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View Full Version : Trouble with Conrad Johnson PV12A


Frankyc2003
23-10-2010, 08:28
Morning all,

Recently I acquired a Conrad Johnson PV12A (the one with phono stage). The unit is around 11 years of age.
All good until recently.
It started popping and hissing and 'spurting' on one channel... The 'funny noises' were not affected by volume though! Always the same pretty much...
First instinct was that the tubes or one tube was on its way out.
Swapped them for new ones (Mullard NOS 12au7), and to my surprise the 'funny' noises had swapped sides, now coming from the opposite channel !?!

I am a bit confused really...:scratch:

So does anyone has a clue of what is happening...
And also any recommendations as to who to contact re: Servicing a tube preamp in the London area?

Many thanks

looking forward reading your answers!

F
Stratmangler
23-10-2010, 08:43
Have you swapped the new ones around, and did the problem move ?
If you haven't, do so, and see what happens.
You may have replaced a good valve with a duff one.
Frankyc2003
23-10-2010, 08:46
Yes, i have indeed.
I replaced the the tubes involved in the preamp section and swapped them around twice.
As the problem occurs on both Cd and TT... I left the phono section alone and untouched.
Ali Tait
23-10-2010, 09:29
Join the WD forum and you can ask John Caswell to have a look at it. He lives in Wokingham. He does the repairs and builds for WD,or at least he used to until they were sold. He's a nice chap and very k.owledeable. He'll sort it.
YNWaN
23-10-2010, 10:00
It could well be that some capacitors need replacing - valves do like to cook them a bit and this seems to shorten their life span.
Ali Tait
23-10-2010, 10:01
Yes indeed,a common occurence with valve amps,especially ones of this age.
Frankyc2003
23-10-2010, 12:57
Join the WD forum and you can ask John Caswell to have a look at it. He lives in Wokingham. He does the repairs and builds for WD,or at least he used to until they were sold. He's a nice chap and very k.owledeable. He'll sort it.

Thanks, when you say WD, you mean Western Digital?
excuse my ignorance...:)
Stratmangler
23-10-2010, 13:00
http://www.world-designs.co.uk/forum/
Frankyc2003
23-10-2010, 13:07
http://www.world-designs.co.uk/forum/

:doh:

you see, I am pretty ignorant!

Thanks a lot for the info!

Cheers