Hi from a newby and Bush TR82C Distorted at high signal strength

[Wanderingfree]

Hi all. Newby here

I have a Bush TR82c Mk1 I Think as it has OC44's & 45's.
The radio is in good condition visually I have dismantled and cleaned it up including the MW/LW switch.
it seems to to tune on both wavebands but when I get a strong signal it distorts.  It doesn't look like it's been worked on before (if it has its very tidy) it still has the old electrolitics red and yellow.  What do people do about replacing period components (so it looks authentic) and would you change the electrolitics as a matter of course.
Any idea where I can get a circuit diagram from please.

many thanks

[Crackle]

It sounds like the AGC capacitor may have failed, it looks like it is C10, 4uF.
replacing the electrolytic caps with modern equivalents is going to be difficult if you want it to look authentic.
I generally find that the wax paper caps dont need replacing in these very low voltage circuits.
Mike

[Wanderingfree]

Thank you Mike. I thought it might be. I haven't worked on this sort of kit since the 70's and I am really enjoying it.

Mike

[ppppenguin]

As Mike (Crackle) implies, those red and yellow electrolytics will often need replacing. I would replace all of them without even asking if they are faulty. If they are still OK, it won't be for much longer. You will be using modern parts with modern values. Bascially 10/22/47 and multiples so just use the next one up. Hence 4.7uF to repalce 4uF etc.

Again as Mike (Crackle) says, at low voltages old wax paper caps are usually OK. Unlike in valve sets where a little leakage will be a problem. I would tend to replace them if overhauling a set but fully understand that others will differ.

Generally I'm not fussed about new components not looking authentic in old sets. Others will differ and I respect that.

[Wanderingfree]

Hi thank you for that. I am looking to replace C10, so 4.0 MicroFarad @ 10V. I can find 4.7 MicroFarad but the lowest working voltage 25v is that ok or do I need to do more research?

Mike

[Wanderingfree]

Interestingly. C10 (age cap) circuit says 4 MicroFarad @12v. I have checked it and it is a 10 MicroFarad @ 6volts. It measures 12 MicroFarads but I don't have an ESR meter
Does any one know if there were any modification bulletins?

[ppppenguin]

In general, you can use a higher voltage capacitor than was originally used, assuming it will physically fit. With electrolytics it's better not to use a very much higher voltage rating. A 25V, 35V or even 63V part will be fine but don't use a 200V part.

All electrolytics have very wide tolerances. +/-20% is common. -25%/+100% not unknown. So 12uF is OK. But....

It's common for faulty capacitors to read high with simple testers. It's due to leakage which the tester sees as increased capacitance.

A 10u cap will usually be fine in place of a 4u but in this position it would be worth doing a bit more research to see if the design has changed. Don't worry too much. 10u will work.

Don't forget that electrolytics have to be fitted the right way round. On older caps the +ve end is usually marked + or is red. On modern caps the -ve end is usually marked with a strip and a minus sign. I have no idea why they now mark the -ve end.

[Wanderingfree]

Thanks for your response

[boater sam]

If you wish to maintain authenticity it is possible to drill out the centre of the old Plessey yellow and red capacitors and fit new small ones inside.

Depending on the condition of a set I prefer to do this to a slew of new looking parts.

But then I am a little OCD.

[Wanderingfree]

Hi. Thanks for that. Yes I saw a video of that being done and think I might follow suit. still confused at C10's (AGC Cap) value in the set
as it's 8 Microfarad @ 10v and the circuit says 4 at 12v. I don't know if there was a service Bulletin with an update.

Mike