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+--- Thread: bulging resistors in a 38-116 (/showthread.php?tid=4618)


bulging resistors in a 38-116 - SteveJB - 04-18-2012

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

RE: bulging resistors in a 38-116 - Radioroslyn - 04-18-2012

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!!!

RE: bulging resistors in a 38-116 - murf - 04-18-2012

(04-18-2012, 10:18 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

RE: bulging resistors in a 38-116 - SteveJB - 04-18-2012

(04-18-2012, 10:38 PM)murf Wrote:  
(04-18-2012, 10:18 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


RE: bulging resistors in a 38-116 - codefox1 - 04-18-2012

(04-18-2012, 10:56 PM)SteveJB Wrote:  
(04-18-2012, 10:38 PM)murf Wrote:  
(04-18-2012, 10:18 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?

RE: bulging resistors in a 38-116 - murf - 04-19-2012

(04-18-2012, 10:56 PM)SteveJB Wrote:  
(04-18-2012, 10:38 PM)murf Wrote:  
(04-18-2012, 10:18 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