I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

"Dick" wrote in message
...
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Scope it under load.

Dick wrote:
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.

Transmit, receive or both? You can't rule out the PS entirely if its
only on transmit but you have the added possibility of rf getting in via
the mic, etc.

Yep, scope it under load. You can even use a DMM or VTVM set to AC. Of
course you need to know the original specs or a ballpark idea how much
ripple (%-wise) is to be anticipated in order for the readings to be
meaningful.

GL,
Bill
** Posted from http://www.teranews.com **

On Tue, 08 Apr 2008 14:18:56 -0400, Bill M
wrote:

Dick wrote:
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.

Transmit, receive or both? You can't rule out the PS entirely if its
only on transmit but you have the added possibility of rf getting in via
the mic, etc.

Yep, scope it under load. You can even use a DMM or VTVM set to AC. Of
course you need to know the original specs or a ballpark idea how much
ripple (%-wise) is to be anticipated in order for the readings to be
meaningful.

GL,
Bill
** Posted from http://www.teranews.com **

Thanks Bill. I wanted to use my DVM (Fluke 87), but don't know the
original specs on the power supply. I have been trying to find them
on the Internet.

Dick
** Posted from http://www.teranews.com **

Dick wrote in news:1e9nv3h6uskeei64q8i1j94elo7dhijpsl@
4ax.com:

I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

If you don't have a scope, look at the AC voltage on the DC lines.
Transmit into a dummy load and see if you get AC on the DC line as you
modulate the rig.

You need to have some idea HOW MUCH ac is allowable. Perhaps the specs of
the rig will help.
In any case, the AC should be MUCH less than the DC voltage.







--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

Dick wrote in
:

On Tue, 08 Apr 2008 14:18:56 -0400, Bill M
wrote:

Dick wrote:
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.

Transmit, receive or both? You can't rule out the PS entirely if its
only on transmit but you have the added possibility of rf getting in via
the mic, etc.

Yep, scope it under load. You can even use a DMM or VTVM set to AC. Of
course you need to know the original specs or a ballpark idea how much
ripple (%-wise) is to be anticipated in order for the readings to be
meaningful.

GL,
Bill
** Posted from http://www.teranews.com **

Thanks Bill. I wanted to use my DVM (Fluke 87), but don't know the
original specs on the power supply. I have been trying to find them
on the Internet.

Dick
** Posted from http://www.teranews.com **


The DC blocking cap on your DMM better be good enough for the AC voltages
you're measuring....

a TEK P6015A HV probe and a scope would measure your HV supply ripple.
Safer,too.

--
Jim Yanik
jyanik
at
kua.net

On Tue, 08 Apr 2008 17:17:17 GMT, "James Sweet"
wrote:



"Dick" wrote in message
.. .
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Scope it under load.


With a suitable highvoltage probe.

On Tue, 08 Apr 2008 10:07:52 -0700, Dick wrote:

I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Take a capacitor rated for the voltage in question. Place this cap in
series with your AC volt meter to block the DC component. Measure the
AC component and that gives you the ripple voltage. A bit of math will
give percentages, and all else you need to know.

PeterD wrote:

On Tue, 08 Apr 2008 10:07:52 -0700, Dick wrote:

I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Take a capacitor rated for the voltage in question. Place this cap in
series with your AC volt meter to block the DC component. Measure the
AC component and that gives you the ripple voltage. A bit of math will
give percentages, and all else you need to know.


You want the capacitor to charge first, or you will still be applying
the full DC voltage to the meter. Hook it up, put a jumper across the
meter till the cap has time to charge, then remove it to take your
reading. Be careful and make sure that it's discharged before handling
the cap again.


--
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Add this line to your news proxy nfilter.dat file
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http://improve-usenet.org/index.html


Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

"James Sweet" writes:

"Dick" wrote in message
...
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Scope it under load.

AC coupled.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Thanks Bill. I wanted to use my DVM (Fluke 87), but don't know the
original specs on the power supply. I have been trying to find them
on the Internet.

Here's the schematic in case you don't have it.

http://www.pcs.mb.ca/~standard/117-X%20Schematic.JPG

If it is hum distortion on receive as well the +275 line and the -110
line would be most suspect. I rebuilt a couple of Galaxy supplies
similar to this one and if you start finding bad filter caps it makes
sense to just do a clean sweep of all of them.

I don't know your meter but indeed check to make sure it can handle the
range for AC+DC!

Good luck,
Bill
** Posted from http://www.teranews.com **

"PeterD" wrote in message
...
On Tue, 08 Apr 2008 17:17:17 GMT, "James Sweet"
wrote:



"Dick" wrote in message
. ..
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Scope it under load.


With a suitable highvoltage probe.

Well that's a given. He didn't specify how high the "high voltage" is, if
it's only a few hundred volts, a normal 10x probe should be fine. Up to a
couple thousand, a simple resistor divider will work ok.

On Wed, 09 Apr 2008 00:06:58 GMT, "James Sweet"
wrote:



"PeterD" wrote in message
.. .
On Tue, 08 Apr 2008 17:17:17 GMT, "James Sweet"
wrote:



"Dick" wrote in message
...
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Scope it under load.


With a suitable highvoltage probe.

Well that's a given. He didn't specify how high the "high voltage" is, if
it's only a few hundred volts, a normal 10x probe should be fine. Up to a
couple thousand, a simple resistor divider will work ok.


The high voltage is a little over 900V. The medium voltage is 300V.
Those are the two lines I shorted together momentarily by accident.
That's when the receiver became highly distorted. Don't know the
effect on transmit yet, but expect similar problems. The HV line is
fused. The 300V line is not. The fuse blew instantly. I suspect the
damage, if any, is in the 300V section. The Swan supply was
completely rebuilt with an upgrade board. The only old components
remaining are the power transformer and the choke. Everything else is
new. Everything was working great until I got clumsy with a probe.

