Carl, in this thread: viewtopic.php?f=5&t=194086&p=1620067#p1620067, said,



My 183D is S/N 396 0115. On the back of one manual I have is ER 328. This manual has the 6J5, and R36 and R37, a voltage divider, mentioned in this thread by Dave Doughty: http://www.antiqueradios.com/f/viewtopi ... 4b49162964 .



My 183D is S/N 396 0115. It has the 6SN7. I also have a manual with ER 396 on the back page. The schematic in this manual has 6SN7 and R36 & R37, also shows R36 & R37 in the parts list.

My 183D radio does not have R36 & R37, instead has R36 @500 ohms 10 watt, and no R37. I have a schematic which shows R36 as 500 ohms, but no manual to match this schematic. I believe I got the schematic as a file from an ARF member, can't remember the circumstances.

What started this, is I had the same problem described in the first thread, on a strong signal I could not advance the RF gain past 8 1/2 without a lot of distortion. I carefully read the thread (183D AGC) and discovered the R36 only, NO R37 discrepancy in my radio. I fixed the RF gain problem by replacing the RF gain control, which had a break in the wire winding, but still worked partly. The 500 ohm R36 looks original and works very well.

My question: Does anyone have a manual (if such a manual exists?) to match ER 396, and that manual shows 6SN7 AND 500 ohm R36? I guess some confusion is inevitable.

Thank you for your attention and possible replies,

Bill

Bill,

I have the ER 396 manual and it shows R-36 and R-37 as 1000 ohms each. The serial number of mine is 430-0237. There is also another number on the back of the manual, SM-400-654. Don't know if this helps you, but if I can provide more info, let me know.

Dick

Thanks, Dick for your offer of help. I have an ER-328 manual and an ER-396 manual. They both show R36 & R37 as 1000 ohms. My radio and a schematic I have show only R36 as 500 ohms. I don't have the manual or the parts list to go with that schematic. The 500 ohm R36 might be what Carl refers to as a minor production change.

From your serial #, i.e., 430-xxxx, I might guess that there are further revisions beyond my 396-xxxx.

That is a very nice looking radio that you bought. 183D is a super radio.

From looking at your photos, I think I see two tan cylinders near the big orange capacitor. My R36, 500 ohms looks just like those. If they are the 1000 ohm pair, R36 and R37, then you have the voltage divider version. I am unable to correlate a voltage divider with your serial number, but further replies might clear this up.

Thanks again, Bill

Here's a very good site for 183D stuff: http://www.retrevo.com/search?q=nc183d&rt=_

The first article has some photos which can be enlarged a couple of times which shows the two 1000 ohm resistors.

Bill

Bill,

I have to take it back out to the shop in the garage to start replacing the components that Carl recommended. Trying to work up the courage to lift it again. It's only a 60' trip but 68 lbs for a 75 year old guy is a challenge. Can't believe I used to buck hay bales all day long. When I get it out there and the EMTs are finished, I'll try to get some closeups for you.

Dick

Thanks, Dick for your reply. I hear you on the 68#. I am a couple of years younger, but I put a towel under the 183D and roll it around. Also, I have a cement floor and audio/visual carts.

The R36/R37 thing is kind of moot since the radios are working, but I figure to gather as much detail as possible.

Thanks,

Bill

Well, it's out in the garage and it's going to stay there until my iron pumping #3 son shows up. Surprise! There is only one 500 ohm 10 watt resistor, the square body. The cylindrical resistor is R-42. The single 500 ohm is the same resistance as the two 1000 ohm in parallel shown on the schematic. It would appear that the 2 resistor design was a kind of safety valve and why it was modified puzzles me. Maybe later I'll study the schematic to see what the effect of a single 1000 ohm resistor would be. Until then, as you said, it's working. I'm just pleased that I have it. It's a beauty and a beast in the same package.

That was quick, thank you for your reply. Your radio is set up the same as mine in that area. National went from two parallel 1000 ohm 2 watt resistors to the 500 ohm 10 watt. The net change was an increase from 4 watts to 10 watts. Maybe the two 2 watt resistors were cheaper than the 10 watt or vice versa. They almost always do the cheapest thing. Good luck and please keep me posted.

Bill

Checked Just Radios individual resistor prices. Two 1000 ohm 2 watt resistors are $1.78. One 500 ohm 10 watt resistor is $0.79. So nowadays they would save $0.99 by going to the single resistor.

Bill

That buys a quart of gas!

That would buy over 5 gallons back then!

Yes the R36/37 change is one of those production changes that doesnt get documented until the next run and manual. Since its a non operational change its just something to note and then ignore.

ER 396 is the manual I distributed to several and I believe someone also sent it to Ken, K4XL, of BAMA.

Carl

Thanks, Carl, I have a schematic which shows it, but no manual.

I pumped many thousands of gallons @ $0.219. Everybody bought "two dollars worth" back then.

Now I am coming up against National (non)documentation again. My NC-109 schematic shows C28 as .047 uf and there sits a big old paper 0.22 uf. No parts list seems available.

Thanks again for your help. The 183D is really working well.

Bill

The lowest gas I remember was in Olathe, KS in 1960 when a price war had it as low as .169. Then I was transferred to USN ET School at Great Lakes, IL and reality set in again, it was .259

With a 51 Buick Roadmaster convertible and Dynaslow, 12mpg was on a good day. Wish I had that car today. All white with blue leather and cruise with the top down and those PP 6V6's easy to hear.

Carl

That's a great color combination on a very nice car. Very desirable today.

Bill

The BAMA website also has a pdf of 'National Service Notes' that cover some changes and clarifications of National radio repair in different models.

Thanks, Wally, I will go to BAMA and download that.

Bill

Edit: Went to BAMA and National and got some good luck. Since I was there last they have added a late 183D manual which shows the elusive 500 ohm resistor C36 on the schematic AND the parts list. No sign of the ER #, though.