A little tip: It fails its self test in a very intimidating way if you
execute it without a test harness attached to three of the four DUT
connections. Most people at surplus places don't know that. 'Nuff said. ;)
-Dave
On 02/05/2014 03:45 PM, Ian McLaughlin wrote:
Great, Now I've got *another* saved search on eBay - for a broken 4276A :)
Ian
On Feb 5, 2014, at 12:22 PM, Dave McGuire <mcguire at neurotica.com> wrote:
On 02/05/2014 03:21 PM, Dave McGuire wrote:
On 02/05/2014 03:14 PM, Ian McLaughlin wrote:
Mine's a cheap Chinese DT-9935 - $140. Free shipping from most Ebay vendors.
I do like HP gear, but the 4276A is a bit steep for me :)
I got it broken for even less than that and fixed it. =) I love doing
that...learn a lot in the process too!
(not to gloat, of course...just sharing the fun..)
--
Dave McGuire, AK4HZ
New Kensington, PA
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--
Dave McGuire, AK4HZ
New Kensington, PA
Great, Now I've got *another* saved search on eBay - for a broken 4276A :)
Ian
On Feb 5, 2014, at 12:22 PM, Dave McGuire <mcguire at neurotica.com> wrote:
On 02/05/2014 03:21 PM, Dave McGuire wrote:
On 02/05/2014 03:14 PM, Ian McLaughlin wrote:
Mine's a cheap Chinese DT-9935 - $140. Free shipping from most Ebay vendors.
I do like HP gear, but the 4276A is a bit steep for me :)
I got it broken for even less than that and fixed it. =) I love doing
that...learn a lot in the process too!
(not to gloat, of course...just sharing the fun..)
--
Dave McGuire, AK4HZ
New Kensington, PA
---
Filter service subscribers can train this email as spam or not-spam here: http://my.email-as.net/spamham/cgi-bin/learn.pl?messageid=545BF5528EA311E3B…
On Wed, 5 Feb 2014, Dave McGuire wrote:
On 02/05/2014 03:14 PM, Ian McLaughlin wrote:
Mine's a cheap Chinese DT-9935 - $140. Free shipping from most Ebay vendors.
I do like HP gear, but the 4276A is a bit steep for me :)
I got it broken for even less than that and fixed it. =) I love doing
that...learn a lot in the process too!
Unfortunately, I'd likely break one further.
Doesn't mean I wouldn't learn a lot, though. I've learned a LOT from doing things wrong the first five times. ;)
-Dave
--
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects
On Wed, 5 Feb 2014, Dave McGuire wrote:
On 02/05/2014 04:17 AM, Mark Wickens wrote:
Fans would click for a second and then kick right back off. It
stopped doing that until I removed all the drives. Plugged 'em back
in after opening the PSU to look for obvious faults and found none.
Everything is working fine now...Strange.
I had a hard disk taken out by a power spike. I also had firmware
corruption that required reflashing the EEPROM, but I don't remember if
that was related to the PSU. They draw 30 watts when switched 'off' so
it's definitely worth turning them off when not in use.
Twitching fans might indicate over-current protection kicking in.
If it's a repetitive twitching, it's probably the error amplifier or
the voltage divider feeding it. (those will be difficult to test
individually unless they're discretes, of course)
It was a single twitch and it then kicked right off. Light never came on.
One other thing I've seen recently with older switching power supplies
is the output capacitors' ESR going up due to age, causing their time
constant to exceed that of the regulation loop...creating, you guessed
it, an oscillator.
That would certainly explain it. It wouldn't explain why they went back to normal later...unless they're temperature sensitive.
I know one thing however - switched mode PSU experts are few and far
between!
This is painfully true. I *design* the damn things and I shy away
from working on them most of the time. Direct AC-driven ones are RIGHT
OUT in my book.
I prefer linear supplies with simple rectification. ;) I understand /those/!
-Dave
--
Cory Smelosky
http://gewt.net Personal stuff
http://gimme-sympathy.org Projects
On 02/05/2014 03:21 PM, Dave McGuire wrote:
On 02/05/2014 03:14 PM, Ian McLaughlin wrote:
Mine's a cheap Chinese DT-9935 - $140. Free shipping from most Ebay vendors.
I do like HP gear, but the 4276A is a bit steep for me :)
I got it broken for even less than that and fixed it. =) I love doing
that...learn a lot in the process too!
(not to gloat, of course...just sharing the fun..)
