[TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
- From: "Larry E" <videotech@xxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Wed, 20 Jul 2005 16:16:11 -0400
Damon, thanks for the reply, got in the IC and resistor today, whatever is
shorting IC601 and opening R608 is worse off than before, installed new IC
& resistor and set did not start by itself, front led was on (not blinking)
12v standby was
there, started set with 117 on variac and R608 made a loud snap and fried it
& IC608.
Before I plugged in the set I pulled and checked on the cap tester
C602,603,604,605,606,607, 608,612,615,616,617,618,& 621, checked for shorts
on Q654, 656, & 659.
Checked for shorts on T604 & 605, HOT is not shorted, main fuse does not
blow so it
doesn`t appear to be outside the power supply, checked from hot to cold
ground for short
none found, I can`t troubleshoot the dam thing because only the 12v supply
runs in standby and it blows up
with more than 97 volts applied through the variac, I would think as quickly
as it blows
that it would have an obvious short, but I sure can`t find it, any ideas
appreciated., Larry E
Larry Eastman
American TV & Electronics
Crystal River, Fl. 34428
----- Original Message -----
From: "Damon" <DamonEB@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, July 15, 2005 11:22 PM
Subject: [TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
> 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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