Hantarex MTC-900 Issues

[SirPeale]

My first Hantarex, so I'm unfamiliar with it.

Power on, it displays a yellow bright screen.  No picture at all that I can see.  Lines going thru the screen like the screen was turned up too high, but with the screen control turned all the way down.  Turn it up and it just gets brighter.

Both fuses are okay.  I wanted to measure B+ but wasn't sure where to measure it from.

Placing my black lead on frame, and the red lead on the large while resistor mounted on the left, I get 0VDC closest to the rear, but -30VDC(ish) on the other end.

Where do I go from here?  I'm stumped.

[Ken Layton]

The R.H. Belam Company in New York is the official Hantarex distributor/parts/service center: www.belamny.com

[SirPeale]

No ideas, eh?  Damn.

I have replaced every electrolytic cap on this.  Just an FYI.

[Ken Layton]

I have written a repair guide to the 900/E. There's a difference between the 900 and 900/E.

Remember that some capacitor polarity markings on the board may be incorrect on Hantarex monitors too.

[SirPeale]

Which caps?  I was very careful to put them all in the way I took them out, but I suppose I could have made a mistake.

What is the difference between the 900 and 900E? 

[SirPeale]

There isn't a label on this monitor any more, but I'm 97% certain it's a 900, not a 900E.

[qrz]

schematic here:  www.freeinfosociety.com/electronics/schemview.php?id=2244

check the collector voltages on TR28,31 and 34. ( rgb driver xistors)
per print , boost voltage at c51/72 should be > 200v
if voltage missing , check r131,145, b6 coil,d25
base voltage on TR27,30,33 should be 12 v . if missing , check IC4 ,D27, r116


qrz

[SirPeale]

Thanks, qrz.  Only problem is I don't know how to use them!  I can follow a diagram, identify components, but don't know how to use it to troubleshoot.

I'll try the suggestions you gave there.  I'll look up the data sheets on those parts to see which legs are collectors.

[SirPeale]

The R.H. Belam Company in New York is the official Hantarex distributor/parts/service center: www.belamny.com

As soon as I told them what monitor I was working on, they said "fogeddaboudit!"  They only deal with new stuff.

[Ken Layton]

Which caps?  I was very careful to put them all in the way I took them out, but I suppose I could have made a mistake.

What is the difference between the 900 and 900E? 

I've only worked on a 900/E. Never touched a 900.

[qrz]

  I'll look up the data sheets on those parts to see which legs are collectors.

many times the mounting tab will be tied to the collector ( to-202, 220 packages, etc ) 
the pin designations may also be silkscreened on the pcb....


                         tab

                   xistor body
                   printed #

                         leg

                        1 2 3
                        b c e

1 base
2 collector
3 emitter

 this order WILL vary per device number . research when in doubt

qrz
                       

[grantspain]

blanking problem,have you checked r59(2k2),r144(2r7)

[SirPeale]

blanking problem,have you checked r59(2k2),r144(2r7)

I have now that you've mentioned it.  They tested fine.

Someone on RGVAC mentioned that it could be a couple shorted color transistors.  Red and green together would produce yellow.  I examined the neck expecting to see three...and there are six.  They're all the same.

I started looking at my collection of TV chassis for transistors that would cross.  The original part is a BF871, which crosses to an NTE171.  I found a chassis that the transistor looked similar, so I crossed it - a 362-7 - which crosses to an NTE171 as well.  Regrettably only three on the neckboard, but at least I could eliminate one color as a possibility in this matter.  I chose red.

I removed the two red transistors from the Hantarex and replaced them with the ones from the junk chassis.  Replaced the chassis and fired it up...and instantly toasted R142.

[SirPeale]

It toasted R145 as well.  I plugged it back in after replacing R142 and it was glowing quite brightly.

I did note that the transistors I put in had slightly differing numbers underneath the "362-7".  One says "A23 514" and the other "A23 506" but I'm not sure what that means.

[Ken Layton]

I've heard that Hantarex can be very particular on replacement transistors. I'm told they must be originals and many times the NTE ones won't work.

I would suggest talking to Jomac in Australia about your problem. I think his new "Ultimate Monitor Repair" book at Star Tech Journal has a chapter devoted to Hantarex monitors.

[SirPeale]

Hm, that's a problem...they don't make them any more.  And they're rare as hen's teeth, no one carries them.  No one mainline, anyway.

