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Stewart Warner R-137-A - Printable Version

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Stewart Warner R-137-A - murf - 05-01-2018

Got this Stewart Warner Ferodyne R-137-A from a friend and just had to clean it up and re-cap it.
Seems to work pretty good after the re-cap.
Only issue I have noticed is a static noise when first fired up as if the switches are dirty.
But it does it even when you are not playing with any of the switches.
After about 10 minutes of warm up, it goes away.
Suspected a bad tube that improves with warm up. swapped out the tubes with no change.
Cleaned the tube pins and still no change.
Looked for any cold solder joints or suspect resistors with no luck.
Any ideas from the pro's?
murf

RE: Stewart Warner R-137-A - David - 05-01-2018

Try cleaning the tube sockets. Have a set of tip cleaners for a welding torch works great for removing junk out of old sockets.

RE: Stewart Warner R-137-A - murf - 05-01-2018

I think you could be right.
If I play with one of the 6f5 tubes, I can get it to settle down.
I suppose pipe cleaners are too big?
Will try tomorrow.
murf

RE: Stewart Warner R-137-A - Eliot Ness - 05-02-2018

+1 on the tip cleaners, Harbor Freight usually has a set something like this:

https://www.harborfreight.com/6-piece-tube-brush-set-61923.html

Depending on the size of the pipe cleaner it might work along with some electronic cleaner.  Also check to make sure one of the tube socket pins isn't too loose.

RE: Stewart Warner R-137-A - murf - 05-02-2018

Tried cleaning the tube sockets tonight and still no luck.
Starts as soon as it is fired up.
If you turn up the volume, it will kind of drown it out.
So the static or crackling does not get louder with increased volume.
Even tried cleaning the tuning condenser again.
Sure acts like a tube problem.
Murf

RE: Stewart Warner R-137-A - gregb - 05-02-2018

Hey Murf, does it have a candohm resistor in the chassis? It sounds to me like a bad resistor and if it has a candohm that would be the first one I would sub out. If not, start checking the other resistors and see if any are high and change those first. It's also possible there is a bad ground connection. Lots of things can cause this issue.

Gregb

RE: Stewart Warner R-137-A - Arran - 05-02-2018

Murf;
  It could be a flaky grid cap lead, those are known to break internally or develop cold solder joints since they sit right on top of a tube.
Regards
Arran

RE: Stewart Warner R-137-A - murf - 05-03-2018

Good idea,s guy's.
Will check the cadohm resistor as well as the grid caps and let you know what I find.
murf

RE: Stewart Warner R-137-A - murf - 05-03-2018

Well, we struck out again.
Cadohm resistor checks right on.
Grid caps look good.
This chassis has multiple globs of solder on the chassis that are used as ground connections.
Would it do any good to get my big iron out and remelt the solder on the questionable looking piles of solder?
While I had it playing tonight I realized that a good way to describe the static noise I have is the type of static you get when there is a lot of electricity in the atmosphere during a thunderstorm.
I will have to check other resistors and see if anything is out of tolerance.
murf

RE: Stewart Warner R-137-A - gregb - 05-03-2018

One thing Murf on the candohm, measuring does not tell if it is noisy. You have to make a new resistor and disconnect the original, connect your made up one and see if there is an improvement. Many of the ones I have seen measure just fine but they are noisy when in circuit.

Gregb

RE: Stewart Warner R-137-A - murf - 05-04-2018

What kind of wattage for these resistors?
I am guessing 4 to 5 watt resistors?
Murf

RE: Stewart Warner R-137-A - gregb - 05-04-2018

For testing purposes pretty much what ever you have as this is just temporary to determine if the candohm is causing the issue or not. If this proves that the candohm is the problem them you will have to determine wattage. With the test resistors in place you will only play it long enough to decide if the candohm is the issue or not.

Gregb

RE: Stewart Warner R-137-A - murf - 05-11-2018

Looking at 2 caps that I have not replaced yet and thought I better ask about them first.
One is a 12 mfd x 15 volt attached to one of the 6C5 tubes. What would be a good re[placement for this one?
Then there is a .01 mfd x 400 volt cap that has a flexible resistor attached to each end of the cap.
What is the purpose of the resistor attached? 
Replace cap with resistor attached as it is now?
Still have not had time to play with the cadohm resistor.
Been hard to find the time lately with the spring yard work needing to get done also.
murf

RE: Stewart Warner R-137-A - murf - 05-29-2018

Ok guy's,
Got it to load the pics of the questionable caps tonight.
You can see the extra long 15 volt cap in one picture and the other picture shows the cap with the flexible resistor attached.
Wondering what the purpose of the flexible resistor is that is mounted to the cap?
I have replaced those caps before by just reattaching the resistor to the new cap.
But always wondered why it was done this way.
The other pic that shows the extra long cap with the weird values.
What would be a suitable replacement. Don't have anything even close to those values.
Thanks, murf

[Image: http://i1161.photobucket.com/albums/q509/murphy51051/th_DSC_0363.jpg][Image: http://i1161.photobucket.com/albums/q509/murphy51051/th_DSC_0362.jpg]

RE: Stewart Warner R-137-A - Radioroslyn - 05-29-2018

>One is a 12 mfd x 15 volt attached to one of the 6C5 tubes. What would be a good replacement for this one?

It's the cathode bypass cap for the 1st audio stage. Value isn't very critical 16 or 22mf is fine @ 20 or 25v

>Wondering what the purpose of the flexible resistor is that is mounted to the cap?

Don't know not enough info. What is it connect to??? Tube and pin #. Best guess is that it's one on the cathode resistor for the rf,mixer, or if amp tubes . All 3 have a 300 ohm resistor and a .1mf cap across it. If so 400v is a bit of an over kill as there is only 10v or so there.