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Quad 303 crackling noise

Conan

Conan

Loop digger
I'm currently using a Quad 303 with a passive amp and Falcon Acoustics Q7.
Recently I have noticed some crackling when adjusting the volume and sometimes no volume from the left channel.
Tried the passive with a Quad 306 with no issues so can only conclude that the problem is the Quad 303.

Any ideas of what this could be and what shall I do to fix it?

Many thanks
C.
 
Plenty of power and the amp is sounding lovely. Its just when I change the volume.
Any idea what things should I be looking for?
 
It's the passive pre that's faulty. Amps are different sensitivities hence passive used at different points of vol control range with each power amp.
 
Conan said:
Plenty of power and the amp is sounding lovely. Its just when I change the volume.
Any idea what things should I be looking for?
Click to expand...

Does it do it with the source component (I assume a CD player) disconnected? Could possibly be a DC issue (i.e. an issue with the source component).
 
Conan said:
I'm currently using a Quad 303 with a passive amp and Falcon Acoustics Q7.
Recently I have noticed some crackling when adjusting the volume and sometimes no volume from the left channel.
Tried the passive with a Quad 306 with no issues so can only conclude that the problem is the Quad 303.
.
Click to expand...

If you don't have (or can't borrow) another preamp to try to check the suggestion above, I also think it worth lifting the top and checking the caps on the driver boards ... unless of course it has been serviced relatively recently.

I had a 33/303 combo I was using some years back that developed crackling noises. Most of the time it seemed fine with no real loss of quality or power, the problem was intermittent and unpredictable.
In the end I bit the bullet and had a look inside, both the preamp and the 303 had capacitor problems but the worst was the 303 where most of the caps on the driver boards were split and one had actually blown its top. Fortunately the power caps were intact. I was quite amazed that it had carried on working to be honest.

Doesn't really take much time or skill to have a peek, the driver boards can be hinged down with care ...... the 303 is a bit wieldy though.
A fair few websites out there that can help you with the process, DADA being a good starting point and Keith Snook may have an online guide (can't remember right now)
 
You are certainly not the first human to venture in there. The PSU and output cap spec is correct with voltage to spare. I am however surprised the driver boards haven’t been recapped. Those orange caps will be pretty crusty by now. If it was mine I’d fully service it. I’d certainly clean it, test the rail voltages, bias etc. It is worth getting it as good as it can be IMHO. Lovely amps, with a rebuild it will be good for another 25 years trouble-free service at least.
 
This is what I meant:

52299586225_5402fe1000_c.jpg


It may be that whoever replaced them put some lacquer or glue around the bottom, possibly to hold them in place - I have come across that before (but usually with small caps on circuit boards)
The one on the right looks to have a very slight bulge, the left a slight dip .... maybe nothing though - or camera distortion.

The caps on the driver boards look to be clean (apart from the dust obvs) with no discernible bulges or cracks as far as the photos show but, as Tony says, they also look to be old skool originals and may well be out of spec ....
 
miktec said:
It may be that whoever replaced them put some lacquer or glue around the bottom - I have come across that before (but usually with small caps on circuit boards)
The one on the right looks to have a very slight bulge, the left a slight dip .... maybe nothing though - or camera distortion.
Click to expand...

The caps have to be hot-glued onto the plastic board thing, there is no other clamping arrangement.

PS Not sufficiently safe IMHO, I’d want them either firmly clamped or through-hole mounted on a proper PCB.
 
Thanks guys.
I sprayed contact cleaner and the problem is not there anymore.
Any recommendations for me to send the amp for a refurbishment?
 
Conan said:
Thanks guys.
I sprayed contact cleaner and the problem is not there anymore.
Any recommendations for me to send the amp for a refurbishment?
Click to expand...

Great stuff - glad you got the crackling sorted :)

Don't know what current Quad policy is but I used them about 7 years back for a 33 service and they had a very reasonable fixed labour cost + parts.
Did take months and they charged me for a 'Quad approved' box because I didn't have the original packaging - but otherwise OK ...

Obvs there are quite a few other alternatives out there but haven't used any to comment - some I saw looked quite pricey at the time.
 
Conan said:
Thanks guys.
I sprayed contact cleaner and the problem is not there anymore.
Any recommendations for me to send the amp for a refurbishment?
Click to expand...
I see your in Birmingham, I wouldn't be looking anywhere else than Amplabs in that case. Rob recently serviced my 34 & 306 & currently has my 303. He has a bit of a waiting list at the moment but is worth the wait, there are probably few people on the planet who know Quad amps as well as Rob does. Very reasonable prices as well, £130 for service on the 303.
TS
 
TonyScarlett said:
I see your in Birmingham, I wouldn't be looking anywhere else than Amplabs in that case. Rob recently serviced my 34 & 306 & currently has my 303. He has a bit of a waiting list at the moment but is worth the wait, there are probably few people on the planet who know Quad amps as well as Rob does. Very reasonable prices as well, £130 for service on the 303.
TS
Click to expand...
Good shout
 
Just an update of the noise in the 303.
Today I opened the pre amp and sprayed contact cleaner on the ALPS volume control pot and voilà! No more noise.
Still thinking in sending the 303 to Amplabs for a refurbishment
 
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