Adjusting the local oscillator and CB radio frequency.
24:51 - Patreon Supporters: defs.link/?u=fcb3a1
24:58 - Outtakes.
SN_912039772
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Nice video! Watching from Brazil!
I have been reparing ham radios and amps for 40 years and I enjoyed tour video. Thanks
Nice repair, Scott and I love the outtakes! Thank you for including them. You can cross-check your Marconi modulation level indication using your oscilloscope, the formula is (Vmax - Vmin / Vmax + Vmin) X 100.
Thanks for the formula, I will look at that next time.
I worked in aircraft for 40 years.. When you have a seized shaft or a pot or rotary switch use ZEP. One or two drops will do it.Super effective penetrating oil.
Another nice fix. And the out takes? Love them.
Thanks Dave
Enjoyed the repair......Cushdie!
It’s a bit different eh.
C 70 or d9 is usually removed for better modulation with noise canceling mics. They are notorious for low modulation with an amc curcuit active.. This is not recommended for standard or power microphones due to splatter. Just opening the adjustment is usually enough for most applications except for the N.C. Mic's
Properly tuned with a road king telex mic and no alc gives a reasonable amount of mod with a minimum of distortion or splatter. For trucking use there is no comparison of a properly tuned system with this setup. The driver will be heard and understood 👌thru the noise, when a stock radio will not .
Proper adjustment is far better than disabling the AMC, in a way the AMC is a compressor, allowing quieter audio to be relatively louder without the loud parts being too much.
Nice, RF stuff
I’ve got so many radios to do… and with the lockdown I got bored enough to start looking at them, or should I say that I finally got the motivation, that’s probably more accurate.
Is this one of your older videos? I miss seeing these repairs, the older radios were so much better then the ones made today.
I recorded it a couple of weeks ago, yeah I’m not a fan of the modern radios.
@@TheDefpom They just don't make them like they used to. I have a uniden Grant so I'm going to change the caps in then send it out to get aligned and that's going to be my base radio.
Glad to see these videos again.
Nice video and I love the out takes if only I could edit my videos to remove the mistakes, I will one day:-)
IF cans should all be OK, seeing as they are all wax dipped before being put in the cans, so the thin wires likely still have a wax coat on them, plus the tiny capacitor is also wax filled, though of course those capacitors do fail shorted.
how come nobody repairs the night watch lights????
Because they are electroluminescent backlights, and singly the driver isn't what is wrong, the actual backlight is, and it is a major pain to try and fix, not worth the effort.
I can see by the fantastic equipment you dont just do cbs.