I just finished a recap on a Philco 48-200 and its working, but it's very faint even with the volume turned all the way up.
It's pretty selective...I can get all the local stations, but I can barely hear them.
Common causes?
Anythjng that lowers gain.
Bad resistors, open RF transformers, bad tubes, stuck voice coil in the speaker, low B+ voltage....
Have the loop ant connected???
Terry
(07-01-2016, 09:10 PM)Radioroslyn Wrote: [ -> ]Have the loop ant connected???
Terry
Yup. Sound increases if I touch the loop. But is still very faint.
A number of resistors seem out of whack..if I'm reading the schematics (and the band color guides) correctly.
Some of them are tiny little b#$@#$%s that run between pins I don't know how to even test them let alone replace them.
In a tube device most resistors couldbe simply measured across while in-circuit.
(07-01-2016, 10:03 PM)Tgace459 Wrote: [ -> ]A number of resistors seem out of whack..if I'm reading the schematics (and the band color guides) correctly.
Some of them are tiny little b#$@#$%s that run between pins I don't know how to even test them let alone replace them.
Hi, Tgace. I have a 49-500 that has those little boogers in the tube sockets. If you can determine that with the tube out of the socket that there is no continuity between the leads, you can test them in place. That's how I tested some of them in my chassis. Seemed to work. Still don't know if there is some reason they need to be down in the sockets except to save space. Replacing them looks like it could be a pita for sure. Ed
Well. Resistors didn't change anything. I jumpered it to another transformer/speaker in another AA5 and got the same results. Going to see if I can borrow the same line-up of tubes from a friend to try and see if it's a tube issue.
Checked any voltages??
Terry
Think I found the problem. My friend with the tube tester said that 5OA5 is kaput. Grid short....
Well...this radio was an interesting experience. After replacing the 5OA5 it was still playing very faint. Resistors all were replaced or within spec.
I took a wooden dowel and started tapping and probing things till "boom!" it started playing full volume. It was a .22mfd cap I used to replace the "special condenser" .2 mfd that was in it originally. One end was loose so I thought that was it and re-soldiered.
Nope. Now it wouldn't regain volume with any quantity of prodding. So on a hunch I simply disconnected it and voila it plays normally.
Anyone know why?
Your new cap might be bad, yes ask me how I know. If you have another just use a couple of jump wires an see what happens. Someone may have worked on the set in the past and installed cap incorrectly I have found a few like that myself. Good luck you will get her working again. David
Yeah. I tried a couple of other caps to see if I had a bad one but always with the same results...
Looking at the schematic, it shows a .22 mfd cap coming off of pin 6 of the 5OA5 tube and going to ground. On my radio it goes from the 6 pin to the 5 pin of the 7A8 tube (along with the 470k resistor its paired with). I tried a couple of other ground points...always makes it go faint.
I've just left the D**n thing off and it seems fine.
There should be nothing between 5 and 6 pins of 7A8.
That is there should be nothing connected to pin 6 other than your antenna input and the tuning cap/trimmer cap.
The special cap is connected between the common (all the cathodes) and the chassis.
There was/is a resistor (470,000 ohm if I recall correctly) and a .22 cap attached to pin 6 of the output tube....any idea where they "should" go? When I replaced the stuff that was in place I had my problem. I wonder if (as was mentioned earlier) someone else didn't tinker with this years back (it was an old Philco cap that was in place though).
This was the model with the 5OA5 output tube. I see there are 2 different tube versions and schematics for this model.