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west
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 Posted:
Fri Sep 30, 2005 4:43 am Post subject:
Re: Warm start options |
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"Iain M Churches" <tael@kolumbus.fi> wrote in message
news:dhg62k$o20$1@phys-news1.kolumbus.fi...
| Quote: |
"west" <westley@Tampabay.rr.com> wrote in message
news:uUI_e.113614$xl6.108888@tornado.tampabay.rr.com...
"Iain M Churches" <tael@kolumbus.fi> wrote in message
news:dhdbq3$fol$1@phys-news1.kolumbus.fi...
Modern valve/tube amps seem to use a delay start
for their HT.
In the past I have uses a mechanical timer relay
on the secondary of the mains transformer
before the FWB, or a DLS16, a neat octal
thermal relay which glows incandescently for
about 45secs before closing.
I like the idea of a relay which would not switch the HT
at all, but be used to keep the bias for the output valves/
tubes at say -80V until the cathodes were warm.
At the moment, the only negative aspect I can see about
this arrangement is that the psu caps will be allowed to
charge to peak voltage as the output valves are drawing
no current. But, providing one makes allowances for this
it should not be a problem.
Does this seem like a good idea?
Any other suggestions?
There's a plethora of approaches you can take, Iain. Which is the best?
The
answer, I believe, can break the record for the longest thread ever on
RAT.
One of the basic tenets in electronic design is to be parsimonious with
parts.
Hi West
Yes. I am looking for what that great audiophile Tina Turner calls
"Simply the Best":-)
Wouldn't a temporary -80v bias require an additional circuit?
The bias supply is -80VDC with a 25k/2W pot across it, with bias
fed from the wiper. My idea was to have a timer relay which would
be connected to the top of the pot (-80VDC) while the timer was
running, and then switch to the wiper after 45s to set the bias at the
normal level and let the valves draw current.
Does that make sense?
Would it be better than switching the HT?
Cheers
Iain
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In the spirit of your concerns, what about the PS caps keeping the HT on a
bit longer than the rest after flipping the switch to the OFF position?
west
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Iain M Churches
Guest
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| Posted:
Fri Sep 30, 2005 11:12 am Post subject:
Re: Warm start options |
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"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in message
news:nftoj15nnh1bfgj08mgoc3gf07v90ick0g@4ax.com...
| Quote: | On Thu, 29 Sep 2005 10:46:46 +0300, "Iain M Churches"
tael@kolumbus.fi> wrote:
I did not go into detail, but it is wired just as you describe,
and operates a power relay. The thermal relay switches off
after the delay time has been reached. That should ensure
that it lasts for many years. I did find though in the case of the
DLS 16 that they vary enormously. So I had to pick and match
and vary the voltage across the heater to get a pair (one each
channel psu) that would switch at almost the same time.
If I'm following you correctly, you're operating *after*
the power transformer's secondary. You might really
enjoy the freedom of design you'd get from separate
filament and HV power transformers.
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In the past I have used two transformers with bias and
heater voltages from a separate transformer
On this amp, due to lack of space on the chassis, I have
had to go for the one transformer solution.
| Quote: |
I know; I know; "I'm not worthy" you say. BZZZT.
Yes you are. Live now. Life's short.
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:-))
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I'm just not convinced that this *does anything*
useful or important. And has the serious disadvantage
of lacking a silent startup that comes free by *not*
doing it.
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I thought that by applying a large negative bias, I
could prevent the OP valves from drawing current while
the cathodes warm up. Surely that's both useful and
important?
Do you think then that the start-up will not be silent
then, using the above method? I haven't decided
which method to use, so any help/experience/ideas
would be appreciated.
Cordially,
Iain |
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Iain M Churches
Guest
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| Posted:
Fri Sep 30, 2005 11:15 am Post subject:
Re: Warm start options |
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"west" <westley@Tampabay.rr.com> wrote in message
news:ey%_e.152938$p_1.112508@tornado.tampabay.rr.com...
| Quote: | In the spirit of your concerns, what about the PS caps keeping the HT on a
bit longer than the rest after flipping the switch to the OFF position?
west
Hi West. My interest here is to find a way to let the cathodes reach |
operating temperature before the OP valves draw current.
Iain |
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