Mitsubishi cs-2710ra vertical problem

[ladybug]

My trusted Mitsubishi cs-2710ra died, it displays thin horizontal bar
on the middle of the screen. I can see picture elements in the bar .
I'm debating if it makes sense to fix it or just trash it. I'll attemt
to fix it first by myself but I need help to troubleshoot it. Please
help me to troubleshoot it or give me suggestions what to look for.

Thanks!

 

[longman]

My trusted Mitsubishi cs-2710ra died, it displays thin horizontal bar
on the middle of the screen. I can see picture elements in the bar .
I'm debating if it makes sense to fix it or just trash it. I'll attemt
to fix it first by myself but I need help to troubleshoot it. Please
help me to troubleshoot it or give me suggestions what to look for.

Thanks!

Check the electrolytic capacitors on the board that the yoke coil plugs
into. Most of the time that is the problem. You may need to replace
more than one.

 

[ladybug]

Check the electrolytic capacitors on the board that the yoke coil plugs
into. Most of the time that is the problem. You may need to replace
more than one.

Do I need to unsolder caps for checking? How can I see if cap is bad
with multimeter? If you can get a hold of schematics can you tell me
which caps to check?

 

[rb]

It's best to use a ESR meter for finding bad caps

 

[Leonard Caillouet]

It's best to use a ESR meter for finding bad caps

Actually an ESR meter will not identify all or even most of the bad caps in
this set. Some will have high esr, most will be physically leaking
electrolyte, and some will be low in capacitance. This problem may be
caused by leaky caps at the vertical output IC and/or in the 12V supply.
Ther will be at least a dozen more that need to be replaced or more problems
will be occurring soon. The circuit traces that are corroded from the
electrolyte leakage will need to be repaired and all of the residue from the
caps will need to be washed from the board. We fix these all the time and
they are a "pay me now or pay me more later deal." We don't even touch tem
if the client does not want to pay to have all the bad or failing caps
changed. Just fixing the vertical circuit is a sure way to get a recall in
a few weeks or months with an unhappy client.

Leonard

 

[ladybug]

Does anyone can point me to a repair manual or schematic?

 

[Leonard Caillouet]

You can get it from Mitsubishi, but it will likely be a waste of $$$. It
will not tell you how to fix the set.

Leonard

 

[kip]

Why dont you read what people have posted for you.

kip

 

[ladybug]

Why dont you read what people have posted for you.

kip

I did read. I just don't want to replace every single cap "on the board
that the yoke coil plugs
into". I want to be more specific because I need to get new caps
first.

 

[Leonard Caillouet]

I did read. I just don't want to replace every single cap "on the board
that the yoke coil plugs
into". I want to be more specific because I need to get new caps
first.

No need to replace every single cap. I said that you will find perhaps a
dozen bad caps in the set. Two dozen if you are very unlucky. I also said
that you can fix the immediate problem with just a couple of caps in the
vertical ouput stage and perhaps one on the 12v regulator.

No tech who fixes these type of problems would need the service manual
unless a trace was corroded away beyond recognition of where it went. In
order to fix this set you need to:

1. Identify the leaky, high esr, and low value caps, which will require an
ESR meter, a capacitance meter, and reviewing the instructions posted
several time in the past for finding leaky caps. Google the group for
Mitsubishi, capacitors, and my name for instructions on finding the leaky
caps.

2. Clean the board of electrolyte and corrosive residue.

3. Repair the damaged traces and bad solder joints.

4. Replace the bad caps and perhaps the vertical output IC.

If you don't check all of the caps for leakage you will be fixing it again
in a few months.

Now you have been given much more information than you will find in the
service manual regarding solving your problem. You can spend the $$ if you
wish.

Leonard

 

[ladybug]

I replaced 5 leaky caps that I found but it didn't change anything. I
suspect that vertical output IC went kaput. After all it died suddenly
without gradual picture srinking. Is it LA7838 chip? Is there a way to
test it with multimeter? What is a good place to get a replacement?

 

[Leonard Caillouet]

I replaced 5 leaky caps that I found but it didn't change anything. I
suspect that vertical output IC went kaput. After all it died suddenly
without gradual picture srinking. Is it LA7838 chip? Is there a way to
test it with multimeter? What is a good place to get a replacement?

If you want serious help, post some specifics. You probably did not get all
of the caps that are bad. There will be at least a dozen. Do you have both
the 12v and 28v supplies at the output IC? Which caps did you change?

Leonard

 

[ladybug]

If you want serious help, post some specifics. You probably did not get all
of the caps that are bad. There will be at least a dozen. Do you have both
the 12v and 28v supplies at the output IC? Which caps did you change?

Leonard

I replaced C458, C450, C460 all 100uf. Also C559 and 2G1. I defenately
missed some.... On the IC I have 12v on pin one but no 28v. Is it
supposed to be on pin 8? Nothing there.

 

[Tech Data]

I replaced C458, C450, C460 all 100uf. Also C559 and 2G1. I defenately
missed some.... On the IC I have 12v on pin one but no 28v. Is it
supposed to be on pin 8? Nothing there.

Then you need to backtrack to the flyback. You have an open current
limiter, probably a 1.2 ohm 1/2 watt. And yes, if it's an LA7838 pin 8
is your primary VCC and should be 28 volts or so.

www.techdata-kicksass.net

 

[ladybug]

Also trace from c458 to pin 9 was corroded and read open. I got that
taken care off.

 

[ladybug]

Then you need to backtrack to the flyback. You have an open current
limiter, probably a 1.2 ohm 1/2 watt. And yes, if it's an LA7838 pin 8
is your primary VCC and should be 28 volts or so.

www.techdata-kicksass.net

You're right R558 reads open. Why did it burn and where can I get a
replacement?

 

[Leonard Caillouet]

Now look over to the left of the board as you see it from behind and find
the leaky caps around the heat sink near the front of the board. There will
be several, perhaps about 10. There are two that will be on the vertical
board with the regulator. If you don't get them , and the rest of the leaky
caps on the main board, you will be doing this again soon. Check ALL of the
black colored polar electrolytics made by rubycon, nichicon, or sme.

Leonard

 

[ladybug]

Now look over to the left of the board as you see it from behind and find
the leaky caps around the heat sink near the front of the board. There will
be several, perhaps about 10. There are two that will be on the vertical
board with the regulator. If you don't get them , and the rest of the leaky
caps on the main board, you will be doing this again soon. Check ALL of the
black colored polar electrolytics made by rubycon, nichicon, or sme.

Leonard

There are plenty of leaking caps on the front left of the board where
you said but I don't see any vertical board with the regulator. Where
is it? I'm also out of replacement caps and need to buy a bunch for
this repair. Can you recommend a place to buy and preferable type/brand
of electrolytic caps? I also need a 1.2 ohm current limiter

 

[Leonard Caillouet]

I may be thinking of another set. I buy most of my caps from Tritronics
which is good if you are on the east coast. There are lots of similar
distributors all over. Get 105 degree caps. They don't stock 35V caps,
just use 50V instead. None of these will matter.

Leonard

 

[ladybug]

Looks like almost all the caps that I have made by rubycon. I'll try to
replace most of them. How can I get off the board leaked acid? Do I
need to replace caps on the tube board? None of tube caps seems to be
leaking. What is the correct part for 1.2 ohm current limiter?