| Author |
Message |
John Stewart
Guest
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 Posted:
Sat Sep 03, 2005 4:45 am Post subject:
Re: Tube Amp Power Supply |
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I vote for Jon Yaeger's diagnosis. Cheers, John Stewart
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Mark
Guest
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| Posted:
Sun Sep 04, 2005 9:07 pm Post subject:
Re: Tube Amp Power Supply |
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"Patrick Turner" <info@turneraudio.com.au> wrote in message
news:4318875C.FEBF065B@turneraudio.com.au...
| Quote: | It seems that after the CLC you have the CT of the OPT
and the B+ supply to the rest of the amp.
What are the actual loads connected?
Are they constant? you say not only does the B+ drop,
but the output tube current reduces.
So where is the mystery current going?
So what rectifier tube do you have? have you tried replacing it with
another?
Its possible the HT winding has high DC resistance and which is getting
very
hot.
what is the DCR of the whole of the 440-0-440 winding?
|
Hello Guys!
Today's Sunday, so finnally got some time to do some measurements on the
amp.
I got the following results today. The previous was normally measured in the
night
on weekdays, but today I did in during the day.
This time I moved the amp meter to right after the 5AR4 rec tube and before
the caps
and the rest. Current moved up slowly to 190mA ~ 195mA and stopped.
Time - Secondary VAC
0:00 - 448VAC
0:30 - 441VAC
0:45 - 440VAC
1:00 - 436VAC
1:30 - 433VAC
1:45 - 434VAC
2:00 - 432VAC
The B+ today measured from 480VDC and slowly went down to 476VDC
Current drop a little to around 185mA after 2 hours.
Do you think its something to do with the mains voltage dropping during the
night?
Todays measurements seems to be okay, not too far off as earlier.
Would a computer AVR be useful to prevent too much drops in the mains? Or is
it bad for
audio use?
Regards,
Mark |
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Jon Yaeger
Guest
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| Posted:
Sun Sep 04, 2005 9:31 pm Post subject:
Re: Tube Amp Power Supply |
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in article 431b1c85$1_1@news.tm.net.my, Mark at chanfh@gmail.com wrote on
9/4/05 12:07 PM:
| Quote: |
"Patrick Turner" <info@turneraudio.com.au> wrote in message
news:4318875C.FEBF065B@turneraudio.com.au...
It seems that after the CLC you have the CT of the OPT
and the B+ supply to the rest of the amp.
What are the actual loads connected?
Are they constant? you say not only does the B+ drop,
but the output tube current reduces.
So where is the mystery current going?
So what rectifier tube do you have? have you tried replacing it with
another?
Its possible the HT winding has high DC resistance and which is getting
very
hot.
what is the DCR of the whole of the 440-0-440 winding?
Hello Guys!
Today's Sunday, so finnally got some time to do some measurements on the
amp.
I got the following results today. The previous was normally measured in the
night
on weekdays, but today I did in during the day.
This time I moved the amp meter to right after the 5AR4 rec tube and before
the caps
and the rest. Current moved up slowly to 190mA ~ 195mA and stopped.
Time - Secondary VAC
0:00 - 448VAC
0:30 - 441VAC
0:45 - 440VAC
1:00 - 436VAC
1:30 - 433VAC
1:45 - 434VAC
2:00 - 432VAC
The B+ today measured from 480VDC and slowly went down to 476VDC
Current drop a little to around 185mA after 2 hours.
Do you think its something to do with the mains voltage dropping during the
night?
Todays measurements seems to be okay, not too far off as earlier.
Would a computer AVR be useful to prevent too much drops in the mains? Or is
it bad for
audio use?
Regards,
Mark
|
Why not measure mains & B+ concurrently?
A 1V change in mains voltage will give you about a 4V change in B+.
A 16V delta corresponds to a 4V mains drop. Nothing to lose sleep over.
An AVR may or may not degrade the sound. My adjustable AC power supply
makes some amps sound awful.
Jon |
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Patrick Turner
Guest
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| Posted:
Mon Sep 05, 2005 4:44 am Post subject:
Re: Tube Amp Power Supply |
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Jon Yaeger wrote:
| Quote: | in article 431b1c85$1_1@news.tm.net.my, Mark at chanfh@gmail.com wrote on
9/4/05 12:07 PM:
"Patrick Turner" <info@turneraudio.com.au> wrote in message
news:4318875C.FEBF065B@turneraudio.com.au...
It seems that after the CLC you have the CT of the OPT
and the B+ supply to the rest of the amp.
What are the actual loads connected?
Are they constant? you say not only does the B+ drop,
but the output tube current reduces.
So where is the mystery current going?
So what rectifier tube do you have? have you tried replacing it with
another?
Its possible the HT winding has high DC resistance and which is getting
very
hot.
what is the DCR of the whole of the 440-0-440 winding?
Hello Guys!
