United American Bosch Corp. 45-A Schematic

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Product Information:
Model:45-A
Manufacturer:United American Bosch Corp.

Schematics Content:

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Page 1:

BOSC PAGE 5~1
UNITED AMERICAN BOSCH CORP. S?h?m?1?
f_\ Color Code
' ' ELECTRICAL VALUE L J
$20,000 01172 l/:tlatt --- C-16 8 mfd. electrolytic
0 ohms 1 wa - --- C-1'7 8 mfd. electrol ic
7500 ohms 1/4 watt c-1 .05 - 2 ply c-1s .1 mfd. - 2 plyyt
2ooo ohms 1 4 "tt c-2 .25 - 2 ply c-19 .05 mm. _ 2 ply
1/2 meg. l 4 watt G-5 .002 - 4 ply C-20 .05 mfd. - 2 ply
40,000 ohms 1/4 watt C-4 .05 - 5 ply C-21 .5 mfd. 200 V. in can
50,000 ohms 1/4 watt C-5 .05 - 2 ply C-22 .5 mfd- 200 V. in can
1/2 meg. Volume Control C-6 .05 - Z5 ply C-25 .5 mfd. mica
1 l'llBg>> 1/4 IBCU 0-7 .0001 mfd. mica C-24 .001 mfd. nice
5,000 ohms 1/4 watt C-8 .0001 mfd. mica C 25 ---
l/4 meg. 1/4 watt C-9 .005 - 5 ply C-26 .0001 mica
1/2 meg. 1/4 watt c-10 .25 - 2 ply L-1 R.F. choke can
`/'\ 600 ohms 1/2 watt C-11 .005 - 4 ply L-2 Choke coil
v5,ooo ohms 1/4 "ze c-12 .cos _ 5 ply 1.5 R.F. choke C011
4,000 ohms 1 'att C-15 10 mfd. electrolytic L-4 R.F. Choke coil
--- S-14 .005 - 5 ply 'I'-1 Power Transformer
--- -15 .05 - 5 ply T-2 Choke coil
--- STANDARD WEE COLOR CODE T-5 Output TI'aI'1Ef0I'm9I'
Plate .... . ........ Blue R>>ll>>A. RESISTOR COLOR CODE
"B" plus ......... Red
Grid ...... ... Green
Screen .... ... Green and White E291 2.12 RQ
Cathode . .. .. . Black
A.v.c. Red acyeuow or White 0 - BI-ACK 0 - BLACK -0 - BLACK
"B" minus ........ Black and White 1 ? BROWN 1 ' BRWN 0 ' BROWN
Overhead grid .... Green rubber 5 ' 5; ' QERANGE 3830*
/_\ STANDARD vounm CONTROL WIRING g I ggm 5 2 GR?g" 000001 omg",
Arm Green 6 - BLUE 6 - BLUE 000000 - BLUE
Low side .. Black Z I gg" 3 I Egg"
High ..... ... Red and White 2: 'HITS 9 _ WHITE

Page 2:

PAGE 5-2 BOSCH
Alignment Data UNITED AMERICAN BOSCH CORP.
T2 - #105451 Power \\_//
R?F? Amp]-if \ Detector and Oscillator
'I'-1 #107122 Power Transformer
Power Pack Terminal Strip
1 #106450 vibrator
` O Q 4/ Power Pentode Output
Bla. J( d?.' Q 2nd Det. Avc A.F. Amplifier
IN % \>> o . . ? S @ :I Ls. Amplifier \,/
l?.\T=? - o #104580 _ and LP. coll
~ -.- ~- R #105111 Speaker
Output Transformer . D *_ '_
Oscillator Trim. Condenser ,` _/" o
Detector Trim. Condenser ,V ~
R.F. Trimmer Condenser /-1-" g 'HP ?
#49 Black lead -
R8 - #104605 Volume Control <=?"""?" field "nd "?1?? #51 Blue lead _ vols. cell
and Switch
_ #50 Green lead - field not "Al
A ADJUSTING AND AL IGNING INSTRUCTIONS
All of the adjustable condensers, commonly called trimmer condensers, are very acou->>
rately adjusted at the factory and will not need any further adjustments unless a coil
or I.F. transformer is changed, or the adjustments tampered with in the field. There-
fore, DO NOT attempt to change the setting of any of the trimmer condensers unless it
is definitely known that adjustment is necessary, and a test oscillator is available,
then proceed as follows:
1. Connect output meter across voice coil of speaker terminals #49 and #51 (Fig. #l).
2. Set test oscillator at 175 kilocycles (using .1 mfd. antenna condenser).
5. Connect test oscillator lead to grid of the first I. F. tube.
4. Adjust condenser on primary of second I. F. transformer on top of set to peak on
output meter.
5. Connect test oscillator lead to grid of first detector tube. *,'
6. Adjust condenser on primary of first I. F. transformer (under set) to eak.
7. Adjust condenser on secondary of first I.F. transformer to peak. (There are two
small holes on side of housing for adjustment #6 and #7.)
The above procedure lines up the I. F. stages properly and our attention can now be
turned to the oscillator and R. F. adjustments, which are made as follows:
. Set test-oscillator at 1500 kilocycles (using .1 xnfd. antenna condenser).
. Connect test-oscillator lead to grid of first detector.
5. Set gang condenser at 1500 kilocycles as follows:
(a) Open gang to fullest extent.
(b) Close slowly to thickness of approximately .O15">>
4. Peak oscillator trimmer on end of condenser gang.
5. Set test-oscillator at 1400 kilocycles.
. Connect test-oscillator to antenna lead (using .0002 mfd. antenna condenser).
. Peak other two condensers on gang.
8. Do not touch oscillator trimmer at 1400 kilocycles setting of gang. \_/
This set should now be fully aligned and normal sensitivity prevail.

Page 3:

B C PAGE 5-3
UNITED AMERICAN BOSCH CORP. g?9:inE_DEUR't*?-
TEST I NG
(Cl) SPEAKER: Check field supply with voltohmmeter at speaker reading between points
#49 and #50 (Fig. #1) on speaker terminals (5.8 volts or over). Unsolder blue lead
from speaker (#51) and test across terminals #49 and #51 for continuity of voice coil.
(Reading full scale ohmmeter.)
(e SECONDARY OUTPUT TRANSFORMER! After unsoldering blue lead from terminal (#51 Fig.
#1 , test with ohmmeter between blue lead and terminal #49 (full scale reading - ohm-
(I) CHASSIS: After checking the components listed above, test the voltages as they ap-
pear on voltage chart and Fig. #4. The resistance measurements as found in "Resistance
Chart" and Fig. #5. It any particular reading obtained is very different from the chart
reading, the trouble is located in the portion of the circuit associated with the points
at which this discrepancy occurs. Referring to circuit diagram and location drawings
(Figs. #1, #2, #5), each part making up the circuit may be ind vidually tested until t e
faulty part is specifically located.
RESISTORS CONTROL UNIT PARTS (45A)
Ohms Bod % P2 104986 Dial late
106579 Resistor s?x-Ip asse I 105090 Knob ?vo1ums control)
105247 7,500 Purple Green Red 104977 Knob (tuning)
105265 750 Purple Green Broln 105088 Frame assembly
101211 B00 Blue Black BPO!!! 106895 Flexible shaft (volume control)
105249 5,000 Green Black Red 106892 Flexible shaft (tuning)
105278 100,000 Brown Black Yellow 104892 Thumb screw - dial light assembly
105245 2,000 Red Black Red 104997 Dial scale
105246 1/2 meg. Green Black Yellow 105114 Set screw - flexible cable
105251 40,000 Yellow Black Orange 105151 Spring
105276 50,000 Green Black Url-H59 76592 Felt washer
105281 1 mag. Brown Black Green 105179 Stud - dial scale and bracket
105279 1/4 meg. Red Green U-P81139 105 Lock washer for thumb screw
105277 75,000 Purple Green Orange 104557 Screw - mounting
106551 4,000 Yellow Black Red 81009 Nut - mounting
104605 Volume control with switch 104592 Washer - mounting
62872 Lock washer - mounting
??"`DE'sERS 105958 mal nga: cable assembly
105500 Suppressor condenser for generator 1?68?9 Lamp
102495 Condenser .1 mfd. - 2 ply 00113
106586 condenser .os me _ 2 ply, short
106844 Variable condenser, complete 105452 R.F. Choke coil ?powar pack)
105852 Condenser .002 - 4 ply 105854 R.P. Choke coil power pack;
102495 Condenser .05 - 2 ply 104580 LF. Coil complete (chassis
102492 Condenser .05 - 5 ply 104583 R.F. Coil complete (chassis)
106917 Condenser assembly 104584 Antenna coil
106878 Electrolytic condenser 104585 Detector and oscillator coil complete
106855 Condenser and choke coil assembly 105451 Choke coil assembly
105455 Condenser for assembly 106855 106855 Condenser and choke coil assembly
105775 Condenser .001 mica 105824 Choke coil for condenser and choke
105568 Condenser .5 - 2 ply assembly
105000 Variable condenser
102497 Condenser .25 - 2 ply CABLE AND CABLE ASSEIBLIES
102492 Condenser .os - 5 ply
106417 Condenser .001 mica 108544 Dial light cable assembly
105659 Condenser .005 - 5 ply 105452 Antenna cable
105745 Condenser .005 - 4 ply 106545 Battery cable assembly
105741 Electrolytic condenser 10 mfd. 105160 Speaker cable
MAIN ASSEMBLIES ',l'Rl\NSFOR@lS
106856 Chassis and power pack assembly 105470 Output transformer
106891 Control unit for llodel 45A 107122 Pwgr tx-angfgg-mer

