NC183D color and other information

[ke7trp]

That was easy,  I changed the caps and did the AVC alignment again.  This time the Null was much better and now the AVC is working. Its clear on strong BC stations and when I flip AVC off its major overload.   SUCCESS!!

I swapped the 6SN7 tube with the one from the HRO 60. No change.  I then started checking the resistors around that tube.  I found the 25 UF cap (cathode of push pull audio)  popped.  Not sure why.  I used a 50 volt 22 UF cap. I Did not have anymore so I used a 47 UF at 350 volt.  I found that 330 ohm resistor was 100 ohms.  I changed it out to new 330ohm 2 watt and put the 47 uf cap in. 

No change.  S meter is 10 DB over with the  rig tuned off of a station and its also 10 db over when in standby.   So this is the minimum reading I can get still.  On strong BC stations, it pegs out as normal.

Anything else to check on that Pesky S meter?

C

[Jim, W5JO]

Clark check to see that you have AVC action on all tubes where it is attached.  That should be the 1st and 2nd RF and 1st and 2nd IF amps.  You should see the grid voltage vary on all 4 tubes from low to high are you tune in a strong signal.  If it doesn't then look to see where you are loosing it.

What does the S meter do when the set is turned on and you disconnect the antenna and short the terminals?  Are you using a coax input with one terminal grounded or balanced input for the antenna?

[ke7trp]

If I ground the antenna terminal, The meter goes to 10 DB over 9.  If I unhook the antenna, It goes to 10 DB over 9.  I can change bands, It goes to 10 DB over nine.

10Db over 9 is the baseline for NO signal. 

The AVC as of now is fixed.  I tuned all around the BC band and nothing distorts the Front end anymore.

I started checking resistors at that 6SN7 tube,  ALL of them are seriously out of spec.  Like double, or tripple out of spec.  I stopped and shut everything down.  When I have time tomorrow, I am going to have to start changing resistors.  I am sure this is the problem  Not one of those dang resistors in that audio section is even CLOSE to what the schematic or the value of the resistor itself is supposed to be.

I am looking at about 20 bad resistors would be my guess.  I have come this far, Why not finish it?  Once its working 100%, i will pass it on to another AM'r that wants it and then put that money towards a clean Grey tone reciever that will match the 50 and 60 on the table.

meanwhile, If you can think what in that circiut would cause the S meter to never zero, Let me know
C

[kb3rdt]

Normal, I have an NC-300 I had 5 S-units of noise I change most of the Resisters bam noise floor droped mine was in I F over load bad resisters so any over 10% value change it!

One thing to check on all tube is the screen resisters!

[Jim, W5JO]

Do check all the screen resistors and bypass caps but I looked back and you said you have a 1K pot for the zero function of the meter.  That pot should be 1K, that is R 39.  Be sure the values of R 31, 49, 69 and 71 are all correct.

[KB2WIG]

" If I unhook the antenna, It goes to 10 DB over 9.  I can change bands, It goes to 10 DB over nine.  "


Well, at least you would be honest fer the corntest signal reports....


klc

[ke7trp]

This is not noise or static.  The speaker is silent. This is the S meter not returning to 0. Even shorted Antenna jack, it reads 10 DB over 9.  I am sure its the resistors.  After doing some last minute Xmas shopping, I am going to start changing them.

Normal, I have an NC-300 I had 5 S-units of noise I change most of the Resisters bam noise floor droped mine was in I F over load bad resisters so any over 10% value change it!

One thing to check on all tube is the screen resisters!

[ke7trp]

I am having a tough time here.  The manual on BAMA is for the 183D with the 6J5. Anyone have the manual or schematic for the later version?

C

[ke7trp]

WE FIXED IT.  Thanks for the help Jim!

I replaced those resistors you listed and the the S meter Zeros perfectly and swings up on strong stations.  I am so happy right now.  The main culprit was the 47K ohm resistor on Pin 5 of the 6sn7!  It checked 315K.   When I replaced that one resistor, the rig came to life.

AVC FIXED!
S meter FIXED!
Audio tone quality FIXED!

Its actualy a really strong and great sounding rig!

Clark

[Jim, W5JO]

Congrats Clark,  Don't use it too long, you will want to keep it.  Actually I have a third one that I have refurbished.  I regret selling or trading the previous two so much that when this one came along I couldn't resist and am planning to keep it.  Easy to band change, sensitive, good looking and sounds wonderful.  Did you check the cap used to change tone.  In mine it is a ceramic but I believe in yours it may be a paper.

Duplicolor makes a Grey paint for their Pickup and Truck line of paint in a spray can that is a good match for it.  I don't remember the color but is has just a bit of flake in the paint like all of the 183D receivers I have seen.  Since the lettering is engraved you can take the case completely apart, strip the paint and repaint with the Duplicolor it is only a bit lighter but is really pretty when done right.

