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Valve - plate red hot !

Gerard said:
Out of 12 Electro Harmonix 6CA7 in the last 10 months only 6 still function! the JJs are going to have to be very poor to be worse than that?

The people at Watford Valves seem quite keen on the JJs
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If you are losing valves at that rate it sounds as if they are being over run, or else modern valves are a very great deal worse than they were back in the sixties and before.
 
Gerard said:
Out of 12 Electro Harmonix 6CA7 in the last 10 months only 6 still function! the JJs are going to have to be very poor to be worse than that?

The people at Watford Valves seem quite keen on the JJs
Click to expand...

I repair valve amps virtually everyday, both hifi and also guitar amps for bands so I get to see a lot when it comes to valve reliability ;)
In my own experience, EH has been much more reliable for myself and my customers than JJ! The "winged C" Svetlana's seem to be about the best of the current crop....
As Barry said, it could well be that your amp is running the valves very hard.

There is an article which I authored about valve reliability and associated matters on my web site, which you may find interesting.... Unfortunately the site is down at the moment whilst I'm changing web hosting so try in a few days!
 
As best I can remember about the Electro Harmonix :

2 soon became noisy and could not be used.

1 noisy straight out the box and couldnt be used

1 went as my original post

2 others appear to be working but show zero on bias so I guess they are deceased.
 
Arkless Repairs said:
There is an article which I authored about valve reliability and associated matters on my web site, which you may find interesting.... Unfortunately the site is down at the moment whilst I'm changing web hosting so try in a few days!
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Yes I was looking for that yesterday as I had remembered reading it some time back - I came across the dead link yesterday. I will have a read when it is back up.
 
Arkless Repairs said:
Always a sucker for KT88's here... I'd be a bit wary though with these these different valve options... EL34 and 6CA7 are equivalent and generally use a 1K screen grid resistor.... the other options are also equivalent to each other but would normally use a 470R resistor.... the bias is also quite different from one to the other... by about 18V... that could easily be encompassed with a generic bias pre-set but it would be a large range to see in practice.... just saying ;)
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KT120s are better - more power, more linearity and more slam.
 
I am amazed by the number of valves you have got through, Gerard. Power valves should last years without blowing up (unless you have them on 24/7 of course). I would get the amps checked.
 
Gerard said:
As best I can remember about the Electro Harmonix :

2 soon became noisy and could not be used.

1 noisy straight out the box and couldnt be used

1 went as my original post

2 others appear to be working but show zero on bias so I guess they are deceased.
Click to expand...

Well I only deal with several hundred a year ;)
 
PsB said:
I am amazed by the number of valves you have got through, Gerard. Power valves should last years without blowing up (unless you have them on 24/7 of course). I would get the amps checked.
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This is worrying, I just turn them on for listening sessions and off at the end, probably on for 2-3 hours at time, perhaps 4-5 times a week.
 
PsB said:
I am amazed by the number of valves you have got through.
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Me too! hence the £11 a valve JJs, I can't bring myself to spend £240+ (8 x £30) for KT88s or the Svetlana Winged Cs at the rate I've gone through the EH in the last 10 months.
 
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