Useful tube life time of 845
la...@my-dejanews.com
I am using a pair of Unison Research 845 power amps. Somebody told me that
the useful life time of 845 is about 100,000 hours. I wonder whether it is
true because the average useful life time for ordinary power tubes are only
around 2000 - 5000 hours. Could anybody kindly tell me the useful life time
of a 845?
By the way, there are still some N.O.S. 845 (e.g. RCA, UE, Philips. etc)
sometimes could be found in the market, Could anybody kindly tell me which
brand is the best? Thanks.
Andy.
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Ned Carlson
On Sat, 06 Jun 1998 04:03:52 GMT, la...@my-dejanews.com wrote:
>I am using a pair of Unison Research 845 power amps. Somebody told me that
>the useful life time of 845 is about 100,000 hours. I wonder whether it is
>true because the average useful life time for ordinary power tubes are only
>around 2000 - 5000 hours. Could anybody kindly tell me the useful life time
>of a 845?
Run at close to ratings, about 3000 hours sounds about right.
Ned Carlson Triode Electronics,2225 W Roscoe Chicago, IL, 60618 USA
ph 773-871-7459 fax 773-871-7938
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daveslagle
> >I am using a pair of Unison Research 845 power amps. Somebody told me that
> >the useful life time of 845 is about 100,000 hours. I wonder whether it is true
do some simple math.... 100000 hours is 11 years of constant use....
> because the average useful life time for ordinary power tubes are only
> >around 2000 - 5000 hours. Could anybody kindly tell me the useful >?life time >of a 845?
a life date on tubes is stupid... its just a manufacturers dream... if
they can specify a hour lifetime... why can't they specify a bias point
or matching??? I know my tubes are only good for 3000 hours, but you
gotta pick 10 to match a pair? I doesn't seem right..
> Run at close to ratings, about 3000 hours sounds about right.
on an 845... or any tube... adding a suggested hour life is stupid...
its just a set of measuring factors.... if it biases out at 85ma... 3000
hours later it may measure 60ma... but what about another tube from the
same batch that started out at 60 ma???
i dunno but putting a lifespan on sound just seems like a ploy to make
the boys who sell tubes more $$$$
to snag a line from a good friend... lightbulbs are rated at 5000 hours
or so.. do you time them and replace them??? If you hear a problem....
fix it, beyond that.... get a life and save some money.
Ned Carlson
On Sat, 06 Jun 1998 03:06:59 -0400, daveslagle <dsl...@earthlink.net>
wrote:
>
>> because the average useful life time for ordinary power tubes are only
>> >around 2000 - 5000 hours. Could anybody kindly tell me the useful >?life time >of a 845?
>
>a life date on tubes is stupid... its just a manufacturers dream... if
>they can specify a hour lifetime...
They can do it based on average tubes in suggested
usage. This is no miracle, it's just statistics.
Used under different parameters, the average life will
be different. This goes for mechanical parts as well
as tubes.
> why can't they specify a bias point
>or matching??? I know my tubes are only good for 3000 hours, but you
>gotta pick 10 to match a pair? I doesn't seem right..
Golly, you ever tried to match 2N3055's? Makes tube matching
seem easy.
From what I've seen, typical factory tolerance on plate current
is (roughly) anywhere from 15%, to -20 +40%, depending on the
tube in question. Even given the best case situation, say 10%,
then getting a matched pair with a 2% match from a random pair
chosen from a group of 10 is pretty low.
Bear in mind that in the old days, the manufacturers' cost to make
a 6SN7, for example, was approx thirty five (35) cents.
You're only gonna get X tolerance when you're knocking out
tubes for 35 cents net cost.
Sure, you can get tube made to tighter tolerances.
And it costs, too. The Newark list on 6SN7 in
1960 was $1.14. 5692, the industrial version with
tighter tolerances and 10,000 hour warrany, listed for $8.15.
And 5842/417A was $18.00
BTW, Newark's list for 845 in 1960 was $20.80.
>
>> Run at close to ratings, about 3000 hours sounds about right.
>
>on an 845... or any tube... adding a suggested hour life is stupid...
>its just a set of measuring factors....
The 3000 hour figure comes from the usual replacement time
(ie: how often customers reorder) for 845's used in RCA transmitter
modulators. As I qualified my remark, the figure is given for tubes
used at close to maximum ratings, as they would be used in such
an application.
> if it biases out at 85ma... 3000
>hours later it may measure 60ma... but what about another tube from the
>same batch that started out at 60 ma???
