KiT 6550 Hum

[TimN]

The original ratings for C1,2,3 & 4 were 100uF 450V. As I have already invested in some Mundorfs of that rating at great expense, I hope they will be OK!

As for C5, that was rated at 120uF 500V. I am unable to locate any of that rating, so I am considering either leaving it alone (it looks OK) or using a 100uF 500V as identified by Greg as it is sort of in the ballpark. Advice would be appreciated.

[bob orbell]

100uF will be fine Tim. . Bob

[Mark]

Originally Posted by bob orbell

Mark wrote, It can get as complicated as your time, wallet and ears permit, but I suggest that low esr caps are the best bang for your buck, and buying a selection, burning them in. ---- Can you PLEASE explain the part or the capacitor that BURNS, , sorry, but I think it is the most stupid saying of all time in the Hi FI world . Bob

Hi Bob,

As I am sure you are already very aware, there are many words/phrases in common use in the english language which are nonsense when taken at face value, but they continue to be used because people know what they mean. The only example I can think of right now is "Sex Shop"(!) which will probably trigger an alarm at WD Towers and get me banned :-). A "Sex Shop" (that's only the second time the word has been mentioned on this forum ?) doesn't sell sexual intercourse or allow you to buy a different gender (whatever that means these days). Nevertheless everyone knows it sells pornography and maybe also "erotic" clothing and other associated items. I am sure other forum members can think of better examples, and may even want to start a thread !

Back to capacitors and "burning in". I assume you know this, so for the sake of any who don't, the sound of new hifi changes over time - generally improving. A commonly quoted time period is 100 hours for speakers, but reviewers and others report shorter and longer times for different speakers. It is also well known that the "sound" of electrolytic capacitors change over time from new. Perhaps I read too many websites with a lot of US contributors, or it's my subscription to Stereophile, but I use the words "burning in" for this process. Breaking in might be better but as far as I am concerned it's a case or "you say tomayto and I say tomarto", and you could also ask "breaking what ?"

Which reminds of a better example : "breaking wind" !

Mark

[bob orbell]

Aha, breaking wind sounds so much better than burning, any way, please reframe from using that crazy fraze burning, simply because nowt burns, if it does, you are in trouble. Bob

[A Stuart]

Would you compromise and accept "burping in", Bob?

Alastair

[Phil Y]

Another vote here for Mundorf electrolytics. I have used them more than once and have been very happy with the results.

Phil.

[bob orbell]

Originally Posted by A Stuart

Would you compromise and accept "burping in", Bob?

Alastair

Definitely not Alastair, it is not rude enough, but a good try . Bob

[willslenco]

Interestingly the term "burn-in" was first used in 60s and meant "the continuous operation of a device as a test for defects or failure prior to putting it to use." This sort of makes sense to me in the context of valves, but it does not describe the perceived changes to electronic equipment that is being referred to here.

Also "running-in" as in "The operating of a new engine (especially that of a motor vehicle at less than its normal speed until proper working has been established" doesn't really fit the bill either.

Maybe "settling-in" might be a better option, considering "settling time" is already used in electronics?

[TimN]

Well I have been busy! I have had to re-wire the input circuitry and have replaced a number of components and the B9a sockets as one of the originals was cracked. It seemed that every time I brushed against the existing wiring it fell away from its connection.

It has taken me a while as I have never built an amplifier before. It would have been easier and probably not much less expensive to build a brand new KT88 kit from scratch, but I have learned from the process.

But I am almost ready to switch on again now. Does anybody have any advice at this critical time? I have my rubber gloves on order from Amazon and on the way.

Looking at the test voltage table in the instructions, attached, I am not sure I understand it. Where not specifically stated is the test voltage to the earth point? e.g. LC - V4 pin 1, RC - V3 pin 1?

Also, what does the label refer to? e.g. aT and g1P?

Any help and advice would be most appreciated.

[John Caswell]

Hi Tim,
"aT" is the generally accepted nomenclature of the "A"node of the "T"riode section of the ECF80.
Similarly "g1P" is the "G"rid 1 of the "P"entode section of the ECF80. An ECF80 being effectively a dual valve - a triode/pentode
It is the usual norm/problem of all sorts of industries where those that work in them have accepted abbreviations.
Not much can be done about it apart from learning the aforesaid abbreviations.
We also have the problem that in the UK/Europe the "Anode" of a "Valve" is so called whereas in the USA if is referred to as the "Plate" of a "Tube".
I. could go on but that will only confuse you and others further. Welcome to the club!

John