07-07-2015, 10:27 PM
Hello,
This is my first post after lurking for a bit. I am relatively new to all of this radio business, having recapped 1 Admiral 5X12N successfully so far, and having limited success on a Motorola 57CC1, a Philco F-809, and a Crosley 58TA.
I have now picked up a 46-1209 code 121. After getting a copy of the Sams Photofact and ordering caps and resistors I took time to get somewhat familiar with what I was looking at underneath the chassis.
The AM section worked although it had some loud hum, and was very weak volume-wise, no audible signal of the shortwave, and the phono works as expected. I started recapping and checking resistors as I worked through the chassis and quickly realized even though it was a large chassis, that things were still very tightly packed. (I have tried up until this point to replace the entire component, but found it necessary to clip leads on a few and wrap new leads to them hoping to prevent damage from the soldering iron.)
So far, I have replaced all three electrolytics, all paper caps but 1 which is buried underneath the band switch wafers, and a large majority of the resistors. My first power up after replacing these was a success in that nothing burned up, but I had no sound from the AM band at all and saw that the plates in the 7X7 tube were glowing so I shut everything down.
Back to the bench. I started tracing all of the components I had replaced until this point (lesson learned: check work periodically) and found that I had swapped two resistors accidentally on the 6V6, the 2nd IF Plate Decoupling resistor (1000 ohm) and one of the output grid resistors (330K ohm), and used the wrong value on the other output grid resistor. I corrected these and closely inspected my other work and did not find anything standing out.
Second time powering up was much better. I am finally able to detect signals, but still without much volume and a tiny bit of distortion. I have the volume turned all the way up and most stations are still barely at a conversation level and it seems to only pick up very local stations but at the right location on the dial. The plate glow is still present on the 7X7 but it much less intense than before. With what little knowledge I have at this point, I suspect that the micamold caps on this chassis might not all be mica caps but the mica-looking paper caps. On the 7X7 tube there is only one component I have not replaced and that is the 100 pF Audio Plate bypass, and that looks suspiciously like a paper/mica cap. Would this cap, if it was leaky, cause these symptoms of little volume except on very close by stations, some distortion and cause the plate to glow? The phono plays great with no volume problems. I have no capacitor checker at this point, and not sure how to secure the chassis given it's size to safely check voltages.
Also, how do I get to the capacitor underneath the band switch to replace it? The switch looks to be riveted to the chassis.
Chase
This is my first post after lurking for a bit. I am relatively new to all of this radio business, having recapped 1 Admiral 5X12N successfully so far, and having limited success on a Motorola 57CC1, a Philco F-809, and a Crosley 58TA.
I have now picked up a 46-1209 code 121. After getting a copy of the Sams Photofact and ordering caps and resistors I took time to get somewhat familiar with what I was looking at underneath the chassis.
The AM section worked although it had some loud hum, and was very weak volume-wise, no audible signal of the shortwave, and the phono works as expected. I started recapping and checking resistors as I worked through the chassis and quickly realized even though it was a large chassis, that things were still very tightly packed. (I have tried up until this point to replace the entire component, but found it necessary to clip leads on a few and wrap new leads to them hoping to prevent damage from the soldering iron.)
So far, I have replaced all three electrolytics, all paper caps but 1 which is buried underneath the band switch wafers, and a large majority of the resistors. My first power up after replacing these was a success in that nothing burned up, but I had no sound from the AM band at all and saw that the plates in the 7X7 tube were glowing so I shut everything down.
Back to the bench. I started tracing all of the components I had replaced until this point (lesson learned: check work periodically) and found that I had swapped two resistors accidentally on the 6V6, the 2nd IF Plate Decoupling resistor (1000 ohm) and one of the output grid resistors (330K ohm), and used the wrong value on the other output grid resistor. I corrected these and closely inspected my other work and did not find anything standing out.
Second time powering up was much better. I am finally able to detect signals, but still without much volume and a tiny bit of distortion. I have the volume turned all the way up and most stations are still barely at a conversation level and it seems to only pick up very local stations but at the right location on the dial. The plate glow is still present on the 7X7 but it much less intense than before. With what little knowledge I have at this point, I suspect that the micamold caps on this chassis might not all be mica caps but the mica-looking paper caps. On the 7X7 tube there is only one component I have not replaced and that is the 100 pF Audio Plate bypass, and that looks suspiciously like a paper/mica cap. Would this cap, if it was leaky, cause these symptoms of little volume except on very close by stations, some distortion and cause the plate to glow? The phono plays great with no volume problems. I have no capacitor checker at this point, and not sure how to secure the chassis given it's size to safely check voltages.
Also, how do I get to the capacitor underneath the band switch to replace it? The switch looks to be riveted to the chassis.
Chase
