[Marsupial]

In the philco paperwork for 47-1230 there is a mention of a C328 0.01mf B+ bus bypass condenser.

It is mentionned in the troubleshooting section, but I cannot locate it in the parts placement drawings. 

Or in my radio. 

Anyone knows where it is located? The shematics has it in contact with C421 and R315 but those are at the opposite side of the chassis. 

Alternatively, I have one non-identified 0.01mf cap touching R304, R307, R309, R310 and C308... Are they the same? 


Help much welcomed.

[Marsupial]

After much analysis of both Sam's and Philco service manual schematics, I came to the conclusion that C328 is literally absent from my radio.

And the additional cap it connecting to R307 on one end, and ground on the other.

I assume these are a few production changes made to filtering capacitors. The are the only 2 actual changes I've seen between my radio and the schematics. I've also seen mistakes in the schematics and parts placement, which is why I like having two sets of documents.


So, the mystery cap has been replaced by a modern counterpart, and I am considering adding C328 to the circuit.

Any reason I shouldn't?

[criageek]

Hey Mars - I've attached a photo of the 2nd 47-1230 I did with C328 circled...this is after recapping (I restuffed them).  Check out my capacitor cross-reference which includes locations for all caps:  https://philcoradio.com/phorum/showthread.php?tid=19577

Rich

[Marsupial]

Hey Rich,

that is exactly where my mystery cap was. 



How can it be C328 if it doesn't connect to R315? R315 is at the left soldered directly to the 6V6 socket

[criageek]

I'm going partially on memory here, but also on some of my pictures and the schematic.  I believe it IS connected to R315 in a roundabout way.  R315 is connected to the 6V6, pins 4 and 6.  Pin 6 is unused on the tube so is just being used as a terminal for a wire into the IF can (Z302) as well as C317.  Pin 4 is actually B+ and is connected to many places.  If I remember right there is a wire running from what I've called TS7, terminal 5 (where the top end of C328 is connected) up to the filter cap, C102B.  From there I think there is a wire that works it's way down to 6V6-4.  You should be able to measure continuity from TS7-5 to 6V6-4.

Rich

[Marsupial]

See, that is where it gets fuzzy...

That terminal for this capacitor, also touches R304 and R307.
Now, on the schematics, I see that R304 touches C328, but not R307.

I see the same on the Sam's schematics. R307 and R315 aren't touching.


But, it would make sense that the one missing and the one extra cap of the same value are in fact the same...

[criageek]

My documentation says that R307 (68k) should be connected from TS7-4 (not TS7-5, which is where C328 is connected) to 7R7-5.

Rich

[criageek]

I've attached the documentation from my 2nd 47-1230 restoration in case you're interested.

Rich

[Marsupial]

I must say I didn't look up much the resistors, as I didn't change most of them; therefore, I relied on the parts placement drawings.
We know the parts placement drawing can very well be wrong, there's lots of errors in them...

Double checked in my radio, and for sure R307 doesn't touch the mystery cap, that I relabelled C328

Thanks a lot for helping out. This might also help out future people attempting similar restorations.