Stan
:Stan
pinched wire maybe...how do the coils look inside the can?
Neal
Have you checked the signal generator? Try setting your signal generator to 500 KC. See if you pick up a signal on a radio tuned to 1000 KC? Unlikely both IF's want to align at 380 KC even with a circuit problem.
Norm
::OK...here's another strange issue. Subject radio is Ward's Airline 15BR-1547A which was DOA. It has been recapped and resistors checked/replaced as needed. All voltages measure normally except the 12BE6 pin, which is showing -2.7v. The IF cans "want" to align at 380kc and I cannot "force" them to 455kc. Both cans appear to be original. This has got to be a drop-dead obvious problem, but I am just not seeing it. Help please. Thanks!
::Stan
:
:pinched wire maybe...how do the coils look inside the can?
:
:Neal
Neal
:Hi
:
: Have you checked the signal generator? Try setting your signal generator to 500 KC. See if you pick up a signal on a radio tuned to 1000 KC? Unlikely both IF's want to align at 380 KC even with a circuit problem.
:
:Norm
:
:
:
:::OK...here's another strange issue. Subject radio is Ward's Airline 15BR-1547A which was DOA. It has been recapped and resistors checked/replaced as needed. All voltages measure normally except the 12BE6 pin, which is showing -2.7v. The IF cans "want" to align at 380kc and I cannot "force" them to 455kc. Both cans appear to be original. This has got to be a drop-dead obvious problem, but I am just not seeing it. Help please. Thanks!
:::Stan
::
::pinched wire maybe...how do the coils look inside the can?
::
::Neal
:Hi
:
: Have you checked the signal generator? Try setting your signal generator to 500 KC. See if you pick up a signal on a radio tuned to 1000 KC? Unlikely both IF's want to align at 380 KC even with a circuit problem.
:
:Norm
:
:
:
:::OK...here's another strange issue. Subject radio is Ward's Airline 15BR-1547A which was DOA. It has been recapped and resistors checked/replaced as needed. All voltages measure normally except the 12BE6 pin, which is showing -2.7v. The IF cans "want" to align at 380kc and I cannot "force" them to 455kc. Both cans appear to be original. This has got to be a drop-dead obvious problem, but I am just not seeing it. Help please. Thanks!
:::Stan
::
::pinched wire maybe...how do the coils look inside the can?
::
::Neal
Do you have plate voltage?
No one has replaced the I.F.’s with a set of Stromberg Carlson’s, in its checkered past past…have they ? heh..heh…heh
73's de Edd
:which pin has -2.7v ?
:Do you have plate voltage?
:
:
::Stan
:
:pinched wire maybe...how do the coils look inside the can?
:
:Neal
:Have not pulled the cans yet in hopes problem would be more obvious since they both exhib the same behavior.
I think we all agree now. It isn't drop dead obvious, or maybe it is.
The IFs should align to 455 but align to 380, 455 being out of range. It seems like the IFs have too much capacitance, and you can't get it out to reach the proper higher frequency. Either that or the primary or secondary of the IF cans have grown loops, not too likely.
Looks like silver mica disease. Your radio is from 1951, when Silver Mica was at is zenith (pun intended).
The most common form of silver mica causes leakage between stages across the IF can through leaky silver mica capacitors. The less common type is leakage within the silver mica capacitor or bad connection to it. It does not cause any errors in voltage measurement but does detune the IFs. (I think the pin 1 of the 12BE6 reading is a red herring.)
If the capacitors on the IFs are on the schematic, tear down the detector IF and replace the silver mica wafer with capacitors of that value.
If the capacitors are not called out on the schematic, here is what to try. As above remove the IF closer to the detector and rebuild it, but only put insulating tape in place of the silver mica wafer. Install it back in the radio, and place 100 pF capacitors across the primary and secondary
As the guys said, you need to be sure your generator is really putting out 455 KHz. Inject the signal at the grid of the last IF stage. Add 33pF capacitors to primary and secondary until you get a signal you can peak on both primary and secondary.
You shouldn't need more than 4 of these on each side. The required total capacitance will be around 150pF.
Then try to peak the input IF without rebuilding it. I think your problem is in the detector side IF and that the input IF is OK.
