National Co., Inc. 686S Schematic

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Manufacturer:National Co., Inc.

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Page 1:


MODEL 6863

.5.0 :0.59. ::: :31...- .Umo .id 0.5. Emu

...0>m000u 0:0 mo 15:00 .ala :ami 0:.. new ...0.00: 039.03200 00005520 :01:3 50::
m:1..:...0>m0000 0:... :we 0...:0 ou 1... 00:92.: .9.: mm ...0: Zoo :asm .10:10:05 m::::0..

(C)John F. Rider

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HA GE i PAGE v2 -5

National HRC-7

To eliminate oscillator drift occurring dur-
ing stand-by periods, the following Changes
have been made. These changes allow the
h-f oscillator, bfo oscillator and output tubes
'to remain on all the time whether the B+
switch is turned on or off.

1. Move the B+ end of R24 from the
B+ tie-point to pin 6 of V9, 6,17.

2. Connect pin 6 of V9 to pin 5 of 51
using 8% inches of red wire.

3. Move red lead supplying pin 4 of Sl
from the cold terminal of bsw to the hot ter-

4. Move red lead running to tie-point located
on chassis between C31 and C37 from pin 4
of 51 to the cold terminal of bsw.

5. Change the value of R21 to 3500 ohms,

National 6865, 58553, SPUSSSS, 12865
The 68653 power unit is the same as the
6865 except that it is equipped with mount-
ing brackets. The SPU6865 is the same as
the 6865 except that it is designed for rack
unting, The 12865 is similar to the 6865
except that it is designed to operate from 12
ivolts d.c. The voltages available at the out-
put socket are 12 volts dc. and 165 volts at

The following capacitors have been added
to the 6865 and 12865 power units:
1. C203, 0.01 pf, 300 vdcw, added from the
junction of fuse F101 and switch 5101 to
' 2. C204, 0.0043 ,.f, 500 vticw, frprn the B+
terminal to ground.
1 3. C205, 0.0001 pf, 500 vdcw, across output
socketA from LZOl to A+.

RCA A~82, Ch. RCI-1094i A-SI, Ch.

The original carriage in all of the above
models used a pull-out handle on the top front,
the carriage now in use has a handle under the
lower front edge. The same plastic frame may
be used for all models, A plug button (sup-
plied with each plastic frame) is used to cover
a center hole which is unused on all models
except A-108.

Frame-Stock N0. 76161 is used as :i replace-
ment for frame Stock No. 75549 or 75571

Frame~5tock N0. 76162 is used as a replace-
ment for frame Stock No 75633 or 75684

The new type of pull-out handle (lower front)

is available as Stock No. 76125. If the original

pull-out handle (top front) is desired it will
be necessary to drill two holes in the frame.

The holes arc .20 H diameter and are located

.625" each side of the center line and_13/ "

down from the top.

In Models A-91 and A>>105 the color ot'wire
used in the connecting cable has been changed.
A black-white wire has been used as a sub-
stitute itliA the black wire (pin 1 to speaker)
and a brown-white wire has been used as a
substitute tnr the brown wire (pin 8 to
speaker). A brown wire goes from pin 2 to
the jewel lamp and a black wire goes from
pin 3 to the jewel lamp.

Ili Model AASZ a substitute speakeri
(stamped 92569-9B) has been used in some
instruments. lt requires a different speaker
cone than the one listed in the A-SZ Parts
List. Speaker 92569-913 uses Stock No. 75875
cone,I Speaker 92569-9W uses Stock No.

RCA Q10-3, Q10 Series, C11, lic-549C

Model Q10?? is identical to other sets of
the Q10 series with the exception of the
cabinet which is black and uses ivoi'y color

The output transformer mounting has been
revised to minimize thc possibility of break-
down, especially in tropical areas. The trans-
former ili later production sets is mounted
on insulation board which is, in turn, mounted
on the dial back plate support.

Capacitor C11, 0.047 pt, must be dressed
away from the metal chassis and in such posi-
tion that inserting the chassis into the case
will not change its position. The side of C11
which may short to chassis is the side which
connects directly to the selenium rectifier. If
this side contacts the chassis it will place the
chassis at power line potential.

