Hantarex Polo Shutdown question

[Mongo]

The History:

So I got a Hantarex POLO 25 inch from a buddy. He said it worked but the flyback was smoking so he shut it down and gave it to me.

I go to replace the flyback and find a burned capacitor and a small hole burned through the board. Apparently a common problem. I replace the cap, Flyback, and HOT. Monitor fires right up and looks good. I shut it down after a few minutes and cap it. I turn it on again and it looks GREAT! So I leave it on to "burn in" and leave the room. I come back some time later and it is dead. No blown caps, not ticking, no smoke lingering in the garage, fuse not blown.

I start going down the flowchart. I test TP6 (the wire jumper dead center closest to the tube) and I my DMM reads a fluctuating DC power between 0 and 10 VDC. Not sure if I should follow the 0 Volts path on the flowchart or the Low Voltage path. I live 40 miles from the parts store but only WORK 2 miles away. I would like to grab at least one of everything I might need (the usual suspects) on the way home so I can get this working over the weekend.

The only testing I have done at this point is: R103 is good. C112 is good. D105-112 all read good. When I saw how hard ZD101 was to reach, I decided to stop for the night and just get a new one from the parts store and that is where I left off....

 

[Mongo]

So... all components in the flowchart for both low voltage and zero voltage from the power supply suggested in the flowchart test good. I have no way to test IC101.

T101 tests bad so looks like I will be picking up a replacement BUZ90A and a new 3842 Monday and see where this goes...

 

[TheEnglishTear]

So... all components in the flowchart for both low voltage and zero voltage from the power supply suggested in the flowchart test good. I have no way to test IC101.

T101 tests bad so looks like I will be picking up a replacement BUZ90A and a new 3842 Monday and see where this goes...

If all else fails, reach out to M K L. He is the expert on these and he helped me get mine sorted away

 

[M K L]

It would be safer to do a light bulb test first. Desolder the HOT and solder a 40 or 60W incandescent light bulb to the emitter and collector pads (on the chassis). Yoke connector needs to be in.

If it lights up the switching power supply is OK. If it doesn't, remove the light bulb and keep the HOT off circuit.

Lift the yellow side of the jumpers so they're not connected to the board anymore:

Connect the light bulb to the (now lifted) P112 jumper and to a ground point (like the small heat sink just below). If the light bulb doesn't light up, check input voltage to the PSU using the points shown below (don't use any other ground). It should be more than 120VDC (not AC!):

 

[TheEnglishTear]

See? M K L knows what's up. Thanks again for helping me solve my issues! But alas....I JUST bought a super chase...and guess which monitor it has in it that is having issues? (Sigh) here we go again :/

 

[Handbakedarcade]

It would be safer to do a light bulb test first. Desolder the HOT and solder a 40 or 60W incandescent light bulb to the emitter and collector pads (on the chassis). Yoke connector needs to be in.

If it lights up the switching power supply is OK. If it doesn't, remove the light bulb and keep the HOT off circuit.

Lift the yellow side of the jumpers so they're not connected to the board anymore:

Connect the light bulb to the (now lifted) P112 jumper and to a ground point (like the small heat sink just below). If the light bulb doesn't light up, check input voltage to the PSU using the points shown below (don't use any other ground). It should be more than 120VDC (not AC!):

I know this post is ancient, but I am trying to fix a polo 1 and struggling. I have done your test above, the light bulb did not light up when connected to hot position. it did not light up when connected to lifted p112. The dc voltage on the points you have shown is around 340vdc.

i have fluctuating voltage on pin 7 of ic101. Between 10vdc and 16vdc, but it never stays high or on the same voltge for more than a split second.

Q2 was dead and was a BU290A and i have put in a BU508AF and not entirely sure if that is OK or not.

Any advice appreciated!

cheers.

 

[M K L]

What's Q2? There are no parts named Q. The MOSFET in the PSU is T101. If faulty replace it with IRFBC30 or P4NA80. IC101 UC3842 may be bad. Socket it if you replace it. Look for bad solder in the whole PSU area.

 

[Handbakedarcade]

What's Q2? There are no parts named Q. The MOSFET in the PSU is T101. If faulty replace it with IRFBC30 or P4NA80. IC101 UC3842 may be bad. Socket it if you replace it. Look for bad solder in the whole PSU area.

sorry, not Q2, T101 was bad. Will see if I have an IRFBC30. UC3842 was bad and have replaced for new. thanks for the reply.