I'll fiddle with this a bit more tomorrow.  It's late.

I'm not even sure if these old ones are bad.  I ran them thru the usual tests, they were reading funky, but I could have been doing something wrong.  I'll try again tomorrow.

[grantspain]

if you look at both datasheets you will see the pinout is different
nte171 is 1.emitter 2.base 3.collector
bf871 is 1.emitter 2.collector 3.base
thats why you fried the resistors

eBay Link

[SirPeale]

That's a darn good reason; why does the the NTE quickcross say it's compatible then?

[grantspain]

well if you twist the nte then it is compatible
i think you are missing a voltage,maybe meter the test points on the neck card using the schem as a pointer
i think 200v is missing
if this was a later chassis i would have said the lm1203 video amp ic is dead,this is the same fault but an earlier design using more components
there must be a common problem or some of colours would be o.k

as for hantarex,even the tech in the u.k does not support before mtc9000

[SirPeale]

well if you twist the nte then it is compatible
there must be a common problem or some of colours would be o.k

but if you twist the legs you'll touch them together.  I suppose I can be careful...but I bet that those transistors I put in there are toast now.

As for the yellow, if red and green were full on it'd look yellow, right?  I just hope it's not a tube fault.

[grantspain]

dunno could be a tube fault i guess,if you remove the green and red drive transistors and power on and still get a yellow screen then i would say thats a screwed tube
i still think its a voltage missing
an earlier reply from qrz will almost certainly reveal the culprit

[qrz]

That's a darn good reason; why does the the NTE quickcross say it's compatible then?

spec wise it likely is ..... there should have been a note about the pin orientation.

and be aware that many times an ecg/nte, sk (etc...) is more expensive than an original device .
and yes, exceptions do exist .

qrz

[SirPeale]

spec wise it likely is ..... there should have been a note about the pin orientation.

and be aware that many times an ecg/nte, sk (etc...) is more expensive than an original device .
and yes, exceptions do exist .

I was aware of the price difference.  NTE are usually much more expensive.  I always try to go original if I can.  The replacements I used were ones I pulled from a junk TV chassis.

I checked the specs after the fact and noted that it said there could be differences.  Too little to late I suppose!

[SirPeale]

I removed both TR27 and TR28 to see if the screen would drop a color.  It remained yellow.  I'm guessing a tube fault. 

I forgot I *do* have a rejuvenator, found it when I was cleaning out my van.  Problem is I don't know if it works or not.  I'll hook it up later and test it out.

[SirPeale]

I forgot I *do* have a rejuvenator, found it when I was cleaning out my van.  Problem is I don't know if it works or not.  I'll hook it up later and test it out.

So much for that idea.  It's a Sencore CR143.  Older than old.  It's got like 15 pages dedicated to which BW tube has what settings, and two for color tubes!

I could probably build an adapter...I've got plenty of sockets from donor TV chassis.

[qrz]

the cr70 has a "universal adapter" for the oddball crt . its terminated with test clips for pin attachment.
might do the same with the cr143  ?

yellow would be due to missing blue .   still would like to know the rgb collector voltages

qrz

[SirPeale]

the cr70 has a "universal adapter" for the oddball crt . its terminated with test clips for pin attachment.
might do the same with the cr143  ?

yellow would be due to missing blue .   still would like to know the rgb collector voltages

qrz

Where do I put the test leads?  Obviously red on collector leads...black on the frame?

Wouldn't removing the drivers from the neckboard turn those colors off entirely?

TR27 and TR28 are for red, correct?

As for the adapter, I've got a perfectly serviceable socket, some heat shrink, and existing adapters in a size I'll never ever use.  I'll build my own.

[Nipedley]

I had some trouble with BF871's on a hantarex chassis, I managed to get some replacement's from here..

http://www.cricklewoodelectronics.com/Cricklewood/product.php?productid=6986&cat=0&page=1

 

[SirPeale]

Dammit, all those links bring me to sites over the pond! 

[SirPeale]

If I did it right, the collector voltage was ~180VDC.  Still need to replace one of those resistors.

[qrz]

that means the 200v source is likely working .
now, are the collector voltages high or low on the other two output xistors ?

[SirPeale]

If I remember correctly, it was much lower than 200V.

[SirPeale]

Finally!  I think IC4 is bad.

edit: and I don't have one!  Crap.

