On Jan 29, 3:32*pm, flipper wrote:
On Fri, 28 Jan 2011 17:40:48 -0800 (PST), Patrick Turner
wrote:
On Jan 29, 7:27*am, flipper wrote:
On Fri, 28 Jan 2011 12:03:55 +0100, "GRe"
wrote:
"Patrick Turner" wrote in message
...
[...]
The vast majority of users are technically illiterate, through no
fault of their own.
They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.
Obviously (on paper) ARC's operate within spec even at .au supply.
VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)
VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see:http://www.audioresearch.com/vt200.html
VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see:http://www.audioresearch.com/VM220.html
Those specs are technically 'not quite right' as 'harmonization'
specifies 230VAC +- 10% for a range of 207VAC-253VAC. In the former
240VAC countries the spec is 230VAC +10% -6% and in the 220VAC
countries it's 230VAC +6 -10, so they didn't have to change a blessed
thing, which results in the same 'fully harmonized' 230VAC +- 10% spec
as far as equipment manufacturers go. Maybe ARC is using 'round
numbers'.
Further, country power specs are 'on the grid' and not your wall
outlet. "Service voltage" (outlet) can be down to 85% of nominal,
which is why design engineers see operating specs that don't 'match'
the country power spec. I mean as far as steady state voltage goes.
The 'every day' problems are transients and brownouts.
To cover operating conditions the amp should cover 185VAC to 253VAC
but you might put the 'country power' range on the label to avoid
confusion.
Something doesn't jive, though, because Patrick says the amp's label
states 220VAC and that isn't consistent with the above spec. That
leads me to believe it might be a 'pre harmonization' amp that was
intended for 220VAC continental Europe use.
And therein lies a problem because harmonization only 'pretends' to
harmonize by inventing a new spec that's simply wide enough to
encompass the existing power systems but it didn't actually change a
blessed thing on the ground. In theory that's 'not a problem' for
*new* designs, which should take into account the extended +-10%
range, but it leads to a perception problem that "we're all on the
same power now so what works in France should work in the U.K." Except
(for the most part) France was and is still 220VAC +-6% while the U.K
was and is still 240VAC +-6% so what was 'once upon a time' built for
220VAC is over voltaged on 240VAC.
All 'harmonization' did was to 'force' manufacturers into making
equipment that works in both 220VAC and 240VAC countries, which they
could and usually did do on their own by either complying with both
specs (one means being transformer taps as Patrick mentioned) or
making models specific to the export region, but, in the process, it
created confusion by pretending something changed. It's also a pain in
the butt for manufacturer's because they can no longer 'fine tune' a
product for the actual mains power as it has to be the mythical, and
wider (more difficult to design for), 'harmonized' voltage of 230VAC
+-10%.
The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.
A bit hard to find but ARC actually say something about it, quote:
"Factors which can shorten tube life include inadequate
ventilation, overdriving loudspeakers at continuously high
volume levels, severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand), or severe interference pulses or electromagnetic
interference. Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;
contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".
[...]
Regards,
Gio- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -
I suspect ARC may have switched to 220V chinese made power trannies.
The only reason you 'suspect' that is it's the only 'suspicion' which
would comply with your perennial determination to declare everyone
else idiots and crooks.
Not everyone is a crook or an idiot.
Sometimes perfectly wonderful people can design amps which would
easily withstand one or two serious improvements.
I managed to complete the servicing on the VT200 this afternoon.
But they have a 27 ohm 1/4 watt plus what appears to be a 1ohm
resistance between the anodes and OPT primary connection. It looks
like an old fashioned carbon comp resistance but may indeed be
inductive, but anyway two had exploded apart from too much heat. I saw
no coil of wire. The other good ones measured 1 ohm.
So during initial testing measured an average of 67mA of anode
current without the screen current, so maybe the Ia + Ig2 was 75mA and
Pda even higher than I thought it was.
I found that they DON''T have 1 ohm R in the cathode circuits but have
0.2 ohm which are 5 watt rated, well made and none were faulty. Only
one screen resistance had failed. I set the bias by measuring the
voltage across 4 x 0.54 ohm 5W resistors in the anode supplies to each
PP 1/2 of each channel. Bias currents varied by a max of 50% and ther
maximum bias currents determined the final overal setting. Pda is now
less than 20W max per tube.
