73's de Edd
Sir David . . . . .
Time to restart the thread before it doubles back up on us.
I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
Voltage referencing:
When you’ve seen one shopping center . . . you’ve seen the-mall. 
:
:
:
:
:
:
:
:
:
:
:
:
:Sir David . . . . .
:
:
: Time to restart the thread before it doubles back up on us.
:
:
:I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
:
:
:And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
:
:
:E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
:
:
:Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
:And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
:Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
:
:
: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
:
:
:( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
:
:
:Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
:
:
:Voltage referencing:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
: When you’ve seen one shopping center . . . you’ve seen the-mall.
:
:
:
:
:
:
:
:
:
:
Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
They are NPN, looking at flat side it's CBE.
C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
C3 - C4 replaced with 10uf 25V (10uf 10V)
BLACK BOX;
#7 AM position 0V (10v)
remeasured #2-#6 in FM position:
#2 9.8 Vdc (20)
#3 6.5 Vdc (12.2v)
#4 6 Vdc (11.4)
#5 5.8 Vdc (11.2)
#6 5.5 Vdc (11.2)
Don't have a clue why they are different than before.
AUDIO PORTIONS TRANS VOLTS:
Col Base Emit
Q7 9 (7.8) 9 (1.1) 8 (.5)
Q8 9.8 (20) 9 (7.8) 9 (7.4)
Q9 73 (72) 9 (7.4 8.5 (6.8)
Again, I measured very carefully--cannot account for the differences....
Have a good weekend...
::
::
::
::
::
::
::
::
::
::
::
::
::Sir David . . . . .
::
::
:: Time to restart the thread before it doubles back up on us.
::
::
::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
::
::
::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
::
::
::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
::
::
::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
::
::
:: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
::
::
::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
::
::
::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
::
::
::Voltage referencing:
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
:: When you’ve seen one shopping center . . . you’ve seen the-mall.
::
::
::
::
::
::
::
::
::
::
:
:Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
:They are NPN, looking at flat side it's CBE.
:
:C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
:
:Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
:
:C3 - C4 replaced with 10uf 25V (10uf 10V)
:
:BLACK BOX;
:#7 AM position 0V (10v)
:remeasured #2-#6 in FM position:
:#2 9.8 Vdc (20)
:#3 6.5 Vdc (12.2v)
:#4 6 Vdc (11.4)
:#5 5.8 Vdc (11.2)
:#6 5.5 Vdc (11.2)
:Don't have a clue why they are different than before.
:
:AUDIO PORTIONS TRANS VOLTS:
:
: Col Base Emit
:Q7 9 (7.8) 9 (1.1) 8 (.5)
:Q8 9.8 (20) 9 (7.8) 9 (7.4)
:Q9 73 (72) 9 (7.4 8.5 (6.8)
:
:Again, I measured very carefully--cannot account for the differences....
:
:Have a good weekend...
:
:COME BACK LITTLE SHEBA......
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::Sir David . . . . .
:::
:::
::: Time to restart the thread before it doubles back up on us.
:::
:::
:::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
:::
:::
:::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
:::
:::
:::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
:::
:::
:::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
:::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
:::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
:::
:::
::: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
:::
:::
:::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
:::
:::
:::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
:::
:::
:::Voltage referencing:
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
::: When you’ve seen one shopping center . . . you’ve seen the-mall.
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
::
::Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
::They are NPN, looking at flat side it's CBE.
::
::C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
::
::Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
::
::C3 - C4 replaced with 10uf 25V (10uf 10V)
::
::BLACK BOX;
::#7 AM position 0V (10v)
::remeasured #2-#6 in FM position:
::#2 9.8 Vdc (20)
::#3 6.5 Vdc (12.2v)
::#4 6 Vdc (11.4)
::#5 5.8 Vdc (11.2)
::#6 5.5 Vdc (11.2)
::Don't have a clue why they are different than before.
::
::AUDIO PORTIONS TRANS VOLTS:
::
:: Col Base Emit
::Q7 9 (7.8) 9 (1.1) 8 (.5)
::Q8 9.8 (20) 9 (7.8) 9 (7.4)
::Q9 73 (72) 9 (7.4 8.5 (6.8)
::
::Again, I measured very carefully--cannot account for the differences....
::
::Have a good weekend...
::
::COME BACK LITTLE SHEBA......
2-14-12
Do you think R55 could be the cause for the breakdown?
:
:
OK . .I have evaluating the transistor voltage readings and I am seeing the very most disparity in the audio related transistors.
Sir David . . . . .
"Have a good weekend... "
Been as busy lately,as a one pawed cat with the diarrhea . . . now continuing. . . . . but, didn't see Sheba around anywhere?
Clarification of :
C1 Elec cap...Actually found a new replacemet part of same values. 35V 470uf
To clarify if you meant that the replacement of the original cardboard tubular PCB mount was actually available in that initially exact same value of (135 ufd @ 150 VDC) . .as I am only running into 100 or 150 ufd values at a 150 WVDC . . . . or sometimes a 120 Ufd if being in Euro rated values.
Otherwise I would tend to be reading that 35V @ 470 (actually C2's) value as being that of C1.
