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 Post subject: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 4:18 am 
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Joined: Aug Thu 30, 2018 8:00 pm
Posts: 9
I have a copy of the manual for this radio, but there is no pars list included. Does anyone know if such a list exists?

Wanting to find replacement screws with strange threads, and also information about the S-Meter, and how it mounts to the radio.

Any advice appreciated, thanks in advance.

Wade, W9EZY


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 5:53 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Albuquerque, NM 87123
Why would a National radio have screws with strange threads?


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 8:05 am 
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He might be referring to the sheet metal self-tapping screws.
The operating manual was not very comprehensive and does not include a parts list. National did not issue any other document for the NC-109. So, if you want a parts list, you have to create it yourself.

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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 8:42 am 
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Joined: May Sat 12, 2012 1:33 pm
Posts: 1729
Location: Rochester, NY.
Mine had mismatched and missing front panel Phillips screws when I got it. I took one down to the corner hardware store to match up and got what I needed. I painted the heads gray and installed them. I don't recall the size, but they are short, self-tappers.
The S-meter is attached to a bracket with mounting nuts and insulator washers from behind. The white dial-scale plate uses a couple of different length screws with 'stand-off' spacers and washers.


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 12:23 pm 
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Location: Cleveland, Ohio
I spent a lot of time restoring my NC-109, as others here have.

To my knowledge, National never published the parts list for the consumer, although I am sure there was one for internal use.

I did the same and matched up sheet metal screws for the panel, cabinet etc. and painted them. I fabricated a replacement back panel and made a replacement chrome strip for the cabinet. I also handmade 4-5 knob inserts out of aluminum flashing, they look near original.

The three top front panel screws on my '109 are #4 with a 7/32" head, about 5/8" in length, original size. They were not 'custom', just standard threads. I have had trouble finding #4 screws with the (7/32 or 5.6mm) head size, the widely available 5mm head is obviously pretty close or you can go with a #6 and make the holes bigger if the head size is critical. The remaining front panel screws are the same size but only shorter.

Let us know specifically what you may need help with as you progress and I am sure NC-109 owners on this forum will continue to assist.

Todd
ka8gef

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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 8:10 pm 
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Hi All,
I was surprised and glad to see so many NC-109 users on this group!

I surely wasn't very clear about what I'm looking for in screws, the ones I am trying to match are for the rear panel, I have an original panel and only 2 screws. I am posting a picture of these screws. They certainly fall into the category of "coarse thread", and I am looking for some that look like these on the outside. They have a hex head, and NO screwdriver slot. I think before I'd substitute today's stainless sheet metal screws for them, I'd scavenge them from an old radio chassis that I have around here.

The s-meter question relating how it is mounted relates to a difficulty with front panel clearance when the chassis is reinstalled in the cabinet. However, if any of you can confirm that this is, indeed, the correct s-meter for this radio, it would be very helpful. I can work it from there. Also, were there any rubber parts or gaskets between front panel and chassis, especially in the area where the meter contacts the front panel?

I will post a couple of pictures of the screw in question, and my s-meter, just as soon as I can figure out how to do that!:)

I plan to re-cap the radio, there are only a few white tubular .01 mfd to worry about, and since National used pretty high quality parts they are probably still usable. But, I have the need to know if "orange drops" can make an improvement.


Attachments:
s-meter.jpg
s-meter.jpg [ 75.66 KiB | Viewed 1791 times ]
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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 8:26 pm 
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I also had a hard time locating a tube layout for this radio, the chassis is not marked showing tube locations. I finally noticed that a tube layout was furnished with the radio on the inside of the back panel. I am uploading a picture of this sticker, and if any of you wants to print a reproduction I still have the original color photo on my phone, so I can upload a color version of the correct size, which is 4.0 W X 4.49 H


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 10:18 pm 
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That is the original meter. The sub-panel, main panel and chassis orientation are a bit cheezy but the meter should clear the front panel easily, mine does by over 1/8". Be careful how the two panels are lined up and that the chassis is positioned correctly with respect to the mounting holes in the cabinet. I hope that the white sub-panel was not bent, that does not appear to be the case(?). Are the three spacers/stand-offs mounted on the dial assembly? Those should assure proper panel clearance.

