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-   -   Help required: Cracked case repair (https://www.vintage-radio.net/forum/showthread.php?t=172682)

Vintage_Man2012 1st Nov 2020 5:06 pm

Help required: Cracked case repair
 
1 Attachment(s)
Hello everyone,

I have decided to repair one of two Kolster Brandes FB10 sets Iíve had on the shelf for a while now. One of them has a rather unsightly crack in the case. The case appears to be made from urea formaldehyde.

Before I go and try and tackle this myself, has anyone got any tips to give the best results?

Thanks
Paul

Boulevardier 1st Nov 2020 5:56 pm

Re: Help required: Cracked case repair
 
There are a couple of recent threads on the forum about repairing cracked plastic, and suggesting reinforcement of any glue repair using fabric, etc embedded into the glue.

vinrads 2nd Nov 2020 9:19 am

Re: Help required: Cracked case repair
 
Hi Paul do you intend to paint the case after the repair? Mick.

Lloyd 1985 2nd Nov 2020 10:21 am

Re: Help required: Cracked case repair
 
First thing to do would be to try and clean as much dirt out of the crack as possible, using IPA and a fairly stiff brush, try and get it as clean as possible, if you can get it all back to white it’ll make the next part go way better! Once clean get some low viscosity superglue, or just the standard Loctite branded stuff, not the gel version, and dribble some into the crack, allow it to overflow just a little. Leave to set overnight, then carefully sand it back with p600 wet and dry paper, maybe even mask off the material around the crack until the glue is nearly flush with the surface. Once flat, polish with Paste polishing no. 5 until the shine comes back. Hopefully you’ll have a near invisible repair that you can get away without painting!

Regards
Lloyd

Tractionist 2nd Nov 2020 10:24 am

Re: Help required: Cracked case repair
 
DavidG4EBT seems to have done a lot of these - I've done three or four too. Whenever the case is in pieces, David tends to reinforce the edges of the segments with tiny pins prior to re-cementing them back together. However, in the instance of your crack (as opposed to a total 'parting of the ways') I'd first clean it up with a drop or two of bleach and/or IPA, and then run some superglue in to it.

However, I would counsel that these cases are nigh impossible to make an invisible repair on. Indeed, even when intact - they seem to yellow and lose their lustre with age. I suspect that they are manufactured out of some form of catalin. In any event, many of us have had to resort to spraying the cabinets with an appropriate paint and colour subsequent to a crack repair.

Hope this helps ....

Tractionist 2nd Nov 2020 10:27 am

Re: Help required: Cracked case repair
 
P.S. Lloyd and I seem to be on the same wavelength! :thumbsup:

crackle 2nd Nov 2020 10:38 am

Re: Help required: Cracked case repair
 
I have repaired cracks like this before.
First I used a pressure washer to blast the dirt out of the crack, that should help to mask it, leave for a few days to dry out. Be careful with the speaker grill bars they can be delicate. If all the dirt does not come out you could try bleach as suggested but that may change the colour of the catalin as well.
Then I use very thin runny super glue to try to get it to seep into the crack.
Lightly rub down with 1000 grit to remove excess glue and polish with Bakelite polish.
Then if you wish roughen the surface on the inside and glue some reinforcing material over the back of the crack using epoxy glue.



Mike

Vintage_Man2012 3rd Nov 2020 5:07 pm

Re: Help required: Cracked case repair
 
Hi folks,

Thanks for your help, I found David's post on the fantastic job he did on his duck egg blue FB10 and I have taken the decision to opt for a similar approach.

I've glued the crack from the inside of the case and let gravity do the work, then filled the crack and sanded the case.

I'm just waiting on the arrival of some etch primer and then I'll get the case painted, although unlike David's duck egg blue I am going to try and keep the colour as close to the original as possible.

Paul

Mr 1936 3rd Nov 2020 5:26 pm

Re: Help required: Cracked case repair
 
I have been recommended (but haven't yet tried) special low viscosity superglue which is good at wicking into hairline cracks. It's sold for repairing and stabilising fossils, so should be appropriate (for old radios that is, not for me !).

The Philpott 3rd Nov 2020 5:28 pm

Re: Help required: Cracked case repair
 
If the crack recurs in future consulting someone who repairs plastic car bumpers may help. (I am thinking stop-drilling and reinforcing from the rear)
It doesn't look like it's stressed too much so hopefully this is an end to it.

Dave

Lloyd 1985 3rd Nov 2020 6:53 pm

Re: Help required: Cracked case repair
 
Quote:

Originally Posted by Mr 1936 (Post 1306742)
I have been recommended (but haven't yet tried) special low viscosity superglue which is good at wicking into hairline cracks. It's sold for repairing and stabilising fossils, so should be appropriate (for old radios that is, not for me !).

