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  #31  
Old 22nd July 2015, 01:13 AM
bikerhifinut bikerhifinut is offline
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Join Date: Jan 2006
Location: Penrith, Cumbria
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Default Re: WD88VA noise

you wont do any long term harm by running it with just the KT88. If that cures the fault then replace the 5687 on the offending side with a known good one.
If the rustling reappears then you know the problem lies in that stage and thats where to look. If not then plug in the ECC83 and if it appears then the fault lies in the first stage circuit.

A.
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  #32  
Old 25th July 2015, 11:49 AM
Riggers Riggers is offline
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Join Date: Aug 2012
Location: Brisbane, Queensland. Aus
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Default Re: WD88VA noise

Well, I think I can announce provisional success. On the right (noisy) side I replaced R4a (the last of John's list to replace), and resoldered C9 (the one that goes into the centre hole of the tag board). The slight problem I think I had during the build was the difference in size between a component leg and the size of the centre holes on the tag board, which are a handy size to attach a thick gauge wire but require a little more skill to solder a thin capacitor leg and get good coverage/contact of solder.

The other thing I did was to clean with isopropyl alcohol any drops/spatters of solder resin from the surface of the tag board. My theory here is that the iron I used (Goot 70W, fixed temperature) may have been too hot initially as I made contact with the solder (resin core 69%tin/40% lead) as I would invariably produce quite a bit of smoking from the solder as it touched the soldering iron tip, and if you looked carefully in the right light you can see little drops of resin which have boiled off on the surface of the tag board, possibly making a short.

Anyway, a few hours of road testing later and we are still noise free.

Hooray!!
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  #33  
Old 25th July 2015, 04:17 PM
bikerhifinut bikerhifinut is offline
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Join Date: Jan 2006
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Default Re: WD88VA noise

Whoopee!
I am pleased mate.
I built one of these in 2007 and I got lucky, hopefully because i got very OCD over the build and triple checked everything. It worked out of the box and apart from the original Svetlana KT88 going gassy on me (eventually), it has never missed a beat and continues to sound "as good as i'll ever need". every change for the better I have made elsewhere in my system hasn't yet shown up any shortfalls in the WD88, at least at moderate to loud volumes, it will get strained if i try to play the amp at "Disco" levels! Then again who wants to listen to their music from across the street?
I suspect you probably had a dry joint rather than flux bridging as i thought resin flux was an insulator, unless of course the spatter carried over some tin/lead particles?
Andy.
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