[Marsupial]

I tested quickly with the phono input, using a small MP3 player. The amp still works.

The issue doesn't seem to be the power supply, nor the amp.

What should I do from there?

[Radioroslyn]

Well it's time to break out the volt meter and start poking around. But maybe before we start going down that road look closely for terminals that you may have bent in handling and replacing the filters. Check for too much solder on your joints that may be shorting. Wiggle the tubes a bit maybe a bad connection there. The chassis looks like it's seen some mouse action. Not good for any of the connections.
Give that a try first.
Terry

[Marsupial]

What should I measure with the voltmeter?

At this point, I haven't found anything newly connecting, or wrong parts placement. I've ran the tests described in Riders volume 19, p.73. - It points to bad capacitors, do I start changing capacitors until I have AM reception back, or should I try to get AM back prior to making replacements, in order to be able to test any upcoming capacitor change.

[gary rabbitt]

What should I measure with the voltmeter?

At this point, I haven't found anything newly connecting, or wrong parts placement. I've ran the tests described in Riders volume 19, p.73. - It points to bad capacitors, do I start changing capacitors until I have AM reception back, or should I try to get AM back prior to making replacements, in order to be able to test any upcoming capacitor change.

Hi,
I would suggest that you do not replace anything further until you solve your problem. The reasoning is, it did work before you installed the filter caps right? Now it doesn't. Starting to replace "other caps" will open a large can of worms, and probably won't get your set going. You will be deeper in trouble if you miswired one of next caps.

So, I'd start making the voltage measurements, usually from the chassis (check the diagram) or a common B- point.
A visual check might turn something up. I have checked a chassis once, twice and 3 times. The 4th time I noticed where the trouble was. So get out the highlighter and make 100% sure your new filters are in correct. You did add the terminal strips, perhaps you forgot to route a wire that was going to another stage? Something grounded where it shouldn't be? Maybe snag a thin wire somewhere? Hard to diagnose here.

With the voltages checked, you can go from there. Remember, some of your voltages might read a little high due to the higher AC voltage in some locations.
Will check back

[Marsupial]

Thanks Gary. Some people seems eager to recap everything all at once, but I personally prefer going on a more organised fashion like you mentionned.

Today I printed the datasheets for all the tubes for the radio, that will come in handy.

I started to follow the readings mentionned in Riders, and identified one capacitor (C419) in the FM stage, that is shorted. I assume its nothing new, but it does connect to the anode of C102A, brigning it to GND and forcing false readings everywhere.

I didn't have time today because of other issues, but the next thing I'll be doing is to replace C419 to remove the undesired GND in order to perform good readings.
Then I'll monitor all I can and also redo a check in the chassis to see if there's anything I missed.

Thanks again, the help is really appreciated.

[Ron Ramirez]

I started to follow the readings mentionned in Riders, and identified one capacitor (C419) in the FM stage, that is shorted.

Hold it!

Before you go any further with that particular cap, read this page on my site.

https://philcoradio.com/library/index.ph...m-philcos/

[Marsupial]

Thanks a lot Ron!

but I was already aware of that special cap, thanks to you mentionning it on another thread about the exact same radio.

Still, the C419 - the cap section of it - is shorted. The 3 legs would read as ground, leading C102A to read as shorted.


BTW thanks a lot for taking the 47-1230 as an example on how to replace this capacitor; otherwise I would have been lost on how to fix it, being that my own capacitor was now short.


Here's readings I did for all the steps on Riders 19-73

With C419 shorted (C102A shorted to GND):
A to C = 154V. (should be 310)
B to C= -5V. (should be -16)
D to C= 0 (connected to C419 that is shorted to GND - should be 190)
E to C= 134V (should be 240)

That's when I realised the C419 is shorted, so I disconnected it and re-did the same checks before reconnecting it.
With C419-to-C102A connection removed:
A to C=188V
B to C=-6V
D to C=187V
E to C=160V

I will want to replace it and redo the same readings... but I wonder if just the bad C419 would cause the voltages to be so low..?

I guess my next step will be to change C419, C314 and C216.


note: altough it is drawn as being between C103 and C102B in the troubleshooting technical drawings, the resistor R100 is placed between C103 and C102A in the schematics, and was like that prior to me changing the caps, so I replaced it like so.

