A brief background, I always enjoyed refinishing furniture, loved the look of old radios and when I saw this radio for sale I phoned the owner. An older lady who was selling it indicated that her family had owned it from purchase, it had never been worked on or repaired so I thought, perfect for a beginner. I have been reading on what to do and what not to do so I figured this radio would be ideal for a “recap”
I have trouble at this time understanding schematics I thought I would replace all the caps, check the resistors and it would be a learning experience that I could use to help me with how to follow a schematic.
Wrong! Nice lady but as the photos show this radio has had repairs and from what I know which isn’t much, they weren’t done very well.
My initial concern was to replace the two electrolytics p/n 66 and p/n 64. As the photo shows they’ve been moved. The existing 22 mfd cap I assume is for the original 18 mfd p/n 66. It is attached to the bias resistor strip and the condenser block circled in yellow. The other 8 mfd cap attached to the same bias strip as the 22 and the other end to condenser block 52. I assume this cap is part of what is supposed to be p/n, a duo 8/10 mfd cap. There is no 10 mfd cap anywhere.
I plan on replacing block 69 with safety caps, change all other caps, check resistors and replace the power cord but as I mentioned earlier, my ability to read schematics at this time is limited so I am appealing for help from members of this forum to walk me thru how and where to connect the replacement caps for these two electrolytic caps. Are the connection points for the existing two caps correct and can I just replace them with new caps? If not, where are the correct connection points and where do I connect the 10 mfd cap that is missing. I know that correct polarity is essential with electrolytic caps so I don’t want to do this wrong and ruin other parts of the radio.
I realize that this is a long post and basic for all of you, but with no electrical background I really need some assistance from knowledgeable members like yourselves that I can gain experience from.
Hello Hamilton,
Welcome aboard and glad to see you here First off, I don't know what tools you have and your knowledge but working on this set if you don't have one you will need a multimeter to test voltages and resistance!
Before you get installing new parts in this set, we teach you about polarity and Schematic drawing symbols.
because we don't want you to destroy your new capacitors or other parts.
Here if you look down below, I posted a couple photos
Then off we go
See where you had drawn that yellow circle that piece which is mounted to the metal chassis is what is called a bias resistor it is basically a big resistor with different taps so if you look on the schematic it is 62,63.
Where the yellow circle is that is where the Negative lead of 64 the 10 ufd capacitor hooks and then the positive side is connected to the metal chassis make sure that 66,64A other two capacitors get mounted with their negative lead mounted to the chassis as you will noticed 64 is mounted differently and if it gets mounted wrong you will see some fireworks and loud bang !
Sincerely Richard
P.S. I hope this gets you started !
(This post was last modified: 11-14-2021, 02:43 PM by radiorich.)
Hello Hamilton,
One thing I forgot to add is that odd shaped dark brown block with screw holding it to the chassis is called a bakelite block and Philco loved using them they contain capacitors and resistors.
So those will need to be gutted out and new parts installed here is a couple links one showing the how to remove the old parts
I see from the photo with the symbols on how to determine the + and - ends of the caps. Thanks for that info, I didn't know that and I can see the difference between 64 and 64A. Replacing the electrolytics are the first thing I'm doing and I appreciate the info about the blocks as well. I have watched a few videos on how to remove and replace the caps and it was on this site is where I read that you should use safety caps in certain areas.
I just want to clarify which yellow circle were you referring too for the - connection for the 10 mfd cap because I have two yellow circles on the photo. Looking at the schematic it appears that the - connection goes to the resister strip but I just want to make sure.
Perfect. Thanks Radiorich, I appreciate your help. I was reading last night about negative bias and even though it’s a bit above my level at this time just seeing the polarity of my three electrolytics make it easier to understand why they’re connected where they are.
Hamilton,
"...make sure that 66,64A other two capacitors get mounted with their negative lead mounted to the chassis..."
The bottom (negative) legs of caps 66 and 64A should NOT be connected to chassis as instructed earlier. Please view the image I've attached (sorry it is rotated, I couldn't figure out how to save it as a rotated image). I have highlighted in red the net that connects to the negative leads of caps 66, 64A, and 64. Note that this red wire connects to the center tap of the HV secondary of the power transformer (item 68). This point is not the chassis! The HV center tap is the most negative voltage in the radio, and it is different than the chassis (which is usually the B- node, commonly referred to as ground).
The chassis is indicated by the triangular symbol that connects to the positive lead of cap 64.
So at the risk of repeating myself, the negative leads of all three of those electrolytic caps (i.e. 64, 64A, and 66) connect to the HV center tap and not to the chassis.
Good Luck
Jon
(This post was last modified: 11-23-2021, 04:36 PM by PAradiogeek.)
I'll mention that the 10mfd bias filter #64 (the upside down one) there is only about 20vdc there. A cap rated @ 50v is fine. I've seen some where they have been replaced with 450v units. Way overkill.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
It’s connected as per PAradio geek suggested and the radio is now working!
Thanks to all I know I will be back for more help after my next radio purchase.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
