Bakelite line filter caps in 41-285
Posts: 79
Threads: 13
Joined: Feb 2014
City: Bristol, RI
Hi all:
Newbie question. On chassis 41-285, why are the two .01 mfd line filter caps along the AC line installed in that odd grounded bakelite box, then buried in tar? I assume the best way to redo them is melt that goop and clear everything out? Do they need to stay in the box for some kind of shielding? Etc? Or can I mount new caps outside it? Thanks,
Ted
Posts: 239
Threads: 10
Joined: Dec 2013
City: Columbia, SC
Philco put capacitors in those blocks, and filled them with tar. It gave them mounting points for other wires and made the chassis cleaner. I have no idea why they had to use tar...
Those two caps filter out noise in the AC line, and give you a cleaner power supply. Each goes to one leg of the line and ground. They should technically be safety caps, but regular ones are usually fine. http://www.justradios.com/safetytips.html
To remove the tar 'plug', cut the four little wires in the rivet holes on the top of the block (I use a razor blade), then heat it with a heat gun on the top and sides. After 20 seconds, use a small screwdriver to push the contents out the bottom. It is a much better idea to mount them inside the old block, both for safety and aesthetics.
Over at the Philco Repair Bench there are articles about the contents and connections of various blocks, and how to restuff them.
(This post was last modified: 02-11-2014, 10:30 PM by skyscraper.)
Posts: 15,473
Threads: 541
Joined: Oct 2011
City: Jackson, NJ
In addition to what Skyscraper has noted,
1. heat on "Low" using a heatgun. In case you do not have "Low" (some heatguns have cool and hot, and some Low and High) use high from a distance. I use "Low" for 10-15 sec, equal time every side.
2. Use a blunt instrument like a small Allen wrench. Sometimes the tool gets in between the two caps that are inside and if it is any sharp it can cut through the warm tar and you get a hole and the tar block still stays inside.
3. If it resists, heat one more time, do not force much.
4. Leave the cap in place (do not unscrew) when you do it and do not unsolder the wires - makes it so much easier, just cut the think wires coming from inside the block (!!!! - very important unless you want to deal with a mess).
5. No regular caps are NOT fine. Use only Y-rated capacitors.
Posts: 347
Threads: 34
Joined: May 2007
City: Raleigh, NC
I'm no expert, but I think Philco potted the caps to keep any moisture from degrading the line filter caps. Since they were connected line to ground, they'd have more catastrophic effects if they shorted or leaked than most other caps in the chassis.
I use X/Y caps from Just Radios, which are disk-shaped. They fit fine, except they stick out the open bottom of the Bakelite box just a tiny bit, not enough to see or to interfere with the fit.
Most of us leave the Bakelite block in place after replacing the caps because it's a convenient place to connect AC and transformer lines to those filter caps, and to connect one or two things nearby to ground. You could do the same thing with a terminal strip, I suppose, but the Bakelite shell looks good.
John Honeycutt
Posts: 15,473
Threads: 541
Joined: Oct 2011
City: Jackson, NJ
"Catastrophic" meaning "becoming the death cap" if someone touched the chassis and Earth at the same time.
Posts: 5,064
Threads: 269
Joined: Nov 2012
City: Bandon
State, Province, Country: OR
Hi Ted welcome to the Phorum. Some Bakelite block cap info that you will find useful can be found here: http://www.philcoradio.com/tech/blocks.htm . A tutorial on X and Y safety caps can be found here: http://www.justradios.com/safetytips.html
Posts: 1,095
Threads: 74
Joined: Jan 2014
City: Annapolis, IL
Ted, check out my bakelite cap rebuild in the thread "70 rebuild". I just finished those and have a few pics posted. Also some useful info in "70 restoration" thread by "morzh".
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
Posts: 79
Threads: 13
Joined: Feb 2014
City: Bristol, RI
Users browsing this thread: 2 Guest(s)
|
Recent Posts
|
Philco Model 76 Highboy
|
Back in Feb I scored a nice model 95 Highboy, see earlier post. Saved from a guy that likes chopping them up into Liquo...slford310 — 09:49 AM |
Philco Model 71B
|
Adding a pic from the other side and the inside. It will be a bit of work and a challenge but that's what makes it fun....slford310 — 09:32 AM |
Philco 89B code 123 newbie
|
Hi Kurt
Welcome to the Philco Phorum. Lots of phriendly pholks (see a pattern here?) who are happy to help. Keep posti...MrFixr55 — 08:36 AM |
Philco 89B code 123 newbie
|
Hello Kurt,
Welcome aboard and you have a nice set to start on !
Yes, the bakelite blocks and I too find them fairly...radiorich — 07:12 AM |
Philco 89B code 123 newbie
|
Getting started on my first Philco here, done some research and hopefully I now know enough to be dangerous. :)
Overal...Kurt P — 01:44 AM |
Delco car radio Peko vibrator converstion issues
|
Richard,
I reviewed the Panasonic specification sheets for this type capacitor and though dV/dt is discussed, there a...Chas — 11:48 AM |
Philco Shipping Crate
|
I picked up a nice set of KLH 20 speakers ca 1980, for $40, and a Telefunken 5083W "Allegro" AM FM SW radio, a...MrFixr55 — 10:52 AM |
Philco Model 71B
|
Absolutely looking at replacing the arch veneer and sides. Good luck stripping the front face ... hope the paint hasn't...GarySP — 10:31 AM |
1953 Music Masters 620-9 Australian Radio Restore
|
That's a very interesting radio Buzz. Looking forward to more installments on this one!Eliot Ness — 10:31 AM |
Philco Model 71B
|
OOPs, Dumb me. The title of the post is Model 71B. DUH!!
Yes, the 71 uses an autodyne detector, but it is more like t...MrFixr55 — 10:21 AM |
Who's Online
|
There are currently no members online. |
|
|