Page 4:

PAGE 5-4< BOSCH _
Chassis View UNITED AMERICAN BOSCH CORP.
Thetubes employed in this circuit are as follows:
1 type '77 radio frequency amplifier.
1 type '7'7 detector oscillator.
1 type 78 intermediate frequency amplifier. '
1 type 75 second detector, A.V.C. and audio amplifier.
1 type 41 output tube.
The antenna is coupled to the first stage by means of a transformer. The R.F. stage is
coupled to the oscillator by means of a transformer. Resistance coupling is employed
between the audio portion of the' type '75 tube and the output tube. The first I.F.
transformer is doubly tuned and the second LF. transformer has a tuned primary.
Automatic volume control is provided by utilizing the potential drop in the collector
circuit of the type 75 tube. The A.V.C. is made a part of the D.C. grid circuits of
the R.F. amplifier and the I.F. amplifier. The ihtermediate frequency employed is 175
An electro-dynamic speaker is used with this set. This speaker has a field resistance
of 4 ohms and s voice coil resistance of 5.9 ohms.
ANT
3_1 _ 100,000 Ohms #105278 R-15 - soo erm #101211
R - vsoo ohms #105247 _ _OS mm_ #102492
R7 - 50,000 ohms #105276 C-10 - .25 mfd. #102497
_ Figure #2

Page 5:

UNITED AMERICAN BOSCH CORP. Voltage
Resistance Chart
BUTTON VIEW
Figure #4
/"" vs 2nd net. Audio
41 Power Amplifier 8: AVC. 'YB IF Amplifier 77 Det. Oso. 77 RF Amplifier
5 - Plate 9 - Plate 15 - Plate 21 - Plate 2'7 - Plate f
4 - Screen 10 - Di Plate 16 - Screen 22, - Screen 28 - screen '
5 - Grid 11 - Di Plate 1'7 - Suppressor 25 - Suppressor 29 - Suppressor
6 - Cathode 12 - Cathode 18 - Cathode 24 - Cathode 50 - Cathode
VOHPAGE CHART V A
Voltages read from ground to following points with Weston lodel 564 Voltohmmeter (six
volt storage battery used).
lf' OSC- C0/L *5'?'L ANTI con. A/FCO/L
Figure #5 `
RESISTANCE CHART
Antenna Coil Output Transformer I. F. Coil
51 - 52 Primary - 22 ohms Primary - 400 ohms #35 - 56 Primary - 95 ohms
55 - 34 Secondary- 5 ohms #157 - 58 Secondary- 85 ohms
R. F. Coil Socket Readings to Ground 'B' Plus Terminal.
45 - 48 Primary - 'IO ohms 6 - 600 ohms #4 to ound about 100,000
46 ->> 47 Secondary- Full scale 12 - 5400 ohms ohms ??h0l8 kick of cond.
24 - 8000 ohms qischarge on contact).
30 - 750 ohms
Det. Osc. Coil "B" voltage 185 under set load (with 6 V.
,"` storage battery).
(?59 to pid cap 78) LF. Primary - '75 ohms Total drain cm car battery 4.5 amps
S 45 - #44) I.F. Secondary - 70 ohms Output 2.5 watts.
40-42) Oscillator Intermediate frequency 175 K.C.

