Troubleshooting B+ Line

J

johnzimm

Guest
Hi everyone,

I am troubleshooting my Mistubishi VS-4503R (45" projection tv, V10B
chassis). The power supply was in bad shape. Replaced:

IC950: SE130N (130V B+ Regulator)
2200uF filter caps (used 105 Deg. electrolytics.)
burnt biasing resistors in primary of B+ switching supply.

checked ON31xx...good
checked IC900...good
resoldered all joints in Pwr Supply

TV already has Factory installed CM Kit for shutdown.

did 100W light bulb test. measured 130.2V with Fluke 87 DMM

reconnected the supply and powered set. Set started to come on and
then shut off. Hit power switch again and set came on and ran for
about 4hrs Scanning was stable, but there was some very slight
"blooming/breathing" of the picture especially during OSD. Turned set
off for the night and tried to turn set on the next day to continue
troubleshooting. TV came on for about 1 second and blew 2SD1555 HOT
(3-way short).

Checked Mitsubishi schematics and replaced 2SD1555 HOT with 2SD1556
(correct HOT for this model). HOT blew in 2 seconds (3-way short).

Disassembled TV.

Pulled and rang flyback (17 rings on Sencore LC-53??).

Pulled and tested (value, leakage, DCR) snubbing capacitors with
Sencore LC53"??"---all ok. measured yokes with Fluke 87 DMM--all
within 0.1ohms (3.2ohms) of each other.

Checked yokes leaking to aquadog with Ohmeter---all open.

found bad 1uF 250V electrolytic on horizontal driver output.
Resoldered all connections in Horizontal Circuit.

Went back to power supply with Sencore LC102 ESR. found high ESR
(150kOhm) on C914 in primary of B+ switching supply. Replaced with
good 47uF 50V electrolytic.

Does anybody know if C914 could cause HOT shorting? I have since read
that it can cause Mitsu VS TVs to turn on and then turn off. Haven't
read about them causing HOT shorts. I don't have chip docs for IC900,
the swithcing IC, that this capacitor is connected to.

I want to ring the yokes in place without disassembly and the Sencore
LC-53"??" is in a repair shop that is friendly to me and the Ringer in
the LC102 (which I can take home) has been "blown up" by one of the
people in our electrical department. I have had the LC102 sent out for
repair and plan to ring the yokes with it when it comes back.

I have resoldered all joints in B+ line (as well as all joints in the
power supply). I was planning to do the rest when I can get the TV up
and running again.

I am sure there are other potential problems brewing in a set this
old, but I am doing this, more or less, for the experience of learning
about TVs and TV repair. Its so much more fun than my regular design
engineer job.

As a novice, I would be delighted to hear from anyone who has any
exerience with Mitsu V10s, C914, or just thoughts in general about my
little challenge...

Sincerely,
John, BSEET
 
John,
Sounds like you on the right track.
Do replace that 47uf 50 volt cap with a 105 degree rated cap as well as the
47uf 100 volt one.
Replace the 1k 1/8 watt resistor in front of the STRS6301 with a 1k 1/2 watt
and the 270k 1/8 watt resistor used for startup.
The other supply needs to have the 10uf 100 volt cap and the 47uf 100 volt
cap replaced and 270k resistor as well.
Always replace C5002 (10uf 50 volt) on the deflection board. This one is
used for feedback in high voltage regulation. The 2200uf 35 volt caps and
100 uf caps in the vertical circuit should also be replaced.
It is a good idea to inspect all electrolytic caps for black goop on the
negative leg and replace when found. There will be a couple of them near the
tuner.
This set will also need a lot of solder rework as you have noticed.

Good Luck,
Bill Jr



"johnzimm" <johnzimm@datacruz.com> wrote in message
news:831dff77.0312100810.63439c5a@posting.google.com...
Hi everyone,

I am troubleshooting my Mistubishi VS-4503R (45" projection tv, V10B
chassis). The power supply was in bad shape. Replaced:

IC950: SE130N (130V B+ Regulator)
2200uF filter caps (used 105 Deg. electrolytics.)
burnt biasing resistors in primary of B+ switching supply.

checked ON31xx...good
checked IC900...good
resoldered all joints in Pwr Supply

TV already has Factory installed CM Kit for shutdown.

did 100W light bulb test. measured 130.2V with Fluke 87 DMM

reconnected the supply and powered set. Set started to come on and
then shut off. Hit power switch again and set came on and ran for
about 4hrs Scanning was stable, but there was some very slight
"blooming/breathing" of the picture especially during OSD. Turned set
off for the night and tried to turn set on the next day to continue
troubleshooting. TV came on for about 1 second and blew 2SD1555 HOT
(3-way short).