[SirPeale]

They sell them @ Radio Shack.  Shocking, really.  $1.59.

But...the old one wasn't bad.  It read exactly the same way the new one does.  I was quite surprised.  Installed it with no change.

[SirPeale]

check the collector voltages on TR28,31 and 34. ( rgb driver xistors)
per print , boost voltage at c51/72 should be > 200v
if voltage missing , check r131,145, b6 coil,d25
base voltage on TR27,30,33 should be 12 v . if missing , check IC4 ,D27, r116

Collector voltages ~181VDC.  Same with C51.

11.8VDC on TR27, 30 & 33.

Since the boost voltage is supposed to be over 200VDC, should I turn up the B+?

[SirPeale]

I think I've eliminated the tube as a fault.  I had another tube - a 20" - that I hooked up briefly.  I couldn't get the yoke on all the way, but close enough so I could tell that the problem still seemed to be there.  That's a good thing.

But the problem still exists, so...

[SirPeale]

Removed TR30, now instead of an all-yellow screen I have one that's all red.  When I have a chance I'll pull the other to see if I get a blue picture of some kind.

[grantspain]

i think you are nearly there with this 

[SirPeale]

i think you are nearly there with this 

You think so?  Here's hoping.  Problem is I've already either removed or replaced the remainder of the color drivers, so I'm not sure what's going on there.

[SirPeale]

I'm going to have to give up on this unless anyone has any more suggestions.

All the voltages everyone has suggested have been spot on.

I've pulled every driver from the neckboard now, and it's still coming up with a yellowish screen if I turn the screen control up halfway.  Now, however, if I turn the screen all the way down the yellow goes away, and I'm left with a slight red hue with retrace.  That sounds to me like a red short in the tube.  Maybe.

I still can't get *any* kind of picture to appear, in any color.

[SirPeale]

Interesting reading...

"G1 normally is a negative voltage. Most tv picture tube do not use G1
voltage. If the G1 voltage is missing or zero voltage to the picture tube
the monitor display will becomes very bright with retrace lines (diagonal
lines or flyback lines) across the screen and sometimes the monitor will
goes into shutdown mode."

which sounds exactly like my problem.  Now I need to find where to measure my G1 voltage from.

[grantspain]

its nothing real daft like the dag earth disconnected from the neck card(don't bite my head off,just a suggestion)
according to the schem the 900 does not use -190v g1,it marks g1 as pin 5 which is to earth(thats of course if i am reading the correct schem)
have you checked also
r144 2.7ohm
r59 2.2kohm

[SirPeale]

its nothing real daft like the dag earth disconnected from the neck card(don't bite my head off,just a suggestion)

Nope.  And it should still fire up, even if it were disconnected, right?

according to the schem the 900 does not use -190v g1,it marks g1 as pin 5 which is to earth(thats of course if i am reading the correct schem)
have you checked also
r144 2.7ohm
r59 2.2kohm

I'll check those resistors later.  Thanks for letting me know which one was G1.

[SirPeale]

Those resistors checked out fine.

[lanman31337]

Slightly off-topic, but you guys are amazing with your work.  My father-in-law does repairs like this, and the wealth of knowledge is huge.  My hat is off to you fellas.  I'm scared to crack open televisions and monitors.

[SirPeale]

I spent the last hour going over this board, touching up solder joints and replacing the drivers in the neckboard.  I also took a cotton swab and cleaned the bottom of some kind of scum.

The good news is that it isn't driving full force anymore.  You can turn the screen control down now and it goes dark.  And you have to turn it up a decent amount to see scanlines now.  It's still a yellow tinge.

The bad news is that there *still* isn't a picture of any kind.

Something to note: the brightness and contrast controls don't seem to have any effect.  Yes, I've checked D9 and D34.  The pots themselves seem  okay.

[grantspain]

something in the video amp circuit,probably missing a voltage
are you the schem to trace things?
see i said you are nearly there

[SirPeale]

Better now than I was.

Randy Fromm's flowchart describes this problem and the parts to check.  Unfortunately there isn't a flowchart for this monitor.  I'll be curious to see what parts are affected.

[grantspain]

if you had this problem on a later chassis like a polo then one of the first things i would have suggested is replacing the lm1203 ic which is a video amp/decoder.the 900 chassis does not have this ic but a load of components doing the same job-the fault has to be common to that circuit

[SirPeale]

It's a large board, it's going to take me a while to go thru it.

