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Question for the engineers

Discussion in 'TAG McLaren Audio Owners' Forum' started by johnson, Jun 1, 2005.

  1. johnson

    johnson
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    As most of us know, capacitors have a limited life span.(albeit in the thousands of hours.)
    My question is this,(remembering there are quite a few thousand hours in a year alone) with regard to the av32 and 192 being always on to maintain sonic purity from the start, would it be better to use the front button to completely turn off the unit (and have some warmup time needed)
    to conserve the life of the capacitors and all other circuitry?
    I ask only because it looks like we're going to get questionable backup in the future from IAG.
    Before I get flamed, I'm not suggesting we should do this, merely asking the more lerned in this field if it's worth considering!
    Regards
     
  2. Miron

    Miron
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    Good question!
    I am pretty sure there will be quite a few opposite opinions on this one.

    Since DVD32R has standby transformer I leave it in standby while my T32R normally gets switched off. I diud the same with my SP in the past.
    DP is what makes me unsure. It gets really hot and I am really not sure what's worse, to leave it on or to force it in the heat cycle .

    I know of some people who always leave it on as well as few guys who always switch their gear off. I am unsure myself.
     
  3. Miron

    Miron
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    Yknow what, I'll start a poll. Last one showed I was in minority, wonder about this one.
     
  4. liam_b

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    I power down (completely) any unit not having a dedicated (internal or not) very low power consumption standby power system, this makes the most sense for the enviroment and equipment lifetime. There's just no sense in having an item powered up for a whole day/week to use it for only a small part of that day/week, over a year this can use up thousands of hours of lifespan of 'wet' capacitors (used in the psu). Remember there's 8,760 hours in a (non leap) year!
     
  5. roversd1

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    A proper engineer would give an answer but, I'm using equipment every day for a least four hours that is over 30 years old.

    Its still going strong.
     
  6. johnson

    johnson
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    I understand, good point.
    I do just wonder how close to it's original spec your equipment is running!
    How much capacitance your caps still have!!
    Regards
     
  7. liam_b

    liam_b
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    To try and quantify these unknown numbers I went to ELNA's website and read the technical blurb on capacitor life.

    The life time guaranteed (in hours) in the catalog means this capacitor will perform within the stated specification (usually ±20% of the initial capacitance) for this period of time at the maximum rated voltage and temperature.

    For example, RA3 (typical in TAG unit PSUs) series has 1000 hours life time, and is rated at 85ºC. Therefore, it will operate for 1000Hrs continuously at 85ºC. After 1000Hrs, the capacitor will still work, but the tolerance will gradually increase until the electrolytic solution is finally dried up and then eventually become open circuit (depending on the series, it might take longer as twice the life time should take twice as long to dry up).

    The life time will increase dramatically, if the capacitors are operating at lower than the maximum rated temperature. The general rule is that, for every 10ºC decrease in operating temperature, the life time will be doubled.

    Therefore, for example, a RA3 series capacitor operating:

    At 95ºC will have 2,000 hrs. life time (1000 X 2).

    At 85ºC will have 4,000 hrs. life time (2000 X 2).

    At 75ºC will have 8,000 hrs. life time (4000 X 2).

    At 65ºC will have 16,000 hrs. life time (8000 X 2). [just under 2 year warranty period]

    At 55ºC will have 32,000 hrs. life time (16000 X 2).

    At 45ºC will have 64,000 hrs. life time (32000 X 2). [just under 8 years]

    Now anybody still wonder why DVD32Rs keep dieing? Easy just like the DP they can get rather warm, this lifetime calculation appies equally to all the little surface mount electrolytics used all over the circuit boards, anywhere they get warmed up the lifespan decreases, though you can't do much about this except make sure your equipment is well ventilated.

    The effects to the life by derating of the applied voltage etc. are neglected because they are small compared to that by the temperature.

    Now if you really want to know about this stuff go and Google 'Arrhenius equation'. :eek:
     
  8. Plump

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    I actually do not know why but I always swithch my units off (and every time I switch them on I pray for them to boot OK, especially DVD32R)!
     
  9. johnson

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    Hi,
    With regard to the life cycles of capacitors, How is it possible that Bryston offers a 20year warrenty when they use electrolytics just like everyone else?
     
  10. liam_b

    liam_b
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    Simple really - they make sure that the calculated lifespan due to temperature, voltage and ripple current gives enough hours to cover the warranty period. 175,000 hours is a lot though!
     
  11. johnson

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    Hi,
    Are there caps out there, that will last that long?
     
  12. liam_b

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    Yes in fact most electrolytics from reputable makers will last that long as long as the voltage, temperature and ripple current is kept under control they will meet the life time required.

    The wear out mechanism is the loss of electrolyte, typically due to gasing off caused by excessive voltage (goes BANG! ie explodes), excessive ripple current (goes BANG if too high) and age (slowly degrades capacitance).

    Even storing electrolytic capacitors unused causes a very slow degrading, due the interaction of the chemicals in the electrolye.
     
  13. mlinhares

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    So the bottom line is: always switch off you gear?

    I ask this because I always left them in standby. In fact the way all components work so well together was one of the main reason to buy an all Tag setup. But if switching off will increase reliability and life time, than obviously I will leave them switched off.
     
  14. johnson

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    I think it's just the av32r,192 that are "always on".If the target is to keep capacitor life as long as possible, power these down.
    Obviously they will require a longer warm up time to reach best sound quality.
     
  15. Moreo

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    ...and what about the "theory" that switching equipment on and off will also have a negative effect on lifespan of all components? Leaving them on keeps the units on a more or less continuous temperature, voltage etc. and thus will have a positive effect?
     
  16. liam_b

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    There's a simple trade off -

    1. power down completely if not being used frequently enough to justify standby.

    2. leave in standby if being used frequently enough or you want instant warmed up performance.

    I would like to point out to everyone that TMAs first real TMA product, the AV32 was designed in 1998 and that Dr.Zucker stated on a few occasions that there was some regret that a proper low power standby was not designed in. The second product, the T32 has a low power standy. The DVD32 improved on that being about less than 5 watts in standby.
     
  17. alexs2

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    There are always two sides to an argument,and the one that turning gear on and off may shorten component life is often raised.....most of my gear is turned off when not in use,with the exception of the AV32RDP and a few other odds and ends,and my previous AV32R was well into it's 3rd yr without any problems before it was sold.

    With respect to capacitor life in hot environments,any number of old valve amps still function well with their original caps,and FWIW,my ancient Krells are still on their original set of coke-can sized caps,and they endure a properly hot environment inside those things.

    In the end,you still have to use your gear,and at some stage,something will most likely fail,but also most likely after a long time.
     
  18. GrahamMG

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    In my experience, PSU's in kit tend to go on forever (releatively) if always powered, its when they are very old and you ask them to power cycle they normally fail.......
    An example, we had 6 off Delphi DD42 plasmas on one of the main areas here (and these were £12k each at the time), they were on continuiously for nearly 5 years without, surpirsingly, any issues. When the area was decommissioned we moved the units for re-use elsewhere and 5 of the 6 never came back on......
    My DVD32R is over 5 years old, always been in standby, always works...... Our old AV32RSP (very early model) is now around 7 years old and that still works every day (never switched that off either), our DP is over 3 years old and that works every day (sometimes all day) and is never switched off..... My AV192R is over 2 1/2 years old and never gets swicthed off either apart from once and it had a head fit until it warmed back up. Sorry guys but I'm a firm believer in leaving the lot in standby if you ain't using them..... I can appreciate that holidays and stuff might have you turning the lot off though, after all that is only once a year for most mortals so shouldn't really be a problem until they get very old? Anyone know what the going rate for changing the PSU CAP's is in a AV192R? Spending a £100 or so every 8 years don't sound like a bad deal really.....
     
  19. asha_bristol

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    I'm no expert on the lifespan of electronic components. However, I can say this based on personal experience:

    Around 8 or 9 years ago both myself and my best mate bought identical Audiolab 8000LX amplifiers within weeks of each other. From the word go, I kept mine permanantly powered up (it only being switched off when absolutely necessary - i.e. when moving house) but my friend didn't see the point and always turned his on and off. I also bought and plugged mine into an MK filtered block, which at the time cost me around £40. This was at a time when filtered blocks and mains cables were NOT a hi-fi thing, therefore my mate (like most other people at the time) laughed and opted for the standard £1.99 block. Our amps had both been used in similar situations, i.e. racked in our living rooms and well looked after.

    Anyway, to cut to the chase. After around 6 years my mates amp started developing small faults, nothing major, but things like taking a long time to warm up on a particular channel and odd things like that. Mine never exibited any such symtoms and is still working fine to this day (my mate now has it on his home cinema setup).

    Maybe the above was more down to luck than judgment, I don't know. Maybe, the filtered block had more of an effect on prolonging the life of my unit than leaving it on all of the time did?

    Anyway, my mate now has a filted block and keeps all of his hi-fi powered up permanantly, as do I.

    As a side note, if my 8000LX has been on permanantly for about 8 or 9 years and is still going strong then I don't think there is any need to worry about how long the capacitors last. 8 or 9 years is a good life for any electronic product in my book, and besides, they can always be replaced anyway.

    Any views on the above more than welcome.
     
  20. GrahamMG

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    In the UK I'm not a fan of "mains conditioners/filtered leads" etc. and don't believe they make any kit last longer (lightening strikes accepted maybe!), in fact connecting amps to these things might have a detrimental effect on the amps output being restricted...... Apart from that it would appear we agree....
     
  21. asha_bristol

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    The jury is still out on mains filters as far as I'm concerned too as I have no actual evidence to support either theory. As for sound quality improvements, well they weren't any that I could readily tell. If anything, my gear sounded a little 'different', akin maybe to swapping my interconnect with a different make, albeit one equally as good - in other words no actual improvement but at the same time it wasn't detrimental to the sound quality either.

    My thinking at the time when I bought it was that any rubbish that can be filtered out of the mains must be a good thing in terms of reliability, if not performance?
     
  22. GrahamMG

    GrahamMG
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    Each to his or her own..... Its your money...
     
  23. johnson

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    Hi
    Remember this thread?
    I have been having problems with my av192.
    After lots of help from Stevesky, it's gone back to IAG.
    They've found the problem.

    Capacitors have dropped way below spec and are only just about coping with the power draw.
    infrequent Error67.

    Just thought this may be of interest.
    Regards
    Simon
     
  24. thomasholmlund

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    Well another thing to keep in mind is that almost all electronics/components are sensitive to high temperature drops, i.e. don't open the window near your equipment a cold winterday... that's what I've heard/told. But you maybe already knew that.
     
  25. Dr Udo Zucker

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    Hi, a well designed electronics unit can be powered down when not required - or better said, if you don't need such unit for the time the unit requires to cool fully down, switch it off.

    Above is particularly the case for units drawing a lot of power and hence getting hot, e.g. the AV32R DP and the AV192R. Of course there are two different types of stress being put on a component depending on the user's behaviour: thermal stress because of long periods of elevated temperature or thermal stress because of temperature gradients. Both can destroy units as all components have and limited time span. Just think of a light bulb: some fail when power on, others whilst running.

    In addition, the AV32R and AV192R draw such high current, even in standby, that they "burn" a lot of money when being kept online. That's why I regret that we didn't design a standby power supply into them. Having said this, a standby power supply allows powering down a unit whilst being able to be switched on by remote control. So, the thermal behaviour is of the type: temperature cycling.

    Hope this helps...
     
  26. Miron

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    yes, but you still keep them in standby :)
    (same as most of people here.)
     
  27. Dr Udo Zucker

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    Hi Miron, I don't. I always power down all my equipment when not in use, hence I prefer (like Graham) a power on/off button:) .
     
  28. GrahamMG

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    I should add that whilst I was at the BBC, it was a prerequisite that items had a power off button to save the planet etc. The law changed to allow for a low power standby circuit (if memory serves me correctly less than 2 watts) which the BBC now accept, the TAG design predates this requirement so Udo didn't have to add this feature.

    Personally my own TAG kit stays in standby so saves the thermal cycling which I took the view was the deciding factor especially as I use it most nights. The only time I ever switched the units off for a period long enough to allow the units to fully cool down they had a real head fit when re-powered, they did eventually settle down though but......... I worked out that £50 a year in electricity was cheaper than any IAG repair...... I must admit that hearing of Caps drifting enough to stop the unit working does worry me on a unit so young..... Fingers crossed eh....
     
  29. Kenny Glasgow

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    I leave my eqip in standby when not in use. The only time I power down is if I'm cleaning up the phonos (twice a year at most), power cuts (thankfully not many) or when moving house (only one more of them to go...allegedly)
     

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