sci.electronics.repair - 25 new messages in 7 topics - digest

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Today's topics:

* High wattage dummy load/s for audio use - 9 messages, 7 authors
http://groups.google.com/group/sci.electronics.repair/t/275ffe5cac06cb9b?hl=en
* paypal wholesale Lacoste T-Shirt woman - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/74be7a86f4da3829?hl=en
* paypal wholesale 2010 FIFA World Cup Mexico football jersey - 1 messages, 1
author
http://groups.google.com/group/sci.electronics.repair/t/54323b5ebf2a186f?hl=en
* Pioneer CDJ-1000 Mk3 ... - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/bd724168793aed39?hl=en
* TSA shaving mirror out of a hard disk drive (what are those shiny platters
made out of anyway)? - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/680b452b6da0d742?hl=en
* Vertical Lines - 9 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/7824ada624c770ad?hl=en
* DATAMAN s4 eprom programmer , looking for GAL adaptor... - 2 messages, 2
authors
http://groups.google.com/group/sci.electronics.repair/t/2b308026e5f71b8d?hl=en

==============================================================================
TOPIC: High wattage dummy load/s for audio use
http://groups.google.com/group/sci.electronics.repair/t/275ffe5cac06cb9b?hl=en
==============================================================================

== 1 of 9 ==
Date: Wed, Jun 23 2010 12:48 am
From: "N_Cook"

Just curious about these - how were they used? All that is known is they
came from an audio lab.
About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me, from
surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
diameter. Some sort of multiple series and parallel for 2 ohm etc or with L
and C for speaker simulation ?

== 2 of 9 ==
Date: Wed, Jun 23 2010 4:39 am
From: Tim Schwartz

On 6/23/2010 3:48 AM, N_Cook wrote:
> Just curious about these - how were they used? All that is known is they
> came from an audio lab.
> About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me, from
> surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
> diameter. Some sort of multiple series and parallel for 2 ohm etc or with L
> and C for speaker simulation ?
>
>

Nigel,

To me 2.8 ohms is an odd value. I have DALE 8 ohm 250 watt, non
inductive winding resistors. With four of them, I have 8 ohms at 250
watts, or 4 ohms at 500 watts. If I had felt the need I could have done
some more complicated switching and also had 16 ohms at 500 watts.

They are very useful as you can hook them up as a dummy load and view
on your scope, and run rather large amp right up to clipping, all while
not having to listen to any of it. It also makes it easy to measure
power at clipping, as long as you also monitor your mains voltage. (At
clipping, you have to watch the voltage drop at your bench outlet, as
you might be feeding the amp a lower mains voltage than it is specified
for, which will reduce power output. I have a VARIAC to correct for this.)

I have seen one manufactured unit that used 7.87 ohm resistors, as they
figured out the resistance of the wiring and switching. I put together
my own, and did not feel the need for that level of accuracy.

The loads that I have are resistive, so not as difficult to drive as a
speaker might be, but again, good enough for my needs.

You did not specify the make or model of the resistors, or how they
were wired up.

Regards,
Tim Schwartz
Bristol Electronics

== 3 of 9 ==
Date: Wed, Jun 23 2010 6:23 am
From: Meat Plow

On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ǝʇoɹʍ:

> Just curious about these - how were they used? All that is known is they
> came from an audio lab.
> About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
> from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
> diameter. Some sort of multiple series and parallel for 2 ohm etc or
> with L and C for speaker simulation ?

Most newer SS amps are rated to a minimum of 2 ohms.

== 4 of 9 ==
Date: Wed, Jun 23 2010 6:50 am
From: "N_Cook"

Tim Schwartz <tim@bristolnj.com> wrote in message
news:4C21F254.1010302@bristolnj.com...
> On 6/23/2010 3:48 AM, N_Cook wrote:
> > Just curious about these - how were they used? All that is known is they
> > came from an audio lab.
> > About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
from
> > surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
> > diameter. Some sort of multiple series and parallel for 2 ohm etc or
with L
> > and C for speaker simulation ?
> >
> >
>
> Nigel,
>
> To me 2.8 ohms is an odd value. I have DALE 8 ohm 250 watt, non
> inductive winding resistors. With four of them, I have 8 ohms at 250
> watts, or 4 ohms at 500 watts. If I had felt the need I could have done
> some more complicated switching and also had 16 ohms at 500 watts.
>
> They are very useful as you can hook them up as a dummy load and view
> on your scope, and run rather large amp right up to clipping, all while
> not having to listen to any of it. It also makes it easy to measure
> power at clipping, as long as you also monitor your mains voltage. (At
> clipping, you have to watch the voltage drop at your bench outlet, as
> you might be feeding the amp a lower mains voltage than it is specified
> for, which will reduce power output. I have a VARIAC to correct for
this.)
>
> I have seen one manufactured unit that used 7.87 ohm resistors, as they
> figured out the resistance of the wiring and switching. I put together
> my own, and did not feel the need for that level of accuracy.
>
> The loads that I have are resistive, so not as difficult to drive as a
> speaker might be, but again, good enough for my needs.
>
> You did not specify the make or model of the resistors, or how they
> were wired up.
>
> Regards,
> Tim Schwartz
> Bristol Electronics
>

Marked neatly on the curve 2R8 +/-5 % and then 87.31 perhaps 31/52 of 1987.
I picked up the last 3 at a hamfest on Sunday, I did not think to ask how
many he had originally.
I'd not googled the Arcol name stamped on the brackets as they did not look
original to the resistor section, thinking it was just a maker of steel
brackets.
Crinkle form type at top of this image
http://www.arcolresistors.com/images/product-range/wirewound/tubular-family.
jpg
but still leaves mystery of 2R8

== 5 of 9 ==
Date: Wed, Jun 23 2010 7:30 am
From: Grant

On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow <mhywatt@yahoo.com> wrote:

>On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:
>
>> Just curious about these - how were they used? All that is known is they
>> came from an audio lab.
>> About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
>> from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
>> diameter. Some sort of multiple series and parallel for 2 ohm etc or
>> with L and C for speaker simulation ?
>
>Most newer SS amps are rated to a minimum of 2 ohms.