(Excluding NO Q3 voltage, when being in AM mode.
Otherwise, probably due to the higher than normal base bias on the Q7 xstr and upsetting the series direct DC coupled string.
To give some further assist in seeing how much is at fault with the sets power suply levels, how's about now giving the DC voltage across EACH of the
individual R55-----R56-----R57----R58-----R59 voltage divider resistors in the power supply section.
Then go back and measure across R58 with the band switch in either of its FM positions and then place the unit in it AM mode
and see what the voltage across R58 is in that AM mode.
With those numbers I can then compute the present power division with in the power supply, to see what is going on.
Now in the past I think that I lost you on the "Black Box" designated voltage test points
Lets break it down again as there is one glaring situation of no ~8-10VDC on the base and emitter of Q3 transistor.
Note that the voltage comes in from one side of the R22 and R24 resistors at that "Black Box" #7 marker.
Also note, that the SAME "Black Box" #7 is being common to the one side of the R60 resistor
With the set unpowered, taking an ohmmeter reading between those two connections . . power supply area and AM Q3 transistor area . . . it should reveal the same order of a reading as shorting your test leads probes together.
If that is not the case, then inspect the PCB's foil path by dragging one probe along the interconnencting foil path for the possibility of a micro break in the PCB's foil, in getting those separate areas connected together.
Also, there is the possibility of an interconnecting WIRE having been used BETWEEN the two "7" areas, and the possibility of an open joint having occured, with the wire free floating within a solder blob.
Lastly, note that section of the S1 band switch in the power supply area and note that the rotor contact comes off from the right side of R58 resistor and then alternatively switches its connection to two contacts going to R59 to feed to the FM portion, or if switched into the third AM position, it connects to R60 and feeds power to the AM section.
Soooooo, go into power down mode and ohm out again, between that S1 portions rotor and its three switched to contacts.
Don't think that a shorted C51 would be a probability, with the low voltages involved.
Standing by for the info . . . .
73's de Edd
There are 3 kinds of people: Those who can count & those who can't.
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::Sir David . . . . .
::::
::::
:::: Time to restart the thread before it doubles back up on us.
::::
::::
::::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
::::
::::
::::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
::::
::::
::::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
::::
::::
::::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
::::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
::::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
::::
::::
:::: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
::::
::::
::::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
::::
::::
::::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
::::
::::
::::Voltage referencing:
::::
::::
::::
::::
::::
::::
::::
::::73's de Edd
::::
::::
::::
::::
:::: When you’ve seen one shopping center . . . you’ve seen the-mall.
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
:::
:::Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
:::They are NPN, looking at flat side it's CBE.
:::
:::C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
:::
:::Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
:::
:::C3 - C4 replaced with 10uf 25V (10uf 10V)
:::
:::BLACK BOX;
:::#7 AM position 0V (10v)
:::remeasured #2-#6 in FM position:
:::#2 9.8 Vdc (20)
:::#3 6.5 Vdc (12.2v)
:::#4 6 Vdc (11.4)
:::#5 5.8 Vdc (11.2)
:::#6 5.5 Vdc (11.2)
:::Don't have a clue why they are different than before.
:::
:::AUDIO PORTIONS TRANS VOLTS:
:::
::: Col Base Emit
:::Q7 9 (7.8) 9 (1.1) 8 (.5)
:::Q8 9.8 (20) 9 (7.8) 9 (7.4)
:::Q9 73 (72) 9 (7.4 8.5 (6.8)
:::
:::Again, I measured very carefully--cannot account for the differences....
:::
:::Have a good weekend...
:::
:::COME BACK LITTLE SHEBA......
:
:2-14-12
:Do you think R55 could be the cause for the breakdown?
::
::
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:Sir David . . . . .
:
:
:"Have a good weekend... "
:
:
:Been as busy lately,as a one pawed cat with the diarrhea . . . now continuing. . . . . but, didn't see Sheba around anywhere?
:
:
:Clarification of :
:
:
:
:C1 Elec cap...Actually found a new replacemet part of same values. 35V 470uf
:
:
:
:To clarify if you meant that the replacement of the original cardboard tubular PCB mount was actually available in that initially exact same value of (135 ufd @ 150 VDC) . .as I am only running into 100 or 150 ufd values at a 150 WVDC . . . . or sometimes a 120 Ufd if being in Euro rated values.
:
:
:Otherwise I would tend to be reading that 35V @ 470 (actually C2's) value as being that of C1.
:
:
:
:OK . .I have evaluating the transistor voltage readings and I am seeing the very most disparity in the audio related transistors.
:(Excluding NO Q3 voltage, when being in AM mode.
:
:
:Otherwise, probably due to the higher than normal base bias on the Q7 xstr and upsetting the series direct DC coupled string.
:
:
:To give some further assist in seeing how much is at fault with the sets power suply levels, how's about now giving the DC voltage across EACH of the
: individual R55-----R56-----R57----R58-----R59 voltage divider resistors in the power supply section.
:
:
:Then go back and measure across R58 with the band switch in either of its FM positions and then place the unit in it AM mode
: and see what the voltage across R58 is in that AM mode.
:
:
:With those numbers I can then compute the present power division with in the power supply, to see what is going on.
