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A&R A60

anotherA60guy said:
Hi trancera,

Agree that it don't do pop or rock well compared to others. but The dinimished performance appeared about a year after th major recap.

I have the Rogers LS35/a and another DIY Coral Flat6 single driver. Room/hall is 20ftL by 10ftW ish.
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All three of my A60's work fine with Chartwell LS3/5a's, however LS3/5a's and loud deep bass do not really go together.
 
Analog addict said:
Internally there are two fuses for the power supply dc rails and two speaker protection fuses. I'd start by checking them, but if any of them prove to be blown, given the fault you have described I would not advise replacing the fuses until the amp has been checked over. The most expensive part of these amps IMO is the transformer and everything else with the exception of the pots is a fairly simple job to replace.

Hope this helps.
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I have replaced all four internal 1.6A fuses and the amps still dead as a Dodo:confused:

Rich
 
If you check the fuses again, I think you'll find the two rail voltage fuses will be blown.
If so, you have a serious problem, and should leave it alone, and take it to an Amp Dr.
Your output transistors are shot, and so would be the driver transistors.
 
Took my A & R A60 around to a friend's who had this Italian valve amp (which cost around a grand). After auditioning the A60 with his speakers he quickly got rid of his valve amp!
 
My A60 is now working like new thanks to the hard work of fellow forumer 'Analog Addict'. Output trannys were replaced and a full re-cap done in double quick time. I can highly recommend his services to anyone with vintage kit who like me can't tell one part of a circuit board from another.
 
As I have a nice example myself I tried mine out the other night. It's very different to what I have been using. The combination of WD Kel 84 and a Project valve phono stage has a very warm and mellow sound. I love it and have grown so used to it.

The AR sounds stark in comparison...........really different! I think the phono stage may be what it is. After a few hours I became less aware and enjoyed the music as much once again. I don't know which was nearer the Mastertape as they aint here :D
 
My A60 works fine except for the phono stage which pops and crackles intermittently. Which bits are the likely culprits?
 
florette69 said:
My A60 works fine except for the phono stage which pops and crackles intermittently. Which bits are the likely culprits?
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My first thoughts would be either an electrolytic capacitor has gone noisy or possibly a dry joint or crack on the PCB.

Are both channels bad, or is it just one?
 
One channel (so far), although I only discovered this problem by chance when trying out the turntable input recently. I'd sort of assumed a cap was the failing. What's the easiest way to identify the point of failure?
 
florette69 said:
One channel (so far), although I only discovered this problem by chance when trying out the turntable input recently. I'd sort of assumed a cap was the failing. What's the easiest way to identify the point of failure?
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There are so few caps in the phono stage, that it would be omiss not to replace them all, indeed, on an amp of this age, it would benefit from replacing all the electrolytics once you've tracked the fault down; it doesn't take too long. Another source of crackling are the din sockets and source selector being dirty/corroded.
 
Just bagged one on e-bay for £48 including delivery. I spent las week restoring one for a PFM member , liked what it does , so thought why not. Go nicely in my computer system
 
Hi Gang. I've just been given an A60 and T21 (by the Piano professor of one of the London music colleges!). One of the channels had died and was declared inoperable so he was persuaded to buy a new amp and matching tuner. I was recruited to put the set-up together as connecting wires to boxes is not his strong point.

The A60 is a tidy later model, dated 26th June 1984, serial number 21 XXX. The -ve DC supply fuse had blown (I've removed it in the photos below) but nothing else is obviously amis to my utterly inexperienced eye. I fancy learning a little more about working on electronics via servicing this according to Rob's instructions. Is this a realistic place to start? My only previous experience was building a 'Geddon clone, but that is still working 5 years later and the house has not burnt down, so I feel ready for something a little more challenging.

Comments up-thread, if I understand them correctly, suggest that blown power-supply fuses may indicate something major. How do I diagnose?



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Sometimes fuses do just go Duncan, guess it's age, or sometimes if the amp has been turned on with the volume set at full the surge can kill them. Was it 'badly' blown ie violent, blackened? usually worth starting by replacing it with the correct value and trying again. If that blows the most likely suspects are the diodes used in the bridge or the output transistors. Check them all with a meter if you can. The A60 is a fantastic sounding but fairly straightforward and very reliable amp. Most other faults capable of blowing the mains input fuses would show themselves by obvious burning of a component, that might mean they have also fallen victim to a deeper fault though.
Good luck.
 
I concur. Fuses do fail due to age. Every time the amplifier is used, there's some thermal stress on the fuse. Over a long period, this can set in metal fatigue, and the fuse eventually fails for no good reason.

However, I would expect this more on the mains fuse rather than the + or - supply fuses.

I agree with the suggestion to replace the fuse with the correct value (make sure it's a fast-blow fuse as the fuseholder is labelled 3.15A QB) Note that the other fuses are all incorrect, the 'speaker fuses are slow-blow but should be quick-blow, and the +ve supply fuse is a slow-blow too but should be QB.

If the fuse holds good, then the amp would seem to be OK, but if the fuse immediately blows again, then there's a real fault. Rectifier or output transistors as already suggested is favourite.

I'm a bit concerned as to why the fuses have been replaced by Slow-Blow fuses, possibly out of ignorance of the difference, but if there is a fault, it could have been caused by the wrong fuse failing to protect the amp. Anyway, fuses are cheap enough so its worth trying.

S.
 
Thanks a lot. That's very helpful - and interesting - I'll source some QB fuses and try them first.

It wasn't 'badly' blown - no sign of blackening. I'll check with the owner but I'm 99.99% sure he has had this from new and 99.9% sure he has not have taken the top off (I had to plug in his new CD and amp). He did ask a shop to check to see if it was repairable but the fuses looked like they had been there a while. If someone has replaced them, I'm guessing it was some time ago.

Edit: from the man himself: "I am almost 100% sure that no-one has ever touched its guts since it was bought!". Strange!
 
Dowser said:
Sounds like the shop tried changing fuses then?
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That seems the most likely explanation. However the fuse caps had some black tarnish on them which suggested to me that they had been there a while. Still worth trial replacing I think, especially as they should all be quick blowing types.
 
Just seen this.
Definitely the wrong fuses wherever they came from.
Amp looks very clean though with no sign of overheating or distress.

Fit correct fuses and power up.
If nothing blows, leave it on for 10 minutes then check for any DC across the loudspeaker terminals. Any more than about 20mv let us know. Any less - connect some loudspeakers and play something.
 
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