NAD

NAD model 4150 AM/FM solid state receiver.

This unit took a hit to the rear and probably exasperated latent factory created problems and became intermittent. Even though I am not set up for Solid State, I will try to "repair" just about anything once. You never know if it is something simple like a cold solder joint on some hot component lead needing only a touched up.

This is not a restoration but only a "Fix or Repair". I could not locate any readily available schematic or alignment date. No alignments were performed.

The case has been cleaned of dirt and shined up with some Glayzit.

Test setup. Two surplus powered computer speakers do just fine.			This unit took a hit. I will look for cracks in the PC board. I "formed" and straightened the rear panel. Remember! You never bend anything for a client. You are to "FORM" it!	This is a misalignment probably from the hit the unit took. I removed the front panel for inspection of the display and push-button circuit boards.
Flexing the frame cause the FM to cut in and out.	Yup. The FM cuts in and out when I flex the frame. AM seems to be not affected. So I begin a careful inspection, touching up suspicious solder joints that look anything but perfect.	While retouching, I came across this gouge. Where it came from? I do not know. Perhaps some one was in here before me, perhaps the factory. It's not unheard of.	I scraped off the green coating, widened the insulation gap and put jumpers across any suspected cracked trace areas. But, no change in the symptoms resulted. So on with the search.
Hmmm. Found something under the coaxial cable jumper from the FM RF section......	This is the unsoldered resistor wire. It appears to be a load resistor for one of the FM crystal IF filters.	The FM receives some what, when I push on this unsoldered wire. Still intermittent but the sounds of the failure have changed.	Just after finding the unsoldered resistor I found a solder bridge. Dull from the factory. Can you see it?	How about now? It is on the right. Two deposited solder blobs creating a bridge. I suspect when I flexed the board it made and broke the connection. Also heat would cause this to make and break. I simply disordered then applied fresh solder being a bit careful not to use too much solder.
It is circled in Red. Click to enlarge image(s) This is the excessive solder and resulting bridge removed.	I believe that I have found the root cause of the intermittent FM reception. Flexing the frame does not kill the FM reception any more. AM seemed not to be affected.	The repaired solder areas are dabbed in red for tracking.	After soldering the lead wire I found a solder bead hanging from a thread (of what I don't know). It is dull and oxidized, so this is likely old and not from my soldering work today.	I ran this unit a few hour with out any failures. I will continue to run this unit in the shop until it is returned to the owner.

Even today some solid state electronics is collected and appreciated as vintage gear. The best example (for me) are NIXIE tube displays. Picture from; http://en.wikipedia.org/wiki/Nixie_tube

Hit Counter

Contact me including your thoughts and comments.

Please see the LINKS page. I have collected many resources over the years.

135,912 unique web site visitors (14,499,000 hits) from October 2004 through August 2011.

Copyright © 2004 - 2012. All rights reserved.