Makvision Repair Logs & Tips

[angelcare]

Horizontal Issues

Okay, came in with no power. Replaced the flyback and HOT and a couple of caps, don't have the numbers here now.

Now it powers up and I get a pic in the center of the screen. Problem is that I have about 6 inches missing on each side. Horizontal size and positioning has no effect what so ever. Plus the edges are bowed in. Any suggestions? TIA!

 

[Ohmerone]

Here's what's happening with my monitor. Any suggestions?

https://www.youtube.com/watch?v=YloZSbhTN_Q

Need to remove the B+ control board and solder the pins
the board mounted to the heatsink in the back of chassis

I monitor the B+ when I'm testing a chassis, So if the B+
drops as the image moves in then I would need to confirm the B+
circuit is working first!!

The caps need to be replaced I would even if i found just one bad
i would replace all the the caps..if never replaced before.

If i could see the PS i would tell you where to monitor the B+
otherwise i need a schematic to read the location number
but a visual of section is as good.

Okay, came in with no power. Replaced the flyback and HOT and a couple of caps, don't have the numbers here now.

Now it powers up and I get a pic in the center of the screen. Problem is that I have about 6 inches missing on each side. Horizontal size and positioning has no effect what so ever. Plus the edges are bowed in. Any suggestions? TIA!

Got a photo of your chassis so all parts can be seen?
and a photo of the picture image
which chassis is this?
is this the tri-res or standard chassis you have?

 

[angelcare]

Got a photo of your chassis so all parts can be seen?
and a photo of the picture image
which chassis is this?
is this the tri-res or standard chassis you have?

The model I am working on is the M2929D1, tri-resolution. I will try and get pics of the screen and chassis tomorrow.

 

[angelcare]

The model I am working on is the M2929D1, tri-resolution. I will try and get pics of the screen and chassis tomorrow.

Here are the pics of the monitor in question. Excuse the bad camera shots.

 

[Ohmerone]

Here are the pics of the monitor in question. Excuse the bad camera shots.

I would replace the caps first!
This chassis is high res only 30-50KHZ

I would suspect a few caps.
This chassis is complex and need to scope
a few test points to narrow down the suspected circuit.

If tapping around does't change the width then i would suspect
electrolytic's are weak.

Look for any over heated resistors.
Any of the trim pots been turned?
Any trim pots say B+ on the board.
Is the HV pot glued and look ok?
Theres not just one voltage from the power supply
to check, need to monitor all the secondary voltages
like C43 etc on each supply see if they are steady or low?
Get the caps first!
Make sure you have the caps in correctly.
Heres the schematic
http://na.suzohapp.com/pdf/service_pdfs/makvision-schem49-2717-00D2rev.pdf
Make sure you replace the H.O.T with correct one.
Good Luck!

 

[angelcare]

I would replace the caps first!
This chassis is high res only 30-50KHZ

I would suspect a few caps.
This chassis is complex and need to scope
a few test points to narrow down the suspected circuit.

If tapping around does't change the width then i would suspect
electrolytic's are weak.

Look for any over heated resistors.
Any of the trim pots been turned?
Any trim pots say B+ on the board.
Is the HV pot glued and look ok?
Theres not just one voltage from the power supply
to check, need to monitor all the secondary voltages
like C43 etc on each supply see if they are steady or low?
Get the caps first!
Make sure you have the caps in correctly.
Heres the schematic
http://na.suzohapp.com/pdf/service_pdfs/makvision-schem49-2717-00D2rev.pdf
Make sure you replace the H.O.T with correct one.
Good Luck!

Will be back in the shop Tuesday and will start replacing the caps.
What do you mean by tapping around? Physically tapping the chassis?
VR2 is the HV pot and is still glued.
VR1 is the B+ adjustment and I do not know if anyone has worked on this set before it hit my bench.
I'll post back findings Tues. night. Thanks for the direction.

 

[saskvidkid]

Need to remove the B+ control board and solder the pins
the board mounted to the heatsink in the back of chassis

I monitor the B+ when I'm testing a chassis, So if the B+
drops as the image moves in then I would need to confirm the B+
circuit is working first!!

The caps need to be replaced I would even if i found just one bad
i would replace all the the caps..if never replaced before.

If i could see the PS i would tell you where to monitor the B+
otherwise i need a schematic to read the location number
but a visual of section is as good.

Got a photo of your chassis so all parts can be seen?
and a photo of the picture image
which chassis is this?
is this the tri-res or standard chassis you have?

I've attached a pic of the board I think you wanted. I've installed 2 new caps and re-flowed all solder. I will try it tomorrow, and get a full pic of the chasis. Question, do you think it might be a diode that's going bad?

 

[Ohmerone]

I've attached a pic of the board I think you wanted. I've installed 2 new caps and re-flowed all solder. I will try it tomorrow, and get a full pic of the chasis. Question, do you think it might be a diode that's going bad?

Need to add solder to the connector pins on the B+ control board!