Today's Sunday, so finnally got some time to do some measurements on the
amp.
I got the following results today. The previous was normally measured in the
night
on weekdays, but today I did in during the day.
This time I moved the amp meter to right after the 5AR4 rec tube and before
the caps
and the rest. Current moved up slowly to 190mA ~ 195mA and stopped.
Time - Secondary VAC
0:00 - 448VAC
0:30 - 441VAC
0:45 - 440VAC
1:00 - 436VAC
1:30 - 433VAC
1:45 - 434VAC
2:00 - 432VAC
The B+ today measured from 480VDC and slowly went down to 476VDC
Current drop a little to around 185mA after 2 hours.
Do you think its something to do with the mains voltage dropping during the
night?
Todays measurements seems to be okay, not too far off as earlier.
Would a computer AVR be useful to prevent too much drops in the mains? Or is
it bad for
audio use?
Regards,
Mark
Why not measure mains & B+ concurrently?
A 1V change in mains voltage will give you about a 4V change in B+.
|
That much?
Maybe in the US with 120V.
Here in Oz I often see a range of mains from 235V to 250V,
so that if there is +425V from 235~ then I would get +451V from 250~.
Some chinese amps built to run on 220V such as Jolida and designed to have
B+ = +450V will then have +511V with 250~, and then some of the electros blow up,
and if ppl bias the amps as the instructions state the tubes are too hot.
I had a biasing problem when i recently serviced a
Stingray amp which had been bought in europe with 230V mains.
On many days i measure 250~ here.
But our original poster said he had a drop of B+
from 480V to 440V.
That's about 8% change.
Perhaps indeed he has an 8% variation in the mains voltage.
Patrick Turner.
| Quote: |
A 16V delta corresponds to a 4V mains drop. Nothing to lose sleep over.
An AVR may or may not degrade the sound. My adjustable AC power supply
makes some amps sound awful.
Jon |
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vinylbigot
Guest
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| Posted:
Fri Sep 23, 2005 5:37 pm Post subject:
Re: Tube Amp Power Supply |
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Another possibility is to check for the "aw Shit" test.
Swap out the rectifier tube and see what happens.
"John Stewart" <jh.stewart@sympatico.ca> wrote in message
news:4318ECD3.100E362B@sympatico.ca...
| Quote: | I vote for Jon Yaeger's diagnosis. Cheers, John Stewart
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John Stewart
Guest
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| Posted:
Sat Sep 24, 2005 4:43 am Post subject:
Re: Tube Amp Power Supply |
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Patrick Turner wrote:
| Quote: | Jon Yaeger wrote:
in article 43187986$1_2@news.tm.net.my, Mark at chanfh@gmail.com wrote on
9/2/05 12:00 PM:
"Jon Yaeger" <jono_1@bellsouth.net> wrote in message
news:BF3DDD84.320AE%jono_1@bellsouth.net...
Mark,
Question: Does this amp have a C-L-C filter?
Jon
Oh yes - sorry forgot to mention that earlier :)
Mark,
Just for fun, disconnect the 1st section of the electrolytic and bypass it
with a new axial cap of similar value. Measure the B+ over time.
Reasoning:
I have seen a number of amps have electros that fail OPEN. If it is the 1st
cap section, it will drive the voltage down significantly . . . but
typically a lot more than you experienced. The PS becomes a L-C instead of
a C-L-C.
Just suppose, for a minute, that you have a cap section that decreases in
value or there is an increasing equivalent series resistance. It could drop
the voltage like you are experiencing.
Of course, I may be quite wrong, but it's easy to try & rule out.
Jon
Yes, its a possibility the caps are crook.
The ripple voltage at C1 should be = 1,800 x Idc / C uF for 60Hz mains
or 2,200 x Idc / Cuf if mains f = 50 Hz,
So if the Idc is known, and the capacitor value is know from what is on the can,
then the measured ripple voltage at C1 should be what one calculates, so
if C1 = 47uF, then Vripple at 170mA shoulod be with 60Hz mains = 1,800 x 0.17 /
47 = 6.5Vrms .
If the ripple measures say 30Vrms, then C must be a lot lower than it should be.
But it don't explain the slow fall in B+ over 1.5hrs; this is more liklely
to the tied to the temperature of the HT winding wire.
Patrick Turner.
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He is too far from the 'Line Drop Compensator' on the distribution system. Sometimes
called a 'Line Drop Constipator' by the unwashed among us! A magical, high power
auto transformer on a pole near your house whose switch is automatically adjusted by
a control gadget so that the voltage at the load remains constant under various
conditions. Sometimes you will see three of them on succeeding poles doing their
work in a 3-phase system.
Hard to believe, but this very old technology really works.
So there! That is my contribution for this week. What? No tubes? You will have to
read the latest issues of AudioXpress to see what I've really been doing.
Cheers, John Stewart |
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