[Boatanchors] [National] National NC-100XAM? (long)

[Carl]

The RF amps should be 6K7's as the 6J7's are sharp cutoff and will destroy 
the AGC action. If you are into a bit of changes there are some better tubes 
for the RF and mixer without changing sockets.

Carl
KM1H


----- Original Message ----- 
From: "Bob Young" <youngbob53 at msn.com>
To: <national at mailman.qth.net>
Cc: <boatanchors at mailman.qth.net>
Sent: Sunday, May 24, 2009 12:22 AM
Subject: [National] National NC-100XAM? (long)



I just bought a NC-100XAM on ebay, at a pretty good price and very nice 
cosmetically and mechanically, I went and picked it up in the boatanchor 
hauler. I can find no info about this radio, Raymond S. Moore's 4th ed has 
it listed but no info anywhere even though I found a very comprehensive list 
of National Catacomb radios from AMfone under receivers.
The tag says NC-100XA but it also has another tag that says type: NC-100XAM, 
ser # 13, 8-8-40 and order # is blank. It was supposed to have been made for 
the Navy, it's black wrinkle and is a rack mount. It seems similar to the 
army NC-100ASD except for it's range: .54 to 30 Kc like most of them. It has 
the push pull switch (for the meter?) instead of a toggle switch, it's got 
binding posts for the antenna hookups. All tube sockets are porcelain and 
the tube compliment is:
V-101 6J7 (supposed to be 6K7?)
V-102 6J7
V-103 6J7
V-104 6K7
V-105 6K7
V-106 6FG8
V-107 6C8G
V-108 6J7
V-109 6F6
V-110 5Z3 (I think, no number but looks like one).
The seller powered it up but I assume didn't hook up a speaker and there was 
a BIG fuse in it. This back has E102: speaker out (500 ohms?) and E103 which 
I assume is for a field coil, (one of the pins comes from the power 
transformer then to the one of the rectifier tube pins, haven't traced the 
other one). I can't find a schematic for it. The chassis layout is also 
different than the regular NC-100XA's. It has 4 electrolytics, 4 mf 600 V 
cans. and the if transformers are laid out differently. The power 
transformer says NC-100F on it. My main question is do I need to hook up 
some kind of a choke or power resistor to E103 or can I power it up with 
just a 500-8 ohm transformer from the speaker output and leave nothing 
connected to E103? The string that moves the indicator needle is also 
broken.

Thanks,

Bob
KB1OKL

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