And cheapie meter leads might account for the extra 0.8 Ohms?
--
Grant.
--
http://bugs.id.au/

== 6 of 9 ==
Date: Wed, Jun 23 2010 7:59 am
From: Meat Plow

On Thu, 24 Jun 2010 00:30:47 +1000, Grant ǝʇoɹʍ:

> On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow <mhywatt@yahoo.com>
> wrote:
>
>>On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:
>>
>>> Just curious about these - how were they used? All that is known is
>>> they came from an audio lab.
>>> About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
>>> from surface area scaling of 2.5 and 6W ones, these are 210 mm long
>>> 35mm diameter. Some sort of multiple series and parallel for 2 ohm etc
>>> or with L and C for speaker simulation ?
>>
>>Most newer SS amps are rated to a minimum of 2 ohms.
>
> And cheapie meter leads might account for the extra 0.8 Ohms? --
> Grant.

They'd have to be very cheap. Mr. Kook is a talented technician so I
think that we can rule out that factor.

I use a pair of finned 300 watt 8 ohm resistors mounted on a giant power
supply heat sink to raise their continuous rating. Got them from Yamaha
way back in the 80's when I did warranty work for their pro-audio line.
They aren't branded Yamaha. They sent them to our warranty station along
with some other equipment they required to authorize us. If I recall the
total startup cost was a couple thousand bucks but we also had a credit
line with their service/parts dept.

== 7 of 9 ==
Date: Wed, Jun 23 2010 9:10 am
From: AZ Nomad

On Thu, 24 Jun 2010 00:30:47 +1000, Grant <omg@grrr.id.au> wrote:
>On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow <mhywatt@yahoo.com> wrote:

>>On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:
>>
>>> Just curious about these - how were they used? All that is known is they
>>> came from an audio lab.
>>> About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
>>> from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
>>> diameter. Some sort of multiple series and parallel for 2 ohm etc or
>>> with L and C for speaker simulation ?
>>
>>Most newer SS amps are rated to a minimum of 2 ohms.

>And cheapie meter leads might account for the extra 0.8 Ohms?

You'd need at least 90' of them (at 20 AWG)

or 8' of 30AWG, but I've never heard of such slim wire
being used for probes.

== 8 of 9 ==
Date: Wed, Jun 23 2010 9:28 am
From: zekfrivo@zekfrivolous.com (GregS)

In article <slrni24cf9.uu4.aznomad.3@ip70-176-155-130.ph.ph.cox.net>, AZ Nomad <aznomad.3@PremoveOBthisOX.COM> wrote:
>On Thu, 24 Jun 2010 00:30:47 +1000, Grant <omg@grrr.id.au> wrote:
>>On Wed, 23 Jun 2010 13:23:04 +0000 (UTC), Meat Plow <mhywatt@yahoo.com> wrote:
>
>>>On Wed, 23 Jun 2010 08:48:22 +0100, N_Cook ??o??:
>>>
>>>> Just curious about these - how were they used? All that is known is they
>>>> came from an audio lab.
>>>> About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me,
>>>> from surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
>>>> diameter. Some sort of multiple series and parallel for 2 ohm etc or
>>>> with L and C for speaker simulation ?
>>>
>>>Most newer SS amps are rated to a minimum of 2 ohms.

CAR AMPS

>>And cheapie meter leads might account for the extra 0.8 Ohms?
>
>You'd need at least 90' of them (at 20 AWG)
>
>or 8' of 30AWG, but I've never heard of such slim wire
>being used for probes.

I typically get .3 ohms on the Fluke.

I have a couple dummy loads. One with 8- 50 watt gold
chassis resistors attached to sink with fan.
I have four more separate sinks without fan.
I either choose 8 ohms or 4.

greg

== 9 of 9 ==
Date: Wed, Jun 23 2010 10:20 am
From: Cydrome Leader

N_Cook <diverse@tcp.co.uk> wrote:
> Just curious about these - how were they used? All that is known is they
> came from an audio lab.
> About 200 watt, 2.8 ohm vitreous resistors. 200watt estimated, by me, from
> surface area scaling of 2.5 and 6W ones, these are 210 mm long 35mm
> diameter. Some sort of multiple series and parallel for 2 ohm etc or with L
> and C for speaker simulation ?

the ones I used were just large (hundreds of watts) ceramic wirewound
resistor mounted in heatsinks. They had to have been 8 ohms or something
really close as to not blow up 1970s and 1980s equipment.

you could hear the music though them if you got close enough.

==============================================================================
TOPIC: paypal wholesale Lacoste T-Shirt woman
http://groups.google.com/group/sci.electronics.repair/t/74be7a86f4da3829?hl=en
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TOPIC: paypal wholesale 2010 FIFA World Cup Mexico football jersey
http://groups.google.com/group/sci.electronics.repair/t/54323b5ebf2a186f?hl=en
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