How to repair National NC 183 Ham Shortwave receiver audio noise

Old receivers are plagued with out of tolerance resistors and leaky caps. The receiver featured is undergoing restoration. Many hours of work will be required. I will post what I can. Hope this info is of value to you.

[@wmccryst]

Thanks for the video. I have restored many of these old boatanchors and as these components age, resistors turn into capacitors and capacitors turn into resistors. Particularly the wax/paper-foil caps and dull-finish resistors. Many of the wire-wound and glossy-finish resistors hold their value well. Mica and ceramic caps generally don't electrically leak, although I have seen mica caps leak in a high-stress (high voltage/high temperature) circuit. Beware of Micamold® caps with the domino appearance as they are not mica, but rather plastic-encapsulated paper/foil caps that can break-down and electrically leak. Many of these receivers have been stored and dormant for decades in less than optimum conditions although I am sure that just normal aging does its damage. Component (resistive/dielectric) materials and manufacturing processes are so much better today. In good condition, these receivers offer hours of fun listening and give the rewards and satisfaction of a restoration job well done. I have a few of the lesser NC series Nationals and am considering getting an NC-183D in May at the AWA Spring Meet flea market/auction.

[@fabinhoosmar]

Bom trabalho colega.....como sempre.....aqui está um gêlo em São Paulo, somente com o ferro de solda ligado para esquentar...........

[@daveedwards5951]

But in-circuit may present an incorrect reading of the resistors....unless one end is DC open...like to a cap.

[@HamRadioAdventures]

Thanks !

[@-Todays-Tom-Sawyer-]

Nice radio Terry. I can safely say that old Hallicrafters suffer from the same issues. Best advice you gave was remove and replace one at a time...(and have a big box of multiple value resistors on hand) Could you do a bit in one of your videos to show the old style domino and colored capacitors and that look like resistors that we might run into. thanks Frank

[@johncunningham5435]

Nice work Terry; I noticed you have a Beckman Meter, if you ever have problem with it "let me know" there are two or three common problems that eventually will pop up. I personally own the Beckman HD110, a great meter.

[@d-labelectronics]

+John Cunningham Hi John, Yes, I love the Beckman 310 series. I bought my 1st one new at Henry radio in CA

[@patrickwall8517]

A lot of old receivers suffer from this. A leaky capacitor in the amp circuit can also cause a hum like this.

[@dinobennet9322]

My National (NC-173) Main Power Transformer (T-21) melted down. Chances of finding an original replacement could be awhile. I was hoping to replace with a generic step down transformer. My schematic diagram, although it's detailed, does not show the step down voltages, so I don't know what to replace it with. Since you work on several radios, can you provide me with the three outputs i need?