Happ MTG-2601 HV shutdown

roothorick

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I'm not 100% sure on the chassis model; I just noticed my pictures don't have the model number in them and I'm a forgetful bastard.

When I apply power, the monitor sounds like it's gonna start for a fraction of a second, then abruptly stops, and no neck glow. It'll do this again if I remove power and try again, so it's not the fuse. HV shutdown, right? My first instinct was to adjust B+ down, but I couldn't find an appropriate pot in the service manual. Anyone have more info on this guy? Thoughts/ideas?

-E- It's an MTG-1901CN, sorry about that.
-E2- I'm starting to think it's actually a 2901; pictures:

IMG_20110402_103154.jpg

IMG_20110402_103145.jpg

IMG_20110402_100634.jpg
 
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Happ confirmed what I suspected -- the chassis is out of warranty. So, I'm gonna be taking a crack at it. Based on other threads about this chassis, first stops are HOT and flyback; I'm gonna play with resistance readings, some datasheets, and searching the forum, but... any tips for testing these?
 
Try using the MTG-1901
The numbers on the chips can be checked on schematic.
If the Ics matchup it maybe good enough to TS chassis

The Bi Polar Switching Regulator, I802 STRS6707 the one in the top picture
on the heatsink..maybe working if its warm?
The transistor on the other side of heatsink Q802 would be a suspect..
If no secondary voltages..

Measure the cathodes of D810,D809,D808, for voltages and circuit resistance
The D810 cathode should also ohm out to the collector of the HOT 2SC4769
And the 24vs to the vertical Chip if they short it will disable the SMPS.

Ic802 is a fixed 120 volt regulator to keep the b+ within range
there is no B+ adjustment,at plugin the SMPS would be up
and running and the Feedback Ic801 sence's the load and will switch off
the Switching regulator if to much.
 
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Thanks for the input!

I'm gonna be putting my thoughts down in this post, editing it as I go.

Discovered I can test voltages relatively easily by probing the adjustment board for power ground. 24V is present, but low -- 22.8V IIRC. B+ is good - 122.7V. I'm gonna take this to mean the switcher is golden. Confirmed the issue -- every power on, the monitor whines for a few seconds than abruptly stops. So what's causing the HV shutdown?

The HOT is Q402. At least, one thread says so, it's right next to the flyback, and it's a really big transistor with its own heatsink, so I'm going to assume so. Reads open, both ways, base to collector. Base to emitter, it's reading short, both ways, but it's still in circuit so that may be just the circuit. (Looking at the diagram, however, I doubt it.) Think I found my culprit.

The flyback definitely has been replaced in the past -- the surrounding area is brown with flux. Ditto the HOT. What could make them work for a while but blow later? Is this flyback bad? Is there an easy way to tell?

I think the flyback is okay. What confuses me is the pin marked "GND" and the pin marked "185" are short, among other things -- but the schematic seems to back all of it up. Huh, okay.

Found a bulging cap in the SMPS area -- C807. Looks like it's supposed to skim ripple from the switcher transformer. Of course, I don't really "get" switchers.

THE CHASSIS FRAME ISN'T GROUNDED! The ground pin on the power connector, cabinet-side, is MISSING. Ay yi yi...

Tried it one last time, did the same damn thing. Buzz, screech, and the crackle of cooling off. I don't know what the owner would think of me walking off with the chassis, so I'm gonna leave it here and come back with some new parts. new C807, new HOT, maybe a new flyback depending on what you guys think.

-------------------------------

A question to you guys: if the HOT is blown, should I just go ahead and replace the flyback too?

Modessitt, if you see this, do you remember which inductor was blown on the one you worked on?
 
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Ordered new HOT (NTE2353, spec calls for a 2SC4769 but the chassis actually has a Fairchild something-or-other in it) and C807 today. I'm kinda nervous that maybe I missed something, but I can always do another order with Mouser. I couldn't find anything decisively "bad" on the flyback so I'm gonna try the flyback in there with the new HOT and see how it goes.

I just thought of this... SMPSes use earth as part of their regulation, don't they? So with the chassis frame ungrounded, the SMPS may be rippling something terrible. I'm gonna pick up some wire and get that bastard grounded.
 
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You should test the HOT out of circuit.if you think its bad!
You can remove the solder from the vertical ic incase
its drawing more current then normal,causing the regulator to switch off
I would suspect something else besides the HOT or fly.
Maybe while your waiting for the parts you can check some other things.
Are you assuming the caps are all good?
Does the fly test bad?
I use a oscilloscope to check the fly
Or test with a flyback ringer. if it looks ok.
If it test bad then go with it but if test good then you need
to check other parts that could cause shutdown.
Also Check Q405 the pin Amp, out of circuit for a short.
was this monitor working and then fail?
 