Then using the white laquer stick, redo the lettering.  Be sure to cover it with at least two clear coats and you will have a keeper.

[ke7trp]

All the paper caps have been changed out already. The only original caps that are left are the green national brand .01s and they check right at .01 on my new digital cap checker.

The tone does work.

There are some minor gripes with the set. 

1.  The tuning and band spread slip.   I cleaned and oiled the bushings very carefully.  This helped free up the main cap and helped things.  I also used a seringe to inject some naptha(lighter fluid) into the friction point of the large wheels and knobs. This really helped matters.  There must have been some greese or oil in there.  Its not smooth but no longer slips every time you turn the knob.

2.  If you turn the volumn down all the way, There is still sound.  You cant cut the audio 100%.  Its possible its just the volumn pot. I will have to look around for one. Its not that big of a deal really. Its very low and you can flip to standby if you get a phone call or someone walks in the room.


The overall condition of the rig is Average at best. There is alot of corrosion on the chassis.  I really dont want to put more time or money into it.  As of right now, Its working and someone will enjoy it.  Its playing the local Am BC station and sounding great. 

I really want a super nice NC183D.  I am sure I will find one someday! I feel good that a saved a junker from the scrap heap!
C

[KM1H]

2.  I have - 2.8 volts on the Grid of the first Tube after the AVC.  If I rotate the RF gain control this goes to -24 volts.

You missed the other 6 tubes that could be causing the distortion.

[ke7trp]

ALL six tubes have the correct voltages. There is no longer any distortion. I fixed the problem yesterday Carl

[KM1H]

Thats what happens when I dont see Page 2, chalk it up to a senile citizen brain fart

[Jim, W5JO]

Thats what happens when I dont see Page 2, chalk it up to a senile citizen brain fart

In my case it is temporary Alzheimer's Carl.  Glad you have only brain farts.

[ke7trp]

I found my Girl this morning.  Very CLEAN and nice NC183D in the correct Gun metal Grey color.  I got this at the Thunderbird ham fest from a fellow AM'r.  Great price.  At first she was dead.  Then about 15 minutes later, I hear loud static from the other room. I run it and she is playing right along.  A tube or a cap must have come back to life. 

As of now, Everything seems normal.  I am going to let this play for the rest of the day and then open up the bottom and have a look. 

Serial 328 0248  Any idea of when this was made and how it fits into the production run Carl?

I will probably recap the rig and check, replace resistors, depending on what I find when I go inside. 

I am pleased to have very nice HRO60, HRO50T and now NC183D!

The other good news is that the Light blue NC183D we fixed in this thread is going to a good home.  A fellow ham and Am'r that is fairly new to the AM community will have the Reciever running with his Ranger. I think this will be a step up over his HQ110 and the 110 can be used with his Viking2. I passed it on at cost with no profit. 

Clark

[W7TFO]

National sure made some good-looking, good sounding, well engineered radios! \

73DG

[KE5YTV]

Wait just a minute Clark.  I saw that slot machine in the background!! Just what kind of joint are you running there?   

Mike

[W7TFO]

Wait just a minute Clark.  I saw that slot machine in the background!! Just what kind of joint are you running there?   

Mike

What old boatanchor isn't another gamble?

73DG

[KM1H]

Serial 328 0248  Any idea of when this was made and how it fits into the production run Carl?

January 1952 which means it should have a 6J5.

Carl

[ke7trp]

6J5.  Is this good or bad Carl?  Convert it?  What was the main reason?  It seems to work perfectly. I checked all the bands and the more time, It plays the better she sounds and works.

P.S the slot machine is a japanese slot out of a gambling parlour in japan.  Its really neat. It has an LCD screen and plays animation when you win and loose.  I also have japanese Pinball, and a bar top video poker and of course the air hocky table that now holds 200lbs of national radios at present time!

C

[KM1H]

First, quit playing with it until its been completely recapped or the lytics and papers in the audio stages unless you want smoked iron for dinner. They are tempermental enough as is especially if its an original.

Early 183D's for the 99th time had a 6J5 phase inverter as did the 183, afer a few runs it was changed to a 6SN7.

The BAMA schematic is for the 6J5. I have a PDF of a later, June 1954, 6SN7 manual if anyone needs it. Just added it to the files.

Carl

[ke7trp]

I realize the 6j5 was in the early radios and was replaced with the 6sn7. I was asking why.  Jeeeeez.

I turned it off and unplugged it.  Your right about the caps.  I will get to work next week on it in my spare time.  All new caps, cord, and will go through the resistors.

C

[KM1H]

The WHY was cuz they redid the S meter circuit and needed an amp and didnt want to have to produce a new chassis so went to a dual triode 6SN7.

[ke7trp]

AHhh.  Oh. Fair enough.  Thanks!

C