Stewart-Warner 950 battery set - Printable Version
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+--- Thread: Stewart-Warner 950 battery set (/showthread.php?tid=7578)
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Stewart-Warner 950 battery set - BrendaAnnD - 09-30-2013
Just got this radio. I suspect that before it hit the USPS, it may have only needed some tweaking and a battery bank. Unfortunately, even though the radio was well packed, they still managed to damage it significantly (and without even denting the case!) Somehow, it was hit hard enough to break all the audio transformers off the chassis, cutting/breaking the wires at various places, and shattering one of the two 112 tubes.
I'm going to try to repair the transformers, wish me luck there. But, all the schematics for this radio that I have thus far found don't seem to match the radio. For starters, the schematics call for 171's instead of 112's, and the part numbers (no parts values) for the bypass caps are different. I've ordered a schematic from Steve, hopefully it will be the right one. In the meantime, does anyone have any experience with this set?
TIA
RE: Stewart-Warner 950 battery set - Jayce - 09-30-2013
There had to be some sort of mark on the box for that much damage to be present! Are you sure it wasn't damaged before it was shipped? If it wasn't damaged before, one has to wonder what the heck happened to damage a radio packed in a box without leaving any external marks!
RE: Stewart-Warner 950 battery set - BrendaAnnD - 10-01-2013
It is indeed confusing, but as the shipper wrapped all unshielded tubes in bubble wrap, and used good packing material for the radio itself, (styrofoam, foam rubber and bubble wrap), plus cardboard reinforcement on the sides of the box, I doubt it was broken before shipping. Those transformers are fairly heavy, and were attached to the chassis with thin brass rivets, which sheared.
RE: Stewart-Warner 950 battery set - Jayce - 10-01-2013
Huh, ok. Guess it was an inertia thing then. Either the package was caused to accelerate fast enough to make those transformers sheer off or was caused to stop suddenly. Either way, I hope you can get it repaired. Guess this is why I always look for radios withing driving distance from me as I have no trust in any of the delivery services anymore. That and even I don't know how to pack a radio for shipment, so I also tend to sell locally.
RE: Stewart-Warner 950 battery set - BrendaAnnD - 10-01-2013
Yeah.. I don't have that option. The only one with old radios within 5000 miles of me, is me.
RE: Stewart-Warner 950 battery set - BrendaAnnD - 10-01-2013
I made a lot of progress on this radio tonight. With no parts placement diagrams, no wiring diagrams (other than the schematic, which is not strictly correct for my radio) and a lot of wires ripped off of where ever they went, it was a challenge. Not the least of which was figuring out all the battery wires, which do not match the schematic.
Finally, I got power to the set, troubleshot what I could, which was the RF deck as far as the detector, then worked at figuring out the connections for the interstage transformer between the detector and 1st AF (I have a couple of Hammond replacements, still want to try to repair the originals.. have to figure out which is which first) First, the +45 source connection on the terminal strip, then the wire that ran from the same terminal strip to the plate of the detector. Insert one Hammond transformer.. the scope readout you see above is the resulting output from the detector/interstage transformer, which is also loaded with a high impedence speaker. There is audible, but low, audio coming out of the speaker as well. Next, work on the 1st AF stage.
RE: Stewart-Warner 950 battery set - Arran - 10-01-2013
There are some collectors in Japan but they mostly play with their own domestic stuff, which is much cruder then U.S and Canada sets from the same era, and of course there is the language barrier. I've heard of some people visiting mainland China and finding old radios there, apparently Philco once had a sales bureau there, along with some of the European and Japanese makes.
Regards
Arran
RE: Stewart-Warner 950 battery set - BrendaAnnD - 10-02-2013
More working tonight. Subbed in interstage transformer between 1st audio and 2nd audio. Don't have a high enough impedence p-p output transformer, so could only use 1/2 of the output section (which is sort of OK, since I don't yet have the other tube, either). I'm using a SE transformer designed for 3V4 output, the the match is at least, if not in the same ballpark, at least in the same league. Given all of this, I'm getting reasonable output, with pretty good quality audio. I'm sure it will be better when I can locate an appropriate output transformer and the other 112A comes in.