You should test the HOT out of circuit.if you think its bad!

Yeah, but how could the circuit cause a false open reading? Oh well, it's a $10 part.

You can remove the solder from the vertical ic incase
its drawing more current then normal,causing the regulator to switch off
I would suspect something else besides the HOT or fly.

We'll see if I feel like driving out there before the parts arrive. I'll probably do that after the parts arrive but before I put them in.

On that note, I'm gonna power it up with just C807 replaced. Who knows, maybe B+ is rippling like crazy (I don't have a scope to test) and pushing HV around.

Are you assuming the caps are all good?

Given the age of the chassis (sold new in 2006 confirmed from Happ) dry caps are unlikely, but it's right about the right age to have gotten hit by the plague, so who knows. How likely is it for failing caps to cause HV shutdown?

Does the fly test bad?
I use a oscilloscope to check the fly
Or test with a flyback ringer. if it looks ok.
If it test bad then go with it but if test good then you need
to check other parts that could cause shutdown.

Unfortunately I have neither of those. I'm trying to save money for a new car so getting a scope is a good ways off. How much is a flyback ringer?

Also Check Q405 the pin Amp, out of circuit for a short.

Another thing to try before replacing the HOT. Thanks!

was this monitor working and then fail?

That's the CC. One day it and the machine next to it (a Silver Strike Bowling) went out simultaneously, which makes me suspect this was originally caused by a line voltage spike. (The SSB PC's power supply had gone into shutdown; cycling power on the machine brought it to life and we couldn't get it to misbehave afterwards.) Not sure how useful that info is, but now that you bring it up, it makes me want to put the SMPS under the magnifying glass again. I really wish I had a scope...
 
I realized after swapping it that the HOT is good. I showed up woefully underequipped, so I'm gonna make a shopping list and return tomorrow. Replacing C807 had no effect, but I'm leaving it in as that cap had a significant bulge.

Q405 is fine.
 
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Damnit, nevermind. I'm wrong.

I'm starting to think it's the flyback. If I have a good B+ (even after HV shuts down) and HV shutdown, what else could it be? I'm looking at the schematic and I can't find any other possibilities. Would it be safe to lift R414 and run it for a few minutes to confirm it is in fact HV shutdown? Even if it blows something else it could give me a hint.

I just went over the rest of the HV shutdown circuit. No evidence of problems, all resistors good, diodes check out. Unless there's a problem with I301 the shutdown is legitimate.
 
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Damnit, nevermind. I'm wrong.

I'm starting to think it's the flyback. If I have a good B+ (even after HV shuts down) and HV shutdown, what else could it be? I'm looking at the schematic and I can't find any other possibilities. Would it be safe to lift R414 and run it for a few minutes to confirm it is in fact HV shutdown? Even if it blows something else it could give me a hint.

I just went over the rest of the HV shutdown circuit. No evidence of problems, all resistors good, diodes check out. Unless there's a problem with I301 the shutdown is legitimate.
Have you removed the solder from the vertical,it will run without the vertical
deflection,if you get hv then replace it, if not put it back.
To eliminate it as being a problem.
Unless someone else has a qiuck fix you might check some more

Key test points on the ic 301 like pin10 for run voltage to ic
and pin13 x-ray check for any volt at plugin? If you like lift one end of D361
to disable the x-ray protect. if the fly is pulsing then you should have dc at pin 13
with zener connected,if no dc then x-ray protect may not being switched on by the fly.
Scoping or dc pin 12 will let you know when you have Horizontal drive to the Horiz-Driver Transistor,to check the ic.

Check the voltage on the optocoupler I801 pins 1 and 2 also 3,4 hot side.
record the voltages.
Haven't seen many problems with this chassis besides caps.
Checking all the test points may offer more details about whats happening
in the circuit. Good Luck!
 
Have you removed the solder from the vertical,it will run without the vertical
deflection,if you get hv then replace it, if not put it back.
To eliminate it as being a problem.
Unless someone else has a qiuck fix you might check some more

I already tried pulling the whole chip out, got the same response.

Key test points on the ic 301 like pin10 for run voltage to ic
and pin13 x-ray check for any volt at plugin? If you like lift one end of D361
to disable the x-ray protect. if the fly is pulsing then you should have dc at pin 13
with zener connected,if no dc then x-ray protect may not being switched on by the fly.
Scoping or dc pin 12 will let you know when you have Horizontal drive to the Horiz-Driver Transistor,to check the ic.

See, that's the problem, I don't have a scope and I presently can't afford one. I'm ready to throw in the towel and just send the chassis to someone.