Checked Mitsubishi schematics and replaced 2SD1555 HOT with 2SD1556
(correct HOT for this model). HOT blew in 2 seconds (3-way short).

Disassembled TV.

Pulled and rang flyback (17 rings on Sencore LC-53??).

Pulled and tested (value, leakage, DCR) snubbing capacitors with
Sencore LC53"??"---all ok. measured yokes with Fluke 87 DMM--all
within 0.1ohms (3.2ohms) of each other.

Checked yokes leaking to aquadog with Ohmeter---all open.

found bad 1uF 250V electrolytic on horizontal driver output.
Resoldered all connections in Horizontal Circuit.

Went back to power supply with Sencore LC102 ESR. found high ESR
(150kOhm) on C914 in primary of B+ switching supply. Replaced with
good 47uF 50V electrolytic.

Does anybody know if C914 could cause HOT shorting? I have since read
that it can cause Mitsu VS TVs to turn on and then turn off. Haven't
read about them causing HOT shorts. I don't have chip docs for IC900,
the swithcing IC, that this capacitor is connected to.

I want to ring the yokes in place without disassembly and the Sencore
LC-53"??" is in a repair shop that is friendly to me and the Ringer in
the LC102 (which I can take home) has been "blown up" by one of the
people in our electrical department. I have had the LC102 sent out for
repair and plan to ring the yokes with it when it comes back.

I have resoldered all joints in B+ line (as well as all joints in the
power supply). I was planning to do the rest when I can get the TV up
and running again.

I am sure there are other potential problems brewing in a set this
old, but I am doing this, more or less, for the experience of learning
about TVs and TV repair. Its so much more fun than my regular design
engineer job.

As a novice, I would be delighted to hear from anyone who has any
exerience with Mitsu V10s, C914, or just thoughts in general about my
little challenge...

Sincerely,
John, BSEET
Click to expand...
 
found bad 1uF 250V electrolytic on horizontal driver output.
Resoldered all connections in Horizontal Circuit.

If this is the bypass cap on the primary of the drive transformer it
is the culprit. Failure causes low drive to the HOT. Common on any
Click to expand...
chassis that uses them.
 
I to am working on a V10 chasis mits, VS-6015R. Check out my threads,
searching for my email domain or brian friedl. Question for you,
however... I just fixed my power supply and put it back in the set to
try it out and with the 75w bulb, got +131v on B+, but when it was in
the set, got +1.2v. Seems that power supply still is sick? Replaced all
of Bill's recomendations already, and checked ic900, and ic950, all
seemed to be ok.

johnzimm wrote:
Hi everyone,

I am troubleshooting my Mistubishi VS-4503R (45" projection tv, V10B
chassis). The power supply was in bad shape. Replaced:

IC950: SE130N (130V B+ Regulator)
2200uF filter caps (used 105 Deg. electrolytics.)
burnt biasing resistors in primary of B+ switching supply.

checked ON31xx...good
checked IC900...good
resoldered all joints in Pwr Supply

TV already has Factory installed CM Kit for shutdown.

did 100W light bulb test. measured 130.2V with Fluke 87 DMM

reconnected the supply and powered set. Set started to come on and
then shut off. Hit power switch again and set came on and ran for
about 4hrs Scanning was stable, but there was some very slight
"blooming/breathing" of the picture especially during OSD. Turned set
off for the night and tried to turn set on the next day to continue
troubleshooting. TV came on for about 1 second and blew 2SD1555 HOT
(3-way short).

Checked Mitsubishi schematics and replaced 2SD1555 HOT with 2SD1556
(correct HOT for this model). HOT blew in 2 seconds (3-way short).

Disassembled TV.

Pulled and rang flyback (17 rings on Sencore LC-53??).

Pulled and tested (value, leakage, DCR) snubbing capacitors with
Sencore LC53"??"---all ok. measured yokes with Fluke 87 DMM--all
within 0.1ohms (3.2ohms) of each other.

Checked yokes leaking to aquadog with Ohmeter---all open.

found bad 1uF 250V electrolytic on horizontal driver output.
Resoldered all connections in Horizontal Circuit.

Went back to power supply with Sencore LC102 ESR. found high ESR
(150kOhm) on C914 in primary of B+ switching supply. Replaced with
good 47uF 50V electrolytic.

Does anybody know if C914 could cause HOT shorting? I have since read
that it can cause Mitsu VS TVs to turn on and then turn off. Haven't
read about them causing HOT shorts. I don't have chip docs for IC900,
the swithcing IC, that this capacitor is connected to.

