Noisey Ric 2

Thanks Trevor, in view of the simple output stage, I will replace all carbon resistors concerned with metal film ones. I have a number of OC81Ds so will try to at least reduce the noise.

Regards,
Rob

Or leaky capacitors,

Or noisy Power supply or dried out electrolytics.

Radio is powered from a battery so can rule out power supply. Caps could also be a problem, I have hooked the workshop amp to the volume pot and the af output there is much reduced in noise.
Soldering iron out after tea......
Rob

I'd find this by shorting the radio at various points to deck. If the noise vanishes, go towards the speaker, if not, back towards the aerial.

Most of this is in a chip - TDA100. These are reliable. I'd go for resistors first. They are known for it...

Cheers,

Steve P.

Hello,

There is another possibility - it's likely that your earphone is much more sensitive than the loudspeaker, so the (otherwise acceptable) background noise from the amplifier is being noticed. It might be worth putting a resistor in series with the feed to the earphones - this could be hidden inside the set, or perhaps in the external plug or maybe in a purpose-made adaptor...

Although before going to this effort, are you able to check other sets with the same earphones?

Performing the usual sort of fault finding will be tricky with this set because the amplifier is quite complicated - there is a fair amount of stuff going on inside that chip, all with AC and DC feedback loops. A blanket change of resistors and capacitors might be the faster way to get a result.

Having said all of that, I've just powered up one here, and have to say that it's quite noisy (volume at minimum, speaker held to my ear). I've got a couple more examples I could dig out and try, but at this stage I'm inclined to suspect that this might be a "feature" rather than a "fault"

Cheers,

Mark

Thanks all for their help on this one, in the end I changed the resistors in the amp and the driver transistor. It seems noticeably less noise now although I will not be sure till i'm listening in bed with no external noise.
Annother Roberts soldiers on, I'm glad to hear that the IC in this is reliable as I had read of troubles elsewhere.
I think that the idea of placing a series resistor in the earphone lead might be a good idea as the earphone is quite sensetive and volume is near minimum to listen comfortably.

Regards,
Rob

Doooh! Looks skyward and shakes head in disbelief!
Having 'fixed' the RIC2, I look forward to bedtime listening except...
nothing! No audio!
Now I'm usually carefull with soldering and I was ready to strip the set when it burst into life.
Hands up all experts that can guess what I have over looked all along.
Yes, the earphone socket is making intermittent connection!
Several squirts of servisol and set returns to normal, also with less noise!
Now I am unsure if my component swapping or the earphone connection has improved the original problem?
One I will look out for next time.

Rob

This article on Paul's site mentions three main failings and one being the earphone socket, I read it this morning but discounted it DOH!

http://www.vintage-radio.com/recent-rep ... -ric2.html

Chris

Hi Rob: this my first post on, what for me is a new forum: could it be that you have next to your bed one of those dreaded R.F. generators called a "Touch Lamp"? Or failing that do you have any B.T. Vision Powerline devices or similar? There are such a lot of "Electrical Noise Generators" in our domestic lives these days that can wreck  am reception!
Cheers
John

I used to have a 'Wake-up' light that gradually increased in brightness. Sometimes if I woke up before it switched on, I'd have the radio on at low level. As soon as the light switched on, the noise on the radio would increase as the lamp got brighter. I sold it (the lamp, not the radio)!

SB