mkr5000
Guest
Tue Nov 22, 2011 6:58 pm
Model number is 19pfl3403 (a real dog I understand) -- anyway, not getting 5.2v but around 4.
I'm not a repair guy but electronics is my life and looks like it may be the dual schottky rectifier -- good AC voltage out of the transformer.
part is a 60v 10a dual -- wonder if a 45v part will suffice? (it's what I have).
after all they're using a 100v schottky for the 13v supply so it sounds like it'll work. THANKS if you know off hand.
Arfa Daily
Guest
Fri Nov 25, 2011 2:51 am
"mkr5000" <mikerbgr_at_gmail.com> wrote in message
news:3111226.55.1321981106144.JavaMail.geo-discussion-forums_at_yqie15...
Quote:
Model number is 19pfl3403 (a real dog I understand) -- anyway, not getting
5.2v but around 4.
I'm not a repair guy but electronics is my life and looks like it may be
the dual schottky rectifier -- good AC voltage out of the transformer.
part is a 60v 10a dual -- wonder if a 45v part will suffice? (it's what I
have).
after all they're using a 100v schottky for the 13v supply so it sounds
like it'll work. THANKS if you know off hand.
It's a bit unusual for diodes - even Schottkies - to go 'weird'. Commonly,
they fail short circuit. I would have thought that a far more likely cause
of your low voltage, is the filter cap following the rectifier. If that goes
open or high ESR, you will get a low reading of the DC volts that you're
expecting, the reason being that if you look at the voltage across the cap
with a 'scope, it will be hashy not pure DC, so the average that the meter
tries to make of it, will be lower. It is very very common for filter caps
following Schottky diodes in SMPs, to fail in this way.
Arfa
Ian Field
Guest
Sat Nov 26, 2011 8:43 pm
"Arfa Daily" <arfa.daily_at_ntlworld.com> wrote in message
news:lwCzq.58011$925.34242_at_newsfe16.ams2...
Quote:
"mkr5000" <mikerbgr_at_gmail.com> wrote in message
news:3111226.55.1321981106144.JavaMail.geo-discussion-forums_at_yqie15...
Model number is 19pfl3403 (a real dog I understand) -- anyway, not
getting 5.2v but around 4.
I'm not a repair guy but electronics is my life and looks like it may be
the dual schottky rectifier -- good AC voltage out of the transformer.
part is a 60v 10a dual -- wonder if a 45v part will suffice? (it's what I
have).
after all they're using a 100v schottky for the 13v supply so it sounds
like it'll work. THANKS if you know off hand.
It's a bit unusual for diodes - even Schottkies - to go 'weird'. Commonly,
they fail short circuit. I would have thought that a far more likely cause
of your low voltage, is the filter cap following the rectifier. If that
goes open or high ESR, you will get a low reading of the DC volts that
you're expecting, the reason being that if you look at the voltage across
the cap with a 'scope, it will be hashy not pure DC, so the average that
the meter tries to make of it, will be lower. It is very very common for
filter caps following Schottky diodes in SMPs, to fail in this way.
Arfa
Its also worth remembering that Shottky-barrier rectifiers have higher
junction capacitance - I usually fortify the replacement electrolytic with a
mylar or polycarbonate at least 1uF.