[modessitt]

Well, i don't usually visit here anymore, but I may have some info that may be relevant - and may not.

I was working on a different model Hantarex (MTC9000) that was dead, and came to life with a cap kit, but couldn't for the life of me get a picture on it.  This is what I ended up with:



I also checked every damn thing i could think of and got nowhere.  I wasn't even getting flashing in the lines to indicate it was TRYING to draw the picture.

After a few weeks of scratching my head, I decided it needed a fresh set of eyes, so i took it to a buddy's house for him to look at.  He also did what you are doing - replaced the IC, changed out transistors and diodes and caps and whatnot.  Nothing worked.

Finally he just pulled out his meter and started doing continuity checks on every trace.  He finally found a trace on the neckboard that wasn't showing continuity from part to part, even though nothing looked evident to the naked eye (or under a magnifying glass for that matter).  He jumpered the trace and the picture came up just fine, and is now one of my prettiest monitors.

Just thought it may be relevant to your issue...

[SirPeale]

Well, i don't usually visit here anymore, but I may have some info that may be relevant - and may not.

Why not, mate?

[SirPeale]

I would suggest talking to Jomac in Australia about your problem. I think his new "Ultimate Monitor Repair" book at Star Tech Journal has a chapter devoted to Hantarex monitors.

I sent him an email last night.  His reply was:

If you post on www.arcadecontrols.com  I'm sure plenty there will be able to help you, I get around 40 of these requests per day so as you can imagine there isn't enough hours in a day to respond to them all , unless of course your intention was to send it to me for repair.

[SirPeale]

I have written a repair guide to the 900/E. There's a difference between the 900 and 900/E.

I'd like to get a copy, if that's okay.  My email is in my profile.

[SirPeale]

Jomac emailed me back with another reply. 

You couldn't have picked a more difficult monitor to tackle for you first effort , the color drive circuit is well over engineered to the point it can only cause problems .
A couple of things you need to establish , 1st find a ground point SP5 on neck board , measure all voltages with meter on DC , Check pin SP1 which is brightness pin , voltage should go up down as you adjust brightness , maximum 12 volts.
As this voltage drops the brigtness on the screen gets brighter , so to test of neck board itself is ok , momentarily short SP8 pin to Gnd , this will give maximum brightness .
To test all colors on CRT , you can momentarily short one end of R141 , 143 or 146 to Gnd , this will drive each color flat out one at a time and tell you if tube is ok .

Next using same ground point , measure SP10 , this is red input from chassis to neckboard , it should go up and down when you adjust RV3 red control on the chassis
Measure voltages at IC1  5 volt regulator , facing you , input on left is 12volts , Center pin is gnd , right pin is 5 volts .

[modessitt]

Well, i don't usually visit here anymore, but I may have some info that may be relevant - and may not.

Why not, mate?

I spend all my time over at the KLOV forums now.  While this is a good place to talk monitors, the arcade section isn't that lively for my tastes, and I'm not that into MAME stuff.  Since i fix the arcades for a living, it makes more sense to participate over there...

[SirPeale]

I'm still beating on this thing.  This is the first time I've touched it since my last post on the matter.

Jomac gave me some things to check.  He said to check the voltages on IC1, they should be 5 and 12V, with the middle pin as ground.  I'm not getting that at all, I'm getting 27V and 30V.  Also he said to meter SP5(gnd)  to SP8(brightness) and that should be a maximum of 12V.  I'm getting zero.

[grantspain]

there is a 12v regulator you should check

[SirPeale]

there is a 12v regulator you should check

Is that IC4?  Because I've already replaced it.  Though I suppose it could have gone bad again since I've done a lot of work since that point.

[grantspain]

yes thats ic4,the readings you are getting are off the scale
maybe worth metering back to ic4 to see whats happening

[SirPeale]

Definitely.  I'll give it shot. 

[SirPeale]

I've verified the voltage on IC4 - 12V(ish) out.  What's the input voltage supposed to be?  It's also very close to 12.

[grantspain]

the specs note 19v as input and 12-12.5 output for 7812

[SirPeale]

Five volts off input...what should I check?

[SirPeale]

Also, since I'm missing the brightness voltage, that comes right off the flyback.  Could the flyback be bad?

