D-Lab Tech Tip Troubleshoot Repair National NC-300 Ham Radio receiver Standby function

This receiver came to the shop with Standby/Mute malfunctioning. If your mute function fails, the receiver will feedback when you transmit. This could result in a very expensive repair to your receiver if not addressed quickly. I have seen this fault a few times in the past, so thought it would be great to share this with you. Normally the standby function of the NC-300 is very desirable, no annoying pops when cycled. I have actually put Nationals circuit in other brands of vintage receivers. The fix I am demonstrating in the video, is quick & inexpensive. However, it would be best to replace the main filter capacitor, since it is obviously nearing the end of its life. That is not the option that the owner chose. So take it for what its worth. The video will aid you with discovering the fault. However you wish to proceed after that is your decision.

[@W1RMD]

Beautiful receiver! If I had to buy only one vintage receiver, THIS would be it! The dial matches my Johnson Invader 2000 perfectly! The face and dial reflect the best of mid- century "atomic" design. It would be nice if they manufactured knobs like these for projects. They would definitely give an amp project a very nice touch. Thanks for showing this! 73's -W1RMD

[@waynethompson8416]

73 de WB4RHA

[@DirtFloorJIm]

Just by dumb luck I happened upon this video. Yesterday I noticed my NC-300 was doing the exact same thing.

[@mikebracey8832]

Thanks Terry, a very informative tech tip. Mike / KE5YTV

[@waynethompson8416]

Great video...just so very short!

[@superhet7281]

Interesting video! VERY unusual for a low-voltage section of an electrolytic to fail before a high-voltage section. IMHO the owner is shortsighted for doing this the cheap way.

[@d-labelectronics]

Hams are frugal. I do as directed. The RX will be back

[@Denvermorgan2000]

@@d-labelectronics They are like guitar players they want it cheap as possible they don’t think about it might blow part in during a gig.

[@Nirky]

Is the reason you didn't put the replacement 50uF cap next to the bad 50uF section because you didn't want to install a terminal strip?

[@richardbrobeck2384]

I would had replaced the whole multi electrolytic capacitor . Because if one section has gone bad the rest will soon follow it .

[@d-labelectronics]

I would too, if the customer asked, that is not the case

[@Magic_man-Gaming2014]

May I ask If you have any spare time fixing the radio I have I'm not so sure if it will ever work anymore. And the radio has no schematics that I could find on the internet.

[@timmooney7528]

How ironic, because I was going to ask about looking at a Sherwood receiver a friend dropped off because it wouldn't power up. My guess is something blew after the power came back on after a storm. Fuses and transformers test ok.

[@HamAndShortwaveRadio]

Nice1:-)

[@vicmiller7191]

Fantastic Ham Stuff, Thanks for sharing Vic KE8JWE

[@d-labelectronics]

HI Vic, I will keep Ham stuff in the mix

[@vicmiller7191]

@@d-labelectronics FANTASTIC, And this one was a good one to remember. Great tip for sure.