bulging resistors in a 38-116
Posts: 236
Threads: 43
Joined: Oct 2010
City: Atlantic Highlands, NJ
What would cause a resistor to bulge out in the middle? I have several like this on a 38-116 (125) that I just started to restore. I haven't seen this before. Is it a manufacturing defect that occurs over time or a sign of overheating or some other trouble with the set?
Thanks,
Steve
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Hi Steve,
Most of time it's over heating. Most manufactures are trying to cut costs and may use a part that is close to it's max dissipation which over many years of faithful service tend to lower in value. My general rule is if the resistor show signs of heating or discoloring it gets checked. Any resistor over 1M gets replaced as those seem to be out of spec more often than not.
Have fun!!!
Terry
Ps How's the ol'gal coming along? If in doubt on any part that is marginal go ahead and replace it. This will save you time later when something fails and you got to pull the set apart just because it wasn't replaced the first time around.
I'm sure you will be very pleased with the performance of this set once it's one of Philco's BEST sounding sets when put back in "like new" shape electrically It and the 37-690. I've got the 37 model and it's great!!!
(This post was last modified: 04-18-2012, 09:51 PM by Radioroslyn.)
Posts: 668
Threads: 144
Joined: Jun 2011
City: Elko,MN.
(04-18-2012, 09:18 PM)SteveJB Wrote: What would cause a resistor to bulge out in the middle? I have several like this on a 38-116 (125) that I just started to restore. I haven't seen this before. Is it a manufacturing defect that occurs over time or a sign of overheating or some other trouble with the set?
Thanks,
Steve
My guess is that they must have gotten a little warm over the years.
I have found about 15 resistors out of tolerance on the 38-116 I am working on.
Did you notice if you have those 2 resistors I asked you about earlier?
I found in the sub chassis there is a really fine hair like wire attached to a cap that was not really connected too great.radio was cutting out due to this.
If you see that hair like wire,be extremely careful.
It is kind of buried in the middle section of the sub chassis.
Good luck with your restore.
These are a bugger to work on.
murf
Posts: 236
Threads: 43
Joined: Oct 2010
City: Atlantic Highlands, NJ
(04-18-2012, 09:38 PM)murf Wrote: (04-18-2012, 09:18 PM)SteveJB Wrote: What would cause a resistor to bulge out in the middle? I have several like this on a 38-116 (125) that I just started to restore. I haven't seen this before. Is it a manufacturing defect that occurs over time or a sign of overheating or some other trouble with the set?
Thanks,
Steve
My guess is that they must have gotten a little warm over the years.
I have found about 15 resistors out of tolerance on the 38-116 I am working on.
Did you notice if you have those 2 resistors I asked you about earlier?
I found in the sub chassis there is a really fine hair like wire attached to a cap that was not really connected too great.radio was cutting out due to this.
If you see that hair like wire,be extremely careful.
It is kind of buried in the middle section of the sub chassis.
Good luck with your restore.
These are a bugger to work on.
murf
Hi Murf,
I haven't seen that wire yet, but I do have a code 125. Do you mean two caps or resistors? I can't find that thread, but I do have one cap buried in the back of the sub chassis, looks like a .05.
Maybe it would be a good idea to show some pics. This weekend i'll have more time for that. I am just starting on this so I haven't gotten too deep into it yet.
Steve
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
(04-18-2012, 09:56 PM)SteveJB Wrote: (04-18-2012, 09:38 PM)murf Wrote: (04-18-2012, 09:18 PM)SteveJB Wrote: What would cause a resistor to bulge out in the middle? I have several like this on a 38-116 (125) that I just started to restore. I haven't seen this before. Is it a manufacturing defect that occurs over time or a sign of overheating or some other trouble with the set?
Thanks,
Steve
My guess is that they must have gotten a little warm over the years.
I have found about 15 resistors out of tolerance on the 38-116 I am working on.
Did you notice if you have those 2 resistors I asked you about earlier?
I found in the sub chassis there is a really fine hair like wire attached to a cap that was not really connected too great.radio was cutting out due to this.
If you see that hair like wire,be extremely careful.
It is kind of buried in the middle section of the sub chassis.
Good luck with your restore.