[grantspain]

i thought you had put a new flyback in,
check
byv95c-d27
100uf 25v-c85
0.5ohm-r116
this is gonna be an epic repair post btw

[SirPeale]

i thought you had put a new flyback in,

Nope.  If it comes to that I'll just ditch this.  Epic indeed!

[grantspain]

probably end up being cheaper to get a replacement chassis

[SirPeale]

probably end up being cheaper to get a replacement chassis

That's why I'd ditch it if it needs a flyback.  I've got a million components lying around in old TV chassis I can rape from.  Flybacks are a different matter.  I priced them for this monitor not long ago, and it was like $40 plus shipping.  Heck with that, I can get a junk game with a working monitor and use that.  If I can fix this, then good, it'll go in a game and get sold off, but at this point it's my "Everest".

[grantspain]

dunno on this,never seen a flyback lose just one winding(poss though i guess)
what voltage are you missing,190v video?

[SirPeale]

i thought you had put a new flyback in,
check
byv95c-d27
100uf 25v-c85
0.5ohm-r116
this is gonna be an epic repair post btw

D27 - good
R116 - good
C85 - near as I can tell, good.  I even just replaced it with a brand new one.  Same thing.

I seem to be missing 12V on the neckboard (brightness).  No voltage there at all metering SP5 to SP8.  That goes right back to the flyback.  I can trace from there back but so far all I've tested have been okay.

IC1 is getting way too much juice.  Should be an input of 12V and output of 5V, right?  There's an input of 30 and output of 27.

[grantspain]

yeah sorry,knew about the 12v .i thought you meant another

something skying the 12volts out,hhmmmm
d8,d6,r175(560ohm),d17
you know i never give up with a fault,i keep going-took me 3 weeks to fix a ceronix once ,kept on going back to it in my spare time-turned out to be a broken track

[SirPeale]

yeah sorry,knew about the 12v .i thought you meant another

something skying the 12volts out,hhmmmm
d8,d6,r175(560ohm),d17
you know i never give up with a fault,i keep going-took me 3 weeks to fix a ceronix once ,kept on going back to it in my spare time-turned out to be a broken track

I'll do the same.  Only reason I won't fix this is if it's the flyback.  Everything else I should be able to source from TV chassis.

[mcfreak]

If it would help you, I have two Hantarex 900E chassis's that I was trying to get working.  One had a blown flyback and the other wouldn't stop vertical rolling.  I switched the flybacks and now the other one is very dim, even if everything is turned all the way up. 

Would either of these help you in your quest to get your monitor working or be worth shipping for you?

[SirPeale]

HECK YES.  At the very least I could limit the problem to one board or the other, then concentrate specifically on that board to finalize the repair.  It's extremely frustrating, to say the least.  I know the problem is in the brightness circuit, but haven't found it yet.  Then again, I haven't touched it since my last post. 

[Ken Layton]

If you throw in the towel on this chassis, the Wei-ya model 1220H (requires isolation transformer) universal replacement chassis will work. Just $45 from Alva Amusement.

[SirPeale]

Thanks, Ken.  But half of the fun on this is figuring out exactly what's wrong with it.  If I can fix it for the cost of a few scavenged parts, fine.  If it needs something major like a flyback, I'll give it away.

[Carlito]

Hi Peale,
   Was just wondering where you got the cap kit for this particular monitor?  I checked bob roberts and only the 900/E is listed.  The monitor is working ok, but the colors are a little washed so i'm hoping a cap kit fixes it.

Thanks for any information and I hope you get yours working.

[SirPeale]

No kit.  I work on these things a lot, so I've got a bulk of caps here.

[SirPeale]

I got a MTC 900/E from mcfreak.  As he described, it comes up dim, but usable.  So I've definitely got a good tube. 

I was going to swap boards from one chassis to the other (power supply, etc) but I'm not sure just how compatible they are.  They look so very, very close.  Connection @ P23 (I think) isn't there on my 900, but is on the 900E.  As an experiment I connected the two to see if I'd get a picture (I didn't). 

I went through every resistor on the power supply looking for an open one, but didn't find any.

[SirPeale]

I have to empty my storage facility so I brought this home to poke around on again.

So I'm metering resistors in the brightness/contrast circuit before I re-read this thread to acquaint myself with the issues again.  Forgot about the missing 12V until I reread.

