Window counter balance replacement

A quick learner from Longmeadow, MA says:

Hi, I've attached photos of the 2 main pieces of my older counter balances. The windows are double hung vinyl and the counter balances are wearing out and breaking. 

Photo window is the center portion, 2 plastic pieces which the 1/4" aluminum rod goes through. One end attaches to the spring, the other to string which is tied into the top plastic piece and also to the pivot lock in photo (window 3).  Photo window 2 is the attachment to the top of the window frame, showing the spring with the rod inside it. 

Hope some of this makes sense. I know it's older but I need some form of replacement as it doesn't make sense to replace all the windows in the house.  Happy to send more photos or anything else if needed. I added a photo of the window's tag. I am unable to determine the manufacturer. 

A local supply house (ABC) thought it was Simonton but they said it is not theirs. There is a stamp on the glass, Hampshire Glass Company, a local company. They don't manufacture the windows, just a supplier.

Please help, Thanks Tim

Thumbnail of the uploaded file named window 2.jpg
Thumbnail of the uploaded file named window 3.jpg
Thumbnail of the uploaded file named window.jpg
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Tom from SWISCO responded:

Hey, Tim. We can definitely help with this balance. Now, you have an older rod-type, which isn't a style that's made anymore. However our channel-type Series 775 can be used as a substitute. If you review our pictures, you'll see that it has the same style shoe and installs at the top using a screw, same as yours. 

The only question then is length and strength. You'll have to get the length off your old balance (make sure to round down) and weigh your sash to decide these attributes. Let me know if you need any help!

A quick learner from Longmeadow, MA says:
Hi Tom, Thx for the reply. I've reviewed the photos of the 775 and the installation instructions but still have a couple questions. The pivot shoe I currently have appears to be closer to 1 1/2" than 1 1/4". Will it fit snugly enough in the frame channel or does that matter much?

I'm not sure how to measure the length. From top of the spring mount block (where the screw goes in) to the bottom plastic piece of the balance it is 24". The aluminum rod that goes through the spring dead ending at the top mounting block and on the other at at a plastic piece is 23". Then the pivot shoe extended via string which is shown in the installation instructions of the 775. The 775 will operate in the same so that I need a 24" 775 is that correct?
Thx, Tim
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Tom from SWISCO responded:

A difference between 1-1/2" and 1-1/4" is significant. If your shoe is that big, then I don't think ours will work. However I've never seen a shoe in this style that came in that size. I would triple check your dimensions to be 100% sure.

To measure this old rod type balance, you want to measure from the top of the top nylon cap to the bottom of the bottom nylon cap. Don't count the shoe or the cord in your measurement. If this measurement is 24" for you, then you want our S775-24 .

How to install a S775 balance
How to install a S775 balance
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