Also, what I assume to be R214 was reading (with one leg open) 74000 ohm. In the schematics, it talks about 47000 ohm.

here's a close-up picture of the new filter caps. not that we can really see much from there, I'll need to make better ones next time I'm in the chassis.

[Image: http://i146.photobucket.com/albums/r253/...0_9379.jpg]

[Marsupial]

Ron,

There is an error in the Riders drawings, so it repercuted to the same error in your modified drawings.

the pins at wich the C419 are connected are wrong. They aren't what I saw in my 47-1230, and they aren't what I see in the diagrams. The C419 is connected from GND to R410, the 4th pin from the bottom of the lug strip, not L404, 3rd pin from the top of the lug strip. Note that the 3rd top and 3rd bottom are bolted to the chassis (GND) so the result is that the lead wire needs be placed to the other side.

here's how I think it should be drawn
[Image: http://i146.photobucket.com/albums/r253/...9-WHAT.jpg]

In any case, shorting to the GND resulted in no AM at all, my alternate connections returns AM.

Can you please change that drawing to help future 47-1230 restorations? And, thanks for posting about this capacitor, I wouldn't have known what to do, or what to look for. It was while looking at your drawings that I realised what was going on!

I started to follow the readings mentionned in Riders, and identified one capacitor (C419) in the FM stage, that is shorted.

Hold it!

Before you go any further with that particular cap, read this page on my site.

http://www.philcoradio.com/tech/ftcap.htm

[Ron Ramirez]

D**n it, I wish I still had that 47-1230 I worked on here for reference...

but it wasn't mine, and I put that page together after working on that set for someone else.

Makes sense...since one leg of R410 connects to one leg of C419 in the schematic.

Thanks for the tip. It shall be changed.

[Marsupial]

it was when I was changing the capacitor that I realised the mistake; but what trigerred me into thinking the drawing - the vintage riders drawing - was wrong, is that both legs of the capacitor are connected to the 2 GND pins of that lug strip.

That's the second "mistake" I see on the riders drawings, and I haven't been using it for long... I am quite happy to have the schematics to compare to.

I have a picture of that capacitor's legs in my camera, taken prior to removing it, for reference.

[Ron Ramirez]

You should post the photo so others can see it.

Philco schematics sometimes have errors in them. Some mistakes were caught and corrected; others weren't. It is when the mistakes weren't caught and corrected, that things get interesting for us, decades later, as we try to get these sets going again.

[codefox1]

Thank God there are roughly only two basic models of humans. If I had it to do all all over I would have become a doctor. Am trying to convince my son to do so, and it is possible. Any power commmands I can use?

[Marsupial]

Here's the C419 before.
[Image: http://i146.photobucket.com/albums/r253/...0_9388.jpg]
you can see the 2 leads up top are on lugs aside one another.
Oh, and I see in that picture another wire that needs changing...

here's C419 after
[Image: http://i146.photobucket.com/albums/r253/...0_9392.jpg]
you can see the left leg has a wire soldered to it. I reused the same fabric sleeve to insulate the legs.



I don't think I posted the new C102A/C102B and C103...
[Image: http://i146.photobucket.com/albums/r253/...0_9379.jpg]

[Marsupial]

I figured I should post progress pictures.

[Image: http://i146.photobucket.com/albums/r253/...0_9420.jpg]

most of section 1 has been recapped already, and I am looking at attacking section 2.

The "original" 5Y3GT was weak, delivering only about 160V on B+. a "new" one fixed that. I currently have one spare of most of the tubes.

[Marsupial]

Making some readings before changing some capacitors from the amplification section.


Here is what I read on my 7F8

across the heater, I get 6.76VAC

for section 1:
grid : 2.1 mVDC
plate: 142 VDC
cathode: 2.5VDC

from grid to cathode: 2.2V

section 2:
grid: -1 VDC
plate: 109 VDC
cathode: 0 (sometimes fluctuates in the milivolts)

from grid to cathode: 0.5V

If I understand the schematics correctly, the two plate voltages are OK. However, following riders 19-77 "section 4 - trouble shooting" on FM bands, the grid-cathode measurments are off? They state section 2 grid-cathode voltage should be " negative approx 3 volts"
They seems to talk about a bad oscilator...?? I am not sure I follow...



In any case, I changed a few other caps on the amp section. here's what it currently looks like
[Image: http://i146.photobucket.com/albums/r253/...0_9447.jpg]