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Hantarex polo 25 no image

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justez View Drop Down
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    Posted: 11 Sep 2020 at 7:34am
Hello,

I am trying to fix a hantarex polo 25.
I have connected a 40w bulb to the collector of the bu508.
The light bulb lights correctly and I have the following values.

TP6  +140V
TP8   +27V
TP9  +15V

BU508 is ok and I hear Flyback works but i have no image.
Normally in tp6 I have 145v, I don't know if I have to increase the voltage of the PS, or there is another problem that I can check.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 8:23am
140v is a little low but nothing important

have turned up the screen volts on the flyback and still no raster?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 8:46am
Originally posted by gunblade gunblade wrote:

140v is a little low but nothing important

have turned up the screen volts on the flyback and still no raster?


Yes, it was the first thing I did.
Is there any way to measure in the socket that the screen line is arriving correctly?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 8:57am
you can read the g2 with a hv probe/meter
do you have tube heaters?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 10:02am
Originally posted by gunblade gunblade wrote:

you can read the g2 with a hv probe/meter
do you have tube heaters?


I don't have a hv probe/meter.
I do not see light in the tube.
I tested r37 and c20 and seems ok.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 10:06am
there could be a lot of things causing this, is the horizontal drive transformer reading 27 ohms one side and around 1 ohm the other?
is the 2.2k load resistor on the side of the chassis reading ok?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2020 at 11:35am
Originally posted by gunblade gunblade wrote:

there could be a lot of things causing this, is the horizontal drive transformer reading 27 ohms one side and around 1 ohm the other?
is the 2.2k load resistor on the side of the chassis reading ok?


Yes, I checked, 2.2k resistor, is ok.

Drive transformer in another chassis that I fix its malfunction, it no longer allowed the PS to start and blocked the chassis in protection mode.
But I'm going to test it anyway.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 15 Sep 2020 at 4:55pm
Originally posted by gunblade gunblade wrote:

there could be a lot of things causing this, is the horizontal drive transformer reading 27 ohms one side and around 1 ohm the other?
is the 2.2k load resistor on the side of the chassis reading ok?


I finally found a burnt resistor here



But I still don't have an image.

Now, At pin 7 of the flyback there is voltage, about 127v

I checked the signal with oscilloscope in tp32 but I don't have a square signal


There has to be something else that messes up the signal, somewhere else where I could test?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2020 at 7:27am
could be a bad flyback
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2020 at 8:54am
Tomorrow I get a new one from efiter diemen, I'll try it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2020 at 9:00am
how is r240 looking?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2020 at 9:16am
Originally posted by gunblade gunblade wrote:

how is r240 looking?

r240 is ok.
In TP32 there is voltage one 27v but no square signal.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M K L Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2020 at 11:44am
It's the horizontal drive that you should check. Without that a good flyback will never work.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2020 at 7:08am
Originally posted by M K L M K L wrote:

It's the horizontal drive that you should check. Without that a good flyback will never work.


In the horizontal section, check with the bulb to the HOT collector that B + (138v) arrived correctly
The horizontal transistor and the transformer measured them and they are ok.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M K L Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2020 at 8:19am
It's the pulse signal that goes from pin 3 of IC104 and through T113, TH102, T114 to pin 1 of the flyback. All the parts and B+ can be good but if no pulse comes from pin 3 the flyback will not work.

Edited by M K L - 17 Sep 2020 at 8:20am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote justez Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2020 at 1:11pm
Originally posted by M K L M K L wrote:

It's the pulse signal that goes from pin 3 of IC104 and through T113, TH102, T114 to pin 1 of the flyback. All the parts and B+ can be good but if no pulse comes from pin 3 the flyback will not work.


Ok, I am going to check Tp23 and Tp27 with the oscilloscope and check the signal.
I have also purchased a high voltage test probe from Diemen.
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