IF cans most susceptable to silver mica disease have slug or inductor tuning. If your IFs are capacitor tuned (using screws) let us know we will scratch our heads a bit more.
Best Regards,
Bill Grimm
Hi Stan,
: I think we all agree now. It isn't drop dead obvious, or maybe it is.
: The IFs should align to 455 but align to 380, 455 being out of range. It seems like the IFs have too much capacitance, and you can't get it out to reach the proper higher frequency. Either that or the primary or secondary of the IF cans have grown loops, not too likely.
: Looks like silver mica disease. Your radio is from 1951, when Silver Mica was at is zenith (pun intended).
: The most common form of silver mica causes leakage between stages across the IF can through leaky silver mica capacitors. The less common type is leakage within the silver mica capacitor or bad connection to it. It does not cause any errors in voltage measurement but does detune the IFs. (I think the pin 1 of the 12BE6 reading is a red herring.)
:
: If the capacitors on the IFs are on the schematic, tear down the detector IF and replace the silver mica wafer with capacitors of that value.
: If the capacitors are not called out on the schematic, here is what to try. As above remove the IF closer to the detector and rebuild it, but only put insulating tape in place of the silver mica wafer. Install it back in the radio, and place 100 pF capacitors across the primary and secondary
: As the guys said, you need to be sure your generator is really putting out 455 KHz. Inject the signal at the grid of the last IF stage. Add 33pF capacitors to primary and secondary until you get a signal you can peak on both primary and secondary.
: You shouldn't need more than 4 of these on each side. The required total capacitance will be around 150pF.
: Then try to peak the input IF without rebuilding it. I think your problem is in the detector side IF and that the input IF is OK.
:
: IF cans most susceptable to silver mica disease have slug or inductor tuning. If your IFs are capacitor tuned (using screws) let us know we will scratch our heads a bit more.
:
:Best Regards,
:
:Bill Grimm
Best regards,
Stan
:Hi Stan,
: I think we all agree now. It isn't drop dead obvious, or maybe it is.
: The IFs should align to 455 but align to 380, 455 being out of range. It seems like the IFs have too much capacitance, and you can't get it out to reach the proper higher frequency. Either that or the primary or secondary of the IF cans have grown loops, not too likely.
: Looks like silver mica disease. Your radio is from 1951, when Silver Mica was at is zenith (pun intended).
: The most common form of silver mica causes leakage between stages across the IF can through leaky silver mica capacitors. The less common type is leakage within the silver mica capacitor or bad connection to it. It does not cause any errors in voltage measurement but does detune the IFs. (I think the pin 1 of the 12BE6 reading is a red herring.)
:
: If the capacitors on the IFs are on the schematic, tear down the detector IF and replace the silver mica wafer with capacitors of that value.
: If the capacitors are not called out on the schematic, here is what to try. As above remove the IF closer to the detector and rebuild it, but only put insulating tape in place of the silver mica wafer. Install it back in the radio, and place 100 pF capacitors across the primary and secondary
: As the guys said, you need to be sure your generator is really putting out 455 KHz. Inject the signal at the grid of the last IF stage. Add 33pF capacitors to primary and secondary until you get a signal you can peak on both primary and secondary.
: You shouldn't need more than 4 of these on each side. The required total capacitance will be around 150pF.
: Then try to peak the input IF without rebuilding it. I think your problem is in the detector side IF and that the input IF is OK.
:
: IF cans most susceptable to silver mica disease have slug or inductor tuning. If your IFs are capacitor tuned (using screws) let us know we will scratch our heads a bit more.
:
:Best Regards,
:
:Bill Grimm
Glad to hear the good news! Having spare IF cans is great when working on 1950's radios. It looks like you are all set.
Best Regards,
Bill
Yes your schematic shows "slug-tuned" IFs.. ecause the arrow is shown in the inductor and not in the capacitor on the schematic.
Did you replace the with the same slug-tuned types?
If so it may be just a matter of time b4 these go bad too.
You may want to practice repairing the old IF cans now.
:Great Stan:
:
:Yes your schematic shows "slug-tuned" IFs.. ecause the arrow is shown in the inductor and not in the capacitor on the schematic.
:
:Did you replace the with the same slug-tuned types?
:
:If so it may be just a matter of time b4 these go bad too.
:
:You may want to practice repairing the old IF cans now.
: