[Joe Rossi]

Good Evening fellow Phorumanians,

I recently acquired a Sparton 581X AM Radio, circa 1940.   My cousin passed away and the family wanted me to have it.  Cabinet is in fine shape, although something gnawed away at one of the wax caps, a couple of wires, and the dial string.  I have 3 Sams books on dial string winding, but they don't include this model.  Would any of you fine folks happen to have a source I could reference?  I'll have some photos shortly.  Thanx!

[klondike98]

its not in the two books I have (which are probably the same as yours) sorry...

Steve Johnson seems to have the schematic/manual but I wouldn't know if it had the dial string diagram on it, might be worth an email http://www.antiqueradioschematics.org/sparton.htm and http://www.antiqueradioschematics.org/contact.htm

[Paul Philco322]

Can't wait to see, could not find an image online.

Paul 

[Joe Rossi]

Thanks Bob.  I will contact Steve to see if he has anything to assist.  Appreciate you looking!  Paul,  The photos are on my iPad and I have to transfer them to my laptop.  Try and do that today!  Joe

[OldRestorer]

I could not find it in volumes DC-1 - DC-5.
What is the chassis number?

Me

[Arran]

 I found a diagram on Nostalgia Air but it doesn't show a dial stringing diagram:

http://www.nostalgiaair.org/pagesbymodel...018825.pdf

I could have a look in Riders, unless that was where Kirk looked it up already. Beitmans as well possibly. I also have a mixture of Canadian and U.S built Sparton service folders, which I can have a look at, though the layout may differ with the nearest Canadian built model.  It honestly doesn't look like it would be too difficult to restring, but then again I've restrung the dial cords on several dozen sets by now so what would take me 20 minutes might be unfathomable to someone else.  Does this set have a short slide rule dial or an aeroplane style dial (pointer in center that sweeps around) ? The aeroplane style is easier.
Regards
Arran

[Joe Rossi]

Arran and Me , thank you both for looking.  It is a Model 581X, I believe that the prior year 580X is near identical.  In the last photo right bottom corner there is a number stamped into the chassis, 332511.  Would that be the chassis number or the chassis part number?  I do have a complete Beitman and Riders, and 3 volumes of Sams dial string diagrams.  This is not in any of them.  I have attached photos for your viewing pleasure.  The tubes are still Sparton branded; I assume they are original.  Thanks again!



           

[Paul Philco322]

Looks mint.

Paul 

[Arran]

Joe;
  I also looked in Beitmans, in one of the Sams dial stringing guides that I have (didn't look in the other yet but the one I looked in supposedly covered sets made from 1938-47) and also in the Canadian Sparton service folders and manuals I have, no diagram for this model. However it looks like an aeroplane style dial and pointer so the stringing should be simple, other then figuring out the length, if you already have three of the Sams dial stringing manuals I would have a look at the dial layouts most similar to the Sparton, like a Philco 38-15 for example.
 Typically what it will have is a drum behind the dial plate, the drum will have a groove around the perimeter with a notch or a hole with a bushing in it. First the dial cord has two ends with a loop at either end, one loop will attach to a tension spring, the end of the spring will slip over a hook on the inside of the drum (or sometimes there will be a series of holes and a hook on one end of the spring), the  loop on the other end will slip directly over a hook on the inside of the drum. Sometimes you will have to remove the dial pointer and the dial plate to get at the inside of the drum, but even if you don't it makes it much easier to restring the dial cord if you do. Next there is usually a preferred position in which to have the tuning cap, either fully open or fully meshed, whilst working on the dial cord, since you will be pulling and tugging at it to get everything where it needs to go.
   I'm not sure how to explain the next part but here is how the dial cord works, the drum takes up cord in one direction, and supplies it in the other, while a portion of the cord is wrapped around the tuning control shaft about 2-1/2 times, it's basically a large loop. So if lets say the tuning cap rotates clockwise with the dial the cord the cord will leave the left side of the drum and be taken up on the right side, when it rotates counter clockwise the cord will leave the right side of the drum and be taken up on the left side. On some of these dials, because of where the notch is on the drum, you will need to wrap an extra turn of cord around the drum or the tuning cap won't open all the way. I would get a roll of braided fly backing fish line (at least 25 pound test) from a sporting goods store, and start experimenting with making loops, seeing how far it will stretch, etc., the Sams books will give you an idea of where to start.
Regards
Arran

[Joe Rossi]

Thank you Arran.  I am printing out your post and will have a go at this soon.  In some purchases I've made I have acquired 2 different sizes (thicknesses) of dial cord.  I'll let you know how this all works out, waiting for the other replacement parts to arrive.  Joe

[Joe Rossi]

Hello Friends!  I had just begun to refurbish the Sparton 581X, when on closer inspection, the L1 "IF Rejection Coil" was mostly consumed by a mouse.  I have no idea what an IF Rejection Coil is (see schematic link below) or does, and I think it may be made of unobtainium.  Has anyone run into this item?  Where to find one?  Looking at the schematic, I'm inclined to believe that the radio will work without it by attaching the antenna directly to the primary of L2.  The schematic also shows a little 'gimmick' coil in the same area.  The mouse probably ate that too, along with parts of the wax caps.  I hope he/she was happy with their snack.  Thanks,  Joe


http://www.nostalgiaair.org/pagesbymodel...018825.pdf

[Mondial]

Don't worry about that IF rejection coil. You can just remove it completely.

The original purpose of L1 and C3 was to serve as a trap to eliminate interference from high power marine radio stations which were in operation at the time when the radio was built. These stations operated in the LF band at frequencies around 400-500 kHz, and could cause interference at the IF frequency when picked up by the antenna. Today these stations no longer exist, and therefore the rejection circuit is no longer needed.

[Joe Rossi]

Don't worry about that IF rejection coil. You can just remove it completely.

The original purpose of L1 and C3 was to serve as a trap to eliminate interference from high power marine radio stations which were in operation at the time when the radio was built. These stations operated in the LF band at frequencies around 400-500 kHz, and could cause interference at the IF frequency when picked up by the antenna. Today these stations no longer exist, and therefore the rejection circuit is no longer needed.

Thank you very much, friend!  I'd never heard of that coil before, I appreciate the explanation.  More pics as I progress.  Joe

[Arran]

Joe;
  Mondial is right, that IF rejection coil is what other manufacturers called a "wave trap", basically a band reject filter that blocks RF interference. You don't need it anymore, I don't think that many sets used them past the early 40s. There doesn't seem to be anything on longwave anyhow other then some beacons, and I don't think any of those are at 400-500 KC.
Regards
Arran

[Joe Rossi]

Joe;
  Mondial is right, that IF rejection coil is what other manufacturers called a "wave trap", basically a band reject filter that blocks RF interference. You don't need it anymore, I don't think that many sets used them past the early 40s. There doesn't seem to be anything on longwave anyhow other then some beacons, and I don't think any of those are at 400-500 KC.
Regards
Arran

Thanks Arran!