I want to ring the yokes in place without disassembly and the Sencore
LC-53"??" is in a repair shop that is friendly to me and the Ringer in
the LC102 (which I can take home) has been "blown up" by one of the
people in our electrical department. I have had the LC102 sent out for
repair and plan to ring the yokes with it when it comes back.

I have resoldered all joints in B+ line (as well as all joints in the
power supply). I was planning to do the rest when I can get the TV up
and running again.

I am sure there are other potential problems brewing in a set this
old, but I am doing this, more or less, for the experience of learning
about TVs and TV repair. Its so much more fun than my regular design
engineer job.

As a novice, I would be delighted to hear from anyone who has any
exerience with Mitsu V10s, C914, or just thoughts in general about my
little challenge...

Sincerely,
John, BSEET
Click to expand...
--
BFriedl
A+ Certified Technician
AIM: UACybercat
** Bear Down Arizona! **
******* Go Cats! *******
 
If you get 130 volts good with a 75 watt bulb then the power supply isn't
your problem.
Probably shorted H.O.T. or bad flyback.
Remove the connector (PA I think) and check for a short.
Don't overlook the 2 other voltages supplies from the STRS6310 side of the
SMPS.
Check their loads for shorts.

Good Luck,
Bill Jr






"BFriedl" <junk-remove-@bfriedl.com> wrote in message
news:vmRBb.32177$o9.27761@fed1read07...
I to am working on a V10 chasis mits, VS-6015R. Check out my threads,
searching for my email domain or brian friedl. Question for you,
however... I just fixed my power supply and put it back in the set to
try it out and with the 75w bulb, got +131v on B+, but when it was in
the set, got +1.2v. Seems that power supply still is sick? Replaced all
of Bill's recomendations already, and checked ic900, and ic950, all
seemed to be ok.

johnzimm wrote:
Hi everyone,

snipped
Click to expand...
 
doh! Never thought of checking for a short there...good thing the power
supply still works. Forgot to mention that i get HV sound, but no audio
when set is connected to ext1 or ext2. Also, convergance board was not
conneced this whole time, as this board was the first indication of bad
power with fried inductors l8001 and l8002. What could be the reason for
no audio?

Bill Jr wrote:

If you get 130 volts good with a 75 watt bulb then the power supply isn't
your problem.
Probably shorted H.O.T. or bad flyback.
Remove the connector (PA I think) and check for a short.
Don't overlook the 2 other voltages supplies from the STRS6310 side of the
SMPS.
Check their loads for shorts.

Good Luck,
Bill Jr






"BFriedl" <junk-remove-@bfriedl.com> wrote in message
news:vmRBb.32177$o9.27761@fed1read07...

I to am working on a V10 chasis mits, VS-6015R. Check out my threads,
searching for my email domain or brian friedl. Question for you,
however... I just fixed my power supply and put it back in the set to
try it out and with the 75w bulb, got +131v on B+, but when it was in
the set, got +1.2v. Seems that power supply still is sick? Replaced all
of Bill's recomendations already, and checked ic900, and ic950, all
seemed to be ok.

johnzimm wrote:

Hi everyone,


snipped
Click to expand...
--
BFriedl
A+ Certified Technician
AIM: UACybercat
** Bear Down Arizona! **
******* Go Cats! *******
 
Thanks so much for your help Bill. Rest assured, I have been well
educated in regards to the 105 Degree Electrolytics.

Is there a safe way to clean the "flux" residue from the manufacturing
off of the PCBs? This stuff is just a mess to work around. I tried
using Isopropyl Alcohol and it wouldn't even make a dent in that
gunk...

Sincerely
John, BSEET

"Bill Jr" <bill@nospam.usa2net.net> wrote in message news:<w2OBb.1040$Dt6.41657@twister.tampabay.rr.com>...
John,
Sounds like you on the right track.
Do replace that 47uf 50 volt cap with a 105 degree rated cap as well as the
47uf 100 volt one.
Replace the 1k 1/8 watt resistor in front of the STRS6301 with a 1k 1/2 watt
and the 270k 1/8 watt resistor used for startup.
The other supply needs to have the 10uf 100 volt cap and the 47uf 100 volt
cap replaced and 270k resistor as well.
Always replace C5002 (10uf 50 volt) on the deflection board. This one is
used for feedback in high voltage regulation. The 2200uf 35 volt caps and
100 uf caps in the vertical circuit should also be replaced.
It is a good idea to inspect all electrolytic caps for black goop on the
negative leg and replace when found. There will be a couple of them near the
tuner.
This set will also need a lot of solder rework as you have noticed.

Good Luck,
Bill Jr
Click to expand...
<<<<snip>>>>
 
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