The PHILCO Phorum
Newbie Cap Question - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Newbie Cap Question (/showthread.php?tid=5544)

Pages: 1 2

Newbie Cap Question - TheGorper - 12-01-2012

I am attempting to restore a family hand-me-down Philco 91 type 126.

The electrolytics were already replaced once by someone (maybe my father) with paper dry electrolytics probably in the 1960's. I have yanked both of those out and replaced them with brand new electrolytics based on what I have read out here and other places.

I see many out here saying: "I have replaced all the caps in my radio". Other places say the mica caps and other smaller caps usually don't need to be replaced.

Can some of you help out a newbie and help me understand what really needs to be replaced and what doesn't? And how can I test the caps to check them myself?

RE: Newbie Cap Question - codefox1 - 12-01-2012

Clear schematic and notes from forum moderator (not free, not me, but very much worth it)
http://www.philcorepairbench.com/schematics.htm

Fuzzy schematic and notes (free, and good enough to get started)
http://www.nostalgiaair.org/PagesByModel/884/M0013884.pdf

Basically you should replace all the "fixed condensers" which translates into paper capacitors which cannot be reliably tested once they are as old as this. I find it easy to replace the small carbon resistors at the same time, as they have invariably drifted up in value, and cost only pennies. This will make a huge difference in performance and longevity of the set. surprisingly the most dependable components in these old timers, with a few exceptions, are the tubes.

You can get through this and will have a fine set in the end. Take your time and ask plenty of questions.

Lots of sources for parts, Just Radios, Jameco, Mouser, Digikey, many more. Mostly you should make an exhaustive list of everything you want, including a few spares of common value components, solder, deoxit, tools, etc... so you don't get ripped off on shipping.

Let us know how it goes.

RE: Newbie Cap Question - TheGorper - 12-01-2012

Thanks. That was very helpful.

I had already purchased a good clear schematic and diagrams of the part placement in the chassis. So I can find all the caps and resistors but was confused about what really needed to be replaced.

Thanks for the advice. It has been a fun project already and is getting better.

Replaced so far:

Electrolytic Caps
Power cord
Dial Cord
Broken tube
Power cord plug

Rebuilding speaker

Have wires with missing insulation to replace(mouse nibbled)

Shadow meter bulb burned out etc.

But I am having a lot of fun!

RE: Newbie Cap Question - TA Forbes - 12-01-2012

+1 what Codefox wrote.

Personally, I prefer replacing all wax/paper caps. They are usually leaky anyway, and are not trustworthy. Since some of them are connected to your B+ supply, failure could lead to damage up to and including your power transformer.

It is a good idea to restuff your bakelite blocks. There are several ways to do this described in this site.

Having done a couple of 91s, I recommend you also check your different transformers and filter choke for continuity.

RE: Newbie Cap Question - TheGorper - 12-01-2012

So where are the paper caps hiding?

I know there is a .18 MF under a bakelite block but is it paper?

Going to look for the post that talks about replacing those.

Thanks again.

RE: Newbie Cap Question - TheGorper - 12-01-2012

Please disregard my prior posts.

Found all the great info on bakelite cap rebuilding and understand now.

Thanks for your patience with my newbie questions.

One thing I dont have yet is a Philco parts list. I have one that lists parts for my radio like 4989K but is there a comprehensive Philco parts list somewhere?

RE: Newbie Cap Question - codefox1 - 12-02-2012

Well the short answer is that there are lots of lists here there and everywhere, but you need to know that substitutions and changes were done all the time, some not documented. If there is a specific part you have a question about, give us a description and photo. Assume if it looks to be original and still patent (coils and windings only need apply for amnisty,) leave it be.

RE: Newbie Cap Question - TheGorper - 12-02-2012

A few quick followup questions:

1) "Since some of them are connected to your B+ supply" - What does B+ mean? I see this a lot out here on the forum.

2) I have some capacitor banks that are not in the black bakelite "boats" but in sheet metal boxes. P/N 06713 and P/N 04830 do these internally have paper caps that need replacing as well? If so I am guessing I need to take these metal boxes apart as well to replace them (see pics).

[Image: http://www.dropbox.com/s/6yqxh8wwwkpbri7/2012-12-02%2018.36.14.jpg]

[Image: http://www.dropbox.com/s/g82u63jz872hvcg/2012-12-02%2018.36.31.jpg]

RE: Newbie Cap Question - morzh - 12-02-2012

B+ supply supplies the voltage for the plates of the valves.

The metal box caps are a snap to open up and stuff, even compared to bakelites.

RE: Newbie Cap Question - TheGorper - 12-02-2012

Thanks very much. Will add them to the "fix list".

RE: Newbie Cap Question - Radioroslyn - 12-02-2012

B+
Dates back to the old days of radio (1920's) when they used batteries for power. Back then you had an A battery which supplied the filament voltage usually a was a 6v car battery. It would run down and would be carried to the local gas station to be recharged. And don't tip it over on the carpet as the acid would spill out a eat up the carpet.
The B battery supplied the high voltage or plate voltage for the toobs. Usually was several 22 1/2 v or 45v or 90v jobs wired in series to provide the proper voltage. Most often 22 1/2v 90v 135v 180v. B+ is a reference to the plus side of the HV source. Whether it is from batteries or an ac power supply. A bad/leaky paper cap can put a load across the HV or B+ line that it can burn out the power transformer and or the rectifier toob.
The C battery used to supply the negative voltage to bias the control grid of various stages of the radio set, mostly the audio output. Sizes are usually 4 1/2v and 22 1/2v
Wellcome to the Phourm!!!
That the long answer to a short question!
Terry

RE: Newbie Cap Question - Radioroslyn - 12-02-2012

Just for the heck of it which cabinet does your 91 have?? I have one years ago that was a chairside set with a separate speaker. It's a great player ones you get it working!!!
Terry

RE: Newbie Cap Question - TheGorper - 12-02-2012

Thanks Terry. That helps a lot to clear that up.

The radio is a 1933 Philco Highboy - 91H.

Jim

RE: Newbie Cap Question - Radioroslyn - 12-02-2012

Where in NC? got kin in MEBANE, NC
Terry

RE: Newbie Cap Question - TheGorper - 12-03-2012

Kannapolis, NC