Cone Repair on 602B & 604B

[slial]

I have some very small repairs to make on the cones of these two Duplexes. The small holes in the 602 are in the surround and the small tear in the 604 is in the area of the surround, although the cone and surround are of the same material and piece and not separate.

I am wondering about the best way to go about repairing these. The issue of concern on the. 604B was repaired, likely long ago. The small tear has occurred outside the edge of the repair. I wonder and worry that the repair caused stress and ultimately the new damage. And considering this is a 604B, I do not want to do anything to compromise the integrity of the original cone. This cone is really thin, even compared to the 602.

I have reached out with a message to Great Plains Audio requesting advice and guidance on the best process to repairing these. Any advice here would be greatly appreciated as well. I'd also be happy to post photos if that would help matters any, at least in terms of assessing the extent of the issue.

Scott

[juniper]

You may want to post some pictures, so the pros here can evaluate the damage...

[Cal Weldon]

I have reached out with a message to Great Plains Audio requesting advice and guidance on the best process to repairing these.

Hi Scott, sounds like you are taking work away from them so don't be disappointed if they don't reply.

There are any number of ways to do the repairs and, as juniper has said, a picture or two would be very helpful in determining the course of action. It may be as simple as facial tissue and cut back PVA glue.

[slial]

I will upload the photos this evening. As for GPA, they actually replied and indicated they only do full cone replacements and not repairs. At this point I would like to avoid that if possible. The only come they can supply would turn my B into an E.

[slial]

Here are some photos. I have included photos of both obvious areas of some need and some that might be suspect.

604B:

Images reflect 2 older repairs (one of which is near the new tear), a small hole, an older repair, a small spot that seems creased and might be suspect.

Attachment 1904

Attachment 1905

Attachment 1906

Attachment 1907

[slial]

602b:

image-34.jpg

image-35.jpg

image-36.jpg

image-37.jpg

image-38.jpg

[Cal Weldon]

When it's at the surround like that and the surround is paper I would consider using cut back rubber cement. The solvent is acetone and you'll have to be careful how much you thin it. Usually 10:1 is enough. Try even less to start and gradually add acetone until you think it's right. You want it easy to apply thinly but not so runny that it's hard to control. It's hit and miss and there's no way I can help more without being there. I would use facial tissue or TP as a scrim. Do the repair on the back on the cone if possible and just lightly dress the front (no tissue) after the patches on the back have set. Some have also tried a cut back silicone but I haven't found a good way to clean or prime the cone and the silicone tended to delaminate over time.

[slial]

Does anybody have any photos or detailed description of this process? I am sure I can handle it in house but also want as much info ahead if time. One thing is sure...I'll practice on a less important cone to get the hang if it.

[Cal Weldon]

Get some of those little children's art class paint brushes from your local dollar store [make sure they won't melt with the acetone] and while you're there pick up some flat toothpicks [not the round kind]

Use one brush to gently clean the area with a small amount of acetone. Then apply a small amount of the rubber cement solution with a different brush and lay a small piece of tissue [pre-cut to the required size] over the cement. use the skinny handle part of the paint brush to form the tissue into place in and around the accordion part of the surround. Apply another small amount of cement over the tissue and smooth it out making sure that a little cement is taken beyond the edges of the tissue and feather it out as best you can. Use the blunt end of the toothpicks to remove any excess. More is not better here, just like too little is no good. Make sure you get it looking right before you walk away as once is begins to set, you'll only make a mess if you try and fix anything. When it's dry to the touch, turn the driver over and use a brush to apply a small amount of the solution [no tissue] to the affected area on the front of the cone. Let dry for 24 hours.

[slial]

How much larger than the wound should the tissue be? Should the small year that is visible in the photos be glued down before being covered with the tissue/glue combo? The sides of the tear line up perfectly and I would think that securing that down first would simplify matters with the tissue.

Are there any other methods or materiala out there I should be aware of, or is this the tried and true approach?

Scott

Get some of those little children's art class paint brushes from your local dollar store [make sure they won't melt with the acetone] and while you're there pick up some flat toothpicks [not the round kind]

Use one brush to gently clean the area with a small amount of acetone. Then apply a small amount of the rubber cement solution with a different brush and lay a small piece of tissue [pre-cut to the required size] over the cement. use the skinny handle part of the paint brush to form the tissue into place in and around the accordion part of the surround. Apply another small amount of cement over the tissue and smooth it out making sure that a little cement is taken beyond the edges of the tissue and feather it out as best you can. Use the blunt end of the toothpicks to remove any excess. More is not better here, just like too little is no good. Make sure you get it looking right before you walk away as once is begins to set, you'll only make a mess if you try and fix anything. When it's dry to the touch, turn the driver over and use a brush to apply a small amount of the solution [no tissue] to the affected area on the front of the cone. Let dry for 24 hours.