The 2600chm, 6-watt resistor R13 now be-
ing used in Model BX57 is of improved design.
The original resistor was a ceramic type and
the type now being used is a flat armored type.
When the new type is used to replace the
original type, it is necessary to drill a .120"
diameter hole in the front apron of the chassis
to accommodate a self-tapping screw for
mounting purposes.

RCA C11. RC-lUSSC, 80-10651)

The value of capacitor C3 in these chassil
is 9.1-1138 Auf. C3 is located across oscillator
coil L2.

RCA Record Changers RP-l'lSA,

.I The record changers are thc same as the
RP-176 except for the following differences.
The pickup a'nd arm assembly for the RP-
176A is: Stock No, 72716, Arm, Pickup arm
complete, less pivot arm, crystal and cable.
The motorboard sub-assemblies, complete
with all welded and riveted parts, less detachv
able operating parts, are designated as stock
numbers 72717 and 70844, for RP-l78;\ and

RCA X551, Ch. RC-1089B: X552.

R4, the 3.3-megohm avc filter resistor preA
viotlsly connected to the junction of R12|
47,000 ohms, and the phono jack Ji, is now
connected to the junction of R12 and terminal
2 of the 2nd i-f transformer TZ.

RCA SVSU, Ch~ lic-618, RC-SIBA:

Under Alignment Procedure, Critical `Lead
Dress, the following additions should be mallet

17. The f-m oscillator coil should be
cemented to its support. Amphenol No. 912
cement is recommended for this purpose. If
it is necessary to loosen the coil, use Amphenol

18. Capacitor C41 should be waxed Or
cemented to the chassis apron, The f-m
response curves are shown in the accompany-

ons primes

If-m wrpomc mmm' for
Model: 81/90 and 8V91.

Ili Chassis RC-618 the value of R35 is 560
ohms; and R31, the 1-megohni resistor across
C4, is used only on early chassis.

Chassis RC-618A is the same as Chassis
RC-618 except for the following changes
which have been made. A hlament choke
coil 1.6 has been added from pin 2 of V8 to
pin Z of the 6AV6 a-f amplifier V5. A 0.005-
;otf ceramic capacitor has been added from
pin 3 of the 6AU6 driver V3 to ground. A
0.005-/1/ti ceramic capacitor has been added
from pin 5 of V7 to ground. A 100-ohm,
1/Z-Wfptt, tixrtl composition resistor R36 has'
been added from pin 4 of V 8 to pin 4 of V6.
Capacitor C11, 5 Milf, has been added in
parallel with C12, and C13 across taps D and
B of thc oscillator coil L4

RCA 8R71, 8R74, 8R75, Ch ITC-10507

times used between pin 7 of Sl Rear and the
phono outlet. R33, 1000 ohms, 17% watt, has
been added from F to G of the a-ni oscillator
coil. A 0.005-ptf capacitor, C10, has been
added from pin 3 of the 6AU6 driver, V3,`
to ground. Filament choke coil L6 has been
added from pin 3 oi V5 to pin 2 of V6. A
S-nptf capacitor, C11, has been added in paral-
lel across C12 and C13. A 0.00544( capacitor,
C44, has been added from pin 5 of tilhe V5

RCA 811541, C11. fic-10551.; BX542,

These instruments are almost identical to
the previous production of these instruments
which used Chassis RC-10651 and RC-1065K,

RCA SEYS, Ch. H5132

To aid in hum reduction in Record Changer
9EY3, resistor R8 and capacitor C4 have
been changed in value. R8 has been changed
from 470,000 ohms to 270,000 ohms. C4 has
been changed from 0.002 ,uf to 0.004716, 600

Regal 7151
Model 7151 is electrically the same as Model

Spartan 130, 132, 135, 1.39. Ch. 51110

Inability to procure type 12AV6 tubes in
production quantities for the above models
using radio chassis type 5A10 made it neccs-r
sarytto make the following production sub-
stitution. In the future, these models will use
a lZAT6 tube in the 2nd detector and avc
lcircuit in place ofthe original 12AV6 as showli
in the schematic diagram. As these tubes are
`interchangeable, a change in other components
of the circuit is not necessary.

?J'ohn F. Rider

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