Check the voltage on the optocoupler I801 pins 1 and 2 also 3,4 hot side.
record the voltages.
Haven't seen many problems with this chassis besides caps.
Checking all the test points may offer more details about whats happening
in the circuit. Good Luck!

Isn't I801 part of the switcher? I know I have B+ at the neckboard, even after the shutdown. It's reading 122.7V on the multimeter, but I don't have a scope. Is there an easier way to check for ripple?
 
I'm surrendering on this one, and sending it to Chad. I simply don't have the tools, I think.
 
repair

By any chance did you ever find out what the problem was ? I have a monitor doing the same thing. But if I lift D361 disabling X ray protection. It works great. I cant find any adjustment for High Voltage.
 
By any chance did you ever find out what the problem was ? I have a monitor doing the same thing. But if I lift D361 disabling X ray protection. It works great. I cant find any adjustment for High Voltage.


Check your Pm!



Suspect D404 an NTE 577
 
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I am having the exact same symptom with one of these monitors. It is installed in a dedicated Millipede atari cabinet with original giant style power supply. I noticed that a 4A fuse at F6 was blown when I first opened it up, but replacing the fuse did not help the monitor problem. I hear it briefly whine when powered on, then it crackles as it shuts down.

I notice a previous poster "lifted" D361 to disable the protection circuit. What did he mean by "lift"?

I would like to perform the same test.
 
I am having the exact same symptom with one of these monitors. It is installed in a dedicated Millipede atari cabinet with original giant style power supply. I noticed that a 4A fuse at F6 was blown when I first opened it up, but replacing the fuse did not help the monitor problem. I hear it briefly whine when powered on, then it crackles as it shuts down.

I notice a previous poster "lifted" D361 to disable the protection circuit. What did he mean by "lift"?

I would like to perform the same test.

Im not sure which chassis you have but the plan is the same.

If you have correct b+

Lift one end of D361 or remove it from the chassis

this tip is for trouble shooting only!!

Its not a good idea to disable the shutdown only when needed.

If it comes up then the fly is triggering the shutdown..

Or the B+ is to high..

I would not suspect the flyback it will disable the Horiz OSC when their to much

current from issues around the flyback as well.

The d361 diode may be common to most of their chassis but have to

check each chassis.

Need to monitor the B+

if you don't have B+ then lifting one end of D351 wont help.

and you need to check the power supply.

Where is F6 in the power supply of the game board?




post a picture of your chassis maybe we can see something you missed.
 
I'm going to jump into this thread here. Not trying to hijack, but I have the same exact monitor doing the same exact thing. I have a b+ of 123 volts. I'm going to lift the zener and see if I get HV back. Btw, mine was intermittent. Now it no longer works at all. I did order cap kits from Zanen but I really don't think that is going to be the issue. I checked multiple caps with an esr meter and found no bad ones.
 
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Firstly, please forgive my sloppiness. Given that it's a millipede, my monitor is the 19 inch version. MTG-1901

How do I check for B+ and and how do I know from the schematic or manual what the spec value for B+ is?



Here is a pic of the power supply. The 4A fuse that was blown was the one at the bottom of this pic, between the two yellow wires.

Here are some chassis shots:



 
Heres the Schematic MTG-1901

http://na.suzohapp.com/pdf/service_pdfs/support/visionpro/49-1329-vp2_schematic.pdf

If you don't have any secondary voltages at, C818 or C811 or R818 then

I would check Q801 and d802,fuse and the others in that same area.

The str I802 would be a suspect as well does the heat sink get warm after its

on for a few minutes if no then it maybe dead replace it.

From my experience Q801 and around it were an issue when you don't have B+

The B+ diode can be an issue it does fail, not always shorted.

sometimes you may hear a whine and then it stops and then works it because d810 RU3

The resistors around Q801 look overheated for me so check them as well

When you have secondary shorts you may hear ticking, confirm

theres no shorts on all three test points.


If there is a short, using your ohm meter, remove the part and see if the short is gone.

Like the HOT on the 123v B+ line

and the vertical ic, and remote board on the 24v line

now the 12v supply at R818

So caps first then check for shorts on all the supply voltages.

Before you order caps and you can add more parts to your list if needed.

Resolder the standup large watt resistors in the power supply too.

Let us know what you find..
 
I'm surrendering on this one, and sending it to Chad. I simply don't have the tools, I think.



Well don't tell Chad but Travlingtech

after he lifted D361 it came up and then after some testing parts

around the fly he

found D404 checking bad and or C411

either one can draw to much current

but after replacing those parts he said it worked.

D404 I would suspect first but a shorting c411 on the abl line

could be the problem too.
 
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