Club 80-90 Forums

We have a non digital Roberts Radio R250 which we haven't used for a long time. Now we have a use for it and it has a problem, a similar problem to ones I have encountered over the years with aging audio equipment. The on/off + volume has points when it all cuts out, you can usually get it at a certain level and it will stay OK but try and adjust and the volume changes but sometimes will cut out and with further movement (almost wrote twiddling but that would be open to interpretation) come back again. There is also some crackling when adjusting which doesn't appear to be a faulty speaker but this particular control.

For those who might know about these things. Is this something that can be easily fixed, is it just that something needs cleaning or oiling or once a control starts doing this does it need replacing?

Old transistors that started to do this were usually just thrown away but this is a Roberts and we quite like it.

Paul

Try a few drops of oil into the volume control,inside the radio at the back of the volume control where the three tags go into the printed circuit board,turn the volume control up and down as you apply the oil [use some tissue to wipe away any excess oil].

I wouldn't introduce oil - it will only attract dirt and make it worse. Use switch cleaner if anything or meths. If it is very old the carbon track may be too worn or damaged and replacement would be the best option. Easy enough to replace though usually and cheap enough to buy. Its value should be marked on it somewhere.

Try some of this:

http://www.maplin.co.uk/p/servisol-cont ... 00ml-jp17t" onclick="window.open(this.href);return false;

It might help, otherwise the pot needs changing. Don't throw it away!

This is generally a sign that the carbon track has worn. It usually occurs bang on your favourite volume range for obvious reasons. They were fairly bog standard pods years ago but you might still be able to get them. The resistance range will be stamped on the pod and you'll need a logrithmic scale rather than a linear version. You need to be able to desolder/solder to remove old one and replace with new (if you can source one).

Dunno whether that oil tip above will help.....


E D I T: too slow but I'm submitting it anyway

Well it works for me [washes away the bits of loose carbon ] we use to dismantle volume controls and fill them with white grease,worked every time![at Radio rentals]
Seen the adds for the Roberts 250...99quid!!

dave friday wrote:Well it works for me [washes away the bits of loose carbon ] we use to dismantle volume controls and fill them with white grease,worked every time![at Radio rentals]
Seen the adds for the Roberts 250...99quid!!

Me too! I used to work for British Relay TV. We used to call such things 'dirty pots' [potentimeter]
Ahh, bring back valves

dave friday wrote:Well it works for me [washes away the bits of loose carbon ] we use to dismantle volume controls and fill them with white grease,worked every time![at Radio rentals]
Seen the adds for the Roberts 250...99quid!!

That's what the switch cleaner is for - bad workshop practice using oil and grease IMHO- they are designed to run dry. Short term solution that would create more problems in the future.

Was such a thing available in the 70's though, I would have thought we would have used it had it been around?

It's all coming back to me now...Radiospares switch cleaner [carbon tetrocloride sp? ,etc the best was/is? electrolube...
Tv sets with "fireball" tuners etc.

dave friday wrote:It's all coming back to me now...Radiospares switch cleaner [carbon tetrocloride sp? ,etc the best was/is? electrolube...
Tv sets with "fireball" tuners etc.

Yes, could have been the RS product as I remember we used a lot of their products. They are still going strong too, last time I looked anyway...

The grease mod was to new radios..we never had one come back!!

New Kentish Campers wrote:Was such a thing available in the 70's though, I would have thought we would have used it had it been around?

Yep it was as Dave says Carbon Tetrachloride, did that have a lovely smell.

New Kentish Campers wrote:Was such a thing available in the 70's though, I would have thought we would have used it had it been around?

Meths or surgical spirit was the easiest to use . When I worked at the at the MAFF laboratory we had pure alcohol at hand for pots.
I remember carbon tetrachloride being banned - main uses were dry cleaning, degreasing and in refrigerants I think.

At one point we used "wd40" but had to stop using it as it melts some types of plastic!!