Yes, I had some that was branded Loctite, can't remember the number off it now though, it could have been 420 or 406, it was really good stuff, had the consistency of IPA, and it really did wick it's way into even the tiniest of cracks! Sadly, I lost it in a house move, where it was so good at wicking, it wicked it's way out of the closed bottle, and all over the inside of the box it was in! Really must get some more..

Regards,
Lloyd.

David G4EBT 3rd Nov 2020 9:15 pm

Re: Help required: Cracked case repair
 
4 Attachment(s)
Much depends on whether you want to keep the cabinet as it is. I've restored several KB FB10s for myself and my younger (adult son). I don't think I've ever paid more than a tenner for them - mostly less, off the scrapper pile at Golborne or NVCF. Some have had chucks missing from them, others, just cracks. I've invariably resprayed them, but if you want to keep it original, most of what I've written below is irrelevant.

The closest example to you're cracked one is shown in the pics below. (A fiver from Golborne, 2018).

Quite how they get damaged like that yet the dial remains intact is a mystery, but a rather lucky stroke!

Depending on the nature of the damage, I've used car body filler, Ronseal catalytic 'High performance' wood-filler, which sets rock hard in minutes, sands really well and would be quite a good match for the case and is what I'd have used had I not intended to spray the case.

As I was only concerned about making a strong repair and less concerned about how it looked, on this occasion I cleaned out the crack and used a two-part epoxy known as 'Super Steel', applying some inside the cabinet for added strength. When applied it looks black, but when sanded is a light grey colour. I then rubbed it down with 220G wet and dry and likewise, sanded the rest of the case to give a key for a high build primer. I primed the set then sprayed it blue at my daughter in law's request.

Pic 1: Shows the crack.
Pic 2: The crack filled and sanded.
Pic 3: The case primed.
Pic 4: Sprayed blue gloss acrylic.

I don't care that they never made a blue one and nor does the recipient.

Others have been pink, green and red.

If chunks have ben missing, I've bridge the gap with wire from paper clips drilled edgeways into the case on each side of the gap, then built up with filler, sanded to the correct profile, primed and sprayed. I'll add a few more pics.

(I've also restored the electronics as there's not much point in putting lipstick on a pig that doesn't 'oink'!)

David G4EBT 4th Nov 2020 9:16 am

Re: Help required: Cracked case repair
 
5 Attachment(s)
Some pics of the repair I made to another FB10 cabinet with a chunk missing at the rear cable entry aperture. Over the years, I've restored six in all, some with quite large chunks missing. Sprayed in a range of colours - red, green, blue, pink (1), cream...As I said in my earlier post, most were no more than a fiver - many visitors to BVWS Swap-meets or at car boot sales who see a damaged Bakelite receiver seem to consider them write-offs, fit only for scrap as donors of parts, so they have little appeal. (I've done likewise with other small damaged Bakelite radios, EG: Murphy U198, Philips Philetta).

I've used wire armatures to support filler to bridge the gaps and have created card templates from the undamaged areas of the cabinet to use to get the correct profile of the repair when sanding to shape with 220g wet and dry paper. For example, if the bottom front RH corner has a chunk missing, I've made a couple of stiff card templates using a 'Profile Gauge' on the undamaged front LH bottom corner, which will be a mirror image of the RH side:

https://www.toolstation.com/vitrex-p...BoC_mgQAvD_BwE

This particular example only had a piece missing at the rear so was an easy repair. As the damaged was minor and at the rear, once cleaned up and the electronics restored, maybe some would have just left it as it was, but it was always my intention to respray it anyway.

Pic 1: I created an armature using paper clip wire. The sides of the gap were drilled 1mm to insert the wire, held in place with blobs of superglue.

Pic 2: Isopon P38 two-part Car body-filler applied and shaped to the correct profile:

https://www.amazon.co.uk/Easy-Sandin...86771113&psc=1

Pic 3: Repair primed.

Pic 4: Whole cabinet primed.

Pic 5: Cabinet sprayed gloss racing red.

Hope that's of interest and help.

Vintage_Man2012 16th Nov 2020 6:15 pm

Re: Help required: Cracked case repair
 
Thanks David,

I certainly admire your restorations, your rebuild on the case with the chunk missing is fantastic.

I am happy to report, I've now completed the repair on mine and it is looking in similarly good condition to yours, certainly worthy of promotion from the workshop to inside the house!

Best wishes
Paul


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