Anyway...I got to R203 and R204.  Resistors that should have read 22K were reading 8K.  I was ecstatic!  I thought this was the problem.  Didn't have any on hand, so I managed to get myself to Radio Shack and purchase them.  I even bumped them up a bit from 1/4W to 1/2W.

I removed the first one and metered it...and of course it's reading 22K!  Same with the other.

What causes a resistor to read wrong in circuit like that?

[SirPeale]

I was metering the voltage between SP5 and SP8 and still getting nothing.  Then I got a bright idea: what if I metered between SP5 and the heatsink that IC4 is on.  Presto!  I have 12V.  So somewhere the ground is being dropped.  Now to figure out why and where.  I was thinking about taking an alligator clip and attaching one end to the heatsink and the other to SP8, any reason I should not?

There was also some funky wiring on the underside of the board.  I'm not sure if it's factory or not, but I untacked the ends and put some electrical tape on them.  I know where they go so if push comes to shove I can put them back, but those wires are not on either of the 900E chassis I have.

[grantspain]

maybe you have hairline crack on the track somewhere

[SirPeale]

I'm thinking something similar, but I'm not sure where.  I've traced the ground connection back quite a ways but I've gotten lost.

[SirPeale]

Jumping it didn't help.  Didn't hurt either, luckily.  Instead of the voltage being 12V it was like 10.18.  Something's pulling it down.

[SirPeale]

This is driving me crazy; most of it from my own inexperience with this level of troubleshooting.

I've been using the schematic extensively.  Wherever there's a ground point on the schematic I /SHOULD/ be able to test for continuity all over the board, right?   Say from SP16 I should be able to connect to the frame and have continuity, or to the neckboard, or wherever.

[SirPeale]

Using my 900E as a reference (since they're darn close) I determined that there's some kind of grounding problem going on.  On the good chassis you can hit any ground point and get continuity with any other ground point.  Not so with the bad one.

So I got the bright idea to alligator clip pin 12 from the flyback to the frame.  Horizontal Output Transistor blew.  Now I've got one on order.  Luckily they're not much, and I've got an order to place.  Anyone else need a cap kit?  K4600?  K7000?  K4900?  Sanyo EZ?

[Ken Layton]

Sounds like this chassis is going to be better if you convert this to a Wei-ya chassis.

[SirPeale]

I have a chassis that works already, I'm doing this for the challenge.

[SirPeale]

Now I'm not sure if the HOT is blown.  I removed one from a known good working unit, and it tests the same as the one I removed from my borked chassis.

[grantspain]

can you remove the B+ from the flyback and do the lightbulb trick then meter the voltages

[SirPeale]

Bumping this because I'm going to take yet another stab at this in the very near future.

[grantspain]

ok are will still with no picture but bright screen?
if so i had the same fault on a polo chassis this week,the 200v to the drive transistor was missing,traced it back and found a bad cap and open circuit resistor.
using the 900 schematic the same circuit will be c51,r145,r131 and d25,check for min 192 volts at r145

[SirPeale]

Last I can remember it was not doing much of anything.  Have not yet gone back to it.

[shagster]

Hi,i found this thread after a google search.Looks like you have the exact same problem i had with my mtc900 chassis,a red screen with retrace lines.Anyway i was lucky cause i have two mtc900s,one wont power on.Either would this one till i noticed the lopt had about four cold solder joints,once i reflowed them i had power
Then i just compared transistor values on each board with my dmm and found TR33 on the neckboard didn't read the same between collector and emiter as on the other neckboard.So i replaced it,powered it up and got a black screen,no more red retrace line screen
Put a game into it and,it didn't work
After a lil head scratching i noticed the game had no sound,tested the voltage on the harness and i was missing the 5 volts output,the 5 volts has a dodgy wire,gave it a wiggle and on comes the game.I got very lucky with this,but theres no better feeling when ya can get these things running again
Thats my third chassis repair
Anyway i just thought i'd share this with you as its the same problem.Hope you get yours sorted

[shagster]

Update,turned it on the next day,yellow tinted screen,no retrace lines.
Thought i'd just try to reflow the blue transistors,didn't work,plugged it in and now i got a blue screen with retrace lines!
Looked at the schematic and found the three transistors relating to blue on the neckboard,removed and tested the transistors and found TR26 was shorted,replaced that and now its working fine again,for now

Actually,i think this is a mtc 900/E chassis
Wonder what the hell the E stands for!