National NC-183D advice and help

[n7ioh]

I have two NC-183D receivers that I am working on, both the newer models.  The serial numbers are, 372-0102 and 357-0620.  I would like to know when they were built and how you determine that?  

I will be going through and replacing ALL the old electrolytic caps and ALL the old carbon resistors.  This is based on reading a few of the reports of others that have rebuilt theirs and found nearly all the resistors out of spec.  My question here is:  Are there any resistors or caps that should be replaces with something different then what was original and if so what?  Is there anything else I should do while rebuilding these?  Any problems with certain tubes?  This will be my winter project so I would like to do it right.  

Also I am still in need of one original tube shield.  I have been looking on ebay but can't find an original match.  I also have one damaged AF Gain knob that I would like to replace with one in good shape.  The knob that I have has a 1/16" lip on the edge of the aluminum skirt.  This is the one I am looking for so that all my knobs will match.  The earlier knobs that I have seen have almost no lip.  Let me know how much.

One other thing I almost forgot.  In the ACC socket there is this accessory that has a 6J6 tube in it.  I can't find any mention of this accessory in the National manual or accessory list.  It looks like it was professionally built, not home made.  Any idea what it is?

Thanks, Al, n7ioh
Payson, AZ

[WQ9E]

Al,

I agree with replacing all of the electrolytic caps but for resistors I measure and only replace those that are out-of-spec.  I was probably one of the first to write about the NC-183D resistor problem many years ago.  My receiver had every one of the 47K screen dropping resistors go very high in value but other than these only a couple of the 100K were significantly high.  There is a non-zero chance of collateral damage each time you replace a component so it is best not to replace those that don't need replacing.  Most of the resistors can be measured in circuit without un-soldering either end so they are easy to check.

Depending upon the vintage the numerous .01 bypass caps may be paper types in the square package.  The Northern Radio modified NC-183D I just went through had about 30 of this type and almost all were significantly leaky.

Let me check after Christmas, I vaguely recall picking up a few of those shields while working on another National so I may have some.  If so I will send you one.

The 6J6 device in the socket doesn't ring a bell.   The most common item there was a NBFM adapter and a number of hams built homebrew calibrators.  There was a product detector made by the forerunner of Universal Radio and one came in one of my HRO-60s but I don't recall it using a 6J6.

[Pete, WA2CWA]

There was an article in CQ Magazine years ago that used a 6J6 as a product detector. I believe it was also reprinted in ER. Seems to me I remember someone mentioning that National built a number of these for a specific customer and/or usage.

[n7ioh]

Roger, thanks for the good info on the .01 bypass caps, I will look for those.  Clark, ke7trp if I remember correct had to replace almost all the resistors in his NC-183D so I was going mostly by that.  The other reason is because of their age.  I suspect it will just be a matter of time before I will end up replacing more resistors after I start using the rig almost daily.  If it were a lighter weight radio like my Drake gear I wouldn't mind but 60 pounds is a pita to keep pulling apart to replace something I could have replaced in the beginning.  I do agree with you about the potential problems involved when replacing working components.  I will, out of curiosity check the resistors before replacement to see how close they are to spec.  Roger thanks for looking for the tube shield for me.  No hurry, when you have the time.

Pete, thanks, I have been doing a lot of internet searching and it looks like what I have is a the plug in product detector that was actually made by National.  It seems that National made some for Tropical Radio and a few others.  What I'm not sure of is this just a plug and play?  I don't see how it could be as there is no way to switch between AM and SSB.  Also was there any wiring changes to the NC-183D when using the PD?  I really don't intend to use SSB on the NC-183D anyways so I don't know why I am asking.  It came on the NC-183D that I was thinking of selling anyways as I don't really have room for two of these or need two. 

Thanks guys
Al, n7ioh

[Tom WA3KLR]

Al,

Here are 2 threads we had on the NC-183D.  Read all.

http://amfone.net/Amforum/index.php?topic=19922.0

http://amfone.net/Amforum/index.php?topic=30913.0

Merry Christmas everyone.