[johnnygrace]

This is my first tube radio restore and I've been reading a lot and think I am coming to some sort of vague understanding of what I need to do but I have a few questions.....as well I've attached the two different versions of the schematics for the 48-472 in case it helps someone else out in the future...

1st question:
For starters here's what I know about the condition of the radio....
When turned on the AM comes in ok, a bit of hum, but ok(super loud when the volume is turned up all the way), the FM on the other hand is distorted at a much lower volume and nothing comes in clear. I had another radio so took a 12AU6 out of that one and replaced the 12AW6 in the philco and voila the FM now works, although it's still a much lower volume, a lot of stations now come in cleaner...so of course I'm now thinking about replacing all the tubes becaue I have no way to test them....anyone have any thoughts on that? Anyone have tube tester in Seattle and want to help me out?


2nd question:
In the Photo below, I understand that the obviously large paper looking capacitors are in fact paper capacitors and need replacing. I can add up about 23 of those from the parts list and visually. As well on the parts list they are listed as .01uf, .02uf, .006uf, etc. so my assumption is this type I can readily purchase and the voltage/capacites are identically listed today on a website like "antique electronic supply"? Second part of this question is are the other capacitors in the photo, the ones circled, mica and ceramic? I think obviously the traffic light looking one is a mica one, but the others, like the small brown ones almost look like mini paper capacitors, what about the bulbous brown ones and the strange plasticy tan one on the far right? And based off what I've read I shouldn't try to replace any of those first off? If I attempt to crossreference with the schematic this seems correct but hard to see exactly.
[Image: http://www.johngrace.com/files/external/capacitors.jpg]


3rd question:
So im confused about reading the parts list for ordering capacitors. Some of the Identification codes list "cer." after them so I assume these are ceramic capacitors identified as such. Then the ones listed as .01...type values I'm assuming are paper and I can order those, but what about the ones below...for example the "cathode bypass" a giant silver tube in the underside of the chasis. Other forums list this as electrolytic, should I just replace it? As well the "stabilizing cap" large black tube? And the "filter," large black cardboard tube on top of chassis, does than need replacing and what type of capacitor is that, is it just three stuffed into the tube?
[Image: http://www.johngrace.com/files/external/parts1.jpg]


4th question:
This is where the AM antenna is connected, does any of this have to do with FM or is that just the long white cord on the far right? Also the thing circled is broken. Doesn't seem like it needs to be fixed but there was a piece of black wire which came with the radio should that black wire go from the black wire on the broken piece to one of the antenna type terminals?
[Image: http://www.johngrace.com/files/external/back.jpg]


5th question:
How do I make the radio safer at this point? Some online advice is to add a fuse into the power cord. It's easy to trace where the power cord goes into the radio so I can easily replace it so what kind and how do I add the fuse? As well I've read about isolation transformers. Do you guys build them inside your radio to make it safer?


I guess that's it for now. My main concern is making it safe so I don't electrocute myself or a cat, although at this point I don't think I will be plugging it in anymore until the repairs are made, and also putting an order in for capacitors/tubes so I can get started. One last question anyone have a url for wire I can order in case I need some?

[morzh]

A few answers:

2. Most caps are filter/decoupling so standard values of 0.01uF, 0.022uF and such are good replacements, and are readily available from Mouser or anyone else. I buy polyester films.
For looks I stuff them inside old paper tubes but this is up to you.

Do not touch mica caps, they are likely OK.

3. Large caps of more than 1uF are probably electrolytics and can be, with appropriate voltage rating, changed for today's electrolytics. Again, many of us stuff old tubes with new ones, for look and feel thing.
If it is the rectifier filter (the one right after the rectifier tube) it is desirable (many folks do not pay attention to that) to have your ripple current rating correct. I usually go with at least twice the load current.

5. Safety: if your radio has the Mains power transformer you do not need the isolation transformer. Unless you operate it on the bare concrete floor in the basement or outside - then it is desirable. Also you could possibly add (only for those with mains transformer - NOT FOR AA5s) Earth wire to the chassis, to make it safer in case the transformer breaks down.
This will also serve as the Ground that was connected separately before (if it was connected - often it was not).

Fuses: I usually go with a slow-blow about 1.5-2x rating vs. the radio consumption but no less than 1A, so if it draws say about 1A from the Mains (for a large powerful radio of 100-120W total power) use a 1.5-2A slow-blow fuse.

And remember - the fuse is not there to save the device - it is to save your house from the device if it decides to go up in flames. A short circuit will surely exceed 2A many-fold. However the fast-blows need higher rating as they may be quick to react when the inrush happens; it is a well-known phenomenon when old radio fuses burn on turn-on without anything being wrong with the radio - this is how large transformers operate.

[Mondial]

Regarding question #2, the mini brown tubulars and the bulbous brown types with the color dots are both ceramics and like the micas which you have already identified, need not be replaced. These are small capacitance value (pF)caps and are used as either RF bypasses or coupling caps in tuned circuits.

The other small wax covered components look like they might be inductors?

As far as #4, the single white wire is the FM antenna. The AM antenna loop is connected to the terminal board and it seems that the black antenna wire connected to the broken terminal strip with the mica cap.