:
:
:Now in the past I think that I lost you on the "Black Box" designated voltage test points
:
:
:Lets break it down again as there is one glaring situation of no ~8-10VDC on the base and emitter of Q3 transistor.
:
:
:Note that the voltage comes in from one side of the R22 and R24 resistors at that "Black Box" #7 marker.
:Also note, that the SAME "Black Box" #7 is being common to the one side of the R60 resistor
:
:
:With the set unpowered, taking an ohmmeter reading between those two connections . . power supply area and AM Q3 transistor area . . . it should reveal the same order of a reading as shorting your test leads probes together.
:
:
:If that is not the case, then inspect the PCB's foil path by dragging one probe along the interconnencting foil path for the possibility of a micro break in the PCB's foil, in getting those separate areas connected together.
:
:
:Also, there is the possibility of an interconnecting WIRE having been used BETWEEN the two "7" areas, and the possibility of an open joint having occured, with the wire free floating within a solder blob.
:
:
:Lastly, note that section of the S1 band switch in the power supply area and note that the rotor contact comes off from the right side of R58 resistor and then alternatively switches its connection to two contacts going to R59 to feed to the FM portion, or if switched into the third AM position, it connects to R60 and feeds power to the AM section.
:
:
:Soooooo, go into power down mode and ohm out again, between that S1 portions rotor and its three switched to contacts.
:
:
:Don't think that a shorted C51 would be a probability, with the low voltages involved.
:
:
:Standing by for the info . . . .
:
:
:73's de Edd
:
:
:
:
: There are 3 kinds of people: Those who can count & those who can't.
:
:
:
:
:
:
:
:
:
:
:
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::Sir David . . . . .
:::::
:::::
::::: Time to restart the thread before it doubles back up on us.
:::::
:::::
:::::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
:::::
:::::
:::::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
:::::
:::::
:::::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
:::::
:::::
:::::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
:::::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
:::::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
:::::
:::::
::::: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
:::::
:::::
:::::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
:::::
:::::
:::::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
:::::
:::::
:::::Voltage referencing:
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::73's de Edd
:::::
:::::
:::::
:::::
::::: When you’ve seen one shopping center . . . you’ve seen the-mall.
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
::::
::::Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
::::They are NPN, looking at flat side it's CBE.
::::
::::C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
::::
::::Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
::::
::::C3 - C4 replaced with 10uf 25V (10uf 10V)
::::
::::BLACK BOX;
::::#7 AM position 0V (10v)
::::remeasured #2-#6 in FM position:
::::#2 9.8 Vdc (20)
::::#3 6.5 Vdc (12.2v)
::::#4 6 Vdc (11.4)
::::#5 5.8 Vdc (11.2)
::::#6 5.5 Vdc (11.2)
::::Don't have a clue why they are different than before.
::::
::::AUDIO PORTIONS TRANS VOLTS:
::::
:::: Col Base Emit
::::Q7 9 (7.8) 9 (1.1) 8 (.5)
::::Q8 9.8 (20) 9 (7.8) 9 (7.4)
::::Q9 73 (72) 9 (7.4 8.5 (6.8)
::::
::::Again, I measured very carefully--cannot account for the differences....
::::
::::Have a good weekend...
::::
::::COME BACK LITTLE SHEBA......
::
::2-14-12
::Do you think R55 could be the cause for the breakdown?
:::
:::Yea, on the C1, we have an electronic supply place here that never throws anything away--they had the original RCA replacement part in the box...
Getting DC volts of R55-R59 back to you before doing other:
R55 - 73.5v
R56 - 3.2v
R57 - .413v
R58 - .294
R59 - .308
R58 had .295 across in AM & FM.
::
::
:
:
::
::
::
::
::
::
::
::
::
::
::
::
::Sir David . . . . .
::
::
::"Have a good weekend... "
::
::
::Been as busy lately,as a one pawed cat with the diarrhea . . . now continuing. . . . . but, didn't see Sheba around anywhere?
::
::
::Clarification of :
::
::
::
::C1 Elec cap...Actually found a new replacemet part of same values. 35V 470uf
::
::
::
::To clarify if you meant that the replacement of the original cardboard tubular PCB mount was actually available in that initially exact same value of (135 ufd @ 150 VDC) . .as I am only running into 100 or 150 ufd values at a 150 WVDC . . . . or sometimes a 120 Ufd if being in Euro rated values.
::
::
::Otherwise I would tend to be reading that 35V @ 470 (actually C2's) value as being that of C1.
::
::
::
::OK . .I have evaluating the transistor voltage readings and I am seeing the very most disparity in the audio related transistors.
::(Excluding NO Q3 voltage, when being in AM mode.
::
::
::Otherwise, probably due to the higher than normal base bias on the Q7 xstr and upsetting the series direct DC coupled string.
::
::
::To give some further assist in seeing how much is at fault with the sets power suply levels, how's about now giving the DC voltage across EACH of the
:: individual R55-----R56-----R57----R58-----R59 voltage divider resistors in the power supply section.
::
::
::Then go back and measure across R58 with the band switch in either of its FM positions and then place the unit in it AM mode
:: and see what the voltage across R58 is in that AM mode.
