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  #1  
Old 31st December 2010, 01:07 AM
Mark Keller Mark Keller is offline
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Location: Rotherfield, East Sussex
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Default WD88va no output on one channel

Hi everyone,

My WD88 lost output on one channel during an enthusiastic evenings listening with friends.

Since I have had it for a couple of years or so I assumed cooked output valves but not so. Is there anything I should check first before trying to get it repaired (I had it built for me but I am competent with electronics)?

This is my first post and any suggestions would be much appreciated.

Thanks,

M.
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  #2  
Old 31st December 2010, 10:45 AM
John Caswell John Caswell is offline
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Default Re: WD88va no output on one channel

Hi Mark,
At the amp end only initially swap over input cables if the dead channel changes sides you have a faulty source/cable if not replace exactly as is and then swap speaker cables, this should eliminate cables/speakers.
If still no joy next is swapping output valves channel to channel, then driver valve (ECC82), then replacing input valve with known good valve (ECC83). Here as a quick check you can replace an 83 with an 82 and vice versa just to eliminate whether it is the valve
If none of this works it is down to serious fault finding with a DMM etc.
So try this then report back here, or pm me with phone nr. and I will try to help sort it over the phone.

John
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  #3  
Old 31st December 2010, 11:01 AM
Richard Richard is offline
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Default Re: WD88va no output on one channel

As John says Mark but driver is 5687 so cannot be swapped with ecc83 input valve (ecc82/83 can often be swapped for fault finding but 5687 has different pinout).

Start at bottom, check all valve heaters are lit! Past that a broken signal cable/connection, then swap valves across channels, then a voltage check etc.
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  #4  
Old 31st December 2010, 11:08 AM
Mark Keller Mark Keller is offline
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Default Re: WD88va no output on one channel

Thank you both very much for your replies, I will go through the process of elimination and let you know the results.

M.
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  #5  
Old 31st December 2010, 11:32 AM
John Caswell John Caswell is offline
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Default Re: WD88va no output on one channel

Hi all,
Well bless my soul. So it is,sorry, senile decay is definitely setting in, time to call it a day perhaps

John
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  #6  
Old 31st December 2010, 02:07 PM
Richard Richard is offline
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Default Re: WD88va no output on one channel

Quote:
Originally Posted by John Caswell View Post
Hi all,
Well bless my soul. So it is,sorry, senile decay is definitely setting in, time to call it a day perhaps

John
ha ha, err no, I don't think so, just you trying to remember 27000 circuits no doubt , Happy New Year all,
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  #7  
Old 31st December 2010, 02:11 PM
Mark Keller Mark Keller is offline
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Default Re: WD88va no output on one channel

Ok so have swapped inputs, speaker terminals and valves. All heaters are lit, fault still remains on same side.

So I guess it's time for a voltage check. Should I just do it as per assembly instructions or is there a particular order (amp is an XL).

PS when it first failed a couple of days ago I just assumed power valves and used it as an excuse to get a new matched quad of Gold Lions ; ) so those are what's in at the moment not the original Svetlanas. Also I can still hear some low level noise out of the dead channel if that is a clue?

Thanks,

M.
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  #8  
Old 31st December 2010, 02:26 PM
Richard Richard is offline
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Default Re: WD88va no output on one channel

Hiss suggests the output stage at least is connected and working. Swap the ecc83 as there's only the one bottle using a section for each channel so perhaps you've not checked that yet. Then suspect a signal fault on the input. Possibly a loose rca has caused a broken connection for example, signal fault is likely. Then voltages, yes, as per the test sheet is safest but a quick check at anode and cathode to ground, even just comparing working channel with dead one, will often show the fault. Look carefully whilst inside for bulging electro caps that may have failed or any suspect solder connections between tags.
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  #9  
Old 31st December 2010, 02:38 PM
Mark Keller Mark Keller is offline
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Default Re: WD88va no output on one channel

Thanks Richard,

Will do the above and report back. Will probably take a few days.

Thanks for all your help.

M.
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  #10  
Old 6th January 2011, 05:44 PM
Mark Keller Mark Keller is offline
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Default Re: WD88va no output on one channel

Hi,

It was indeed the ecc83, swapped it out for an ecc803 (nearest I could find) and all is OK. A couple of questions?

Should I change this for a proper ecc 83 and should I go for the balanced or cryogenic or normal ones that I see at Watford Valves?

Also any idea what may have cooked it, I am driving the input from an Apogee Duet and have the output on max, it has unbalanced -10 dBV line outputs, will this set the level too high and overdrive the input of the WD88VA damaging the input valve?

For those that are interested the Apogee is driven by a Mac Mini using an iTunes Apple Lossless library and a DROBO disk array, speakers are Sonus Faber Concertinas and a REL R305 Sub.

Again thanks everyone for their help, this is a wonderful forum.

Best,

M.
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