need spring balances and tabs to attach to 1970s vintage wood double hung non tilt windows on metal tracks.

Thank you for your patience during this busy season. Your balances aren't made anymore, but the good news is that you can use our Series 500 spiral balance as a substitute, along with a bottom bracket like our 17-012 (sold separately). We use this combination of parts to repair wood windows like yours all the time and we find it works very well.

Yes, I think the above combination of the Series 500 balance and 17-012 bracket may be viable for your window. However there are a few considerations that you have to keep in mind before you buy anything.

First, you need to be sure that there's enough space between the window sash and the jamb liner for the balance to actually fit. Our Series 500 has a 9/16" diameter tube. If you don't have that kind of room on the sides of your sash, you'll have to make room, which is easier said than done. If you can't make room, or if you don't know how, you may want to consult the help of a local professional.

The second key detail is that the 17-012 bracket needs to screw into the sash at the bottom. Looking at your photos, there appears to be some weatherstripping that would get in the way. That may be a dealbreaker, so that's the next thing you'll have to check. If the 17-012 bracket doesn't have enough room to screw into the sash, then you'll have nothing to connect the balance to.

As for how to replace, it varies from window to window. Plus, the older your window is the more you're going to have to improvise. In your case, I'd wager you have quite a bit of improvisation ahead of you. If you're lucky then all you have to do is remove the old balance and drill holes for the new hardware to screw in, but I don't think the odds are in your favor for this window. This isn't going to be an afternoon's project. You should expect a pretty strong investment of time, energy, and "creative" handiwork, as I like to call it. As mentioned before, if you've never done this kind of project before you may want to contact a professional to do it for you. 

Before you do any of that, though, you need to figure out what size balance you need. That means both length and strength calibration. I'll try to summarize it as succinctly as I can:

• Length: Measure the height of the visible glass and add 3" (if it's the bottom sash) or 1" (if it's the top sash). Do NOT measure the full height of the sash, just the visible glass.
• Strength Calibration: To determine this, all you have to do is remove the sash and weigh it on a scale. Any common bathroom scale will do. We have a weight chart on all Series 500 length store pages that you can use as a reference.

Please feel free to reach out if you had any other questions.