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Author Topic: Need schematic or factory manual for NC-183D  (Read 2114 times)
W7GIF
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Posts: 122




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« on: October 24, 2012, 10:24:25 AM »

I'm restoring a nice NC-183D, and need the schematic or manual that represents this particular serial number. Turns out that National had several schematic/circuit changes during the 183D production.

This radio is from production run # 396, and the correct schematic will be in a manual with "ER: 396" printed on the lower right corner of the back cover.

This radio is worth saving, and there are enough schematic differences in the prod run 372 manual that I've been using, that progress in it's restoration has stalled.

I'd appreciate and gladly pay for for a complete manual for an "ER: 396" or schematic from same.

Thanks......
« Last Edit: October 24, 2012, 10:36:00 AM by W7GIF » Logged
AC5UP
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Posts: 3822




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« Reply #1 on: October 24, 2012, 12:43:28 PM »

Take a look at this:   http://www.antiqueradios.com/gallery/d/149057-1/NC-183D+Late+Version+Manual.pdf
And this:   http://www.antiqueradios.com/gallery/d/149015-1/NC-183D+Newer+schematic+version+B.pdf

Found both here:   http://www.antiqueradios.com/gallery/v/national/?g2_page=1

Nice picture assortment of things National.

PS:  He who masters the search engine masters the world!
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W7GIF
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Posts: 122




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« Reply #2 on: October 24, 2012, 07:13:51 PM »

Take a look at this:   http://www.antiqueradios.com/gallery/d/149057-1/NC-183D+Late+Version+Manual.pdf
And this:   http://www.antiqueradios.com/gallery/d/149015-1/NC-183D+Newer+schematic+version+B.pdf

Found both here:   http://www.antiqueradios.com/gallery/v/national/?g2_page=1

Nice picture assortment of things National.

PS:  He who masters the search engine masters the world!
Thanks Nelson.
I downloaded the manual from the link you supplied, and it is for the #396 production run. My 183D which has a #396 prod run serial number, has an R72 (100 ohms) that's installed in place of the jumper (at R3) on S-1A, and has a factory installed 18,000 ohm R26 (instead of 33,000 ohms). I located another manual for prod run 436, and it has both the added R72 and the 18,000 ohm R26. The manual for the  #436 prod run also showed the CORRECT grid voltage polarity for V4, V5, V6, and V16, and the cathodes of V13 and V14. I've resumed my troubleshooting using the "436" manual/schematic.

Thanks for helping me to eliminate the audio circuitry by applying the phono input. I've found and replaced one fractured 2200 ohm resistor in the front end, and replaced the 220 ohm V5 cathode resistor with the correct 47 ohm resistor. Now, all of the resistor values and tube voltages agree with the manual specs. My next step will be to replace all the Sprague black beauties upstream of the audio with orange drops or ceramics.

Thanks again.......
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K7MDO
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« Reply #3 on: October 24, 2012, 08:21:43 PM »

Be very careful of moving any wires that run in the vicinity of the IF cans.  Particularly tube plate supply wires.  The less you disturb the wires the less chance of generating feedback issues like I did with mine... took a long time to sort it out.  The malady shows up as a squeal at high RF gain settings.. can even be band specific.  Good radio once restored... 73 Tom
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W7GIF
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Posts: 122




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« Reply #4 on: October 24, 2012, 11:52:04 PM »

Be very careful of moving any wires that run in the vicinity of the IF cans.  Particularly tube plate supply wires.  The less you disturb the wires the less chance of generating feedback issues like I did with mine... took a long time to sort it out.  The malady shows up as a squeal at high RF gain settings.. can even be band specific.  Good radio once restored... 73 Tom
Thanks for the heads-up. It sure looks like finding the cause of this 183D's malady (low audio output), is going to be tedious. Thanks to the help of AC5UP, I've been able to give the audio output stage a clean bill of health. But, the front end stages and the AVC remain to be troubleshot. My preferred method of troubleshooting this problem would be to apply a signal at the antenna input, and then measure the signal level at each stage proceeding downstream to the 1st audio. But, that method would require knowledge of expected gain in each stage.....and that information is not readily available. I guess that to avoid resorting to the shotgun technique, I can use the stage gain measurement procedure in the manual, starting with the 3rd IF (hoping that the V8 stage is healthy), and work upstream. Sure hope I don't discover any failures of IF can transformers......and, that I find the bad actor before reaching the RF stages. Sure would be a lot easier/more efficient to use my preferred technique with signal applied to the antenna input. Oh, well.......
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K7MDO
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« Reply #5 on: October 25, 2012, 02:44:42 AM »

The IF transformers are relatively easy to deal with I ended up replacing a couple and found it easy... just make sure and position the attached circuitry in as close as possible to original location.  I ended up with a donor set and that helped a lot as well.

Tom
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KE0ZU
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« Reply #6 on: October 28, 2012, 07:58:29 PM »

Go to this manual, and look at the bottom right corner of the rear cover.   Notice the "ER xxx" number.   You want to be sure, you have the same manual, or as close as possible, to what was issued when your receiver was built.  Some times changes were slight, sometimes not.  Carl, KM1H knows all about this subject.
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W7GIF
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Posts: 122




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« Reply #7 on: October 30, 2012, 06:24:40 PM »

Go to this manual, and look at the bottom right corner of the rear cover.   Notice the "ER xxx" number.   You want to be sure, you have the same manual, or as close as possible, to what was issued when your receiver was built.  Some times changes were slight, sometimes not.  Carl, KM1H knows all about this subject.
Thanks Carl. Yes, since my chassis is a production run (ER) 396, I believed the ER #396 manual schematic and parts list would match what I find in my receiver. But, it doesn't. My receiver has a factory-installed 100 ohm R72, and an 18K R26 neither of which are in the ER 396 manual (no R72, and a 33K R26). But, both are in the ER 436 manual that I found. Since both of these resistors definitely appear to be original factory installed (soldering quality and color), I suspect that there were some 183D's that were shipped before their manuals with revisions to the circuitry were available.
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