RE: Stewart-Warner 950 battery set - marty - 10-02-2013
Hi All;
Brenda Ann, I am truely amazed at Your talents, I have a Radio that I have all the information on and can't get it to work and You have a radio that has almost no information about it and You get it to work.. Congratulations, keep up the good work and keep us posted..
THANK YOU Marty
RE: Stewart-Warner 950 battery set - BrendaAnnD - 10-03-2013
Finally got around to melting most of the tar out of the output transformer... what a PITA. I left some of it in, just got enough out to get the transformer partially out of the can. Once I had it that far, it was pretty easy to access all the wires. I stripped the ends and put on new color coded wires (after ohming the coils out to make sure which was which). I used modern colors (Brown/Red/Blue) for the primary, and Gray and White for the secondary. I've now reinstalled it and connected it up. For testing purposes, I inserted a 71A into the other 112 socket. The parameters are not even close, but amazingly, it actually helped to even out the distortion and increase the volume. Maybe tomorrow I'll try to rebuild one of the interstage transformers... just have to figure out some how which is which..
RE: Stewart-Warner 950 battery set - BrendaAnnD - 10-04-2013
Disappointment: I depotted the detector interstage transformer. One of the wires had broken off inside, so I had to pull the transformer all the way out of the can. There was plenty left to work with, unfortunately, BOTH sides of the transformer are open.
Not a total disaster, I can use one of my Hammond transformers and mount it in the original can, which I have soaking in brush cleaner to remove the remainder of the tar. I had hoped, though, that I wouldn't have to use a $40 transformer. C'est la vie. Did some experimentation tonight. I was trying to 'dim it down' a bit, because the balance of the audio is way toward the bright side (as in no bass at all). At first, I experimented with different capacitor values between plate and cathode of the 1st audio stage. This did make a difference in tonal balance, but just didn't quite give me what I was looking for. Then I struck upon the idea of negative feedback. I grounded one side of the 8 ohm output from the output transformer and connected the other speaker lead through a .001 cap to the grid of the 1st audio tube. This made a significant improvement in audio quality, including almost completely removing any second and third order harmonics in the output. It takes a bit more of the high end than I would like, but I don't have any smaller sized caps in stock. I guess I'll put another .001 in series and see what happens. I don't want to lose the bass I've gained (as well as better volume) though.
I think tomorrow I'll depot that last transformer. These things are a real pain to work with, but I want to try to keep the original look to the chassis, so I need that can. Who knows, maybe I can find the missing wires for that one and repair it. Wish me luck.
RE: Stewart-Warner 950 battery set - sam - 10-04-2013
hi Brenda
(These things are a real pain to work with)
lol you make it look so easy even with out schematic
good luck keep posting
sam8)
RE: Stewart-Warner 950 battery set - Arran - 10-05-2013
The AWA Old Timers Bulletin had an article on constructing a solid state substitute for an audio interstate transformer from I thing around 2003 or so, it's online someplace.
Regards
Arran
RE: Stewart-Warner 950 battery set - BrendaAnnD - 10-05-2013
Well, the radio is essentially finished. I could not remove the third transformer from it's can. Of course, after getting molten tar all over my fingers, I also sort of lost the will to fight it anymore. I mounted my replacement transformer on top of the chassis. I also mounted a single solder lug on which to connect my feedback loop. It works pretty well now. Still need to get the proper tube in there so that there's a balance between the two outputs.
By the way.. you know those pain charts you see in the doctor's office? The ones with the faces numbered 1 to 10? Well, in case there are some of you out there that have yet to experience it (and I don't recommend it), having your fingers coated in molten tar is about a 15.. with a screaming face..
RE: Stewart-Warner 950 battery set - Arran - 10-05-2013
I learned a long time ago that if you need to unpot a potted condenser or transformer it's much easier to bake it in a toaster oven then to try heating it with a heat gun.
Regards
Arran