These are a bugger to work on.
murf
Hi Murf,
I haven't seen that wire yet, but I do have a code 125. Do you mean two caps or resistors? I can't find that thread, but I do have one cap buried in the back of the sub chassis, looks like a .05.
Maybe it would be a good idea to show some pics. This weekend i'll have more time for that. I am just starting on this so I haven't gotten too deep into it yet.
Steve
Most carbon resistors drift higher in value over time, and that would naturally cause less stress on them. Now then capacitrs also leak and drift high, but also fail, and put big strain on voltqage dividers and tend to smoke them before burning them out, or the rectifier, or the fuse or the tansformer, if there is one.
You are the detective. The usual suspects will be the filter capacitors, but call in the rest of the capacitors, and keep close tabs on the resistors. Sure it could be a tube too, but actually least likely. Where is Rick?
Posts: 668
Threads: 144
Joined: Jun 2011
City: Elko,MN.
(04-18-2012, 09:56 PM)SteveJB Wrote: (04-18-2012, 09:38 PM)murf Wrote: (04-18-2012, 09:18 PM)SteveJB Wrote: What would cause a resistor to bulge out in the middle? I have several like this on a 38-116 (125) that I just started to restore. I haven't seen this before. Is it a manufacturing defect that occurs over time or a sign of overheating or some other trouble with the set?
Thanks,
Steve
My guess is that they must have gotten a little warm over the years.
I have found about 15 resistors out of tolerance on the 38-116 I am working on.
Did you notice if you have those 2 resistors I asked you about earlier?
I found in the sub chassis there is a really fine hair like wire attached to a cap that was not really connected too great.radio was cutting out due to this.
If you see that hair like wire,be extremely careful.
It is kind of buried in the middle section of the sub chassis.
Good luck with your restore.
These are a bugger to work on.
murf
Hi Murf,
I haven't seen that wire yet, but I do have a code 125. Do you mean two caps or resistors? I can't find that thread, but I do have one cap buried in the back of the sub chassis, looks like a .05.
Maybe it would be a good idea to show some pics. This weekend i'll have more time for that. I am just starting on this so I haven't gotten too deep into it yet.
Steve
They are resistors #78 and 79 on the schematics.78 being a 70k and 79 being a 14k wirewound resistor.
I can only find the 79 on mine.
Thanks
murf
Users browsing this thread: 2 Guest(s)
|
Recent Posts
|
Philco 91 Speaker Replacement
|
The spider is glued on the cone and so is the voice coil. I think you can use a cotton swab dipped in acetone and carefu...RodB — 02:42 PM |
Restoring Philco 37-604C
|
Yes I saw that. If I knew, I'd probably try to arrange for getting it myself. But I have just got one.
Which does not m...morzh — 01:44 PM |
Philco 38-2 Automatic Tuning
|
When you push the lever, you are supposed to rotate the disk to the desired station.
Then the magnetic tuning will acqu...morzh — 01:42 PM |
Philco 38-2 Automatic Tuning
|
I figure out the muting from another picture that helped. Now I need to know how the automatic tuning works. When I push...dconant — 12:11 PM |
Philco 91 Speaker Replacement
|
How would I go about removing the spider from the cone?dconant — 12:04 PM |
Philco 38-2 Automatic Tuning
|
Hello, I am having trouble getting my automatic tuning to stay unmuted. If I play with the tuning handle I can get it to...dconant — 10:51 AM |
Does anyone make photofinish replacements?
|
Here’s the link to the DIY photofinish section of our site:
klondike98 — 09:46 AM |
Delco car radio Peko vibrator converstion issues
|
Hi Richard,
Thx for posting the schematic. As I remember as a kid, these were great performers for the time, likely...MrFixr55 — 08:56 AM |
Delco car radio Peko vibrator converstion issues
|
hello mr Fixr,
The Electro Powersupply that I am powering the radio with has a huge choke plus a 10,000ufd electrolyti...radiorich — 10:58 PM |
Delco car radio Peko vibrator converstion issues
|
How about putting a choke in the power supply?
The big cap was likely an attempt to stabilize the DC. Kids who cre...MrFixr55 — 09:19 PM |
Who's Online
|
There are currently 3098 online users. [Complete List] » 1 Member(s) | 3097 Guest(s)
|
|
|
|