::
::
::With those numbers I can then compute the present power division with in the power supply, to see what is going on.
::
::
::Now in the past I think that I lost you on the "Black Box" designated voltage test points
::
::
::Lets break it down again as there is one glaring situation of no ~8-10VDC on the base and emitter of Q3 transistor.
::
::
::Note that the voltage comes in from one side of the R22 and R24 resistors at that "Black Box" #7 marker.
::Also note, that the SAME "Black Box" #7 is being common to the one side of the R60 resistor
::
::
::With the set unpowered, taking an ohmmeter reading between those two connections . . power supply area and AM Q3 transistor area . . . it should reveal the same order of a reading as shorting your test leads probes together.
::
::
::If that is not the case, then inspect the PCB's foil path by dragging one probe along the interconnencting foil path for the possibility of a micro break in the PCB's foil, in getting those separate areas connected together.
::
::
::Also, there is the possibility of an interconnecting WIRE having been used BETWEEN the two "7" areas, and the possibility of an open joint having occured, with the wire free floating within a solder blob.
::
::
::Lastly, note that section of the S1 band switch in the power supply area and note that the rotor contact comes off from the right side of R58 resistor and then alternatively switches its connection to two contacts going to R59 to feed to the FM portion, or if switched into the third AM position, it connects to R60 and feeds power to the AM section.
::
::
::Soooooo, go into power down mode and ohm out again, between that S1 portions rotor and its three switched to contacts.
::
::
::Don't think that a shorted C51 would be a probability, with the low voltages involved.
::
::
::Standing by for the info . . . .
::
::
::73's de Edd
::
::
::
::
:: There are 3 kinds of people: Those who can count & those who can't.
::
::
::
::
::
::
::
::
::
::
::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::Sir David . . . . .
::::::
::::::
:::::: Time to restart the thread before it doubles back up on us.
::::::
::::::
::::::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
::::::
::::::
::::::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
::::::
::::::
::::::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
::::::
::::::
::::::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
::::::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
::::::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
::::::
::::::
:::::: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
::::::
::::::
::::::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
::::::
::::::
::::::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
::::::
::::::
::::::Voltage referencing:
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::73's de Edd
::::::
::::::
::::::
::::::
:::::: When you’ve seen one shopping center . . . you’ve seen the-mall.
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
:::::
:::::Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
:::::They are NPN, looking at flat side it's CBE.
:::::
:::::C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
:::::
:::::Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
:::::
:::::C3 - C4 replaced with 10uf 25V (10uf 10V)
:::::
:::::BLACK BOX;
:::::#7 AM position 0V (10v)
:::::remeasured #2-#6 in FM position:
:::::#2 9.8 Vdc (20)
:::::#3 6.5 Vdc (12.2v)
:::::#4 6 Vdc (11.4)
:::::#5 5.8 Vdc (11.2)
:::::#6 5.5 Vdc (11.2)
:::::Don't have a clue why they are different than before.
:::::
:::::AUDIO PORTIONS TRANS VOLTS:
:::::
::::: Col Base Emit
:::::Q7 9 (7.8) 9 (1.1) 8 (.5)
:::::Q8 9.8 (20) 9 (7.8) 9 (7.4)
:::::Q9 73 (72) 9 (7.4 8.5 (6.8)
:::::
:::::Again, I measured very carefully--cannot account for the differences....
:::::
:::::Have a good weekend...
:::::
:::::COME BACK LITTLE SHEBA......
:::
:::2-14-12
:::Do you think R55 could be the cause for the breakdown?
::::
::::Yea, on the C1, we have an electronic supply place here that never throws anything away--they had the original RCA replacement part in the box...
:
:Getting DC volts of R55-R59 back to you before doing other:
:R55 - 73.5v
:R56 - 3.2v
:R57 - .413v
:R58 - .294
:R59 - .308
:
:R58 had .295 across in AM & FM.
:::
:::
::
::
:
:
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::Sir David . . . . .
:::
:::
:::"Have a good weekend... "
:::
:::
:::Been as busy lately,as a one pawed cat with the diarrhea . . . now continuing. . . . . but, didn't see Sheba around anywhere?
:::
:::
:::Clarification of :
:::
:::
:::
:::C1 Elec cap...Actually found a new replacemet part of same values. 35V 470uf
:::
:::
:::
:::To clarify if you meant that the replacement of the original cardboard tubular PCB mount was actually available in that initially exact same value of (135 ufd @ 150 VDC) . .as I am only running into 100 or 150 ufd values at a 150 WVDC . . . . or sometimes a 120 Ufd if being in Euro rated values.
:::
:::
:::Otherwise I would tend to be reading that 35V @ 470 (actually C2's) value as being that of C1.
:::
:::
:::
:::OK . .I have evaluating the transistor voltage readings and I am seeing the very most disparity in the audio related transistors.
:::(Excluding NO Q3 voltage, when being in AM mode.
:::
:::
:::Otherwise, probably due to the higher than normal base bias on the Q7 xstr and upsetting the series direct DC coupled string.