The Fluke 87 is a true RMS DVM with a max input for AC and DC of 1000
volts. I have a Tektronix 475 scope. It has a max input of DC
coupled: 250 V (DC + peak AC) or 500 V P-P AC at 1 kHz or less.
AC coupled: 500 V (DC + peak AC) or 500 V P-P AC at 1 kHz or less.

I don't know much about the use of oscilloscopes. Just enough to be
dangerous. I'm assuming I need some type of probe that will let me
test the 900V line in the supply without damaging the scope. I can
see A/C ripple on the 300V line, but I don't know how much is too
much.

Dick
** Posted from http://www.teranews.com **

On Wed, 09 Apr 2008 00:06:58 GMT, "James Sweet"
wrote:



"PeterD" wrote in message
.. .
On Tue, 08 Apr 2008 17:17:17 GMT, "James Sweet"
wrote:



"Dick" wrote in message
...
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **

Scope it under load.


With a suitable highvoltage probe.

Well that's a given.

I'd never assume that! g

He didn't specify how high the "high voltage" is, if

He said a Swan which is probably an old(er) tube HF rig. I'd guess as
much as a kvolt on the finals.

it's only a few hundred volts, a normal 10x probe should be fine. Up to a
couple thousand, a simple resistor divider will work ok.

Yes, I though about a resistor divider too. I hope the OP doesn't kill
himself!

On Tue, 08 Apr 2008 22:35:59 -0700, Dick wrote:



The high voltage is a little over 900V. The medium voltage is 300V.
Those are the two lines I shorted together momentarily by accident.
That's when the receiver became highly distorted. Don't know the
effect on transmit yet, but expect similar problems. The HV line is
fused. The 300V line is not. The fuse blew instantly. I suspect the
damage, if any, is in the 300V section. The Swan supply was
completely rebuilt with an upgrade board. The only old components
remaining are the power transformer and the choke. Everything else is
new. Everything was working great until I got clumsy with a probe.

use a resistor divider network, and a blocking capacitor rated for the
full voltage.


The Fluke 87 is a true RMS DVM with a max input for AC and DC of 1000
volts. I have a Tektronix 475 scope. It has a max input of DC
coupled: 250 V (DC + peak AC) or 500 V P-P AC at 1 kHz or less.
AC coupled: 500 V (DC + peak AC) or 500 V P-P AC at 1 kHz or less.

I don't know much about the use of oscilloscopes. Just enough to be
dangerous. I'm assuming I need some type of probe that will let me
test the 900V line in the supply without damaging the scope. I can
see A/C ripple on the 300V line, but I don't know how much is too
much.

I'd not use a standard probe even on the 300 volt line. Use a high
voltage probe if you want to use the scope.



Dick
** Posted from http://www.teranews.com **

On Tue, 08 Apr 2008 19:26:04 -0400, "Michael A. Terrell"
wrote:



You want the capacitor to charge first, or you will still be applying
the full DC voltage to the meter. Hook it up, put a jumper across the
meter till the cap has time to charge, then remove it to take your
reading.


Be careful and make sure that it's discharged before handling
the cap again.

What, and miss all the fun? bg

PeterD wrote:
On Wed, 09 Apr 2008 00:06:58 GMT, "James Sweet"
wrote:


"PeterD" wrote in message
...
On Tue, 08 Apr 2008 17:17:17 GMT, "James Sweet"
wrote:


"Dick" wrote in message
...
I have a high voltage power supply (Swan 117cx) that may be the cause
of high distortion in the radio it supplies power to. How would I
test for excessive ripple, etc? The voltages are correct.
** Posted from http://www.teranews.com **
Scope it under load.

With a suitable highvoltage probe.
Well that's a given.

I'd never assume that! g

He didn't specify how high the "high voltage" is, if

He said a Swan which is probably an old(er) tube HF rig. I'd guess as
much as a kvolt on the finals.

it's only a few hundred volts, a normal 10x probe should be fine. Up to a
couple thousand, a simple resistor divider will work ok.

Yes, I though about a resistor divider too. I hope the OP doesn't kill
himself!

Sometimes there's a bleeder resistor on the output of the supply.
Often, it's made up of several series resistors.
Sometimes you can measure the ripple across the bottom resistor and
do the math. Or just install another resistor in the bottom
of the bleeder chain.

Or just unhook the cap, drive it with a pulse generator and look at it on
the scope. The shape of the waveform will tell you the capacitance
and ESR of the cap. If the cap is good and the diodes are good, there
ain't much else to look for.
mike

--
Return address is VALID!

On Wed, 09 Apr 2008 14:22:42 GMT, mike wrote:


Sometimes there's a bleeder resistor on the output of the supply.
Often, it's made up of several series resistors.
Sometimes you can measure the ripple across the bottom resistor and
do the math. Or just install another resistor in the bottom
of the bleeder chain.

Or just unhook the cap, drive it with a pulse generator and look at it on
the scope. The shape of the waveform will tell you the capacitance
and ESR of the cap. If the cap is good and the diodes are good, there
ain't much else to look for.
mike

There are two series bleeder resistors (120K 3W) on the output of the
HV supply, with an electrolytic across each one. If you ground the
bottom of that chain, you get 600V output. The 275V supply is placed
in series with the HV supply for 900V output by moving the fuse from
one location to another. I could send you a PDF of the schematic if
you would like.

Dick
** Posted from http://www.teranews.com **