Page 6:

B C PAGE 5-3
UNITED AMERICAN BOSCH CORP. g?9:inE_DEUR't*?-
TEST I NG
(Cl) SPEAKER: Check field supply with voltohmmeter at speaker reading between points
#49 and #50 (Fig. #1) on speaker terminals (5.8 volts or over). Unsolder blue lead
from speaker (#51) and test across terminals #49 and #51 for continuity of voice coil.
(Reading full scale ohmmeter.)
(e SECONDARY OUTPUT TRANSFORMER! After unsoldering blue lead from terminal (#51 Fig.
#1 , test with ohmmeter between blue lead and terminal #49 (full scale reading - ohm-
(I) CHASSIS: After checking the components listed above, test the voltages as they ap-
pear on voltage chart and Fig. #4. The resistance measurements as found in "Resistance
Chart" and Fig. #5. It any particular reading obtained is very different from the chart
reading, the trouble is located in the portion of the circuit associated with the points
at which this discrepancy occurs. Referring to circuit diagram and location drawings
(Figs. #1, #2, #5), each part making up the circuit may be ind vidually tested until t e
faulty part is specifically located.
RESISTORS CONTROL UNIT PARTS (45A)
Ohms Bod % P2 104986 Dial late
106579 Resistor s?x-Ip asse I 105090 Knob ?vo1ums control)
105247 7,500 Purple Green Red 104977 Knob (tuning)
105265 750 Purple Green Broln 105088 Frame assembly
101211 B00 Blue Black BPO!!! 106895 Flexible shaft (volume control)
105249 5,000 Green Black Red 106892 Flexible shaft (tuning)
105278 100,000 Brown Black Yellow 104892 Thumb screw - dial light assembly
105245 2,000 Red Black Red 104997 Dial scale
105246 1/2 meg. Green Black Yellow 105114 Set screw - flexible cable
105251 40,000 Yellow Black Orange 105151 Spring
105276 50,000 Green Black Url-H59 76592 Felt washer
105281 1 mag. Brown Black Green 105179 Stud - dial scale and bracket
105279 1/4 meg. Red Green U-P81139 105 Lock washer for thumb screw
105277 75,000 Purple Green Orange 104557 Screw - mounting
106551 4,000 Yellow Black Red 81009 Nut - mounting
104605 Volume control with switch 104592 Washer - mounting
62872 Lock washer - mounting
??"`DE'sERS 105958 mal nga: cable assembly
105500 Suppressor condenser for generator 1?68?9 Lamp
102495 Condenser .1 mfd. - 2 ply 00113
106586 condenser .os me _ 2 ply, short
106844 Variable condenser, complete 105452 R.F. Choke coil ?powar pack)
105852 Condenser .002 - 4 ply 105854 R.P. Choke coil power pack;
102495 Condenser .05 - 2 ply 104580 LF. Coil complete (chassis
102492 Condenser .05 - 5 ply 104583 R.F. Coil complete (chassis)
106917 Condenser assembly 104584 Antenna coil
106878 Electrolytic condenser 104585 Detector and oscillator coil complete
106855 Condenser and choke coil assembly 105451 Choke coil assembly
105455 Condenser for assembly 106855 106855 Condenser and choke coil assembly
105775 Condenser .001 mica 105824 Choke coil for condenser and choke
105568 Condenser .5 - 2 ply assembly
105000 Variable condenser
102497 Condenser .25 - 2 ply CABLE AND CABLE ASSEIBLIES
102492 Condenser .os - 5 ply
106417 Condenser .001 mica 108544 Dial light cable assembly
105659 Condenser .005 - 5 ply 105452 Antenna cable
105745 Condenser .005 - 4 ply 106545 Battery cable assembly
105741 Electrolytic condenser 10 mfd. 105160 Speaker cable
MAIN ASSEMBLIES ',l'Rl\NSFOR@lS
106856 Chassis and power pack assembly 105470 Output transformer
106891 Control unit for llodel 45A 107122 Pwgr tx-angfgg-mer

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