NC-270

 


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)

Restored.

 
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.

IMG_4976.JPG (807012 bytes) IMG_4979.JPG (900858 bytes)

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. 

IMG_4990.JPG (1060084 bytes)

I could not resist using Brasso on the threaded rods. 

IMG_4991.JPG (992450 bytes)

I cleaned the whole thing. 

IMG_4992.JPG (1008052 bytes) IMG_4993.JPG (929027 bytes)

Easy to turn. 

IMG_4994.JPG (942282 bytes)

Nice.

IMG_4995.JPG (968922 bytes)

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

IMG_4964.JPG (932212 bytes)

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

IMG_4963.JPG (969578 bytes)

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

IMG_4965.JPG (884201 bytes)

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

IMG_4968.JPG (895282 bytes)

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. 
IMG_4996.JPG (1166376 bytes)

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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