PYE D16T main control knob decomposition

[Atlantic 52]

Hello to all,
A few years back I restored my Pye D16T TV to good working order. The set was stored aside in our dry spare room whilst I have had our Bush TV12A in its place in the living room. Wanting to 'fire up' the set to see it working again I noticed that the two main control knobs, volume & brilliance, had what I can only call a hard white effervescence ring in the central indents. This does break away using my thumbnail but I alarmingly noticed the outer rims had deformed and the mounting shanks had 'swollen' a bit. When I restored the set I washed the knobs in soapy water then T-Cut or Bakobryte polished them (I can't remember which was used) to a nice shine. That condition did last some years but very gradually they have what I can only describe as started to 'decomposed' and I am obviously very upset about it. I did use some thin oil pen applicator oil on the control shafts to make removal and fitting easier (they were very tight originally) and wondered if the thin oil might have been the cause. Anyhow, can anyone tell me if they have had any similar issues and also suggest what I might be able to do to them to arrest further decomposition? I can't imagine being able to find proper replacements. Many thanks, George

[high_vacuum_house]

Good evening,
I think it was a poor mix of ingredients that made up the Bakelite mix before the knob was moulded. Possibly due to shortage or lack of decent or the correct materials as they were made just post war when materials shortages were common?

My D16 console currently has the wrong knobs on it due to this phenomenon. John Evans set has the same issue as well so I don't think it is anything that we can do about it to stop or stabilise the issue.
Christopher Capener

[line sync]

Hi George
I`ve also got a D16t with the knob problem , in fact mine are worse than yours and if I had a camera capable of taking good close ups I`d post a picture.
The knobs are made of plastic not bakelite as are the ones on the B18t but a different shape than the D16 are also starting to deform.
I`ve had both these sets along time and the knobs were perfect when I got them.
Pye did make post war radios with the same shape knobs as the D16 but made them out of black bakelite.

Robin

[petertheorgan]

I have worked on two D 16Ts and the knobs were past saving on both of them , sadly both mine and the one at the wireless and television museum in Dulwich both have incorrect Knobs but the replacements are in keeping

[Techman]

From what everybody seems to know now, it's a pity that those original knobs couldn't have been stabilised somehow while they were still good. They were probably rare survivors at the time when that restoration was done.

[The teleman]

My D16T has exactly the same problem
I think the only solution is to fit some alternatives
that are in keeping with the sets age & style
It’s sad but I can’t see any other way around this problem
Unless anyone can come up with a 3D print of some replacement

Chris

[Heatercathodeshort]

Identical knobs are employed on many very common boring PYE radio receivers of the period. It's a simple matter to remove the lettering but most of the ones I have seen are too faint to read anyway. John.

[Lloyd 1985]

If anyone has a set of knobs that haven’t deformed, or that are not too bad yet, it could be worth making a silicone mould of them, I’m currently using some stuff from eBay, Polycraft GP-3481, which is specifically for making moulds and it copies all the fine detail of the original parts. I’m actually making a new set of knobs for my Ekco A22 with it! Once the mould is made it will last for ages, I’ve got some mould’s I made nearly 8 years ago that still look good. I’ve got some knobs on a PYE P75 that are made of a similar material, and they still look ok at the moment, maybe it’s time to make a mould before they start decomposing!

Regards
Lloyd

[Nickthedentist]

Isn't this phenomenon known as "deliquescence"? Something that's common on 200-series phones' "horns" which support the receiver, I think.

[mark pirate]

This is a common problem, I have a couple of Pye radios where this has happened, it has also a problem with the D18T and LV20, these have warped but do not have the white residue present.

Mark

[McMurdo]

I was going to say 'efflorescence' where deposits are found emerging from the compound, certainly I thought effervescence was something to do with cola.

My own boring Pye radio has those knobs and they look rather melted

[Atlantic 52]

Many thanks to all of you that have replied to my post. I am pleased its not just me but sorry its a common problem! I wish I had taken a mould of them when they were in good fettle a few years back. Its odd to me that its happened quite suddenly in relative terms. Maybe cleaning and handling have accelerated their decay. It would be nice to 'arrest' them from getting worse but I guess its a done deal, they will go like all of us eventually.

[mark pirate]

I don't think cleaning has caused your knobs to deteriorate, it is just a problem with the composition of the early plastics.

This problem seems to be exclusive to early post war Pye sets.
One of my sets has 2 perfect knobs and 2 badly warped knobs.
The first time I saw this, I thought the set had been left close to a fire!

Mark