[TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
- From: "Damon" <DamonEB@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Fri, 15 Jul 2005 22:22:10 -0500
124 V Ac ain't gonna whack the MX0841, most power systems will have 105 to
140 out in the country, and these tv's are built to handle that variation.
Since it fired up ok with the isolation transformer, and SINCE you brought
it up slowly, then I'd take a closer look at what parts are affected with a
large surge of INSTANT 124V rather than 0 20 40 60 80 100 120 124V.
My first guess is the MAIN CAP, next is the inductive kickback circuit
(diodes or caps-since you don't have VDRs) --there are several on the C-E
junctions.....are those the BLUE caps??
How about a blown soft-start circuit......got one of those on the RA-2???
That chassis number seems a little low for that, but the MX0841 were around
the same time the soft start was introduced.
How about the MX0841 itself, is it from Sony or another supplier? (I kinda
doubt that, compared to the open main cap or bad kickback circuit.
Gonna look at schematics, IF I find anything, I'll let you know.
Found a lot of things......
Q659, Q656, and Q654 are your soft start transistors, uses 18V and 11V
supplies from SMPS, uses a winding in regulator transformer T604 to gently
bring up your SMPSvoltages.
C 608/C607 are your half-wave voltage doubler caps, should have about 340V
dc across both caps.
C612 is a damper cap, many more in there-suggest checking all HV caps.
C616/617 are duty-cycle caps
BTW did you check the duty cycle? Don't want one of those transistors in the
MX0841 doing more work than the other.
Damon B
Telrad Electronics
Fort Wayne IN
----- Original Message -----
From: "Larry E" <videotech@xxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, July 15, 2005 4:24 PM
Subject: [TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
> Phil, no vdr`s in this chassis, I`m looking at the isolation issue only
> because I find no
> parts in the primary circuit that are bad, (or the secondary for that
> matter) yet it runs
> if I power it from the variac? I`ve ordered new IC`s and resistors, I`ll
try
> operating
> it from the variac when I get the parts in and if it runs off the variac
> I`ll try
> running it directly from the shop wall outlet, if it runs from my AC
outlet
> then
> Bob Waterman may be right there may be an issue with the customers AC as
he
> said he had a violent strike of lightning 2 days before the set went out,
> you know
> the drill down here, sprinkler system, garage door openers, etc. etc. His
> outlet
> read 124 volts though when I was there, we`ll see when the parts come in,
> Thanks for the reply, Larry E
>
>
> Larry Eastman
> American TV & Electronics
> Crystal River, Fl. 34428
> ----- Original Message -----
> From: "Phil Bader" <tjanphyl@xxxxxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Friday, July 15, 2005 5:01 PM
> Subject: [TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
>
>
> > You are assuming this is an isolation breakdown issue. Maybe not. Does
> > this chassis use VDRs around the MXO841? These VDRs do go bad.
> > Just a thought. I'll polk around when I'm not fixing table radios.
> > Phil
> > Phil
> >
> > Philip Bader
> > Jan Phyl TV Inc. (estab. 1976)
> > 3420 Recker Hwy. Winter Haven, Fl. 33880
> > Fax (863) 299-8821
> > email: tjanphyl@xxxxxxxxxxxxxxx
> > personal/ alt. email: pbader@xxxxxxxxxxxxxxx
> > see our ad at:
> >
>
http://jan-phyl-television-pc-monitor-service.9601288257006.worldpages-ads.c
> om/
> >
> >
> >
> > Larry E wrote:
> >
> > >Hi Guys, My week for headache sets, this Sony RA-2A covers the
following
> models
> > >KP41T65, 46C65, 48S65, 53S65, & 61S65, went to customers house and all
> pins
> > >of IC601 (MX0841AB-F) were shorted to each other, also R608 the .1
1/2w
> > >fusible resistor was open, pulled all of the little blue caps around
> IC601 and checked
> > >them on the sencore, all ok. I ordered a new IC & resistor, installed
> them and when
> > >I powered up the set they instantly blew, pulled set to shop,
> re-installed new chip
> > >& resistor, plugged into variac & brought up slowly, set started and
> worked fine, heres
> > >the fun part, I brought the set back to the customer hooked it up and
all
> I get is a
> > >constant blink of the led, of course IC601 & R608 were blown again,
> Obviously my
> > >Sencore variac being an isolation transformer let the set run but
> connectiong to the
> > >customers AC outlet lets the parts short, I have pulled every cap in
the
> "hot" side
> > >of this power supply and found no shorted caps, checked the 2.2 meg
> resistor
> > >R601, there is no continuity between hot & cold ground, customer told
me
> second
> > >time out that they had lightning problems 2 days before set went down
but
> I see
> > >no arcs etc on board, main fuse was not blown, HOT circuit good, seems
to
> me it
> > >has to be hot & cold ground connected somewhere???
> > >please help if you can, I`m pulling hair out at this point, Larry E
> > >Larry Eastman
> > >American TV & Electronics
> > >Crystal River, Fl. 34428
> >
>
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