Home Up National NC-88 NC-270 SS4H4-C reg



Currently on the bench a good looking National NC-270.  


Front  Rear Top IMG_4961.JPG (1135098 bytes)

To be cleaned.

IMG_4998.JPG (2098729 bytes)


IMG_4971.JPG (1194630 bytes) IMG_4972.JPG (1122391 bytes) IMG_4973.JPG (1187882 bytes) IMG_4975.JPG (922713 bytes)

Mark how it goes back in.

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This is stuck.  I could not adjust FL2 during my preliminary algnment.

IMG_4980.JPG (886085 bytes)

I do not know what I am getting into.  Mark each section.

IMG_4982.JPG (619986 bytes) IMG_4983.JPG (1033060 bytes) IMG_4984.JPG (1135839 bytes) IMG_4985.JPG (711683 bytes) IMG_4988.JPG (973929 bytes)

Pretty simple looking. 

IMG_4989.JPG (955283 bytes)

I will clean off my marks on the chassis top. 

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I could not resist using Brasso on the threaded rods. 

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I cleaned the whole thing. 

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Easy to turn. 

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I'm happy.  Now back to the sweep generator. 

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This is the sweeper set up.  The top generator sweeps the VCO and the scope's X axis. 

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Ringing is from a fast sweep.  And the two separate peaks.  One going up in frequency and one coming down.

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The ringing dissipates and the peaks merge when the sweep rate is slowed.  

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Use the VTVM on the specified test point along with the scope Y axis.  

The sweeping allows quick location of the filter's peak response frequency.  I confirmed this peak by varying my HP606. 
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This unit FL1 and 2 easily peak.  


IMG_4997.JPG (1147756 bytes)

Tomorrow is another day.  A full accurate and precise alignment!



          More pictures later. 


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