:::
:::
:::To give some further assist in seeing how much is at fault with the sets power suply levels, how's about now giving the DC voltage across EACH of the
::: individual R55-----R56-----R57----R58-----R59 voltage divider resistors in the power supply section.
:::
:::
:::Then go back and measure across R58 with the band switch in either of its FM positions and then place the unit in it AM mode
::: and see what the voltage across R58 is in that AM mode.
:::
:::
:::With those numbers I can then compute the present power division with in the power supply, to see what is going on.
:::
:::
:::Now in the past I think that I lost you on the "Black Box" designated voltage test points
:::
:::
:::Lets break it down again as there is one glaring situation of no ~8-10VDC on the base and emitter of Q3 transistor.
:::
:::
:::Note that the voltage comes in from one side of the R22 and R24 resistors at that "Black Box" #7 marker.
:::Also note, that the SAME "Black Box" #7 is being common to the one side of the R60 resistor
:::
:::
:::With the set unpowered, taking an ohmmeter reading between those two connections . . power supply area and AM Q3 transistor area . . . it should reveal the same order of a reading as shorting your test leads probes together.
:::
:::
:::If that is not the case, then inspect the PCB's foil path by dragging one probe along the interconnencting foil path for the possibility of a micro break in the PCB's foil, in getting those separate areas connected together.
:::
:::
:::Also, there is the possibility of an interconnecting WIRE having been used BETWEEN the two "7" areas, and the possibility of an open joint having occured, with the wire free floating within a solder blob.
:::
:::
:::Lastly, note that section of the S1 band switch in the power supply area and note that the rotor contact comes off from the right side of R58 resistor and then alternatively switches its connection to two contacts going to R59 to feed to the FM portion, or if switched into the third AM position, it connects to R60 and feeds power to the AM section.
:::
:::
:::Soooooo, go into power down mode and ohm out again, between that S1 portions rotor and its three switched to contacts.
:::
:::
:::Don't think that a shorted C51 would be a probability, with the low voltages involved.
:::
:::
:::Standing by for the info . . . .
:::
:::
:::73's de Edd
:::
:::
:::
:::
::: There are 3 kinds of people: Those who can count & those who can't.
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::Sir David . . . . .
:::::::
:::::::
::::::: Time to restart the thread before it doubles back up on us.
:::::::
:::::::
:::::::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
:::::::
:::::::
:::::::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
:::::::
:::::::
:::::::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
:::::::
:::::::
:::::::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
:::::::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
:::::::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
:::::::
:::::::
::::::: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
:::::::
:::::::
:::::::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
:::::::
:::::::
:::::::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
:::::::
:::::::
:::::::Voltage referencing:
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::73's de Edd
:::::::
:::::::
:::::::
:::::::
::::::: When you’ve seen one shopping center . . . you’ve seen the-mall.
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
::::::
::::::Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
::::::They are NPN, looking at flat side it's CBE.
::::::
::::::C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
::::::
::::::Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
::::::
::::::C3 - C4 replaced with 10uf 25V (10uf 10V)
::::::
::::::BLACK BOX;
::::::#7 AM position 0V (10v)
::::::remeasured #2-#6 in FM position:
::::::#2 9.8 Vdc (20)
::::::#3 6.5 Vdc (12.2v)
::::::#4 6 Vdc (11.4)
::::::#5 5.8 Vdc (11.2)
::::::#6 5.5 Vdc (11.2)
::::::Don't have a clue why they are different than before.
::::::
::::::AUDIO PORTIONS TRANS VOLTS:
::::::
:::::: Col Base Emit
::::::Q7 9 (7.8) 9 (1.1) 8 (.5)
::::::Q8 9.8 (20) 9 (7.8) 9 (7.4)
::::::Q9 73 (72) 9 (7.4 8.5 (6.8)
::::::
::::::Again, I measured very carefully--cannot account for the differences....
::::::
::::::Have a good weekend...
::::::
::::::COME BACK LITTLE SHEBA......
::::
::::2-14-12
::::Do you think R55 could be the cause for the breakdown?
:::::
:::::Yea, on the C1, we have an electronic supply place here that never throws anything away--they had the original RCA replacement part in the box...
::
::Getting DC volts of R55-R59 back to you before doing other:
::R55 - 73.5v
::R56 - 3.2v
::R57 - .413v
::R58 - .294
::R59 - .308
::
::R58 had .295 across in AM & FM.
::::
::::RADIO IS PLAYING--Replaced R55 and Q7-Q8
MANY THANKS TO EDD & ALL WHO HELPED__U R THE GREATEST...DAVID
:::
:::
::
::
:
:
Sir David . . . . . Failure analysis:
|
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::Sir David . . . . .
::::
::::
::::"Have a good weekend... "
::::
::::
::::Been as busy lately,as a one pawed cat with the diarrhea . . . now continuing. . . . . but, didn't see Sheba around anywhere?
::::
::::
::::Clarification of :
::::
::::
::::
::::C1 Elec cap...Actually found a new replacemet part of same values. 35V 470uf
::::
::::
::::
::::To clarify if you meant that the replacement of the original cardboard tubular PCB mount was actually available in that initially exact same value of (135 ufd @ 150 VDC) . .as I am only running into 100 or 150 ufd values at a 150 WVDC . . . . or sometimes a 120 Ufd if being in Euro rated values.