If you can, please post that color pic, I am sure others could use it, as that tube layout sheet tends to become brittle and fall apart.

My NC-109 did not have a rear panel, so I fabricated one and used phillips sheet metal screws- so I cannot help with the original size. However, if those are truly the original panel screws, they appear to be standard hex head machine screws that you can purchase at most any hardware store or supply house, etc. They look to be 1/4" length but 3/8" would certainly be fine. If you can measure the diameter (thread diameter) I can tell you if those are #6, which is my guess......

Todd
ka8gef

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'Itoshiki oshieo idaki'
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Last edited by KA8GEF on Oct Mon 15, 2018 10:27 pm, edited 1 time in total.

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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 10:25 pm 
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Joined: May Sat 12, 2012 1:33 pm
Posts: 1729
Location: Rochester, NY.
That is the correct meter. In addition to the tubular and electrolytic caps, I would check for resistors that have drifted high and replace those as well. Resistors in 'stressed' circuits seem to be the ones most elevated in value.
I would take those course-thread panel screws down to your local hardware store and buy all new, matching screws for cosmetics.
I remember 'tipping' the chassis slightly while installing it to clear the meter and cabinet interference.


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 11:23 pm 
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Location: Costa Mesa, California
I use McMaster-Carr for most of my odd-ball screw needs. They are reasonably priced and come the next day.

https://www.mcmaster.com/tapping-screws

Norm

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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 11:31 pm 
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Norm, so do I, but didn't find these on McMaster.

Wade


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 11:36 pm 
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Joined: Aug Thu 30, 2018 8:00 pm
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Todd and all,

Here are color copies of the tube layout and the warranty sticker which is also stuck on the back panel. They are to scale, as close as I can make them, and color matched as close as I could on my monitor, which is calibrated with Adobe Photoshop CS5. Monitors are different though, and printers don't match monitors all the time, so YMMV. I think if you play around with them, they can work.
Also, a picture of the inside of the back panel, showing the relative locations of these. The panel is to scale, i.e. 6.5" height.

Wade, W9EZY


Attachments:
NC109 tube layoutcolor.jpg
NC109 tube layoutcolor.jpg [ 108.07 KiB | Viewed 1772 times ]
NC109 warrantycolor.jpg
NC109 warrantycolor.jpg [ 110.69 KiB | Viewed 1772 times ]
NC109 panelcolor.jpg
NC109 panelcolor.jpg [ 101.77 KiB | Viewed 1772 times ]
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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Mon 15, 2018 11:40 pm 
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Wow, the colors varied wildly when posted, they looked alike when I stored them. The color is actually a little bit lighter than the labels on the back panel photo, the tube layout is also close, but the warranty isn't so great. It should be pretty close to the tube layout in color.

I hope you all can use these,

Regards,
Wade, W9EZY


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Tue 16, 2018 4:46 am 
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Here's a better copy of the warranty tag


Attachments:
NC109 warrantycolor2.jpg
NC109 warrantycolor2.jpg [ 99.85 KiB | Viewed 1758 times ]
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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Wed 17, 2018 11:46 am 
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Location: Cleveland, Ohio
Wade, thanks for posting the labels.

As Wally stated, focusing on replacing the electrolytic caps and the few paper ones will be needed. If the electrolytics have not been replaced, you will eventually see them fail, evidenced by hum or even power transformer failure if one section were to short. Orange drops (for the paper caps or in place of audio chain disk caps) typically are of no or little perceived improvement in these types of applications. I would avoid any mica cap replacement unless you clearly have found one that is suspect.

Checking the resistors will probably reveal a handful out of spec, primarily those that are in higher voltage/current circuits (power supply, plate, cathode circuits etc.), as previously noted.

During alignment, be very careful when adjusting those oscillator coils. Minor tweaking will be all that is necessary. The delicate coil wire leads are dressed inside the coil form. If the slug is inadvertently turned too far into the form, the internal lead(s) can easily be severed. This will immediately render the applicable band 'dead', requiring a rather tedious repair effort.

