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Old 28th Jul 2019, 11:51 pm   #1
Demented
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Default Substance applied to Radio circuit board screws ?

As subject title suggests; I’m wondering what is the actual substance, I guess a glue, that was applied to the metal internal screws of Transistor Radios of the the 1970's and 80's.

I believe it must be some kind of screw lock but I don’t recall it being applied to the screw threads, only over the screw and onto the circuit board or plastic radio housing; it’s really tough but rubbery, stretchy and kind of a similar colour to a traditional rubber band.
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Old 29th Jul 2019, 10:07 am   #2
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Default Re: Substance applied to Radio circuit board screws ?

No idea what it is but it may be more of a tamper evident seal than a locking compound. To some extent it could be both, of course.
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Old 29th Jul 2019, 10:56 am   #3
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Default Re: Substance applied to Radio circuit board screws ?

RS still do it 196-5245 tamper seal

but I just use any old nail varnish my daughters have stopped using
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Old 29th Jul 2019, 12:01 pm   #4
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Default Re: Substance applied to Radio circuit board screws ?

The stuff I remember was semi-soft, a bit like dried-out bubblegum.

A similar but slightly more-waxy brown 'goop' was commonplace in Japanese electronics from the 70s onwards - typically slopped over 'open coil' tuned-circuits in things like FM/TV front-ends, presumably to reduce vibration.

This stuff degrades with age, significantly reducing the 'Q' of the coils. Sometimes to the point where the equipment ceases to function! A while back I had a little "Totsuko" SSB transceiver given to me because it didn't work. It had a VXO for frequency-control and the VXO coil was liberally covered with this goop, as was the piece of foam that was stuffed inside the turns of the coil. I was able to unsolder both ends of the coil and remove it from the radio - then dose it with some MEK to dissolve the goop.

Reinstalled, happiness (and VXO function) was restored.

I've seen this 'coil goop' on the FM tuned-circuits of some later Roberts portables - so beware!
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Old 29th Jul 2019, 1:10 pm   #5
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Default Re: Substance applied to Radio circuit board screws ?

I alays thought that was Evo-stik. (Evil-stik?)
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Old 29th Jul 2019, 1:20 pm   #6
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Default Re: Substance applied to Radio circuit board screws ?

Icom used to use the rubbery stuff to lock trimmer capacitors by just applying a big dod of the stuff.

Problem is, 20 years on, we found it rotted the metal parts of the trimmer away.

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Old 29th Jul 2019, 1:32 pm   #7
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Default Re: Substance applied to Radio circuit board screws ?

Mostly in Japanese radios of the 1970's era, any locking compound there was simply enamel paint, not a nail varnish. They had a penchant for white.

The Japanese did produce a professional screw thread locking compound. It was not used in domestic appliances. Olympus used it in their medical equipment, various fiber-optic scopes. It was a transparent red varnish called Neji-lock.

I think this is the same stuff:

https://www.techsil.co.uk/threebond-1401c-200gm

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Old 29th Jul 2019, 2:17 pm   #8
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Default Re: Substance applied to Radio circuit board screws ?

There was some stickey stuff that was intended aid assembly by temporary sticking screwheads to the tool.
I remember it on tuner push-button units in small-screen ITT TV sets and I knew what it was because I had seen the technique shown on Tomorrow's World.
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Old 31st Jul 2019, 11:24 am   #9
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Default Re: Substance applied to Radio circuit board screws ?

I know the substance you refer to. If you want to replicate it this stuff is the most similar you will get.

https://www.selfadhesive.co.uk/3m-tr...SABEgLS5PD_BwE
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Old 18th Aug 2019, 5:22 am   #10
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Default Re: Substance applied to Radio circuit board screws ?

Thank you to everyone who has been good enough to reply, offer opinions and provide a link.

I’m sorry for not replying sooner, I wasn’t notified of replies and I didn’t expect to receive so many, thanks.

My question was out of curiosity, after stumbling across a thread lock question within a drone web-forum; which got me wondering why such a substance it not available as a thread lock for metal screws into nylon/plastic etc;

I seem to remember this stuff being applied over the screws within radio circuit board but not to the thread, although it was quite robust and rubbery without becoming brittle over time, nor did it appear to cause damage to the plastic casing it may of flowed onto during application.
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Old 18th Aug 2019, 1:53 pm   #11
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Default Re: Substance applied to Radio circuit board screws ?

