[TechAssist] Re: Sony KV32XBR test procedure

  • From: "Larry E." <videotech@xxxxxxxxxxxx>
  • To: techassist@xxxxxxxxxxxxx
  • Date: Thu, 14 Nov 2002 15:52:05 -0500

Al, thanks for taking all that time to answer my post, but the
XBR55 uses a different chassis, doesn`t have Q601 & Q602 in the
power supply, but I do appreciate your attempt, Larry E

al wrote:

> Below is a procedure for which you guys can thank the author. al
> 
> Al Leatherman
> alleathe@xxxxxxxxxxxxx
> 973-361-5796
> Mine Hill, NJ. 07803
> http://WWW.ALS-TV.NET
> 
> Here is Dan's article:
> HTH
> 
> This is a fast check for Sony power supplies.  The important thing to
> remember about these supplies is that it is a push pull amplifier.
> The load
> across the 2 transistors must be close to equal or it will
> self-destruct.
> The frequency is the regulating part of the equation.  They are
> designed to
> start at a high frequency out of resonance and be pulled lower by the
> regulator toward resonant frequency to achieve proper regulation. The
> supply
> will oscillate at very low voltages and this is the only way to check
> them
> out.
> After doing the usual repair of transistors and I generally include
> the
> damper diodes (you can use Sony parts but they are subbing to a
> 1N5401).  If
> you don't know why the supply blew up check the Horizontal output and
> look
> for rings around the driver transformer.
> First pull the relay RY602.  This will prevent the set from trying to
> power
> up during repair and testing.
> Monitor the voltage at Q601 collector or R607 is just as good.
> Scope Q602 collector for waveform and DC voltage.
> 
> Lower the AC voltage to 20 volts DC.  The supply should be
> oscillating and
> each transistor should be dropping 10 volts.  If that looks good run
> the DC
> up to 40 Volts.
> At about 80 volts DC the current drawn by the supply should peek and
> start
> to decline with further increase in voltage.  You should also have a
> nice
> square wave of equal duty time with no peeks or ringing.  Each
> transistor
> should be dropping 40 volts.
> 
> You may see a slight bounce in the supply frequency at this time.
> The
> standby is up enough to turn the micro on and the slow start circuit
> is
> trying to bring the run supplies up to full value.  Of course this
> won't
> happen with the relay still out.
> On the latest supplies you must stop and return the set to normal
> operation
> as they do not like trying to run on reduced voltage above 40VAC.
> Older
> sets have no problem and I continue to increase the DC stopping at
> 150 volts
> and 200 volts.  These are nice round numbers that are easy to work
> with.  If
> everything is looking OK then run the supply on up to full value.
> You
> should have 16 volts on D619 reference to cold ground.
> 
> The supply is now running at full voltage.  If you have fixed all
> problems
> on the secondary side you can reinstall the relay and tune for
> minimum
> smoke.
> 
> Daniel Mundy, CET®/CSM
> 
> 
> Glenn Larkman
> 
> ----- Original Message -----
> From: "Larry E." <videotech@xxxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, November 14, 2002 3:00 PM
> Subject: [TechAssist] Re: Sony KV32XBR55 dead set
> 
> 
> 
>>Leonard, thanks for the reply, replaced Q604, C651, C613, now pin 1
>>of IC651 reads 168 volts regardless if plug F61 is in or out of circuit.
>>Pin 9 of IC651 reads zero volts even after replacing Q604, I read a
>>short (11 Ohms) on Diode D652, pulled diode and it checks good, short is
>>on traces, the print I`m using is useless in this area, is this a
>>problem or am I chasing my tail? Thanks for any help you can give, Larry
>>
>>Larry Eastman
>>American TV & Electronics
>>Crystal River, Fl.
>>
>>Leonard G. Caillouet wrote:
>>
>>
>>>Larry,
>>>
>>>I had one do this a while back.  The fix was to replace Q604 2sc3311A
>>>
> (soft
> 
>>>start driver) at pins 8 & 9 of IC651.
>>>
>>>Also, always ESR the electrolytics in the circuit and look for leaks,
>>>especially C651 2.2uF 160V and C613 100uF 25V.
>>>
>>>The two SE135 error amps are always suspect as well.
>>>
>>>I did the same as you, looked to the A board until a tech at sony told
>>>
> me to
> 
>>>just change Q604, even if it checks good.
>>>
>>>Leonard G. Caillouet
>>>Service Manager
>>>Electronics World
>>>Gainesville, FL
>>>352-332-5608
>>>352-332-5668 (fax)
>>>
>>>----- Original Message -----
>>>From: "Larry E." <videotech@xxxxxxxxxxxx>
>>>To: <techassist@xxxxxxxxxxxxx>
>>>Sent: Wednesday, November 13, 2002 1:45 PM
>>>Subject: [TechAssist] Sony KV32XBR55 dead set
>>>
>>>
>>>
>>>
>>>>Hi guys, Sony KV32XBR55 came in dead, replaced IC651, C652,C672,C654
>>>>and C674 as advised, now have 5v & 12v standby but voltage on reg. IC
>>>>pin 1 is only 86 volts, If I remove connector/plug F61/A61 pin 1`s
>>>>voltage goes up to 160 volts so obviously there is a heavy load
>>>>somewhere on the "A" board. I`m using a "similiar" schematic and it`s
>>>>close on the F board but not so good on the A board and the schematic
>>>>for this set is NLA. HOT is not shorted, all low ohm resistors on A
>>>>board are good, any ideas? tia, Larry E.
>>>>--
>>>>Larry Eastman
>>>>American TV & Electronics
>>>>Crystal River, Fl.
>>>>http://www.tvjunkyard.com
>>>>
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>>
>>--
>>Larry Eastman
>>American TV & Electronics
>>Crystal River, Fl.
>>http://www.tvjunkyard.com
>>
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-- 
Larry Eastman
American TV & Electronics
Crystal River, Fl.
http://www.tvjunkyard.com

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