UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Cabinet and Chassis Restoration and Refinishing

Notices

Cabinet and Chassis Restoration and Refinishing For help with cabinet or chassis restoration (non-electrical), please leave a message here.

Reply
 
Thread Tools
Old 3rd Jun 2019, 3:05 am   #1
Boulevardier
Pentode
 
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 225
Default Distorted plastic tuning scale

This scale (7.8cm x 4cm) is from a small transistor "world" radio. It is on soft plastic and has no panel behind it when mounted. It has become distorted over the years - so much so that it is fouling the straight wire pointer that sits above it. It is held in place in small slots in plastic pillars - one at each corner. The plastic scale is about 4mm thickness, and there wouldn't be room to fit a stiffening panel behind it. I'm trying to think of a way to get it back to its flat original shape without damaging it. I wondered if applying a cool-ish iron to the back would do the trick - but I don't want to damage it further with the heat. Any thoughts?

Mike
Attached Thumbnails
Click image for larger version

Name:	front of tuning scale.jpg
Views:	122
Size:	42.8 KB
ID:	184353   Click image for larger version

Name:	Back of tuning scale.jpg
Views:	97
Size:	31.4 KB
ID:	184354  
Boulevardier is offline   Reply With Quote
Old 3rd Jun 2019, 4:49 am   #2
joebog1
Heptode
 
joebog1's Avatar
 
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 781
Default Re: Distorted plastic tuning scale

Depending on how old it is, it may even be nitro cellulose. I wouldnt be using an iron on it.
Its easy to test though, cut a tiny bit from somewhere it wont be noticed ( perhaps behind the front fascia) and see if it burns.
I would try and make a thin stiff aluminium backing plate with cutouts to fit the plastic pillars, then using a non volatile glue ( acrylic contact, water based, for example ) glue it to the backing plate using a very flat "press face" against the plastic, and sit a brick or two on top of it to press it flat. Acylic contact wont let go in the future either!!

A further thought would be to place the dial scale on a piece of glass, apply glue to the aluminium plate and place that on the top of the scale ( back to front of course), THEN apply the bricks.

Just my take

Joe
joebog1 is offline   Reply With Quote
Old 3rd Jun 2019, 5:50 am   #3
Lloyd 1985
Octode
 
Lloyd 1985's Avatar
 
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 1,528
Default Re: Distorted plastic tuning scale

Maybe sandwich it between 2 sheets of glass and warm it with a hair dryer? I think an iron might be too aggressive on that type of plastic.

Regards
Lloyd
Lloyd 1985 is offline   Reply With Quote
Old 3rd Jun 2019, 9:56 am   #4
Boulevardier
Pentode
 
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 225
Default Re: Distorted plastic tuning scale

Thanks - typo in my first post - 4mm should read 0.4mm
Boulevardier is offline   Reply With Quote
Old 4th Jun 2019, 2:57 pm   #5
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 4,089
Default Re: Distorted plastic tuning scale

It won't be nitro-cellulose, probably a plastic. Reminds me of 'Shrinkles' that my children used to colour in and stick in the oven to make miniature badges. Keep an eye on it as heat may make it shrivel up!
PJL is offline   Reply With Quote
Old 4th Jun 2019, 6:29 pm   #6
line sync
Hexode
 
Join Date: Sep 2009
Location: Kidderminster, Worcestershire, UK.
Posts: 404
Default Re: Distorted plastic tuning scale

I`ve had this problem a couple of times on mid to late 30`s radios and would also be interested to here if they can be flattened out.
I`ve tried pouring on very hot water and putting a heavy weight on top until cool but it didn`t work.

Robin
line sync is offline   Reply With Quote
Old 5th Jun 2019, 1:08 am   #7
Boulevardier
Pentode
 
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 225
Default Re: Distorted plastic tuning scale

Seem to have fixed it. I threw caution to the winds and went into battle with an iron. I took it step by step, and started with the lowest setting and a sheet of greaseproof paper between iron and the plastic back. It didn't seem to be harming it (or having much effect), so I gradually increased the temperature and the applied pressure. Got to a point where the plastic was definitely starting to stick to the glass panel below it, and stopped there. Result - job done - flat as a pancake again.

Risky process, and may not help others much - there are so many different formulations of "plastic" - let alone whatever it is they used back in the 40s,50s or 60s.

Mike
Attached Thumbnails
Click image for larger version

Name:	Front of scale.jpg
Views:	66
Size:	43.9 KB
ID:	184457   Click image for larger version

Name:	back of scale.jpg
Views:	65
Size:	17.6 KB
ID:	184458   Click image for larger version

Name:	Saisho.jpg
Views:	74
Size:	63.7 KB
ID:	184459  
Boulevardier is offline   Reply With Quote
Old 5th Jun 2019, 9:18 am   #8
ajgriff
Hexode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 496
Default Re: Distorted plastic tuning scale

Fortune favours the brave! Great result.

Alan
ajgriff is online now   Reply With Quote
Old 5th Jun 2019, 4:43 pm   #9
emeritus
Dekatron
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 3,090
Default Re: Distorted plastic tuning scale

I have a radio that looks like that, bought from Tandy when they were clearing stocks prior to closure. Mine is OK at present, but I will keep this in mind if I have the same problem in the future.
emeritus is offline   Reply With Quote
Old 5th Jun 2019, 4:54 pm   #10
Boulevardier
Pentode
 
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 225
Default Re: Distorted plastic tuning scale

The one I have is branded "saisho", and must have been bought about 20+ years ago. Can't remember where... For what it is, and the price (I think about 20.00 back then), it's not bad - conveniently small for travelling, and batteries (just 2 x AA) seem to last forever. Now, that's what I call portable! Couldn't get this battery life on anything made today.

Mike
Boulevardier is offline   Reply With Quote
Old 5th Jun 2019, 5:12 pm   #11
Boulevardier
Pentode
 
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 225
Default Re: Distorted plastic tuning scale

PS the one thing I resent is the insane graphic design of the tuning scale. For FM band it is coloured red/brown on a matt black background - virtually illegible without a bright light + angling to minimise reflection on the perspex front + a magnifying glass. Air Band is actually on the same scale and switch position as FM, which makes sense as they are continuous frequency-wise, but that section is blue on matt black - still pretty taxing on the eyes... Whoever designed that deserved to be shot!

Mike
Boulevardier is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 9:50 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.