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A&R A60 I can hear buzzing coming out of the speakers

audioflyer

audioflyer

No going back once you heard a ceramic cartridge
A&R A60 I can hear a buzzing noise coming out of the speakers even with volume turned down.

I'm currently servicing my A60 replacing the 40 plus year old capacitors and fitted a new set of pots.
It serial number indicates it's a MKII version but it uses BFRxxx transistor instead of the ZTXxxx devices.

One thing the always bothered me was a low level buzzing coming from the speakers ever when the volume is turned down. Even with all the capacitors changed the buzzing is still there?

In the service manual it mention about changing the smoothing capacitors if there is a low buzzing noise from the speakers. I've tried two sets of smoothing capacitors and it made no difference?

It's like there is an earth loop in the power amp sections did A&R do any modification to rectify this issue?
 
Both speakers or just the one side? All inputs?
Not familiar with the A60, but plenty on here who are.
Could be many things, e.g. a poor soldered joint on a psu cap.
 
a.palfreyman said:
Both speakers or just the one side? All inputs?
Not familiar with the A60, but plenty on here who are.
Could be many things, e.g. a poor soldered joint on a psu cap.
Click to expand...

Both channels, the buzzing was there ever before I decided service it all solder joins are fine.

It's only the power amp sections I can solve it, just wondering if there was a modification done by A&R to the early A60's MKI and MKII. The later MKIII model is total silent.
 
I have a very early A60 (no. 105) still in regular use. It has no hum at all - I’ve just checked at full volume - just a little hiss on line inputs and a little more on phono. I have recapped it, but I don’t remember any hum before I did.
 
If you put in a new volume pot - is it "earthed" back to the chassis ? Some models actually have a wire soldered to the body of the pot.
Ah just read the earlier post ! Already mentioned.
 
TonyScarlett said:
Just a thought, is the volume potentiometer earthed? I have heard of others who have had hum issues for this reason.
TS
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Operajulian said:
If you put in a new volume pot - is it "earthed" back to the chassis ? Some models actually have a wire soldered to the body of the pot.
Ah just read the earlier post ! Already mentioned.
Click to expand...

Problem solved it turn out that the volume pot needed the body earthing, the only issue was I used this:-

https://cpc.farnell.com/omeg/pc2g16eco100kb/pot-dual-gang-log-100k/dp/RE04443

I used some copper tape around the pot and connected an earth wire.

Thanks to all for your help.
 
Radfordman said:
Using an A60 at the moment, the later one in this pic (top one).

A60 3 off by A60man, on Flickr
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Lovely collection. I have a late A60 that’s lain fallow for years. It needs work and the hideous resprayed black cover stripped back to the wood.

PS do your A60s all have a relatively coloured and forward midrange? My good, restored, one has, and I like it.
 
Durmbo said:
Lovely collection. I have a late A60 that’s lain fallow for years. It needs work and the hideous resprayed black cover stripped back to the wood.
Click to expand...

Thank you. The middle one was a black cased one, I stripped it and refinished it. Refinished the other two also.
 
Durmbo said:
Great work. The natural wooden cased A60 is such an elegant design.

Did you see my edit to my previous post?
Click to expand...

As far as I can tell, all three A60's sound similar, and pretty neutral, although I do not use the turntable inputs, and they do differ. The older models use discrete components, the later ones use IC's.
 
Here's a link to one of my A60 with a ( nice) blue Alps pot and a very "chunky" earth as that all I had lying around at the time.
https://flic.kr/p/2kKSvJN

I looked up the Omeg pot through your link - to be honest, I would change it out for the Alps. I am sure it works but the Alps is one of the best of many upgrade possibilities.
Anyhow - glad it's all working and happy listening once again.
 
Conscious I'm reviving a slightly ageing thread, but there is another factor I've encountered that can cause earthing problems (and consequent low-level humming) in the A60.

It applies to the MkII versions with the discrete phono stage, which have an earth wire running from a spade connector on the inside end of the phono earthing post to a point on the PCB that's continuous with the star earth. I don't know whether later versions are similarly affected (they don't have the earth lead to the PCB but I think make this contact via a baseplate screw, so may be more 'robust' in this respect?).

Anyway, in the MkII discrete phono stage version, in order for there to be earth continuity with the chassis (and hence to the mains supply earth) the earthing post has to make good electrical contact with the rear case wall AND the rear case wall has to be in sound electrical contact with the base plate to which the mains earth is connected. In my example this wasn't the case because of perceptible corrosion build-up on the casing screw threads that added significant measurable resistance to the path to earth (there is no good metal-to-metal contact between rear panel and base panel - absent a good screw connection -because of the powder coat on the rear panel).

It pays to make sure all the casing screws make good electrical contact with their threads and to check with a meter that there's no more than a very small fraction of an ohm between the phono earthing post, its spade connector on the inside, and the chassis ground point behind the transformer. Alternatively one could run an earth wire between the earthing post and the chassis ground, always being aware of the possibility of generating earth loops.
 
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