There are few minor mods worth considering, i.e the s-meter signal level, s-meter swing damping, mixer tube improvement, etc., however the receiver does perform pretty well as is- once it is brought back to factory spec (component replacement as needed and alignment).

Have fun...keep us posted.

Todd
ka8gef

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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Fri 19, 2018 2:23 am 
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Posts: 9
Todd and All,

Glad you can use the tube chart.

What do you know about this S-Meter, the manual says nothing about how to calibrate it. Where is "zero" on it? Borrowing from other manuals, most specify 100 microvolts should read S-9 on the meter, I can't even come close to anything like that with the so called meter calibration pot on the rear of the chassis. It does deflect on strong signals, wants to "rest" at about middle of the range.

The NC-109 is working like a champ, it's my first National and a very nice radio, IMO! The ceramic trimmers under the chassis that are used to calibrate each band seem intermittent. I took off the metal rail holding the capacitors and it seems there is some black corrosion around the center post of these capacitors and I suspect that this results in intermittent connections at times. I bought some replacement trimmers on ebay, 4-35 pfd, but they are about half again larger than the original, but of good quality. i ordered a piece of 3/4" brass angle and I plan to mount 4 of these larger caps on that and replace the 1/2" steel angle that is standard on it. I'll let you know how that transplant goes. :)

Again, thanks to all of you for your help!
Wade


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Fri 19, 2018 12:32 pm 
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Wade,

The s-meter pot at the back of the chassis is a zero set 'balance' pot, not for s-meter range or sensitivity. With no signal at the antenna terminals (no antenna) the needle should then be set for zero reading. A common problem is that the pot becomes dirty and intermittent, sometimes beyond 'repair'. Try a good quality contact cleaner. Replacement may be required if this cannot be rectified, it is common to end up with a 'burn' spot on the carbon element. Sometimes a shot of WD-40 will work but do this as a last resort. Also check R46 (100k) value, R46 is located off the pot element terminal and the s-meter amp plate pin 1. The zero setting should remain relatively stable from band to band.

S-meter readings are typically high (common to several National receivers) and can be brought back closer to 50uv input = S9 by replacing R46 (100k resistor) which again comes off the plate of the 12AT7. Replace with a 330K and the average signal level will be in the ballpark. If you do not like the 'swing' of the needle, it can be damped with a 470uf electrolytic across the meter terminals. Make sure polarity is correct.

That 'corrosion' you mention on the trimmer cap metal and screw is probably not what you think it is. It is typically common oxidation of the metal and and should not be an issue with capacitance. Are you sure that these are really intermittent? What trimmers are giving you trouble? The oscillator trimmers will appear jumpy/intermittent when adjusting and peaking on the signal. What is happening to the signal when you adjust the trimmers in question? I would not replace unless they are truly corroded, contaminated or defective due to someone damaging the caps somehow!!! Usually, a few rotations clears up any issue. Do not spray these with contact cleaner.

Make sure that the band switch is making good contact, as well as all tube pins and chassis ground points- and that all components have been checked/replaced as needed before alignment or suspecting a problem with the trimmer caps. During alignment, you will find that the antenna (and to a lesser degree) mixer trimmers will not have a strong peak, sometimes very little impact, on the inputted signal. Again, the oscillator trimmers will appear 'jumpy/intermittent' as you are zeroing in on the targeted signal. For what it may be worth, I have replaced perhaps one trimmer cap in 30+ years of repair and restoration.

Follow the alignment instructions in order, carefully.

Hope this helps....best regards...Todd- ka8gef

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Last edited by KA8GEF on Oct Fri 19, 2018 2:16 pm, edited 6 times in total.

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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Fri 19, 2018 1:11 pm 
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Joined: May Sat 12, 2012 1:33 pm
Posts: 1729
Location: Rochester, NY.
Sometimes sweeping the S-meter pot adjustment back and forth a few times will re-establish a good pot wiper contact. Look for out-of-tolerance resistors and poor (high-resistance) contacts in the meter/AVC circuit. The meter on my NC-109 isn't nearly as optimistic as my NC-98 and is likely a more realistic reading.

