The PHILCO Phorum
Philco 37-620 - 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: Philco 37-620 (/showthread.php?tid=17706)

Pages: 1 2

Philco 37-620 - Alan - 12-27-2017

Hello everyone. I'm new here.  I hope you all have a great New Year!!  I've been reading some of the posts and was looking for some advice.  About 20 years ago I bought a Philco 37-620 in good condition. Just needed some cosmetics. I ran a couple of "tandum" wires where I saw questionable wiring on top (and replaced the power cord) the year I bought it.  You can see them in the picture (but left original wires in place). It has worked great for years. Here is the advice I need.  If it works fine...should I change out any components like capacitors for potential fire hazard?

I have it out of the cabinet to repair the speaker cone (mover put a finger through it)  Thank you for your help!

Alan
Burrke, VA

RE: Philco 37-620 - Radioroslyn - 12-27-2017

Hi Alan and welcome,
> If it works fine...should I change out any components like capacitors for potential fire hazard?
Yes! The blue one on the under side is a replacement from the 50's the others are originals from '37.
The cabinet has been refinished and the colors look really washed out.
http://philcoradio.com/gallery2/1937b/#Model_37-620K
Here's the service if you need it. http://www.nostalgiaair.org/pagesbymodel/212/M0013212.pdf

RE: Philco 37-620 - klondike98 - 12-27-2017

Welcome to the Phorum!
Icon_wave

RE: Philco 37-620 - Alan - 12-28-2017

Wow!  Thank you for all the great information!  Especially the Schematics!  So replace all the paper Capacitors?  Also being new to restorations....I take it the green, red, pink and yellow ones are resistors?  Should I also replace the resistors?  I read at www.justradios.com that it is not advised to replace mica capacitors.  Do you agree? Can you see them in the picture?

Thank you so much again for the help and advice.

Alan
Burke, VA

RE: Philco 37-620 - morzh - 12-28-2017

If it works fine....and you don't feel like full recap.....do change electrolytics and all the paper caps directly connected to B+. The rest might not work great but they won't go on fire.
Caps 20 and 57 and all lytics should be replaced.

This said, the paper caps cause other issues so replacing them is highly recommended.

RE: Philco 37-620 - Radioroslyn - 12-28-2017

Actually here's one that's a bit cleaner. http://www.audiophool.com/Philco.html
Scroll down the 1937 then click 37-620.
Mica caps are usually ok and don't require replacement unless there are issues.
Resistors can be easily check w/an ohm meter, most the time in circuit.
Tolerance is 20% of the value. You use the pictorial in the service info to
determine what parts are what.

RE: Philco 37-620 - Alan - 12-30-2017

Thank you very much!  I have made a Resistor list but still need a little education.  All the resistors make sense and seem straight forward except 2 and one I can't find on the schematic.  Three questions:

1. There are a few called Megaohms at .5watts.  What is the value of a megaohm? Part number 50 as an example.

2. Another example of one without a clear value is #34 which says it is 400 ohm but no watt value--It just says Bakelite--do you know the watt value?

3. #64 (9000 ohms, 2 watts) is just not pointed out in the schematic....is it still part of the 37-620?

Thank you again for the help.

Alan
Burke, VA

RE: Philco 37-620 - Alan - 12-30-2017

Wait I found one more.  What is the Value of #61 that only say Bias Resistor?

Alan
Burke, VA

RE: Philco 37-620 - Radioroslyn - 12-30-2017

#1 It would 1 meg or 1 million ohms. The colors would brown body black end and green dot. It's power rating is 1/2 watt.
#2 can be replaced w/400 ohm 1/2w resistor
#3 Yes it's right above the 5Y4 tube.
#4 It's a wire wound resistor. Most of the time they are ok it's smaller carbon comp resistor that tend to drift in value.

GL

RE: Philco 37-620 - Alan - 01-07-2018

Thank you again!  Now I believe I have identified everything but am not sure about the 2 bakelite parts as shown.  Are these both .015-.015 mfd bakelite capacitors? OR are one or both of them some kind of bus?

Alan
Burke, VA

RE: Philco 37-620 - klondike98 - 01-08-2018

The upper bakelite block appears to be #67 in the diagram (a 3793DG double .015uF capacitor block).  The lower one looks to me like a modification to what is in the schematic and is a bakelite block capacitor that is likely replacing capacitor #57 (a 0.03uF cap).  The bakelite block also has on it a terminal strip that is included in the schematic.  I think you will need to trace out all the connections and components to see how the bakelite block cap is wired up and confirm my speculation.  (I don't have a 37-620 to look at so this is just based on the photos and diagram).  I believe I see the 0.015uF #48 paper cap so the bakelite block doesn't include that one.  Use the schematic to see where the items in the diagram actually are connected (but understand that the schematic shows electrical connections, not necessarily physical locations of the connections)

There is bakelite block cap wiring diagram information in the Phorum tech section.

If you pull the lower block cap out, it will have a number on the side and you can also look up the internal wiring of it, though I also always trace it.  Once in awhile there is a block that is wired up differently than the diagrams.

Here's a thread on how to restuff those bakelite block capacitors. Its not as hard as it looks to restuff them.

RE: Philco 37-620 - Alan - 01-08-2018

Thank you Bob. I can tell I need more time to chase this one down. Thank you for the information on the top one--this is very interesting. Good day today--received my re-coned speaker. Also I can generally read modern Resistors but was wondering what the color covering the entire Resistor means....is there a code key for these? I have the modern code key but it does not talk to the color of the Resistor body...if that makes sense.

RE: Philco 37-620 - klondike98 - 01-08-2018

Alan, read through the info on Chuck's Philcorepairbench page on carbon resistors. His new site does not have it yet but the archived version is still available at: https://web.archive.org/web/20170227075419/http://philcorepairbench.com/carbonres.htm

RE: Philco 37-620 - Ron Ramirez - 01-09-2018

There's also this on resistors:
http://www.philcoradio.com/phorum/showthread.php?tid=14966

RE: Philco 37-620 - klondike98 - 01-09-2018

Thanks Ron...I forgot about that thread!