02-09-2011, 05:00 PM
"I guess the moral of this story is where possible never change more than one cap at a time, and keep checking the radion reception after each change."
You have that right
It's amost always possible to use the change/test method. The only way it would not be practical is if the caps were in a module that you had to disassemble or unwire a section to get to the caps ( 3 or 4 behind Philco pushbutton mechanisms.)
We have all seen guys take a working radio then 'shotgun' all the caps (sometimes resistors too) then have a non-working set. Now, where do we start looking for the trouble? The whole set, that's where. You'd have to trace every connection made, and verify it was all correct according to the schematic. In effect they have created more work than necessary. Lesson learned.
Change the filters first, test. Then one or two caps at a time, test again. As you can see, troubleshooting is easier when you know what cap you just installed. Miswire, or wrong value you know where to look.
Just a quick thought about not receiving below 700. Hope this is the issue. Check for shorting tuning cap plates. You may see one or more plates bent creating a short when you hit 700 on the dial. Static, then no reception sounds like that's what happening. Turn the radio on, bring the tuning just to where the set stops receiving. Tune back and forth a bit. I'll bet it's static just before it stops. Leave the tuning cap in that position
Next, get in there with a good light and magnifier, then look straight down through the plates and see if you can see two touching. It might be touching ever so gently, but it will short out.
If you find a spot that you suspect, you can take a cut piece from a business card , slip it into the gap and see if the reception comes back. Once you find the spot, you can tune out the plates, and make a TINY correction to the plate.
I have seen some plates that have tiny 'hairs' from the aluminum on them and sometimes that shorts out. In that case, running a strip of business card down each will help clear them. But try the other test first.
If you do have shorting plates and still can't find them, there are other ways to deal with it, we will talk about later.
Hope this is all it is, let us know.
You have that right
It's amost always possible to use the change/test method. The only way it would not be practical is if the caps were in a module that you had to disassemble or unwire a section to get to the caps ( 3 or 4 behind Philco pushbutton mechanisms.)We have all seen guys take a working radio then 'shotgun' all the caps (sometimes resistors too) then have a non-working set. Now, where do we start looking for the trouble? The whole set, that's where. You'd have to trace every connection made, and verify it was all correct according to the schematic. In effect they have created more work than necessary. Lesson learned.
Change the filters first, test. Then one or two caps at a time, test again. As you can see, troubleshooting is easier when you know what cap you just installed. Miswire, or wrong value you know where to look.
Just a quick thought about not receiving below 700. Hope this is the issue. Check for shorting tuning cap plates. You may see one or more plates bent creating a short when you hit 700 on the dial. Static, then no reception sounds like that's what happening. Turn the radio on, bring the tuning just to where the set stops receiving. Tune back and forth a bit. I'll bet it's static just before it stops. Leave the tuning cap in that position
Next, get in there with a good light and magnifier, then look straight down through the plates and see if you can see two touching. It might be touching ever so gently, but it will short out.
If you find a spot that you suspect, you can take a cut piece from a business card , slip it into the gap and see if the reception comes back. Once you find the spot, you can tune out the plates, and make a TINY correction to the plate.
I have seen some plates that have tiny 'hairs' from the aluminum on them and sometimes that shorts out. In that case, running a strip of business card down each will help clear them. But try the other test first.
If you do have shorting plates and still can't find them, there are other ways to deal with it, we will talk about later.
Hope this is all it is, let us know.