The tubes were all serviceable. Two which had cooked their series
resistances and one which I found to glow with a red plate all seem OK
and seem stable and happy with the lower bias current.
God only knows why they'd deliberately make it 220VAC, and mark it
220VAC, when everyone 'knows' the harmonized voltage is 230VAC and
their published spec complies with harmonized 230VAC. That is, only
God and you 'knows'.
I don't believe there is any God except the God Of Triodes, and he
sends me a bad electric shock if I ever spout bull****.
I certainly would never want anyone to think I was on a par with some
imagined deity.
I'm just a humble bloke, doin my job, and tryna keep ppl in music
without smoke, noise, and distortion or sullen silence.
All I do know is that ppl here buy ARC stuff and don't care about the
mains voltage and then smoke happens.
Go ahead and tell me how you've done a survey of all ARC amps sold in
Oz and they all have 220VAC markings on them and burned up.
Well, I have at least one colleague who is never surprised with smoke
emanations from ARC amps.
I don't get to see many ARC amps, but those I do see have burned out
parts in them.
The pair of VM220 have a 220Vac sticker. Not very prominent, but there
it is, probably because there are two 110V windings in series.
Then explain how you've investigated and determined it's impossible
the amp was intended for continental Europe 220VAC mains, since the
blooming thing is MARKED 220VAC, but somehow ended up in Oz. (and it
isn't a 'U.S.' marking because our 'large appliance' voltage is
240VAC)
Much stuff people don't want elsewhere in the world ends up in Oz
after its has been sold on E-bay.
I would say much has 110V setting for the USA. Nearly every audiophile
I know has something he bought on E-bay and he has a 240V:110V step
transformer. With preamps it is not critical but with power amps it
only become critical if the mains voltage is too high while ppl ignore
it.
Just to be clear, I don't have the answer to those questions either
but then I'm not running around calling people idiots and crooks when
I don't know for sure.
Well, today while setting the bias on the VT200, I have to remove the
cover allowing access to the two current sensing R in the anode supply
circuit.
Then I have t hold a pair of voltmeter prods to the two ends of a
resistance, read a volt meter while turning a bias pot where the screw
driver doesn't wanto to easily engage the slot. The bias pot is a
single turn and bias setting is very touchy. But I manage because I
have worked so long with tube gear. But an audiophile novice might
find it a terrible struggle and slip with prods and cause a fuse to
blow or he gets a bad electric shock trying to do 3 things at once.
ARC seem to have glued on some flimsy plastic sheeting around the
current sensing R as they have anticipated troubles ppl could have,
and probably in response to those who told them of the difficulties or
the shocks they'd had.
What should be there is a separate adjust pot for each 6550, along
with 16 pairs of sockets to test the bias currents for the 16 tubes in
the VT200.
The best place for such test point and screw adjust heads is on the
front panel of the amp so owners never have to remove a cover or move
the amp to bias it.
A re-green LED to show the bias condition is wise.
It is insanely stupid to expect a large heavy box full of very hot
vacuum tubes to last well when the mains voltage is too high, and the
biasing method is so stupid, and there is no active protection if one
or more tubes goes into thermal run-away.
As long as ppl here in Oz understand that there can be problems and
that there are solutions, I have done all I can.
Well, we can hope no one's listening because if you're not 100% right
on each accusation you're opening yourself up for a defamation
lawsuit.
Its a wonder nobody has sued ARC for causing spinal injuries.
I'm here to promoe ARC product improvement, and never to be too
harsh.
No doubt 1% of people contemplating the purchase of some ARC tube amp
will do a search and our discussions will come to their screens.
People in the USA and where mains voltage is correct may rest easier
than here where mains voltage can be too high.
The crew who run Audigon.com discussion group must have found what I
had to say way too contentious to publish.
Moderated groups are somewhat censored. But here we may discuss
problems and solutions freely.
Other problems in VT100, 120, 200 and derivatives could do with a big
fix by ARC.
I wish them well.
Patrick Turner.