--
Dave McGuire, AK4HZ
New Kensington, PA
On 02/05/2014 03:14 PM, Ian McLaughlin wrote:
Mine's a cheap Chinese DT-9935 - $140. Free shipping from most Ebay vendors.
I do like HP gear, but the 4276A is a bit steep for me :)
I got it broken for even less than that and fixed it. =) I love doing
that...learn a lot in the process too!
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Mine's a cheap Chinese DT-9935 - $140. Free shipping from most Ebay vendors.
I do like HP gear, but the 4276A is a bit steep for me :)
Ian
On Feb 5, 2014, at 12:10 PM, Dave McGuire <mcguire at neurotica.com> wrote:
On 02/05/2014 03:08 PM, Ian McLaughlin wrote:
The best tool for repairing switching supplies (or monitors, for that
matter) - an ESR meter. Out of all of the test gear I've purchased
over the years, this one probably gets the most use! They use such a
low voltage, you can usually use them in-circuit without having to
desolder the component off the board before testing. Only takes a
few minutes to go through a power supply and identify the suspect
electrolytics.
Agreed 100%. I use an HP 4276A for exactly that.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
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On 02/05/2014 03:08 PM, Ian McLaughlin wrote:
The best tool for repairing switching supplies (or monitors, for that
matter) - an ESR meter. Out of all of the test gear I've purchased
over the years, this one probably gets the most use! They use such a
low voltage, you can usually use them in-circuit without having to
desolder the component off the board before testing. Only takes a
few minutes to go through a power supply and identify the suspect
electrolytics.
Agreed 100%. I use an HP 4276A for exactly that.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
The best tool for repairing switching supplies (or monitors, for that matter) - an ESR meter. Out of all of the test gear I've purchased over the years, this one probably gets the most use! They use such a low voltage, you can usually use them in-circuit without having to desolder the component off the board before testing. Only takes a few minutes to go through a power supply and identify the suspect electrolytics.
Ian
On Feb 5, 2014, at 12:05 PM, Dave McGuire <mcguire at neurotica.com> wrote:
On 02/05/2014 04:17 AM, Mark Wickens wrote:
Fans would click for a second and then kick right back off. It
stopped doing that until I removed all the drives. Plugged 'em back
in after opening the PSU to look for obvious faults and found none.
Everything is working fine now...Strange.
I had a hard disk taken out by a power spike. I also had firmware
corruption that required reflashing the EEPROM, but I don't remember if
that was related to the PSU. They draw 30 watts when switched 'off' so
it's definitely worth turning them off when not in use.
Twitching fans might indicate over-current protection kicking in.
If it's a repetitive twitching, it's probably the error amplifier or
the voltage divider feeding it. (those will be difficult to test
individually unless they're discretes, of course)
One other thing I've seen recently with older switching power supplies
is the output capacitors' ESR going up due to age, causing their time
constant to exceed that of the regulation loop...creating, you guessed
it, an oscillator.
I know one thing however - switched mode PSU experts are few and far
between!
This is painfully true. I *design* the damn things and I shy away
from working on them most of the time. Direct AC-driven ones are RIGHT
OUT in my book.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
---
Filter service subscribers can train this email as spam or not-spam here: http://my.email-as.net/spamham/cgi-bin/learn.pl?messageid=EA9D86968EA011E39…
On 02/05/2014 04:17 AM, Mark Wickens wrote:
Fans would click for a second and then kick right back off. It
stopped doing that until I removed all the drives. Plugged 'em back
in after opening the PSU to look for obvious faults and found none.
Everything is working fine now...Strange.
I had a hard disk taken out by a power spike. I also had firmware
corruption that required reflashing the EEPROM, but I don't remember if
that was related to the PSU. They draw 30 watts when switched 'off' so
it's definitely worth turning them off when not in use.
Twitching fans might indicate over-current protection kicking in.
If it's a repetitive twitching, it's probably the error amplifier or
the voltage divider feeding it. (those will be difficult to test
individually unless they're discretes, of course)
One other thing I've seen recently with older switching power supplies
is the output capacitors' ESR going up due to age, causing their time
constant to exceed that of the regulation loop...creating, you guessed
it, an oscillator.
I know one thing however - switched mode PSU experts are few and far
between!
This is painfully true. I *design* the damn things and I shy away
from working on them most of the time. Direct AC-driven ones are RIGHT
OUT in my book.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
