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Help! My A&R A60 just died. Fuses?

M

Musiciseverything

pfm Member
Hi.

I should know better by now to not attempt any hifi modification or repair I I the wee small hours!

I recapped my goodmans magnums last night and once plugged in, it all sounded much improved, until, fuzzy distortion for a few seconds then POP!

I feared it was something a is with my armature handiwork, although I triple checked the job for any shorts. I did notice that there were a couple of breaks in the blue and red sheathing of the speaker cables exposing bare copper, and the way they were connected, it looked as though they could have been touching.

The short of it is ( pun intended ) the amp is no longer putting out signal. Does anyone know if the fuses next to the speaker protection fuses are for protecting the amp from any late night misdoings etc?

any help would be very much appreciated.

thanks, Dave
 
There are DC fuses as well as the speaker fuses (the latter are very bad for sound quality) but it is likely the amp is blown. You may have been lucky...
 
Why have you PM'ed me to ask exactly the same question? As I said above yes there are DC fuses, no doubt what you call "fuses to protect the amp". They probably won't have protected the amp and it will probably be "blown up" unless you have been very lucky.
 
'Fuzzy distortion for a few seconds and then POP!' is never a good sign, however, the manual does mention that the loudspeaker protection fuses may blow if the amp is run into a short circuit. As such, it wouldn't hurt to remove the lid and have a look round the vicinity of the output transistors (located inboard of the heat sink that protrudes out the back) for any signs of burnt components, particularly resistors. Should none appear damaged, test the output fuses at FS1 and FS101. These should be 1.6A fast blow. Using a multi-meter set for continuity testing, it is simply a matter of lifting one end of each fuse out of its clip and touching the probes either end of each fuse in turn.

WARNING: Be careful to disconnect the amplifier from the mains before removing the cover. Also, avoid coming into contact with the exposed terminals of the large filter capacitors that are positioned on their sides. These can hold a charge for quite some time.
 
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Arkless Electronics said:
There are DC fuses as well as the speaker fuses (the latter are very bad for sound quality) but it is likely the amp is blown. You may have been lucky...
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Upon reading your thread on how the output fuses were bad for sound quality, I cut some fuse diameter copper bar and out that there instead. I don’t think it did much, but I left it there anyway, so I really hope I should have put those fuses back in!
 
Arkless Electronics said:
Why have you PM'ed me to ask exactly the same question? As I said above yes there are DC fuses, no doubt what you call "fuses to protect the amp". They probably won't have protected the amp and it will probably be "blown up" unless you have been very lucky.
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On hindsight, I’m not sure why I also pm’d you. I was panicking. I’m autistic. Also for some reason there was nothing showing in my inbox so it looked like nobody was replying to this thread. I was just desperate for some answers!
 
JensenHealey said:
When I had an A & R A 60 the output fuses were fairly regular blowers. My mother used it for ages - even she could buy and change them!
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I had one that kept blowing them - I upped to the next value fuse and it stopped! None of the others I have had blew a single pair, oddly. I did try wiring them out briefly but couldn’t hear any difference. Further evidence of my cloth-earedness.
 
chartz said:
Or the fuse holder is corroded. That happens.
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I had the amp recapped and serviced and the fuse holders were replaced.
Marchbanks said:
I had one that kept blowing them - I upped to the next value fuse and it stopped! None of the others I have had blew a single pair, oddly. I did try wiring them out briefly but couldn’t hear any difference. Further evidence of my cloth-earedness.
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glad you didn’t hear a difference either. I had a hearing exam and full deep clean recently, and was told that my hearing was exceptionally good for my age and not far from perfect. I’m a musician and sound engineer. Although it stands to reason that these thin wires in the fuses could affect sound quality, and I complete bought the theory, I think I’d hear if it had made a difference.
 
Vinny said:
Notifications take anything for an hour or so to something like 12-14 hours to arrive in my inbox.....................
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That’s handy to know! Three days later the notifications hadn’t appeared. It was only seeing the thread in the list of threads that I saw it had a few replies!
 
Musiciseverything said:
Upon reading your thread on how the output fuses were bad for sound quality, I cut some fuse diameter copper bar and out that there instead. I don’t think it did much, but I left it there anyway, so I really hope I should have put those fuses back in!
Click to expand...
I think this means that your amplifier was subsequently automatically enrolled in the Arkless Electronics aftermarket extended warranty program.
 
Musiciseverything said:
That’s handy to know! Three days later the notifications hadn’t appeared. It was only seeing the thread in the list of threads that I saw it had a few replies!
Click to expand...

I suspect that sometimes, not always, a response from you before a notification, stops the notification - the system seems chaotic and slow. Notifications do not always appear in order either - I have had notifications to recent PMs before one for an older PM.

In short - don't rely on them being anything but a long term reminder.
 
As in an earlier thread about this same fuse blowing: https://pinkfishmedia.net/forum/threads/a-r-a60-problem-with-speakers-fuse.239628/page-3

Copied to this thread.

Interesting reading through this thread. These amps are at best 35 years old and the earlier ones are well into their 40th year or more.
After this time some of the components may well just fail - and I am not just talking about the e-caps.
In my experience ( and I am not as expert a repairer as Jez and others on this website ), I look at the following when the amp fuses have blown:-

The power amp output transistors as mentioned. These are attached to the heatsink. Q20/Q21 and Q120/Q121. All of these are type TP3055. These need insulating from the heatsink when they are replaced.

The driver transistors Q18/Q19 and Q118/Q119. These are pairs of ZTX653 and ZTX753. Make sure you get them the right way round.

Then, I take a look at the protection circuit which is made up from resistors R53,54 55,56,57,59,60, capacitors C28, 29, diodes D1,2 and transistors Q16,17 ( Type BC547 ) - along with all their counterparts on the other channel ie R153 etc.

Very, very rarely the thermal feedback transistors Q14 and/or Q114 which are next to the heatsink have failed.

Hope that is helpful.

Happy listening - Julian
 
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