Need to add solder the pins on the main board, that the B+ control board

plugs into. And any large standup resistors on the chassis.

Make sure you didn't open a trace on your B+ board

from removing it off the standoff!!

Make sure you put the B+CB back down on the pins correctly

its hard to get back together, because of the standoff's

take your time and don't miss a pin or

damage the board.


I expect you to replace all the caps in the chassis.


Once the caps are replaced and no bad connections

then test again, I don't think a diode is bad at this point.

Get a picture of the whole chassis and of the power supply area

and look for any over heated resistors.

 

[angelcare]

I would replace the caps first!
This chassis is high res only 30-50KHZ

I would suspect a few caps.
This chassis is complex and need to scope
a few test points to narrow down the suspected circuit.

If tapping around does't change the width then i would suspect
electrolytic's are weak.

Look for any over heated resistors.
Any of the trim pots been turned?
Any trim pots say B+ on the board.
Is the HV pot glued and look ok?
Theres not just one voltage from the power supply
to check, need to monitor all the secondary voltages
like C43 etc on each supply see if they are steady or low?
Get the caps first!
Make sure you have the caps in correctly.
Heres the schematic
http://na.suzohapp.com/pdf/service_pdfs/makvision-schem49-2717-00D2rev.pdf
Make sure you replace the H.O.T with correct one.
Good Luck!

Replaced caps today. VR1 is B+ adjustment, VR2 is HV pot and is not glued.

Board is clean, no work has been done on this one, resistors look good (not overheated).
Replaced the HOT again today and it blew out on power up. Put back the other HOT and get the pics as above.

 

[Ohmerone]

Replaced caps today. VR1 is B+ adjustment, VR2 is HV pot and is not glued.

Board is clean, no work has been done on this one, resistors look good (not overheated).
Replaced the HOT again today and it blew out on power up. Put back the other HOT and get the pics as above.

You might send the chassis off for repair.

Or start checking the voltages.

Unless someone else has a good guess or experience with the issue.

To bad the caps didn't fix it!! You changed them all except the filter cap?


I have not seen the problem before so i would just have to trouble shoot

the chassis and checking a few TP's

A O-Scope would be nice to check waveforms as well.

and you don't have a HV probe to measure the High voltages

so i would ohm the HV pot first, just what the ohms is before turning it

as a reference, not just turn it blindly you could increase the HV to much

and short the H.O.T

Keep in mind heating or cooling semiconductors is a way to

trouble shoot them because they react to different temperatures

when they fail, it could lead to a suspected part.

Looking at the parts on the heat sinks do they look over heated?

This chassis has a lot of jumpers feed thru connections any one or more

could have a cold solder joint, just tapping on the pcb or parts

may not tell you much.


If you could remove the signal cable and keep the monitor on.

How does the image react now.. trying to see which frequency or circuit

the problem could be related to.

The blue HV caps would be a suspect, but dont think so

unless they look bad, not likely to test short. but you can check.

Confirm your yoke is connected good and trace around the connector

on the chassis.


Need to check each supply in the secondary of the power supply.

The Vr1 if turned will decrease/increase the voltage to all secondary voltages.

Not just one, I would not turn it, without knowing what all the

secondary were to start, Its easy to see what the voltages should be

they are posted on the schematic. go to each cap on each line

examples are c33a,c43,c45,c44,c21,c22a,c39. check

the voltage on each cap.



Need to know more voltages to see why your H.O.t failed!

Does your power led change colors as the image changes?

Does the Scan Relay RL2 keep ticking or does it switch once.

with and without a signal.

If the power supply is working good.


Matching the voltages with the schematic will work.

Assuming your H.O.T and Flyback are good.

Remove and ohm the resistance of the mosfets Q43 and Q31

and a quick diode test across each diode for as obvious short.

Just things to try.Good Luck!

 

[angelcare]

Thank you for all your time and assistance Ohmerone.

Looks as though I will have to put this one on the back burner as I have over our 6-8 hour limit on monitor repairs. To many backing up in the shop area.

All caps were changed including the filter while I was in the mood. This did not change anything at all as compared to the original pics I posted.

It does not matter if a signal is applied or not, the picture looks the same each way.

Parts on the heat sinks look okay, just the normal hardening of the heat sink compound.

Yoke connection good and all suspect solder joints have been re-flowed. Did this while replacing the caps.

I had checked the diodes for shorts in the power supply and HV circuits when I first started.

Just letting you know what has been done so far, and will print out your notes for when I revisit this beast.

I'll post back when I get back to this one. Thanks again.

 

[gamefixer]

Believe it or not that pincushioning that your seeing is normal (yes I said normal) with these monitors. As with other junk made in China they put ZERO effort into making these things work past 5 minutes. Dont believe me? Go look at a buck hunter as its booting. All the text based 640x480 screens are a mess. Try pumping a 800x600 image into the monitor, it should clear up. It might even work at 640x480 with a full screen image. These monitors were widely used in Raw Thrills games for some time.

