The AM Forum

Two out of three are done.  The third one is likely just going to be a parts rig due to the condition of the chassis, melted wires, etc.  Mainly the ugly condition of the chassis.  Thank goodness the transformer was good in it since #2 had a bad one.  This one (#2) now works as good as it looks...

By the way; the only mod I did on this was the coupling cap from the 1st audio to the 6V6 output.  It calls for a .001, but these sound way too pinched with that, so I put a .01 in there for now.  Can't believe how the audio opened up on both of them.  May need to back off just a little on coupling, but I'm still in the evaluation mode.  Bass on these little rigs is very nice, and fidelity with it hooked to one of my Cerwin Vega speakers is super.

Good job!  If everyone saved them that way there would be no room for complaint.

73DG

Beautiful. Mine does not have a copper chassis. Do all three of yours have copper?

Hey der Brian!..been awhile since we had a "Q"..hope things are well for ya..nice restoration and because I own two of those now I thought I would add some notes on NC-125s in general..by the way very interesting on the coupling cap and more so since I subbed in a lower value resistor for R47 in my 1st one and found a slightly higher audio output and was just about to experiment with other values and would have to remove that cap to do any resoldering..hmnn interesting..here's the differences between production runs..my "older" NC-125 with SN# 286-0353 DOES have a copper chassis..newer one does not but it DOES have the front interior panel made of copper..older one sports a 0D3 instead of the 0A2..the pwr tranny is a Stancor with horiz plates instead of vert plates..no CWO above pitch control..the phono/nfm jacks are reversed and stamped in the metal..send/rcv switch is the opposite/reversed..and the S mtr has that National "fade to rusty orange" syndrome on the interior..the "newer" one has a much improved black background which you can actually read..the "newer" one is SN# 348-0559..when I picked up the older of the two someone had subbed in a 6SA7 for the 6SB7..not the best idea as it threw the calibration off quite a bit and deafened band A a lot..you can do that in a pinch but be aware of the outcome..a new 6SB7 was installed and all is OK now..speaking of tubes I did sub in a lot of different tubes for the 6V6 but found only the 6L6 the best of the lot..put back the 6V6..had to "match" the rather odd blue/gray/green paint on the matching spkr by going to the local auto parts store and picking a Volvo color which was 99% a match..that's the tuff part so far.
Allright now dat's a "ol' buzzard" reply but I got a question for ya....does urs "roll over" into bass land at the far end of clockwise rotation of the boost control?..somehow I "fixed" this on the older one by changing C-26 but it's buttoned up now and I don't remember what I used..anyhoo that Select-o-ject feature IMHO makes it into a neato BoomBox with bass to spare..I picked the National because of its looks and compatibility to the DX-40/VF-1 overall        c ya 73 de DAVE

Thanks!  Yes, all three of these do have the copper plated chassis, but one is in terrible shape.

Dave, good to hear from you.  We just got home from a small trip.  Let me read over your post/questions after I get settled and will get back with you.  Thanks man...

Amen Dennis!  Thanks..

Dennis,

If the serial number are in order chronologically, the oldest of these three is #358-0970, and the newest is 387-0862.  The S-Meters on all three of these are similar to the HRO-60/50, 183D, NC-98 and others as far as the black back ground.  My HRO-7 and NC2-40D do not have that black as you described.  One thing I have done with those old amber colored meters (they were actually a yellow color before they went amber) is to use a blue LED as a backlight, as the blue tends to cancel the amber color, and make them appear more like they were intended to.  It "cools" the color temperature to the point they look more bright yellow instead of dark amber.

The built in Select-o-ject is sort of a gimmick to me.  First, it greatly attenuates the audio output, and I guess that's my biggest complaint with that.  Yes, the far clockwise position selects about 80 cycles as a peak if I remember correctly.  Increasing the Boost at any point to much will cause the thing to go into oscillation at the selected setting of the Freq control.  It's sort of like a single band parametric EQ, but like I said, it greatly attenuates the total output.  My mod of just a larger coupling cap to the grid of the 6V6 gives a lot of bottom end compared to the .001 they call for.  A .01 may actually be just a bit much, but I still need to soak in the sound a little more before I determine that for sure.  Maybe a .005 or some combo between that and .01 would brighten it up a little.

Overall I'm pleased with the 125's, but they can not compare to the HRO-50 or 60 in real communication performance, but no one should expect that!  I can't say if I will keep one of these or pass them on to someone else.  It is a real bang for the bucks.