[TechAssist] Re: Sony KV32XBR35 Power supply problems
- From: Gary McCartney <gary@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Tue, 25 Feb 2003 10:21:31 -0500
Scott, here is a cut and paste of my saved messages regarding these Sony
power supply problems. Some of these may be slightly different than your
set, I don't know. Hope it helps.
Gary McCartney
McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: gary (at) number63.ca
=========================================================================================
Complaint: Power Supply Transistors keep blowing (Q601 and Q602)
1. Resolder all pin connections on the Standby transformer T805 (which I
have
yet to find on the models I have repaired).
2. Replace VDR601 # 1-807-288-11, and VDR602 & 603 # 1-810-973-21
3. Replace C609/610/611/612 in the Base circuit of Q601/602. (part#
1-136-169-00)
4. Check all components in the secondary of T604 (diodes and capacitors)
and ensure that there is no excessive loading.
5. Resolder all connections to the Horizontal Drive Transformer T502.
(Bad connections here will make the HOT to fail).
6. Change the value of R644 from 6.8-ohm-1/4w to 4.7 - ohm - 1/2w. (I
changed
to 6.8 to 1/2w). but the part # for 4.7 is 57-980-4.7-ohms 1/2wx.
7. Check that the waveforms at the junction of Q601/602 are symmetrical.
You should be able to read a resistance with an ohm meter between the
Base
and emitter of the HOT but from the collector to Base and the collector
to
emitter you should be able to test it like you would test a diode.
Hope that helps
C D Routson
Dave's TV
Cleburne, Tx 76033
817-641-8465
-----------------------------------------------------------------------------------
>The set started to show signs of shrinking or closing on the right hand
side,
>it would blink once in a while. One morning I just heard the relay click
>and that was it. I have replaced two transistors and one resistor but I
>have not tried to turn it on.
>I am not sure if the horizontal output transistor is bad or not, it seems
>like it measures 10 ohms from either lead.
>I could not find specs on this transistor C4927.
>I appreciate any help I can get.
>
>Thanks,
>
>Gabriel
"Sony KV-27V55 // KV-32TS46 // KV-32V15 // and similar models. Stock #
14513. KV-27TS29 Complaint:Power Supply Transistors keeps blowing (Q601
and
Q602). 1. Resolder all pin connections on the Stanby
Transformer
T805 2. Replace VDR601/602/603. 3. Replace
C609/610/611/612
in the Base circuit of Q601/602. 4. Check all components in the
secondary
of T604 (diodes and Capacitors) and ensure that there is no excessive
loading.
5. Resolder all connections to the Horizontal Drive
Transformer
T502. 6. Change the value of R644 from 6.8-ohms-1/4w to
4.7-ohms-1/2w.
(part no#57-980-4.7-ohms1/2wx). 7. Check that the wavesform at the
junction
of Q601/602 is symmetrical.
Hope that his will help...Yvon Roy
----------------------------------------------------------------------------------
From: Thomas Lander <tommydatek@xxxxxxxx>
Subject: RE: kv32s15 sony
To prevent repeated failures of Q601 and 602 You should check the
following
VDR's 601, 602, 603, preferably out of circuit, they should read no
resistance in either direction, if any resistance detected replace it.
Diodes D603, D605 may be leaky and R607, R644, R611, and R612 may be
open. C609 can cause delayed failure of Q601 and 602 and should be
replaced for good measure. The trick to not annihilating Q601 and 602
on
power up is to use a variac, bring it up to 30 volts and read the
voltage
on the emitters 602 should be twice the volts of 601.
Regards,
Tom
----------------------------------------------------------------------------------
I put this together to help others. It is somewhat generic in it's
treatment of power supplies. I believe yours only has a degaussing
relay
and turns the scan on and off to turn the set on and off but the
information
about checking the DC and wave form will be good.
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
HiFi Buys a Tweeters Etc. Company
Atlanta, GA 30331
dmundy@xxxxxxxxxxxxx
mailto:dmundy@xxxxxxxxxxxxx
404 699-3830 X5856
Efax (240)352-7717
--------------------------------------------------------------------------------
Hello Everyone.
Tom:
I always replace the 2SC4834 for 2SC4664 (they are of more wattage and
run
cooler).
Replace T605 (1-423-581-11)
Replace C609,C610,C611 and C612.(EVEN IF CHECK GOOD)
Check R652.(if open replace VDR603).
Check R651.(if open replace VDR602).
Check R644.(if open replace VDR601).
All 3 resistors are 6.8 ohms.
Also check Capacitor that goes to the base of hor.driver transistor (I
think
is C525-50V/.47UF)
Also check all pins for cold solders at Flyback.
I hope this help.
Jorge.
-----------------------------------------------------------------------------
Did you jumper the relay 1st before bringing up the variac? You need to
do
that. You may also have to take it up up 60 v ac to get an unrounded
signal
, but the duty cycle should be apparent at 30 volts ac. This duty cycle
should be 50% so that both the transistors are doing equal work,
tolerance
is 51-53%, but I don't trust that! 30 volts AC should measure about
42-43 Vdc (30v x 1.4 = peak ac). Run it at 30 vac, but bring it up
gently,
you should be able to see a balanced waveform before you even get to 30
vac.
Now if it looks balanced, then verify at 30, then gently up to 60 to
test
for minor slope and flat top (minor ringing on leading edge of flat
top).
If it looks good at 60 Vac then start looking at the horiz circuit or
especially look at the AUDIO circuit for shorts, the audio circuit has
no
shutdown or fusing protection on quite a few models, they just started
to
fuse those circuits in the last 2 to 3 years.
