NC300, In the dishwasher.. LOL

[ke7trp]

Got an old Ratty NC300.. Covered in nicotine, years of Grime..  So bad I figured this was the last ditch effort.. Put it in the dishwasher.. Pots and pans heavy cycle with a couple packets of Cascade ultra.  

To say it came out nice is an understatement.. Its like new!  I dont think 2 hours of hand scrubbing would compare to this!  I am running it again for good measure.. Removed the racks and put pieces in as sections.   All Knobs and controls when into the basket that holds the silverware..

Obviously... Remove items you feel might get damaged.  

I will post pics of the thing when its all done.  Gotta run to AES and pickup the Hammond 600 ohm to 4 ohm transformer for the audio output.  Should be up and running tonight.  It will be used with the GK 500C as that is what leo used in the adds from the 50s..

This is a BEFORE cleaning picture..

Clark

[N2DTS]

Oh, I thought you put the entire rx in the dishwasher!

Brett

[ke7trp]

I did..  LOL. Thats the case and the knobs in that picture.. Just remove items you think might get damaged.  Transformers.. Tubes,  Dials ect.. 

This one was a mess.  Looks like it had been in a barn or patio for 20 years.  Sprayed it down with soap and hit it with a paint brush to get Grime off.. Then tossed her in the dishwasher.. Shes on the second cycle now..

I chose not to do the heated Dry cycle.. I have had a couple cheap kitchen knifes get melted with this machine.. So I turned that feature off.

When it comes out this time.. I am going to wipe it down with some Furniture polish to shine up and to stop rust
Clark

[W1GFH]

I think you'll like the NC 300, having a boatanchor with a backlit, analog tuning dial that actually shows you what frequency you're on is worth the price of purchase. 

If you can get hold of the multi-tap RadioShack 10 Watt 70 Volt Audio Transformer, #320-1031, it will also do your speaker output impedance conversion much cheaper than the Hammond.

[ke7trp]

To late on that info.. I already drove up to AES and got the Hammond.  $20.. Ouch.  Case and knobs came out nice.  All that dirt and Crap is gone.  Just plastic and metal inserts.  The Big insert on the main knob is real bad.  Might look for a replacement.

Got the caps in.  Going to fire it up in a few minutes.  Wish it had BC band for testing. Going to have to get the Sig gen out I guess.  Or an HF Rig and Dummy load.

Question..  This  NC300 is light and Dark grey.. All the ones I have seen are brownish two tone color.. Does this signify a year or version?

C

[W1GFH]

The one I had was light/dark grey. Don't know serial #'s.

The other nice thing about the 300 is that it was designed for ham bands, unlike other older band cruisers, it's "hot" all the way up to 10 meters. When 10 AM opens, you'll appreciate that.

[WA5VGO]

Why do you need a matching transformer? It should have an 8 ohm output.

73
Darrell, WA5VGO

[ke7trp]

Was kind of shocked to see this one go all the way to 225 meg!  THat means I can use it with my Heathkit 2 meter AM Transmitter.  

Only problem I have now is I cant seem to figure out what holds the DRUM.. It moves along with the band switch as normal.. but if you let off the Drum then it derails..  

C

[ke7trp]

This one is clearly marked "600 ohm" on the back Darrell.   

C

Why do you need a matching transformer? It should have an 8 ohm output.

73
Darrell, WA5VGO

[W1GFH]

Here's some info on the paint colors and year models.

http://www.virhistory.com/ham/nc300/nc300.html

600 ohm speaker: y'know, come to think of it, I've never heard of an NC-300 or 303 with a speaker output other than 8 ohm. The antenna terminals should say "300 ohms" on it, and it looks a LOT like a speaker terminal, so maybe......

[Pete, WA2CWA]

Specs for the NC-300 say 8 ohm voice coil for speaker

Specs for the NC-303 say 3.2 ohm voice coil for speaker

[ke7trp]

Here are the final pictures..  Very little testing done..  No BC band.. Have to drag it in the main room and hook it to the big antenna.  It came out spotless clean..  1000 times better.  All bands working up to 10 as normal.

Not sure what to tell you guys about the speaker. This one is labeled 600 ohms and required the transformer.  Maybe older? 

I have one 6BJ6 that is testing 10 on the TV7. I dont have another one.. Still seems to work though!  I will have to locate one and replace it.

[ke7trp]

In the case..  Maybe one day I will paint the case. It needs it.

C

[ke7trp]

No..   Mine has 600 OHM audio output. Its not line out.Its powering the speaker loud. There are no other connections on the back for a speaker.  Just the normal strips for Mute/standby and antenna.  Its not modified. Its clearly original with no extra holes.  I traced this line back to the audio tube directly before we put it in the case because you guys had me wondering.  If I hook the speaker up I get no sound.  If I hook the 600 Ohm transformer up its super lound like it should be.  Not sure what else to say on this.  Maybe they made a few at 600 ohm and then changed them?  Maybe they made some this way to use older speakers? I just do not know.

Someone will probably read this and have an explination.. I am all ears!

[N2DTS]

I had an nc300 and a 303, and both were 8 ohms.
Maybe they made some special ones for the govt?.

