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Cambridge Audio A5 help please?

nitrous

nitrous

pfm Member
Hi all, to cut a long story short my elderly parent’s amp has died. I would like to fix it because trying to get something new they can learn to use will be tricky. The amp has the phono stage fitted, which has a Rega 2 attached.

The symptoms are when switching on, with volume down amp lights up, outside/front panel LED and both red power amp LEDs inside indicating everything is powered. As soon as volume is moved even ever so slightly a huge ‘rustling’ distortion sounds almost at full volume (drivers leap about!) is all that can be heard. There is no sign of the signal from (in this case) DAB tuner or turntable, just the noise.

I was hoping to find leaking caps when I opened up case, but nothing visible.

Any ideas welcome, changing volume pot or caps should be within my capacity.....

Cheers.
 
The only thing I had that was kind of similar was a faulty transistor (Onix OA21). I removed the lid and pluged in an old test speaker. I then tapped all the components with a pencil until I hit the faulty transistor. Everytime I hit it, the speaker would pop and distort. I replaced transistor and everything was ok.

Interestingly, it gave similar symptoms to a faulty volume pot - Adjust the pot and you'd get crackling and rustling type sounds out of the speakers.
 
Hi Fatmarley, thanks for reply. Hadn’t thought of that one. It is both channels which is why I suspect the pot. Not sure what type it is though yet. I have a 10k knocking around I could try.

Thanks.
 
With deference to your parents' conservatism, I note these sell s/h for around £50 on eBay, so a "similar" replacement is plausible.
They must have solds LOADS, eBay is heaving with them!

BugBear
 
bugbear said:
With deference to your parents' conservatism, I note these sell s/h for around £50 on eBay, so a "similar" replacement is plausible.
They must have solds LOADS, eBay is heaving with them!

BugBear
Click to expand...
Bugbear, Hello, yes indeed thought has crossed my mind and may turn out to be the thing to do.
 
You could try some switch cleaner sprayed into the volume pot, but if you don't have any, I have used WD40 on noisy pots which seems to do the trick. I think that you can get a "film" on the track, probably dust, moisture or cigarette smoke.
AP
 
This isn't a cure, but it might be a diagnostic.

With the amp turned OFF run the pot from min to max, back and forth, quickly, several times.

Then test again (ideally with stunt speakers).

If it changes the behaviour, either for better or worse - it's confirmed that the trouble is the pot.

If nothing changes, you've just wasted 5 minutes.

BugBear
 
Thanks chaps, did try cleaning the pot, both methods before my original post and it didn't change the symptoms.

I think I have a solution now, not involving fixing the amp but changing TV and existing radios around in the house that seems to work.

But thanks very much for input. Cheers.
 
Another thought, in case a repair is still at the back of your mind.
I had the exact same symptoms on the vol pot of a very old integrated, turned out to be a dodgy earth connection from pot to board.
 
Cjarchez, thanks for taking time to reply. I”ll remember that for future reference. In this case we have replaced the separates for something new and everyone seems to be happy now! Cheers.
 
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