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  #21  
Old 11th December 2020, 11:14 AM
John Caswell John Caswell is offline
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Default Re: 5U4G substitution

The top caps have ceramic covers on them for obvious reasons. You can rest assured that I have had left hand and right hand fingers on each top cap whilst my amplifier is running with no detriment to me.
I think I will add "This bag of peanuts contains nuts" and "beware this hot coffee is hot". You can protect some of the people etc....


Interesting point Alan, I can see the danger may be a mesh cover over the two tubes. Bob - NO even worse

Education is the way to go.

John

Last edited by John Caswell; 11th December 2020 at 11:18 AM. Reason: Addnl info
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  #22  
Old 11th December 2020, 11:51 AM
snowman_al snowman_al is offline
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Default Re: 5U4G substitution

John,
Please re-read my concern.
Which is not about getting a shock from the top cap ceramic connectors, but to warn those people who do not understand as fully as you do that if the connector is removed there is 450 volts on the valve metal cap with the amp turned on.
So, ''Education is the way to go.''
Alan
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  #23  
Old 11th December 2020, 02:20 PM
Richard Richard is offline
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Default Re: 5U4G substitution

Quote:
Originally Posted by snowman_al View Post
if the connector is removed there is 450 volts on the valve metal cap with the amp turned on.

Alan

Is there? Edit, sorry, I see what you're getting at, HT on the cap connector, not the metal cap on top of the valve itself. Yes I suppose it would be dangerous but first you'd have to pull the connector off then stick your finger inside it whilst it's switched on which seems a pretty daft thing to do.
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  #24  
Old 11th December 2020, 03:02 PM
snowman_al snowman_al is offline
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Default Re: 5U4G substitution

Richard,
Apologies, but you have just proved the point(s) I am making.
Yes there is +425 to 450 volts on the 6D22S top caps (metal caps) when the amp is turned on. They are the cathodes of the rectifier.
And yes if you remove the connectors, with the amp off, there is HT voltage on them until the smoothing caps discharge.
Alan

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  #25  
Old 11th December 2020, 03:59 PM
bob orbell bob orbell is offline
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Default Re: 5U4G substitution

In which case, don't pull the cap off and don't stick your finger in . Bob
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  #26  
Old 11th December 2020, 04:40 PM
John Caswell John Caswell is offline
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Default Re: 5U4G substitution

Unlike a semiconductor amp, valve amp PSU discharge pretty quickly in comparison.
I really would not worry too much about it.
If you are going to be stupid and stick your fingers/tongue or whatever on these connectors you deserve what you get.
Anyone building/modifying these kits or items should have a modicum of common sense, although from what I read I often do not think so.

John
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  #27  
Old 11th December 2020, 05:44 PM
Richard Richard is offline
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Default Re: 5U4G substitution

Thanks Alan, all, yes I see what you mean and feel you're right to point out the dangers of removing the leads with it powered up or for a few minutes afterwards. I've not used these top-cap valves before (as you can see) so it's been interesting thinking it through. Perhaps users could colour them bright yellow with black stripes or somesuch!


That said I like these rectifiers and it wouldn't put me off doing the conversion as I've always been aware of the dangers of breaking a valve and being exposed to HT that way for 40 years and have always switched off and treated them with respect. A situation of more concern would be with small children or animals of which we have neither these days.
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  #28  
Old 11th December 2020, 08:42 PM
colin.hepburn colin.hepburn is offline
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Default Re: 5U4G substitution

Hi All
Well, I have been using the 6D22S in my JE. Labs single-ended Amps separate PSU. for a good few years now and never had any shocks only how good they sounded.
The only thing I do is just check the top caps are settled correctly before I switch the amp on this has just become part of my switch-on process Over time with this amp. As it is possible to move them if you have dusted the amp down. oh and the dog knows not to go near the Amp heís good like that. So I donít worry about it
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  #29  
Old 11th December 2020, 08:44 PM
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Greg. Greg. is offline
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Default Re: 5U4G substitution

As Richard and John have suggested, the voltage threat from a detached valve cap should, in the hands of the average DIYer not be a problem. The builder will already or should already have a knowledgable respect regarding the risks of HT voltage.

However, WAD and WD amps have gained a good reputation over the years and they are now being bought secondhand by punters who do not have the DIY based knowledge. Case in point is all the recent work I did on a KaT6550 which was done for a friend who had bought the amp without any knowledge whatsoever. However, he was well into valve rolling and I hate to think what accident might have befaledl him if whilst tube rolling, he accidentally came into contact with cathode voltage whilst the amp was live or discharging.

I suggest responsible and knowledgable owners would only need to put a notice of the risk on the chassis top if passing the amp onto another, sale or otherwise. Of course, there is no way of covering for the irresponsible seller/supplier. Matthew might want to scrutinise legal responsibilities on this. I suggest this is a good idea because these days, so many litigations do seem to unfairly put responsibility on the company owning the intellectual property.

Thereafter, a sentence of caution added to the FAQ article is essential and is then sufficient. We just need to cover the backs of Matthew and anyone involved with this conversion from initiation right through to the document writer. All easily accommodated
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  #30  
Old 11th December 2020, 08:51 PM
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Greg. Greg. is offline
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Default Re: 5U4G substitution

Good point, Colin on pets and I suppose children or any unrestricted inquisitive person.
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