If it was me, I would replace the output trans with an 8 ohm output one and do away with back to back transformers, or just take audio off the detector and feed it to the marantz.

I liked the nc 300 and 303, but dont think the audio amp was anything to get excited about.

Brett

[ke7trp]

I will look into that. Not much low end on this reciever. 

I just got it to sit next to the King 500 as that is what he used.  If it works decent and sounds good on 160.. I am good.    I have other recievers that are better.  halli's Hammers and 390s.   Dead tired.. I spent alot of time on this thing compressed into two days. Once I start something, I like to finish it..




C

[N2DTS]

Yes, the r390 is a better receiver, and I never liked the art decco style of the 300 series receivers, but it was stable and had that very nice freq readout.

I think it was also a little narrow for AM, no?

Brett

[Fred k2dx]

Some Hallicrafters had 500 ohm outputs, the matching speakers had a transformer in the cabinet. That would be like a 70 volt / 600 ohm PA system output capable of driving a multi speaker distribution system or a very long speaker lead efficiently.

The small cheapo 70v/600 ohm transformers have poor frequency response, no lows at all, as they were intended for pa horns.... the 10watt or higher tranformers usually sound much better.

[w3jn]

Was kind of shocked to see this one go all the way to 225 meg!  THat means I can use it with my Heathkit 2 meter AM Transmitter.  


C

Those are converter bands.  The radio itself doesn't go up that high; it's just calibrated as such for the accessory VHF converters.

Also a 120V/6.3V fil xformer makes a great replacement audio output for a 6AQ5 to 8 ohms.  

[Ed-VA3ES]

You put the whole thing in the dishwasher... chassis and all?  
I have  a '303 that could use that treatment!

[ke7trp]

Its alot of work..   This one was a mess.  Transformers, tubes, IF cans dials ect.. All should come out..  Like I said, use your discretion on that  

I am going to listen to it for a while later tonight.. Time for a late dinner.

Thanks for the tip on the Fil trans!!!
C

[Pete, WA2CWA]

Nooop, they are both 8 ohms.

Ask yourself, why would the 300 be 8 ohms then the 303 which came later be 3.2 ohms?

The manual says 3.2 ohms, but it aint. Mine even says 8 ohms on the back at the terminals.

P.S. The 300 used the 300TS spkr and the 303 used both the 300TS or the NTS-2 spkr. I have both and the 300TS sounds better and is a better match for the output. The NTS-2 spkr is slightly smaller and National may have only ben able to find that smaller 4 ohm spkr at the time to fit the cabinet

The speaker terminal strip on my NC-303 was stamped with 3.2 ohms. From the parts list, the audio output transformer in the 303 was labeled B19435-E whereas the audio output transformer in the NC-300 was labeled A13615. National also used the same part numbers for parts that were common to both units so obviously these two audio transformers have differences. Also there was a slight difference in the output circuitry. In the NC-300, a 100 ohm resistor was bridged across the output of the audio transformer, whereas in the NC-303 a 33 ohm resistor was bridged across the output transformer. The factory service document that I have for the assembly line test and alignment for the NC-300, says an 8 ohm speaker. I don't have any factory assembly line docs for the NC-303. For all practical purposes whether the audio output is 3.2, 4, or 8 ohms, hanging a 4 or 8 ohm speaker on the output wouldn't make any difference  especially on a communication-type receiver.

I have several versions of the NC-300 manual and none of them have a 500 or 600 ohm output.

National also issued a bunch of service addenda on the NC-300 during its life-cycle. It had problems.

[N3DRB The Derb]

on a really nasty radio, thats the only way to go. take out yer dials, xfmrs, ,etc, anything that would be damaged by water and detergent.

you gotta watch out for eh wrinkle though, sometimes it will soften it up. Usually a a few hours in da oven at around 200 degrees will lock it back down again.

teh best ever drying method is a professional force dryer for dog grooming. it has heated air at about 100 degrees with a hose, much better and safer than a air kompressor. faster as well, point it into the radio and let it blow. will totally blow a chassis dry in about 15 minutes. They are like the better hand air dryers in yer restaurant bathrooms. Dry- Eaz is a good brand.

[The Slab Bacon]

A good working 300 is a pretty pleasent rx to use. Be sure to check the tone and sensitivity switches on the backs of the tone and RF gain potz. Mine has crapped out 2 12AT7s in the detector / meter amp. Also if you have a low sensitivity problem, check out the grid parasitic and screen dropping resistors on the first RF amp, IIRC they are a mother to get to.

my biggest dislike for the 300 is that damned 6BA7 first mixer. They are just noisy tubes, and you offtimes still hear some background noise, even with a needle bending signal! !

                                                           The Slab Bacon

[WD5JKO]

Clark,

   I once had a HQ170 that had been through a flood. I should have tried your trick.

I do wonder though, If I put radio gear in the dishwasher, the XYL here would have my head.

So do the dishes now taste like cigerettes?

Running a few cycles through the dishwasher after such a project might be wise. You don't want to leave some chemical film on the dishes..

I always enjoy your posts,

Take care,
Jim
WD5JKO