Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Jan Fri 21, 2022 1:40 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 9 posts ] 
Author Message
 Post subject: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Thu 14, 2017 4:12 pm 
Member

Joined: Feb Sat 14, 2015 4:56 am
Posts: 58
Location: Boerne,TX 78015
I was wondering if anyone has rebuilt the multi section candohm in a Philco 39-55. One section of mine is open and a couple of others are pretty far off their design resistance values. I was going to go through and add up all the tube current draws to calculate the wattage requirements for each section, but was sure someone here has done that already and could share the power ratings they came up with for each resistor.

Here is the schematic:

http://www.nostalgiaair.org/pagesbymode ... 013299.pdf

Hard to read, but the resistances from left to right are 111, 29, 15 and 14 ohms.

Thanks for any help!

Jaime


Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Thu 14, 2017 5:29 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 31285
Location: Maryland 20709, USA
Hi Jaime,

I've replaced a number of Candohms over the years.

Zenith published a list of part numbers with individual section power ratings.
Most have one or two sections with ratings >1 watt while the rest are low-power.
The highest power in any multi-section Candohm is 6 watts.

Here's that Zenith list if you want to peruse it:
http://www.atwaterkent.info/Images/Zeni ... istors.pdf
You might find your part there, since Candohms were made by an independent company.

Unfortunately, I know of no such list for Philco radios.

The simple way to calculate dissipation is using voltages.
If a voltage drop E appears across a resistor R, the power is E * E / R.
I would use a replacement resistor with at least 3 times the calculated value.

- Leigh

_________________
73 de W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Thu 14, 2017 6:32 pm 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 19231
Location: Mountains of Mourne. Ireland.
Image
Error: see post below. ▲ from six-page Service Bulletin No.310 in DjVu format
available here→ https://tinyurl.com/tom-bavis courtesy of Tom Bavis.

I use this DjVu reader (safe download from sourceforge.net) works great.
http://antiqueradios.com/forums/viewtop ... 9#p2746819

If you are using a Windows computer, here is a direct link to the DjVu reader .exe file.
https://sourceforge.net/projects/djvu/f ... rror=netix

Save it to your desktop, open it and follow the installation instructions.


Somewhat more legible Rider's Philco page 9-55 + 9-56
http://americanradiohistory.com/hd2/IDX ... e-0070.pdf

Greg.

Edit: Most all of those 'oddball' values are... http://antiqueradios.com/forums/viewtop ... 2#p2469692


Edit: image updated.


Last edited by egg on Nov Mon 09, 2020 11:25 pm, edited 3 times in total.

Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Thu 14, 2017 7:54 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3926
Location: Charleston, W.Va.
Jaime wrote:
One section of mine is open and a couple of others are pretty far off their design resistance values.
Jaime

Hi Jaime,
+1 to comments already offered by Leigh and Greg.

The only thing which concerns me is your statement above. Not unusual to find one or more sections of a candohm resistor which are either open or shorted. But they being wirewound resistors, it is somewhat unusual to find intact sections which are "pretty far off their design resistance values".

_________________
Poston


Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Thu 14, 2017 10:27 pm 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 19231
Location: Mountains of Mourne. Ireland.
Error: Disregard the multi-section resistor image posted above.
It's for Philco 39-116 a 14-tube radio.

Bulletin 310A contains service data for model 39-55
Image
111Ω 29Ω 15Ω 14Ω is correct.
Apologies for any confusion. Greg.


Edit: image updated.


Last edited by egg on Nov Mon 09, 2020 11:20 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Fri 15, 2017 9:28 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3625
Location: Nr London, England, SS1 3PT
This is a neat way of doing it using 10W metal clad WWs. Of course they don't all need to be this wattage but they are convenient as they come with lugs so effectively can be made up to take the old wiring.

I used a piece of ali metal L strip.

Attachment:
Candohm replacment.jpg
Candohm replacment.jpg [ 60.85 KiB | Viewed 2832 times ]



Gary


Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Fri 15, 2017 3:33 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3926
Location: Charleston, W.Va.
The solution which Gary posts above is a very good one. I too have started using these metal-clad WW resistors with lugs; I purchase mine from Mouser. An arrangement like Gary's photo is especially good where space is at a premium in a tightly-packed chassis, and where a conventional lug strip might interfere with surrounding components.

_________________
Poston


Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Fri 15, 2017 10:21 pm 
Member
User avatar

Joined: Dec Tue 23, 2014 6:51 pm
Posts: 2504
Location: N. Palm Bch, Fl.
Gary posted a picture a while ago, but now seeing it in a chassis is something.
The way you arrange them makes it look very professional. Do you put any goo
(The gray stuff that goes between a proc and heat sink)on the resisters?

Freeman.


Top
 Profile  
 
 Post subject: Re: Rebuilding the candohm resistor in a Philco 39-55
PostPosted: Sep Sat 16, 2017 8:48 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3625
Location: Nr London, England, SS1 3PT
Can do if you want but its unnecessary unless one is really high watts !!

Laid it out on a drwg package and printed it out, stuck the piece of paper on the metal strip and drilled the holes then soaked off the paper.

Attachment:
New Candohm resistor WEB.jpg
New Candohm resistor WEB.jpg [ 41.47 KiB | Viewed 2776 times ]


You can get lower wattage resistors but they are too fiddly for me to work with.

Gary


Top
 Profile  
 
Post New Topic Post Reply  [ 9 posts ]  Moderators: Norm Leal, Marcc

All times are UTC [ DST ]


Who is online

Users browsing this forum: Dennis Wess, Google [Bot] and 24 guests



Search for:
Jump to:  






































Privacy Policy :: Powered by phpBB