Power Supply Tester

  • Thread starter Thread starter RF
  • Start date Start date
Based on the anecdotal evidence, I'd guess that some testers are only
checking for any voltage on a specified "pin," rather than precisely
measuring it, else a false positive with 1.5 V undervoltage would be
unlikely. If the tester is like $10 to $15 I can understand that, any
more and it should do precise testing, given that a $9 DMM can do the same.

michael
Click to expand...


I keep both in my toolbox. I find the tester is most times right, and
is good for a quick-and-dirty check of things. If I have to get into
it more deeply, I haul out the dmm and crank it up.

I got the PS tester at CompUSA and it's come in very handy.
 
One is a 430TX mobo made by some defunct company and doesn't seem to
have any documentation available for it on the web. The other is an
FIC PA-2007 (VIA VP2 chipset) that uses a 5V-only Analog Devices brand
chip to convert between RS-232 and TTL levels and contains its own
charge pump circuitry to generate +10V and -10V for the RS-232 side.
Click to expand...

You're right, of course. I have a FIC PA-2012 that uses the same (?)
chip, an ADM213EARS.

Here is the datasheet:
http://www.analog.com/UploadedFiles/Data_Sheets/385450995ADM206E_7E_8E_11E_13E_c.pdf

I've been aware of such 5V-only chips for quite some time (Maxim also
makes them), but until I saw the Analog Devices datasheet I was
struggling to explain why a designer would opt for 8 charge pump caps
and a more expensive IC instead of simply taking advantage of the
+/-12V supply rails. It appears that this IC is powered from the 5VSB
rail and has a low power shutdown mode in which two receivers remain
active for wake-on-interrupt monitoring.

In any case, your original statement that the motherboard doesn't
"use" these negative rails can be seen to be ambiguous. A PCI-only
board would not need the -5V rail since the PCI spec makes no
provision for same. However, the -12V supply *is* bussed to the PCI
slots, so the motherboard does actually use it.
When I bought this mobo used, its RS-232 ports didn't work except at
slow speeds because two .1 uF surface mount capacitors for the charge
pump were missing. I thought they'd been knocked off during
installation of a PCI card, but apparently they had vaporized when the
previous owner plugged or unplugged a parallel printer or serial
device with the power on. I know that the parallel port could do this
because my friend later unplugged a printer from this mobo and caused
the same capacitors to explode.
Click to expand...

This is bizarre. I can't understand how the charge pump caps for the
RS232 driver IC can be affected by a failure of the parallel port. On
the PA-2012 board the parallel port is connected to a Winbond W83877F
multi-IO chip. I would think that your PA-2007 would be similar. In
any case, for a capacitor to vaporise, I would think that it would
have to experience a large overvoltage. I can't imagine that an
inductive spike from a data cable disconnection would have sufficient
energy to cause this failure (?). If anything, I would expect the I/O
chips to fail well before any passive component. Having said that, I
*have* seen failures in open collector drivers (eg 7406) in 20mA
current loop implementations of RS232 when the data cable has been
disconnected with power applied.


- Franc Zabkar
 
On Wed, 04 Aug 2004 06:35:45 +1000, Franc Zabkar

In any case, your original statement that the motherboard doesn't
"use" these negative rails can be seen to be ambiguous. A PCI-only
board would not need the -5V rail since the PCI spec makes no
provision for same. However, the -12V supply *is* bussed to the PCI
slots, so the motherboard does actually use it.
Click to expand...

The motherboard may route -12V to PCI but what uses it?
Old soundcards with integral amp come to mind but nothing else.
 
Micah Torrance said:
I keep both in my toolbox. I find the tester is most times right, and
is good for a quick-and-dirty check of things. If I have to get into
it more deeply, I haul out the dmm and crank it up.

I got the PS tester at CompUSA and it's come in very handy.
Click to expand...

I got mine at CompUSA as well :-).... Is it a CompUSA brand?
 
On Wed, 04 Aug 2004 06:35:45 +1000, Franc Zabkar



The motherboard may route -12V to PCI but what uses it?
Old soundcards with integral amp come to mind but nothing else.
Click to expand...

Data acquisition cards.


- Franc Zabkar
 
Chinese copy, $3.99 on sale:

http://www.harborfreight.com
Click to expand...

Can anyone suggest a decent quality Digital Multimeter that's suitable
for testing PC measurements and sells online for a reasonable price. I
was looking at Ebay and the Fluke 77-III meter seemed to go for around
$60 and up. I can't recall where I saw that meter recommended, but one
of the big hardware test sites like Tom's Hardware, Anatech etc said
they used that model. I don't know much of anything about electricity
so I probably wouldn't ever use advanced features. I could see
measuring power supply voltages etc. Perhaps there is some good meters
between Fluke prices and ones that probably aren't all that accurate.

Thanks
 
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