The 'tarnish' on the trimmer cap's white metal shouldn't really affect values. Avoid spraying cleaners or lubes on caps or coils, it can de-tune them. Use care it trying to turn a stuck adjustment screw or slug, if the ceramic or ferrite fractures, it will need replacement.

I also replaced the deteriorated audio network 'couplate' with discrete components on mine and gained a small improvement in audio fidelity.


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Sun 21, 2018 3:58 am 
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Thanks, Norm.

I checked the 100K and the zero pot, still can't get the s-meter to read minimum, which I assume you mean pointer all the way to the left. There is a "0" at center of the scale, pretty sure you didn't mean that setting. I checked the 4.7M resistors too, those are pretty close. After replacing the 100K, the meter gets down to about S4 with no antenna attached, but that's it as low as it will go. This was a new 12AT7, but might try another, just to compare. Also, could the S-Meter have a problem? Seems to stick occasionally, but frees itself when signals are present.

The trimmer capacitor for the broadcast band is intermittent and will cause the radio to go dead just shortly after I get it all back into the case! I take it out again and tap on the trimmer, and it comes back to life. I cannot find a replacement for that trimmer that is the same physical size, found some on ebay but they turned out to be nearly twice as big, so that's why I was considering replacing them all. It doesn't seem to be a daunting proposition, considering mounting a new brass angle in there, bolt 4 of the larger ceramic trimmers to that, solder the tails from each to the brass angle and then hook up 4 bare wires to the individual trimmers. I've had the original trimmer bar off the radio and closely inspected all 4 trimmers. I don't know what the black corrosion is, maybe a silver compound that shouldn't cause a problem, but I am sure that the trimmer for the broadcast band is intermittent for whatever reason.

Also, I rewired the accessory socket to accept my Heathkit HA-10 crystal calibrator, and that works great. Not much chance I'll find or even need a National calibrator, the Heath is a 100KC calibrator, very compact, readily available and is useful to me on the broadcast band.

Thanks for your time and advice, very much appreciated!
Wade, W9EZY


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 Post subject: Re: Need Parts List for National NC-109
PostPosted: Oct Sun 21, 2018 4:07 pm 
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Wade...the zero at the center of the s-meter scale represents 0db over s9, or an s9 reading. The line at the far left is the zero you should be setting to.

The movement may be sticking. Try tuning into a strong CW (code) signal, in the AM mode, to see if the needle will swing further left of that S4 reading.

A few other possibilities and checks in no particular order:

Verify the range of that pot with an ohm meter (should be 1.5k).

Does the reading go below S4 when the sensitivity/RF gain is reduced? Should go to zero.

Are you sure that the 100k resistor (R46) is within reasonable tolerance? Also check R19, R21, R22, coming off Z3, the last I.F. stage.

Are you seeing about 105 vdc on pin 1 (plate) of the s-meter amp 12AU7? Another 12AU7 is also worth trying.

Also, the meter will only display actual signal level in the AM and AM/ANL modes, not CW or sideband, where the reading should be zero.

Note that this meter does not zero left when the receiver is turned off. It should fall near full scale.

Sticking meters are somewhat challenging to 'fix'. Normally the problem is due to particles that have accumulated around the magnet and pivoting needle assembly. It takes a very steady hand in removing a metal or misc. particle- otherwise you can quite easily damage the delicate movement. I remember managing a metrology lab staffed with elderly women with decades of meter experience- they set up, ranged, balanced and cleaned analog movements 8 hours a day. I have repaired many myself- but have also destroyed a few. It is quite a craft for those with delicate hands...

Regarding the intermittent, again I would certainly look elsewhere for the source, what you describe is not typical of a bad trimmer capacitor, replacing the lot does not sound feasible either....just my two cents. Tapping on the trimmer does not necessarily mean it is bad, it could be a bad connection or solder joint, including on the osc. coil, a coil winding, wire, component or switching connection specific to that band's circuitry etc. etc.

Let me know of your findings...

Todd
ka8gef

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