Darius D1450 and AT&T CM-1200 "tweeting"

[Stephen Tomchuk]

Hello all,

A few questions re: these 2 monitors I am attempting to repair. The
Darius is a 14" VGA and the AT&T a 15" VGA.

They both are doing the "tweet,tweet,tweet" every second or so
indicating that the high voltage attempts to come up and then is
squelched (originally the Darius had just a click,click out of the low
volt switching supply 'til I found and replaced a shorted 39 V 5W zener
diode on the o/p of the low volt switching supply). A visual check
showed no obvious burned components or bad solder joints. I read through
the monitor repair faq
for a start but would appreciate any more info you experienced monitor
folks might have (although I'm an electronic tech monitors is not my
forte)

I have attempted to find schematics for these units with no luck.
Anyone know of a source for schematics for these?

Thanks,

Steve

[Wild Bill]

hi.. i suspect that what's taking place with the cyclic tweet and/or click,
is the sensing circuit in the SMPS turning the PSU on & off repeatedly.

Check for shorted horiz output transistors, or other low resistance paths
to grounds, causing the cycling. A common cause for HOT failure is that the
horiz drive is dead or too low. There will likely be an electrolytic
capacitor on the primary side of the horiz drive transformer (on the +
supply).. and it may be shorted or have excessive leakage.

There are many other possibilities of course, but this is a fairly common
failure. Replacing the HOT without checking for other faults often results
in the quick failure, or very short life, of the new HOT.

cheers
WB
...................
Stephen Tomchuk <tom...@sk.sympatico.ca> wrote in article
<384F250C...@sk.sympatico.ca>...

[Stephen Tomchuk]

The Darius D-1450 is fixed. It turned out to be a shorted HER303 diode in
the low voltage switching supply.The 39V zener was just a misread on the
part # that threw for a 2 hour loop.

Steve

Steve

[Jef Od]

Hello all. I tried to locate a chat room for this specifically but...this is the only thing that I've found.

I'm not electronically knowledgeable enough to know what to do so, here's my question;
I have a blown HER303 and I'm wondering if I should replace it with a "larger" diode? I ask this since it looks like it stays pretty hot whenever energized.

Oh yea, this is a compact hard drive power supply.

Any help would be VERY appreciated.

~Jef

[Jef Od]

On Friday, February 5, 2021 at 5:47:42 PM UTC-5, Jef Od wrote:

UPDATE: I really don't understand this depth of verbiage but, I found this post and would very much appreciate some "seasoned guidance".

This Mouser diode has both lower reverse recovery time and is rated for 4 Amps at 80C.
http://www.mouser.com/search/ProductDetail.aspx?qs=cfR2GKjf2RmZMQwrlOf4Ew%3D%3D

~Jef