::::
::::
::::Otherwise I would tend to be reading that 35V @ 470 (actually C2's) value as being that of C1.
::::
::::
::::
::::OK . .I have evaluating the transistor voltage readings and I am seeing the very most disparity in the audio related transistors.
::::(Excluding NO Q3 voltage, when being in AM mode.
::::
::::
::::Otherwise, probably due to the higher than normal base bias on the Q7 xstr and upsetting the series direct DC coupled string.
::::
::::
::::To give some further assist in seeing how much is at fault with the sets power suply levels, how's about now giving the DC voltage across EACH of the
:::: individual R55-----R56-----R57----R58-----R59 voltage divider resistors in the power supply section.
::::
::::
::::Then go back and measure across R58 with the band switch in either of its FM positions and then place the unit in it AM mode
:::: and see what the voltage across R58 is in that AM mode.
::::
::::
::::With those numbers I can then compute the present power division with in the power supply, to see what is going on.
::::
::::
::::Now in the past I think that I lost you on the "Black Box" designated voltage test points
::::
::::
::::Lets break it down again as there is one glaring situation of no ~8-10VDC on the base and emitter of Q3 transistor.
::::
::::
::::Note that the voltage comes in from one side of the R22 and R24 resistors at that "Black Box" #7 marker.
::::Also note, that the SAME "Black Box" #7 is being common to the one side of the R60 resistor
::::
::::
::::With the set unpowered, taking an ohmmeter reading between those two connections . . power supply area and AM Q3 transistor area . . . it should reveal the same order of a reading as shorting your test leads probes together.
::::
::::
::::If that is not the case, then inspect the PCB's foil path by dragging one probe along the interconnencting foil path for the possibility of a micro break in the PCB's foil, in getting those separate areas connected together.
::::
::::
::::Also, there is the possibility of an interconnecting WIRE having been used BETWEEN the two "7" areas, and the possibility of an open joint having occured, with the wire free floating within a solder blob.
::::
::::
::::Lastly, note that section of the S1 band switch in the power supply area and note that the rotor contact comes off from the right side of R58 resistor and then alternatively switches its connection to two contacts going to R59 to feed to the FM portion, or if switched into the third AM position, it connects to R60 and feeds power to the AM section.
::::
::::
::::Soooooo, go into power down mode and ohm out again, between that S1 portions rotor and its three switched to contacts.
::::
::::
::::Don't think that a shorted C51 would be a probability, with the low voltages involved.
::::
::::
::::Standing by for the info . . . .
::::
::::
::::73's de Edd
::::
::::
::::
::::
:::: There are 3 kinds of people: Those who can count & those who can't.
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::Sir David . . . . .
::::::::
::::::::
:::::::: Time to restart the thread before it doubles back up on us.
::::::::
::::::::
::::::::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
::::::::
::::::::
::::::::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
::::::::
::::::::
::::::::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
::::::::
::::::::
::::::::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
::::::::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
::::::::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
::::::::
::::::::
:::::::: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
::::::::
::::::::
::::::::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
::::::::
::::::::
::::::::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
::::::::
::::::::
::::::::Voltage referencing:
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::73's de Edd
::::::::
::::::::
::::::::
::::::::
:::::::: When you’ve seen one shopping center . . . you’ve seen the-mall.
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
:::::::
:::::::Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
:::::::They are NPN, looking at flat side it's CBE.
:::::::
:::::::C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
:::::::
:::::::Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
:::::::
:::::::C3 - C4 replaced with 10uf 25V (10uf 10V)
:::::::
:::::::BLACK BOX;
:::::::#7 AM position 0V (10v)
:::::::remeasured #2-#6 in FM position:
:::::::#2 9.8 Vdc (20)
:::::::#3 6.5 Vdc (12.2v)
:::::::#4 6 Vdc (11.4)
:::::::#5 5.8 Vdc (11.2)
:::::::#6 5.5 Vdc (11.2)
:::::::Don't have a clue why they are different than before.
:::::::
:::::::AUDIO PORTIONS TRANS VOLTS:
:::::::
::::::: Col Base Emit
:::::::Q7 9 (7.8) 9 (1.1) 8 (.5)
:::::::Q8 9.8 (20) 9 (7.8) 9 (7.4)
:::::::Q9 73 (72) 9 (7.4 8.5 (6.8)
:::::::
:::::::Again, I measured very carefully--cannot account for the differences....
:::::::
:::::::Have a good weekend...
:::::::
:::::::COME BACK LITTLE SHEBA......
:::::
:::::2-14-12
:::::Do you think R55 could be the cause for the breakdown?
::::::
::::::Yea, on the C1, we have an electronic supply place here that never throws anything away--they had the original RCA replacement part in the box...
:::
:::Getting DC volts of R55-R59 back to you before doing other:
:::R55 - 73.5v
:::R56 - 3.2v
:::R57 - .413v
:::R58 - .294
:::R59 - .308
:::
:::R58 had .295 across in AM & FM.
