[TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
- From: "Damon" <damoneb@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 21 Jul 2005 01:00:54 -0500
He's got a point about frequency, wish I had considered that. Of course we
haven't yet had any lightning until last week. Been way too dry. But if that
frequency isn't at 50Khz to 60Khz max, you will have the MX0841 blow, but
I'd suspect SOME delay before it died....
Damon B
Telrad Electronics
Fort Wayne IN
----- Original Message -----
From: "Leonard Caillouet" <lcaillo@xxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Wednesday, July 20, 2005 3:55 PM
Subject: [TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
> Larry,
>
> Start it up very slowly and as soon as it starts switching measure the
> frequency. If it is below 50kHz you may have a bad switching transformer.
> I have had several of these after lightning. They are a PITA because
there
> is no way to test it other than to start it up.
>
> You may be able to see some heat stress on the windings which are very
tiny.
>
> Leonard Caillouet
> Electronics World
> 1261 NW 76 Blvd
> Gainesville, FL 32606
> 352-332-5608
> 352-332-5668 fax
>
> ----- Original Message -----
> From: "Larry E" <videotech@xxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Wednesday, July 20, 2005 4:16 PM
> Subject: [TechAssist] Re: Sony RA-2A KP-46C65 instantly blows IC601 & R608
>
>
> 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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