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48-482 DISTORTED SOUND
#1

I posted earlier about this radio on the AR forum. See https://antiqueradios.com/forums/viewtop...6&t=365314 

Circuit diagram for this radio is here: http://www.nostalgiaair.org/Resources/637/M0013637.htm

I have finished replacement of all the electrolytics, paper caps and out of spec resistors.

I did an AM alignment but did not touch FM.

I am getting AM and FM reception across the dial but the speaker output sounds somewhat distorted - not bad but not right. I would describe the sound as gravelly or slightly garbled. Also, it seems that the distortion worsens as the station is tuned in. At first I thought it was a bad speaker but substituting in two different known good speakers did not change the distortion.

My radio has a 7B6 tube in place of the 6SQ7G tube shown on the circuit diagram.

I substituted for the 6V6 and 7B6 tubes to see if there was any improvement but got no change.


I checked voltages at the locations where voltages were given on the circuit diagram. They are as follows.

Location      Voltage on circuit diagram    Measured voltage

                          Section 1

C102A                        200                               203
C102B                        187                               187
C102C                        250                               243
C103                          250                               243
C104                          250                               243
-C104                         -50                               -54
Junction R102          -1.3 or -13?                     -16
  &R103
Junction R103          -1.1 or -11?                     -1.2
  &R104  

                          Section 2

Plate 7B6, pin 2         132                               126 
Plate 6V6, pin 3         230                               216
Grid 6V6, pin 4          250                               242

                          Section 3

PL. FM1000, pin 4       200                               157
Gr. FM1000, pin 5        40                                  54

                          Section 4

Plate 7H7, pin 2          240                               235   1st IF
Grid 7H7, pin 3             75                               110     "
K, 7H7, pin 7               .8                                  .6      "
Plate 7B7, pin 3          240                               236
Grid 7B7, pin 3           100                               103
K 7B7, pin 7                  7                                 4.2
Plate 7H7, pin 2          225                               221  2nd IF
Grid 7H7, pin 3             95                                 88     "
K 7H7, pin 7                1.?                                1.4     "

                          Section 5

Plate 2, 7F8, pin 3       112                               134
Plate 1, 7F8, pin 6        90                                101
K2, 7F8, pin 4              4.5                                4.3
K1, 7F8, pin 5              1.5                                  .6
Plate 7W7, pin 2           90                                  86
Grid, 7W7, pin 3           55                                  35

I need some help on this and am looking for ideas.

Thanks, Bob


Messages In This Thread
48-482 DISTORTED SOUND - by rck46 - 10-08-2019, 10:07 PM
RE: 48-482 DISTORTED SOUND - by mikethedruid - 10-09-2019, 01:50 AM
RE: 48-482 DISTORTED SOUND - by Jake Blake - 10-09-2019, 08:01 AM
RE: 48-482 DISTORTED SOUND - by Bill Bacco - 10-09-2019, 11:50 AM



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