Hantarex Polo 25" monitor/ Dead, Dead, Dead

[Hawkypro]

It seems that the  protection circuit has kicked in. B+ measures 190V DC and i know this is to high, it should be about 138V DC. The heater in the tube does not glow either and i dont here any squeal or static when turned on. I did the capkit replacement as well as replacing the flyback. The PSU section is working, TP8- 28VDC and TP9- 17VDC. Im still green when it comes to chassis repair, so anyone who can get me started raising this from the dead would be great. this is my first post -- Hello to all.

Hawkypro

[grantspain]

what about the horizontal output transistor?

[Hawkypro]

grantspain,

The H.O.T.  tests good. I get a high resistance when i check the H.O.T. . That would mean it is a good H.O.T.  Right?

Thanks,
Hawkypro

[Hawkypro]

The H.O.T. - I get .45 at the collector and emitter with the red lead connected to the base.

Hawkypro

[grantspain]

are you getting a ticking sound or just dead?
there is a diode on the psu transx that blows,i will check tomorrow the component position number

[SirPeale]

DON'T check for resistance.  Check for the junction drop.

Also check the bridge.

[D_Zoot]

are you getting a ticking sound or just dead?
there is a diode on the psu transx that blows,i will check tomorrow the component position number

ZD101 is a failure I've seen a couple of times on these.  I remember it well, the first one I ran into kicked my --I'm attempting to get by the auto-censor and should be beaten after I re-read the rules-- for a while, until I finally figured it out.



D

[Hawkypro]

Hey guys,

the .45 drop is volts no ohms (my goof) and zd101 has been replaced. and no ticking sound just dead.

Thanks,
Hawkypro

[grantspain]

test points
tp6 +145v
tp8 +27v
tp7 +85v
tp9 +15v
check these first they are the outputs of the power supply transformer

[Hawkypro]

grantspain ,

I will check these and give you the results ASAP. Thanks for your help. I really want to repair this chassis myself, with the help from people like you and others on this Fourm im sure that will be possible.

Thanks,
Hawkypro

[grantspain]

just a little more info,i know you changed some caps but the ones that are very important are c114,c125,c123,c121,c111,c112 these are the caps in the psu section.other things to check are d116,d117,d118,d119
the h.o.t(bu508af) read using ohms from the ground to the centre pin for dead short

[Hawkypro]

grantspain,

Replaced all of those caps with a new cap kit.
Tested diodes 116,117,118,119 all test good
Test point - tp6 198v, tp7 0v, tp8 28v, tp9 17v
H.O.T - 1.032 M ohms. ( I did not test this out of circuit and the power was off. am i supposed to test out of circuit?) I tested the HOT by grounding the black meter probe and red meter probe to the center pin. Thats the story so far.

Thanks,
Hawkypro

[grantspain]

tp7 should read 85volts,check r130 it should be 3.9ohms
i don't like the reading of the h.o.t,i tend to remove them from circuit first because you can be reading one or two other components

[Hawkypro]

grantspain,

R130 - 4.3 ohms. I took the HOT out of circuit, but not sure what readings im looking for and am i testing it like a transistor or am i just looking for an ohms reading at the collector.

Thanks,
Hawkypro

[grantspain]

read it as a standard transistor,you should have no dead shorts

[Hawkypro]

grantspain,

Old HOT Reads as follows B to E .52v,  1.7M ohms
                                         B to C .47v,  .932M ohms

New HOT reads as follows B to E .52v, 3.46M ohms
                                          B to C .52v, 2.55M ohms

These tests were done out of circuit.

Hawkypro

[grantspain]

i don't recognise those readings,so you have changed the h.o.t yes?and you are using a bu508af or other?

[Hawkypro]

grantspain,

Yes,  I did replace the HOT with a new one.

Hawkypro

[grantspain]

o.k couple of other things,if your new h.o.t has a metal back you need the insulation sheet behind it,if its total plastic package then don't worry.obviously you need to put new heat conductive grease between the h.o.t and the metal plate to which it clips
i have had on occasion broken track or through holes around the large resistors on the outside right of the chassis so that is worth checking
if its a case of the h.o.t blowing all the time then you will need to check c172,c174,d134 and d135

[Hawkypro]

grantspain,

Yes, the insulation sheet is behind the HOT. Also, i will check the the other stuff you have suggested and get back to you with the results.

Thanks again,
Hawkypro

[Hawkypro]

grantspain,

checked c172, c174 - but not sure what measurement you want.
D134, d135 are good.

Hawkypro

[Jess--]

just a quickie

when I replaced the flyback on my hantarex it showed short straight from the HOT to gnd, turned out they changed the pinout on the flyback, so I had to leave one pin disconnected.

check the specs on your flyback (old and new)

[Hawkypro]

Jess-- ,

The flyback is good for the pin out.

Thanks,

Hawkypro

[grantspain]

one last thought,did you make sure you got the correct wires from the flyback to the correct terminals on the neck card as many replacement flybacks have different colour wires to the original

[Hawkypro]

grantspain,

okay, now im confused, there are only two leads from the flyback: Red is the anode which connects to the monitor, and black which connects to the neck board. Or are you talking about the other wires to the neck board from the chassis. These were never removed from the neck board or chassis.

Hawkypro

[grantspain]

you should have red anode cap and two other wires(focus and g2) on the flyback unless i have gone mad
black should go to the neck socket push in connector and red should go to the neck card(position w1)

[Hawkypro]

grantspain,

Sorry for the long delay in my reply. Yes, I do have a red anode cap and two other wires (focus and g2).

Hawkypro