Might be smart to remove the horiz output and audio output (or disable
the
audio B+) to test the power supply and save those transistors. BTW $9.00
a
transistor is rather hi in my opinion, check
http://www.mcmelectronics.com
or some where else.
Damon Brunger
damon101@xxxxxxxxxxxxxx
Telrad Electronic Services
Ft Wayne, IN 46815
---------------------------------------------------------------------------
Do not know why, but there is still a wide missunderstanding about such
a
typical Sony problem.
FIRST : we must know if the power supply died by itself or because a
shorted
HOT
in this case it is fairly obvious that the HOT killed himself first and
the
power supply post mortem..
SECOND: we already have the reason for the power supply collapse, no
use
wondering
why it dies in such circumstances: it is just destiny, vg. it is a
design flaw.
THIRD: We must then find out why the HOT died so young.
there are two answers: first, C4927 are not such strong transistors,
they can
be substituted
with great advantage by D1881 or BU2508D to mention just two. If you
dont
believe me,
take a look at the data sheets.... and live aside the original parts
myth....
FOURTH: The HOT heath sink is so obviously under designed, I sometimes
add
some mor heath sinking
with very good results. Just try it and you will notice the temperature
lowers
down dramatically..
FIFTH: besides all that, PLEASE follow the HOT base path from the
transistor
itself to the
driving transformer. 99 % you will find one or more cold solder points
on the
way.
C4927 can not resist its base left floating for a while, hence the loud
snap
:o))
Last but not least: use C4834 even if he originals are C4664s
Again, the data sheets will tell you why......
Good luck.
Jorge Camboni GY Electronics, Dallas
-----------------------------------------------------------------------------
Hello.
I just copy and past from an article of Nasda.
Common Failures In Sony Direct View TV's
All,
This is a list of the common failures in the Sony Direct View. Most
failures
are caused by Vertical or Horizontal problems. Sony Switch Mode Power
Supply
Rebuild Parts
AA-1 Chassis
Q601
Q602
VDR601
VDR602
VDR603
R607
R644
2SC4834
2SC4834
Varistor
Varistor
Varistor
Fusible 0.1 ohm
Fusible 6.8 ohm
Sony Part #
8-729-019-51
8-729-019-51
1-807-288-11
1-810-053-11
1-810-053-11
1-202-933-61
1-212-853-61
AA-2 Chassis
Q601
Q602
R607
VDR601
2SC4834
2SC4834
Fusible 0.1 ohm
Varistor
Sony Part #
8-729-019-51
8-729-019-51
1-202-933-61
1-810-974-11
The above parts should be replaced as a set.
Always check HOT circuit before repairing power supply.
Resolder horizontal drive transformer and do a good visual check in that
area.
Check Vertical output IC for shorts or signs of overheating
------------------------------------------------------------------------------
We do dozens of these sets each year with no recalls using generic
2sc4824
from Tritronics for ~$1.89 each as compared to ~$9.00 from sony. Just
buy a
lot of about 10 pieces and match them yourself with the diode test on
your
DMM. The matching is a factor but there is nothing magic about it.
Just
look at the duty cycle and verify it at 50% +/- a couple of percent.
Also, we replace the HOT, 2sc4927 with 2sd1881 which runs more
efficiently
and cleaner. Just look at the collector waveform and you can see that
the
timing is right on and the waveform is cleaner than with the original.
Leonard G. Caillouet
Service Manager
Electronics World
Gainesville, FL
352-332-5608
352-332-5668 (fax)
----------------------------------------------------------------------------
Check and replace the following:
PART ID PART#
C609,C610,C611 & C612 113616900
R607 120293361
R644 121285300
VDR602 & VDR603 181097321
VDR601 180728811
Q601 & Q602 872901949
R610 & R609 121636900
The above parts are common on the Power Supply.
Hope it helps'
Panday
------------------------------------------------------------------------
Sony 35" Fixed then Dead Again
replace the small cap tied to the HDT I believe its a .22 uf 50v
Jeff Farnsworth
Lyles TV and Appliance
17 S Washington St
Elkhorn, Wi. 53121
--------------------------------------------------------------------------
In addition to what you replaced,
few other parts goes defective on this unit:
a. C608
b. C611 and C612
c. T603
d. R622, if damaged VDR601 is defective.
I troubleshoot this power supply as a stand alone unit.
Using a 40w light bulb on the B+ line and power up with variable
transformer slowly from zero VAC.
At 36VAC, the supply should be 135 B+ , which remain stable as you
turn the AC up to 120VAC on the Transformer.
Look at the waveform at the emitter of Q601 (53KHz) for any noise or
ripples.
I had a defective T603 once that created your similar symptom.
Check for cold solder joints on the actual pin where the wire from the
transformer solder on to the pins.
At one time the PCB was cheaper to replace than repair in Canada.
Panday
ph 262-723-3477
fax 262-723-3658
================================================================================
tech@xxxxxxxxxxx
Scott wrote:
>
> Hello everyone,
>
> I am working on a Sony KV32XBR35 and I am having some difficulties with the
> power supply. (G Board) The set was dead with F602 open. I replaced Q601,
> 602 (shorted), VDR602, and R623 (almost open). I resoldered as needed, (like
> IC651) and when I would try to power it up, I would shut down. (relay click)
> Found D1409 shorted on the A board going to the audio B+. After replacing
> the diode, the set powered up for about 10 seconds before Q601 and 602
> shorted again. Does anyone have some insight to this power supply, I'm not
> very familiar with it. Thanx for your help.
>
> Scott Beebe
> Ohm Electronics Inc.
> 609 W. Clinton St.
> Ithaca NY 14850
> Voice: (607) 273-8406
> Fax: (607) 273-8743
> www.ohmelectronicsinc.com
>
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