Another one is Loktite 'Stick & Seal' Extreme, red colour or Loktite 'Stick & Seal' Indoor, green colour.
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Old 20th Aug 2019, 7:39 pm   #12
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Default Re: Substance applied to Radio circuit board screws ?

Thanks for the suggestion Terry; although, I’m no expert, it appears the consensus within the Radio Control/Drone Community, is that the likes of Loktite thread lock causes damage to plastic, either making it brittle or just not that effective; it was this opinion that got me thinking of the substance applied to Radio circuit board screws.
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Old 21st Aug 2019, 2:04 am   #13
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Default Re: Substance applied to Radio circuit board screws ?

The Loktite stuff I mentioned is not thread lock, it is like that red stuff you find spread over the top of screws.

Specs indicate it is ok for a wide variety different materials but I haven't tried (or needed to use) it.
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Old 21st Aug 2019, 2:15 am   #14
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Default Re: Substance applied to Radio circuit board screws ?

Thanks for the info & sorry for my misunderstanding; as it’s by Loctite, I thought it was the thread lock which the RC/Drone community appear to shy away from.
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Old 21st Aug 2019, 6:00 am   #15
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Default Re: Substance applied to Radio circuit board screws ?

Quote:
Originally Posted by rambo1152 View Post
There was some stickey stuff that was intended aid assembly by temporary sticking screwheads to the tool.
I remember it on tuner push-button units in small-screen ITT TV sets and I knew what it was because I had seen the technique shown on Tomorrow's World.
For similarly out of the way screws, when putting stuff back together, I use a dot of blu-tak between the driver and the head.

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Old 21st Aug 2019, 9:39 am   #16
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Default Re: Substance applied to Radio circuit board screws ?

Referring back to Post No.1-
After encountering this stuff fixing a 'modern' Bush boombox I can say that the glue (or its oxidation products) do soldering iron tips no good at all. Ideally I would have cleaned 100% of it away before soldering, but in some situations the glue is tougher than the components that it's attached to, and I had to burn some of it to deprive it of its mechanical strength.

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Old 23rd Aug 2019, 11:49 am   #17
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Default Re: Substance applied to Radio circuit board screws ?

I think the stuff you are referring to could be products such as Threebond, as already suggested:

https://www.yoycart.com/Product/27156656020/

I used to work for a Japanese electronics maker and this is what they used (in the 2000s, but probably the same kind of glue back in the 70s, 80s and 90s). I still have a couple of bottles somewhere!

It is used not just as a threadlocker but 'Agent for preventing screw loosening, leaks and rust'.

If you look at the datasheet, you will see some things that would make sense for it's use in economically priced products:

Use of washers, split pins, double nuts can be eliminated.
TB1401 permits use of less accurate screws and bolts. In addition, this enables users to save
much material cost.
Material control can be simplified. Up to now, many kinds of washers, splits pins and other devices
were prepared to meet specific requirements. However, TB 1401 can be used universally
irregardless of shapes and sizes of screws.
TB 1401 can be used again even when designs of machinery are changed.
No skills are required in application.

Applied to the screw head it can prevent rusting; see the following where it (different brand) is shown exactly for putting on screw heads:

https://item.taobao.com/item.htm?spm...d=578633127004


For me it really is iconic for it's ubiquitous use on those paper-resin PCBs in vintage electronics. Second only to wax and that little scrunched up piece of foam in/on coils in transistor radios!!!
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Old 23rd Aug 2019, 12:01 pm   #18
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Default Re: Substance applied to Radio circuit board screws ?

When I was working on light aircraft avionics we had a kit of oddments from Motorola for the weather radars. There was a bottle of what looked like red nail varnish called "staking lacquer". For locking screw heads I assume, I never really found a use for it as it was already partially set.
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Old 23rd Aug 2019, 12:59 pm   #19
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Default Re: Substance applied to Radio circuit board screws ?

I would just use ordinary screwlock.
It is sold by many manufacturers including Locktite.
Studlock is the green non removable kind.
Screwlock is either blue or pink.
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Old 23rd Aug 2019, 3:36 pm   #20
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Default Re: Substance applied to Radio circuit board screws ?

I've heard it described as Sony Bond, which is a type of elasticated gluey stuff dripped over pcbs. If it touches anything hot it turns brown and then conductive, with a clear oily discharge that dissolves the component eventually.
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