>
>i dunno but putting a lifespan on sound just seems like a ploy to make
>the boys who sell tubes more $$$$
'Scuse me, Dave, nobody is trying to put a lifespan on sound..I gave
an honest answer to the question, and qualified it properly as
applying to tubes used a close to max ratings. Your Mileage Will Vary,
esp if they are not used that way.
Perhaps you didn't bother to read what I wrote?
>to snag a line from a good friend... lightbulbs are rated at 5000 hours
>or so..
Which ones, Dave? Some are lots more than others.
>do you time them and replace them???
AAMOF, Dave, in apps where downtime ain't
acceptable, replacing lightbulbs or tubes on a regular
schedule based on projected life is SOP.
>If you hear a problem....
>fix it, beyond that.... get a life and save some money.
Ya know..if no one *asked* how long they lasted,
I'd never say. But people ask this question all the time.
My standard answer they're OK is until they sound bad,
won't bias up, or (in the rare case where someone
has instrumentation to measure this) the power starts to
fall off, in the case of a power amp.
Some folks want some kind of benchmark of when to
replace tubes before the performance falls off electronically
or sonically, we've got to come up with some kind of
number for those people.
If you're looking for conspiracies to sell people stuff they don't
need, I suggest you look at the software business.
That involves like 10,000 times the money as what changes
hands in the tube business. Tell me, do ya *really* need
Windows '98? How many pieces of software "accidentally"
leave out obvious features that just happen to show up in the
next version? This is a running joke here, if these tubes were
software, we wouldn't make warranty replacements, we'd
charge for an upgrade. Unfortunately, some folks *have* latched
onto that idea.
Chris Hornbeck
On Sat, 06 Jun 1998 04:03:52 GMT, la...@my-dejanews.com wrote:
>I am using a pair of Unison Research 845 power amps. Somebody told me that
>the useful life time of 845 is about 100,000 hours. I wonder whether it is
>true because the average useful life time for ordinary power tubes are only
>around 2000 - 5000 hours. Could anybody kindly tell me the useful life time
>of a 845?
>
>By the way, there are still some N.O.S. 845 (e.g. RCA, UE, Philips. etc)
>sometimes could be found in the market, Could anybody kindly tell me which
>brand is the best? Thanks.
I have a few RCA 845's probably older than me, and regularly use some
JAN CUE-845W/VT-43's from United Electronics that spent their early
life in a carollon, and were retired when the bell tower was blasted
by lightning. Three of the six output tubes survived although
transformers were melted (!) and were given to me. Gentler home
use is likely to give a long life indeed.
By the way, I know an older gentleman who has a matched pair of
RCA 845's new in boxes, never used, one owner, preserved in a
null-entropy capsule since the dawn of time, without internet
access, who might want to sell them. I don't have the money
they're worth, but will pass on serious offers to him.
Chris Hornbeck, Guyville
la...@my-dejanews.com
In article <6lbukd$c...@bgtnsc02.worldnet.att.net>,
guyviller...@worldnet.att.net (Chris Hornbeck) wrote:
>
> I have a few RCA 845's probably older than me, and regularly use some
> JAN CUE-845W/VT-43's from United Electronics that spent their early
> life in a carollon, and were retired when the bell tower was blasted
> by lightning. Three of the six output tubes survived although
> transformers were melted (!) and were given to me. Gentler home
> use is likely to give a long life indeed.
>
> By the way, I know an older gentleman who has a matched pair of
> RCA 845's new in boxes, never used, one owner, preserved in a
> null-entropy capsule since the dawn of time, without internet
> access, who might want to sell them. I don't have the money
> they're worth, but will pass on serious offers to him.
>
> Chris Hornbeck, Guyville
>
I am interested in the older gentleman's matched pair RCA 845. Could you
please find out the price which the gentleman asking for and E-mail me at my
above E-mail address?
Andy
Mike and Julie Andrews
Ned is correct. If you look at stats and like cycle testing you will find that some tubes (or
any product for that matter) will fail early in the life of the tube and others never fail. The
recommended change out time for tubes as Ned stated is probably in the point of the life cycle
curve that shows a point of falling off in terms of reliability. Anyone who thinks this is
mumbo jumbo just remember that Shewhart, a major pioneer in stats worked for Western Electric in
the '30s.
Ned Carlson wrote:
> On Sat, 06 Jun 1998 03:06:59 -0400, daveslagle <dsl...@earthlink.net>
> wrote:
> >
> >> because the average useful life time for ordinary power tubes are only