:::::
:::::RADIO IS PLAYING--Replaced R55 and Q7-Q8
:MANY THANKS TO EDD & ALL WHO HELPED__U R THE GREATEST...DAVID
::::
::::
:::
:::
::
::
:
:
:
: : : : : : : : : : : : :Sir David . . . . . :Con-gran-u-lations on going ahead and taking those derived numbers and running with them. : : :That glaring high level across R55 just really made that aspect stand out. And I would expect you being able to take the sets ORIGINAL Q7 and Q8 and be flying with them also. : : : : : : :Failure analysis: : : :In this situation one would see the initial filtering of the powers supply initially starting in the C1 135 ufd 150 ufd cardboard dry electrolytic can. : : :The Q9 audio output is using right up at a tube level threshold of B+ supply level, while the bulk of the set is using the common solid state voltage supply levels of :20-12 and 9 Vdc supply levels. : : :That accounts for your quite high resistance value of required R55, in order to divide the supply on down to those lower levels. : : :The initially rectified B+ is initially dependent upon that C1 filter to convert the supply to the purity of DC to be ripple free enough so as not to present an aural detection within the sets AF audio background. : : :The same hold true for that C2, which does the same thing for the lower level transistor supply voltages. : : :Now it seems that within my findings thru the decades-decades-decades-decades-decades-decades-decades, I seem to find it being, that higher voltage rated dry electrolytics just don't seem to hold up as well as our solid state lower voltage rated types. : : :I can go back to the threshold of transistors initial introductions in the mid fifties and test their circuitrys companion lower voltage dry electrolytic caps and find a failure mode by either low capacitance or Hi ESR to be a rarity. : : :I tend to find the repetetive failure of MOST attributable to a CERTAIN manufacturers run or types of caps and their manner of construction, mainly associated with their seal method and purity of materiel and internal CONNECTIVITY procedure. : : :What I can see happening on your unit was the high probability of C1 either gra a a a a dually loosing its capacitance or possibly quite rapidly. :When the unit was operating normally, there was a moderately hefty ripple current being carried to ground . . . . . what with 135 ufd of capacitance. . . . . and also over in the C2 area, the same was true for the lower voltage derivation area. : : :That left a moderately balanced ripple current being dissipated by both C1 and C2. As the capacitance declined on C1 the ripple curent increased on C2 and in THAT path, it was dependent upon flowing thru R55. : : :As the R55 power dissipation hit its "critical" threshold,its wire wound resistive element opened. : : :The Sams photo reveals it to be a axial leaded, vertically mounted, rectangular ceramic block housed wire wound type of construction of a 3-5 W rating. : : :On common AC-DC tube sets, I tend to find this voltage dropping/filter resistor betwen the 1st and 2nd filter capacitor and is usually going to be either a 1-2 watt common carbon composition resistor. : : :Now when you find that 1st filter capacitance dropping off, there is progressively more ripple current passing to the 2nd filter cap and that intermediate resistor starts taking on more dissipation . . . . . ergo, your sometimes wondering . . . . . why is / has that resistor overheating / scorched ? : : : : : : :73's de Edd : : : : :The brain is a wonderful organ; it starts working the moment you get up in the morning and doesn't stop until you get to work. : : : : : : : |
:
:
:
:
:
:
:
:
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::Sir David . . . . .
:::::
:::::
:::::"Have a good weekend... "
:::::
:::::
:::::Been as busy lately,as a one pawed cat with the diarrhea . . . now continuing. . . . . but, didn't see Sheba around anywhere?
:::::
:::::
:::::Clarification of :
:::::
:::::
:::::
:::::C1 Elec cap...Actually found a new replacemet part of same values. 35V 470uf
:::::
:::::
:::::
:::::To clarify if you meant that the replacement of the original cardboard tubular PCB mount was actually available in that initially exact same value of (135 ufd @ 150 VDC) . .as I am only running into 100 or 150 ufd values at a 150 WVDC . . . . or sometimes a 120 Ufd if being in Euro rated values.
:::::
:::::
:::::Otherwise I would tend to be reading that 35V @ 470 (actually C2's) value as being that of C1.
:::::
:::::
:::::
:::::OK . .I have evaluating the transistor voltage readings and I am seeing the very most disparity in the audio related transistors.
:::::(Excluding NO Q3 voltage, when being in AM mode.
:::::
:::::
:::::Otherwise, probably due to the higher than normal base bias on the Q7 xstr and upsetting the series direct DC coupled string.
:::::
:::::
:::::To give some further assist in seeing how much is at fault with the sets power suply levels, how's about now giving the DC voltage across EACH of the
::::: individual R55-----R56-----R57----R58-----R59 voltage divider resistors in the power supply section.
:::::
:::::
:::::Then go back and measure across R58 with the band switch in either of its FM positions and then place the unit in it AM mode
::::: and see what the voltage across R58 is in that AM mode.
:::::
:::::
:::::With those numbers I can then compute the present power division with in the power supply, to see what is going on.
:::::
:::::
:::::Now in the past I think that I lost you on the "Black Box" designated voltage test points
:::::
:::::
:::::Lets break it down again as there is one glaring situation of no ~8-10VDC on the base and emitter of Q3 transistor.