Mak is garbage, they should have been put out of business a long time ago.

 

[Ohmerone]

Thank you for all your time and assistance Ohmerone.

Looks as though I will have to put this one on the back burner as I have over our 6-8 hour limit on monitor repairs. To many backing up in the shop area.

All caps were changed including the filter while I was in the mood. This did not change anything at all as compared to the original pics I posted.

It does not matter if a signal is applied or not, the picture looks the same each way.

Parts on the heat sinks look okay, just the normal hardening of the heat sink compound.

Yoke connection good and all suspect solder joints have been re-flowed. Did this while replacing the caps.

I had checked the diodes for shorts in the power supply and HV circuits when I first started.

Just letting you know what has been done so far, and will print out your notes for when I revisit this beast.

I'll post back when I get back to this one. Thanks again.

If it doesn't fill the raster on a no signal then


I would suspect the diodes D43,D43A,D43b are breaking down



Look at the part# on them and go to happ and search with those #

on the part. or e-mail parts and request the parts # by location

and give full model of chassis.

 

[angelcare]

Believe it or not that pincushioning that your seeing is normal (yes I said normal) with these monitors. As with other junk made in China they put ZERO effort into making these things work past 5 minutes. Dont believe me? Go look at a buck hunter as its booting. All the text based 640x480 screens are a mess. Try pumping a 800x600 image into the monitor, it should clear up. It might even work at 640x480 with a full screen image. These monitors were widely used in Raw Thrills games for some time.

Mak is garbage, they should have been put out of business a long time ago.

Gamefixer, couldn't agree with you more. These are pieces of s***, but we are stuck with them, as the company keeps buying them as replacements. Have also seen them come in the GT Live dedicated games.

Just finished destroying 2 tubes because they have already been rejuvenated and after being out in games for a 4-6 month period, they are dead.

 

[angelcare]

If it doesn't fill the raster on a no signal then

I would suspect the diodes D43,D43A,D43b are breaking down

Look at the part# on them and go to happ and search with those #

on the part. or e-mail parts and request the parts # by location

and give full model of chassis.

Thanks Ohmerone, will give it a try when I get the time to go back and look at it.

 

[angelcare]

Missing Blue Color

Talk about timing. Guys brought in a Big Buck Hunter Pro to get ready to go out to a location. Problem comes up with the blue color missing. Swap the neck board with a good spare. No dice. Throw a rebuilt D9200 in it and get it out the door.

This afternoon, I pulled the monitor to the bench and decided to check the tube. Rejuvenating did nothing, blue gun was completely shot.

Well, long story short, swapped the chassis with the problem child and now have a spare monitor in queue and another parts board.

 

[gamefixer]

Its sad how these things have deteriorated into the pieces of crap that they are. Look at how many AMERICAN AND CANADIAN built Wells K46/4900 and G07's are still out in service. OK, they had flybacks that went bad but 10+ years not ~6 months.

I hate Makvision and all these other garbage slinging companies.

 

[d7onr8]

Thanks Ohmerone. I was able to use advice from the first page to fix problems on my Wei Ya M3129D. Replaced mylar cap C67 and that fixed the problem with mid-screen retrace lines.

 

[d7onr8]

Believe it or not that pincushioning that your seeing is normal (yes I said normal) with these monitors. As with other junk made in China they put ZERO effort into making these things work past 5 minutes. Dont believe me? Go look at a buck hunter as its booting. All the text based 640x480 screens are a mess. Try pumping a 800x600 image into the monitor, it should clear up. It might even work at 640x480 with a full screen image. These monitors were widely used in Raw Thrills games for some time.

Mak is garbage, they should have been put out of business a long time ago.

Speaking of pincushion, my pincushion pot has no effect on my M3129D. Swapped the remote board and the problem still remains so it's something on the main chassis. BTW, the electrolytic capacitors on the main board have already been replaced. Any ideas what could cause a non-functioning pincushion; could it be a transistor? Looking at the pincushion area of the schematic, it seems like the only transistors in the vicinity are Q28 and Q29 but it looks like they are more related to the Trapezoid function than Pincushion. Any insight is appreciated.

 

[Ohmerone]

Speaking of pincushion, my pincushion pot has no effect on my M3129D. Swapped the remote board and the problem still remains so it's something on the main chassis. BTW, the electrolytic capacitors on the main board have already been replaced. Any ideas what could cause a non-functioning pincushion; could it be a transistor? Looking at the pincushion area of the schematic, it seems like the only transistors in the vicinity are Q28 and Q29 but it looks like they are more related to the Trapezoid function than Pincushion. Any insight is appreciated.

Did you fix it?

Does it do the same on all the tri-res-modes

or just med-res.

is the B+ for that res-adjusted correctly?

Does the width and other analog pots make a different

I don't see Q28 and Q29

more like q34,q35 for output

O-scope the output of Ic10 for a good waveform.

pin may not work correctly if theres an width issue

what have you found?

Got picture's?

also see the notes for this model on this thread