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Effed up Quad 909 (UK made)

Hi, I have what reads like the same issue with my Quad 909. I've recently moved it to France and am wondering if it's worth taking it back to UK for a service or if I can open it up and tackle this myself. Some of what look like useful image links in this thread are no longer available eg the correct position. I used to do a bit of electronic repair as part of my job so I'm not too shy in that regard - like-for-like rather than upgrades.
The buzz exists with the amp powered and nothing other than the power cable attached. You can here it buzzing by placing your ear near the casing.
I'd appreciate any advice. I've also got a list of alternate superior capacitors from elsewhere (I think another @JohnW post) that I'm considering buying and fitting but it's the buzzing that really needs sorting if I'm going to open it up.
 
My UK 909 is also making some noise from the xformer. Doesn't bother me because I can't hear it when I listen to music. Fresh PSU caps didn't change that.
 
Thanks for the tip. The buzz from mine is quite loud. Buzz level doesn't change with audio volume but it can be heard in quieter passages of music. I also know it's not normal because it's only appeared in the last year or so and I've owned the amp for what must be a couple of decades.
 
TheEggking said:
Hi, I have what reads like the same issue with my Quad 909. I've recently moved it to France and am wondering if it's worth taking it back to UK for a service or if I can open it up and tackle this myself. Some of what look like useful image links in this thread are no longer available eg the correct position. I used to do a bit of electronic repair as part of my job so I'm not too shy in that regard - like-for-like rather than upgrades.
The buzz exists with the amp powered and nothing other than the power cable attached. You can here it buzzing by placing your ear near the casing.
I'd appreciate any advice. I've also got a list of alternate superior capacitors from elsewhere (I think another @JohnW post) that I'm considering buying and fitting but it's the buzzing that really needs sorting if I'm going to open it up.
Click to expand...

If the buzz has only occurred since you moved it might be DC on the mains - you could try a DC blocker.
 
@TheEggking
@Barrymagrec

Not likely to need a DC blocker - there is an easy, very cheap but also essential other cap to replace, other than the reservoirs - in fact, more often than the reservoir caps.

I need to check the 909 schematic, but in the originating 405,. 405-2 and comparable bit in the 606, this sort of buzz is caused by c5 on that board, 100uf/50v part used as a bootstrap.

back in a few minutes…
 
...Ah, there it is - opposite polarity for the architectural changes made to the 909: it is now called C7 and is a 47uF/63v electrolytic capacitor.

quad909 botstrap cap.jpg


  • Find that part C7 on each channel in a 909 with a hint of buzz - there is only one on each channel. It will be a through-hole, part of modest size (10-13mm l, maybe that in diameter). Replace with a 100uF/63v/105degC-rated part: that should fix it for a couple of decades.
  • Cost: pennies: used any good commercial -quality part, like Panasonic or Nichicon, or sim.
  • Be careful about checking cap polarity again before soldering in place.

Good luck!
 
wd40addict said:
Gosh, the early posts in this thread show the high regard in which John W was held before his Ponzi dac scheme!
Click to expand...

I think John W is a talented rngineer and I don`t believe he intended to defraud anyone, I think he underestimated the time and complexity of designing and producing a complete piece of equipment and was also unable to stop the development stage and start the production engineering stage because he coul always see a way of making it even better.

Subsequently I suspect he became severely depressed by his inability to progress the project and so everything got worse and worse and ended in total failure. I recognise this behaviour because nearly 50 years ago I was got myself into the same situation, luckily I hadn`t taken any money in advance but I still severely dissappointed my customer.

Others may dissagree, of course.
 
lawrence001 said:
Quad will service a Chinese clone??

Or were Quad amps already made in China many years ago? Or is it still a current model? I had no idea.
Click to expand...
Quad service their own products...as far as I am aware 909s were made in china, I think the early ones were made here...I don't buy into china made is inferior..my 909 sounds great! I think the moral of this thread is don't get it modded..don't faff about with yourself..send it to Quad for a service..just make sure it's boxed well..
 
wd40addict said:
Gosh, the early posts in this thread show the high regard in which John W was held before his Ponzi dac scheme!
Click to expand...
He genuinely meant well… I really don’t know the full story but I think he just got himself in too deep with the M-DAC, I really don’t think he intended to defraud anyone at all. As much as I’m sorry for anyone who lost money, I’m kind of gutted for him too.

I went into business with someone in late 2018 to design and manufacture a specialised piece of technology… we lost, big time, and all of my savings have been wiped out… not something we saw coming. Thankfully we don’t owe anything to anyone else, but what seemed like a good idea and started out well, turned into a disaster.
 
Hi, thanks all for the information here. I have considered a DC filter and may be able to borrow one but also thanks to @martin clark I'll add that to the list. Unless I bottle it and end up taking the unit back to UK for a 'proper' service. I've had my CDP serviced in Peterborough before and found them to be good to deal with.
 
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