Monitor buzzes, Blows HOT, then F701 [video]

I've checked the HVsafety caps for shorts, but have not checked them with an esr meter. They have new solder, now.

I replaced the HOT & fuse, but the buzzing was still there so I powered it off immediately. The sound isn't like a SG noise. It's more of a feedback noise. It is less audible when the speaker is disconnected.

How would I verify that the B+ is not low to ground?



B+ Maybe working Ok.

I would suspect the HVsafety caps or bad connection, you might reflow

pins and trace.

The arcing is the reason for the short of the hot.

You would need to replace the parts again and confirm the B+ supply

is not low to ground, each time your fuse blows.

then try it again.

the bussing you might disconnect the deguasser coil during trouble shooting.

If the B+ is stable and you are getting excessive high voltage cause arcing

everywhere including SG on neck board.

If I have the symptom right?

I would suspect the caps just replace them..
 
before After you replace any parts on the B+ line

you need to ohm the trace for any other parts that are parallel

the H.O.T just make sure you don't have any other shorts on the same trace

before you power up again.

You need to replace the caps,

they won't measure shorted if they were it would kill the B+ Right?

Need to eliminate them.

the deal is the P~P voltage is to high and the PS is not running to high

so I would suspect the values of these parts have change to much

making a much higher p~P voltage over driving the flyback yoke you name it.

Check with parts people for the replacement values, keep the same values

on the part no need to redesign the circuit.

It can be a problem arcing and shorting out parts so nows a good time

to send it out for repair since its not the tube or yoke.

Good Luck!
 
Okay. So.

I have replaced the HV caps then started testing everything I possibly could.


Flyback:
From GND to Flyback pins 4,5,6 I have continuity...

From Pin 11 of Flyback to pin 10 I also have continuity.

I tested my old flyback vs the new ones, they are the same electrically (from my basic tests) and have no continuity between them.

HOT:
Between my Emitter and Base pads on the board I have continuity, 0 ohms.
Between my collector and pin 11 of the flyback I have continuity, which also means pin 10 as well.


Will compare to my working chassis and see whats up.
 
I would look closely at the HDT (T602). Any cold solder on either side of that will cause the HOT to blow.
 
I haven't read through the thread in detail, but have you looked at the deflection yoke? I've run into several of these monitors where the glue from the rubber wedges actually eats into the horizontal windings and causes several turns to short together. Sometimes it shorts to the back of the CRT as well. I think the yoke from the XM-2001 will work, but I have yet to find a replacement otherwise.
 
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I would look closely at the HDT (T602). Any cold solder on either side of that will cause the HOT to blow.

I've looked for a replacement, but haven't found one yet. The solder on mine has been reflowed, but the part has not been replaced.


I've replaced IC601 and 701. No change. Same issue. I have an ESR meter now and will test every single poly cap and will report back...
Edit:
Could T602 be the culript?

T602 has been on my list to find a replacement for. They don't normally go bad, but it is possible. I don't think you can test it without current flow (correct me if I'm wrong).
 
Flyback:
From GND to Flyback pins 4,5,6 I have continuity...

6 is part of the primary winding along with 10 and 11 and if 6 is shorted to ground so are 10 and 11. Desolder pins 6, 10, 11 so they're no longer touching the surrounding pads. If they're still shorted to ground it means the short is in the flyback, i.e. the flyback is bad.
 
The yoke is not the problem. The hot blows with it unplugged.



You need to check the high voltage?

the spark gaps on the neck board are sparking too.

another reason the high voltage is to high!

seen on another thread somewhere

The Sound is from hi voltage arcing somewhere.

that will short the hot!

Is yours make the same arcing sound??
 
I'm not going to turn this monitor on until it 100% matches electrically to my good working chassis. I have a lot of work ahead of me, but I feel that this is the only way forward. I should not have 0 ohms between my emmiter and base solder pads without a HOT installed.
 
I'm not going to turn this monitor on until it 100% matches electrically to my good working chassis. I have a lot of work ahead of me, but I feel that this is the only way forward. I should not have 0 ohms between my emmiter and base solder pads without a HOT installed.

I'm not sure what what the resistance is for t602 but it looks as though the base and emitter tie to ground. The emitter straight to ground and the base through t602 then to ground.
 

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Is this all you have to add to the conversation? Belittling people? Wow.

That's not what happened. You posted something that points to a HOT collector line shorted to ground and I gave you tips which you ignored and now you worry about something completely normal.
 
Emitter to base on my known good working chassis is 2 ohms. Emitter to base on my bad chassis is 0 ohms. This makes no sense? T602 has a winding which will have SOME sort of resistance.

I didn't ignore what you said. I measured exactly what you told me to do. All is good. Not only that but you didn't read that I have already tested the flyback in the good working chassis, and it works just fine.
 
What does it mean all is good...

You posted this:

Flyback:
From GND to Flyback pins 4,5,6 I have continuity...

Do you confirm that pin 6 has continuity to ground? If so it's a problem because pin 6 (165V supply to the RGB amps on neckboard) is in the primary winding with 10 (B+) and 11 (HOT collector) and a primary winding shorted to ground is bad news and you need to find what's causing the short.

Either that or what you said about pin 6 shorted to ground is not true.
 
The Sound is from hi voltage arcing somewhere.
that will short the hot!
Is yours make the same arcing sound??

Mine sounds more like an oscillating feedback, than an arcing sound.


I'm not going to turn this monitor on until it 100% matches electrically to my good working chassis. I have a lot of work ahead of me, but I feel that this is the only way forward. I should not have 0 ohms between my emmiter and base solder pads without a HOT installed.

It seems like the only way to get 0ohm without a HOT installed, would be to have a bad T602 or R603, as those are the only path from base-to-ground. My good board is still put away, but I will pull the T602 off my bad board to get a reading.



EDIT: see pic for T602 out-of-circuit reading from bad board...

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Do you confirm that pin 6 has continuity to ground? If so it's a problem because pin 6 (165V supply to the RGB amps on neckboard) is in the primary winding with 10 (B+) and 11 (HOT collector) and a primary winding shorted to ground is bad news and you need to find what's causing the short.
Either that or what you said about pin 6 shorted to ground is not true.

Continuity != short. Both of his statements are correct because he was testing in-circuit. He also swapped out a known-good flyback further back in the thread.
 
I fixed my issue with pin 6 of the flyback to ground, the solder connections on the T1,2,3 connector had excess wire and was jumping pin 1 to 3.

I'm back where I started, monitor buzzes a bit, then the hot goes poof again. Have a look at the updated picture of what I have replaced /tested.

Green is tested good, Purple is replaced, Blue has been verified between both new and old parts.

https://forums.arcade-museum.com/attachment.php?attachmentid=346196&stc=1&d=1522385856
 

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I fixed my issue with pin 6 of the flyback to ground, the solder connections on the T1,2,3 connector had excess wire and was jumping pin 1 to 3.

I'm back where I started, monitor buzzes a bit, then the hot goes poof again. Have a look at the updated picture of what I have replaced /tested.

Green is tested good, Purple is replaced, Blue has been verified between both new and old parts.

https://forums.arcade-museum.com/attachment.php?attachmentid=346196&stc=1&d=1522385856


I did suspect an issue around the flyback traces..

the old fly is probably good.

I would add a ground wire to the pin 7, not sure wheres it is on the board

if a heat sink is part if it, you could have a floating ground during startup.

off the flyback, if the High voltage is good.

Does the H.O.T get warm to hot fast, under a minute or short and be cold?

What have you found?
 
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