:::::
:::::
:::::Note that the voltage comes in from one side of the R22 and R24 resistors at that "Black Box" #7 marker.
:::::Also note, that the SAME "Black Box" #7 is being common to the one side of the R60 resistor
:::::
:::::
:::::With the set unpowered, taking an ohmmeter reading between those two connections . . power supply area and AM Q3 transistor area . . . it should reveal the same order of a reading as shorting your test leads probes together.
:::::
:::::
:::::If that is not the case, then inspect the PCB's foil path by dragging one probe along the interconnencting foil path for the possibility of a micro break in the PCB's foil, in getting those separate areas connected together.
:::::
:::::
:::::Also, there is the possibility of an interconnecting WIRE having been used BETWEEN the two "7" areas, and the possibility of an open joint having occured, with the wire free floating within a solder blob.
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:::::Lastly, note that section of the S1 band switch in the power supply area and note that the rotor contact comes off from the right side of R58 resistor and then alternatively switches its connection to two contacts going to R59 to feed to the FM portion, or if switched into the third AM position, it connects to R60 and feeds power to the AM section.
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:::::Soooooo, go into power down mode and ohm out again, between that S1 portions rotor and its three switched to contacts.
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:::::Don't think that a shorted C51 would be a probability, with the low voltages involved.
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:::::Standing by for the info . . . .
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:::::73's de Edd
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::::: There are 3 kinds of people: Those who can count & those who can't.
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:::::::::Sir David . . . . .
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::::::::: Time to restart the thread before it doubles back up on us.
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:::::::::I carried forward and accumulated all of your supplied voltage readings, starting with the AUDIO section transistors and then the power supply's divisions test point.
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:::::::::And then you threw in that series of all of the units other transistors, now, before we proceed, confirm the accuracy of your readings, as you might have misread the Q7 and Q8 devices, note the great disparity of the voltages given versus, the voltages given in Sams schema references as per the ( ).
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:::::::::E.G. is your negative metering lead ground reference being made to ground . . .the neg lead of C1 filter cap would be fine .
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:::::::::Assuming that you pulled that C1 electrolytic capacitor of 135 ufd and replaced it . . . . with what new capacitance value ?
:::::::::And it is a tubular electrolytic lined up vertically. Also, what value was used for C2.
:::::::::Also back when you gave the DC voltage reading for Q8 collector, you gave (?), but I saw that the C2 filter supplied that voltage and was the same as test block #2, with it being an ~18.8 volts.
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::::::::: Also on Q7 note that its emitter is being placed at the top of the xstr symbol, where one typically sees the collector being positioned.
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:::::::::( Invariably, this was merely done to make a better drawing " line flow path" into the interconnected Q8 base connection . . . .but you might not have caught it).
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:::::::::Will you please confirm for me again if there is actually " 0 " voltage on all of the CBE elements of the Q3 oscillator transistor, if the band switch is put into AM reception mode ?
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:::::::::Voltage referencing:
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:::::::::73's de Edd
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::::::::: When you’ve seen one shopping center . . . you’ve seen the-mall.
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::::::::Q7 - Q8 Replace with 2N3904 the tech gave me at the electronics supply store.
::::::::They are NPN, looking at flat side it's CBE.
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::::::::C1 Elec cap...Actually found a new replacement part of same values. 35V 470uf
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::::::::Q3 looks original--has insulator on E. Measures "0" all legs in AM mode.
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::::::::C3 - C4 replaced with 10uf 25V (10uf 10V)
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::::::::BLACK BOX;
::::::::#7 AM position 0V (10v)
::::::::remeasured #2-#6 in FM position:
::::::::#2 9.8 Vdc (20)
::::::::#3 6.5 Vdc (12.2v)
::::::::#4 6 Vdc (11.4)
::::::::#5 5.8 Vdc (11.2)
::::::::#6 5.5 Vdc (11.2)
::::::::Don't have a clue why they are different than before.
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::::::::AUDIO PORTIONS TRANS VOLTS:
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:::::::: Col Base Emit
::::::::Q7 9 (7.8) 9 (1.1) 8 (.5)
::::::::Q8 9.8 (20) 9 (7.8) 9 (7.4)
::::::::Q9 73 (72) 9 (7.4 8.5 (6.8)
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::::::::Again, I measured very carefully--cannot account for the differences....
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::::::::Have a good weekend...
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::::::::COME BACK LITTLE SHEBA......
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::::::2-14-12
::::::Do you think R55 could be the cause for the breakdown?
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:::::::Yea, on the C1, we have an electronic supply place here that never throws anything away--they had the original RCA replacement part in the box...
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::::Getting DC volts of R55-R59 back to you before doing other:
::::R55 - 73.5v
::::R56 - 3.2v
::::R57 - .413v
::::R58 - .294
::::R59 - .308
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::::R58 had .295 across in AM & FM.
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::::::RADIO IS PLAYING--Replaced R55 and Q7-Q8
::MANY THANKS TO EDD & ALL WHO HELPED__U R THE GREATEST...DAVID
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:::::MANY THANKS, Edd for the huge amount of time you gave to helping me figure this--y'all sure know your stuff!!!
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