I've never worked on a chassis design like this. What is new to me are the paper capacitors. Most of them are .1 uf with a 200 ohm resistor next to it according to the schematic. I don't see a resistor near these capacitors. A search leads me to believe the resistor is part of the capacitor unit. These capacitors have three electrical leads, the two on top and the chassis mounting leg. These provide the terminals for capacitor and resistor. I just wanted to verify my assumption is true.
A related issue is that the schematic shows chiefly 200 ohm resistors with each capacitor, but I measure 100 ohms at each. What value resistor do I replace it with?
If memory serves me correctly the resistor is wire wound around the cardboard form of the capacitor. Typically wire wound resistors don't change value like carbon resistors. They are very stable under load even overload. I would suspect that it came from the factory that way.
When I've serviced some of these early sets I've just clipped the ground wire off of the cap. And soldered a new one in it's place (cap). The resistor is used to decouple rf signal from getting into the hv supply. The value isn't all that critical. Same with the cap it's job is to couple any rf signal to ground but not short the hv to ground...
If it oscillates when you get done or you can't sleep at night go ahead and add 100 ohms @ 1/2w in series.
Lot of working room eh.
Kestas
Are you talking of backelite blocks with resistors inside? Those are wire-wound and are next to the paper cap piece, both potted.
Nah this before bakelite blocks.
Not a bakelite block. I attached a picture of a typical capacitor. I believe the resistor is wound concentric with the capacitor as one unit.
What's the best way to gut the capacitor? I'd rather do it with the resistor intact if possible.
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> What's the best way to gut the capacitor? I'd rather do it with the resistor intact if possible.
That likely isn't happening.
The best way to remove the guts is with heat. First, try to unsolder the tiny leads of the capacitor (and resistor if applicable) from the solder terminals.
Now, if you have an old toaster oven that you no longer use for food, this would be the best choice. Bake them for about 30 minutes at 225 to 250 degrees Fahrenheit. If you do not have one of these, the capacitors will need to be heated in some way until you can remove the innards. The components are sealed inside with a black waxy substance, just like Philco bakelite blocks were sealed. Grab the end of the capacitor which mounts to the chassis with a pair of needle nose pliers while the unit is hot, and push the stuffing out with an old screwdriver.
Here's how I rebuilt my Philco 65, from my blog.
Philco model 65 Repairs - Part 1
Philco model 65 Repairs - Part 2
Philco model 65 Repairs - Part 3
Philco model 65 Repairs - Part 4
Philco model 65 Repairs - Part 5
Philco model 65 Repairs - Part 6
Philco model 65 Repairs - Part 7 (Epilog)
Part 4 details how I rebuilt the capacitors in my set.
You mentioned some of the capacitors in your set having resistors of 100 ohms, not 200 ohms. This is interesting, as the original Philco data specified 200 ohm resistors in those capacitors. I suspect this may be another case of Philco making a running change and not documenting it.
Please do me (and all of us) a favor. Please specify exactly which capacitor/resistor assemblies measure 100 ohms instead of 200 ohms, Use the Philco part numbers as shown on the schematic; i.e. whether it is (5), (6), (9), (10), and/or (27). My 65 set oscillates if I turn the volume control up too high; I'm now wondering if I need to change some of my 200 ohm resistors to 100 ohm? I would need to study the schematic further.
Oh, and 1/2 watt resistors are suitable for replacements for these resistors. You can use 1 watt if you wish. They don't have to be wirewound.
Oh....in 86 0r such there are those. Forgot, methinks caps inside resistors ... I thoight of restuffing but nothing fit. So I paralleled the cap, having bitten off the wires of the original first.
The yellow film caps fit those Philco tubular caps just fine.
And if you read my blog articles, you noticed that I used hot glue to reseal them after I restuffed them.
Philco used that type of capacitor from the model 511 series (1928) until models 76 and 95 (1929). They switched to the bakelite blocks in 1930.
As I recall, the 511 series had the resistance wire wound on the outside of the tubular capacitor bodies. I don't remember right now if model 86 was the same, or not. Model 87 does not have the resistance wire on the outside - it is on the inside of the capacitor body, just like in model 65.
Here are the resistance values I measured at each location:
(5) 107 ohm
(6) 102 ohm
(9) no resistor
(10) 103 ohm
(27) 245 ohm
As I said, I plan on restuffing the capacitor while keeping the resistor. I want to keep the architecture as clean as possible in the chassis. Plus, I believe wirewound resistors are reliable.
If not, I may try to stuff the resistor inside with the capacitor... though I don't know how much heat the resistors will generate.
Actual recapping will take place much later. I'm now only taking inventory of what I'll be replacing for about 10 radios before I place an order for parts.
Well, the old wirewounds may not survive after the capacitors are heated and gutted...
That said, do what you want, it's your radio.
And with that I bow out of this conversation.