Hantarex Polo 25, the B+ is way too high. :(

jehuie

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So I'm running through RF's flowchart to troubleshoot this thing and the B+ is still reading too high even though I followed it all the way to the end.

It reads 235 volts DC.

The steps I've done so far:
- Fuse F101 is not blown
- Monitor is not making a ticking noise
- Checked B+ and found it higher than 138 volts
- Replaced C114
- Checked B+ again and it's still too high. Chassis looks good, don't see any bad solder joints or cracks except one which has been repaired
- Measured at the collector of T114 and got the same as B+
- Checked voltage at IC104, pin 1 and got a big fat zero
- Replaced IC105, T108, R198 and tested D129 with basic diode test since I couldn't find one locally and it tested ok so I just put it back in.

That's the end...checked B+ and it's still at 235. Checked voltage at IC104 pin 1 again and still get a big fat zero there.

So....I will break out the schematics and pour over them. But was wondering if anyone has ever seen anything like this before and might have some tips as well.

Thanks!
 
Bump after 5 days.... :)

Or alternatively, does anyone out there know where I can get a dirt-cheap, clean, rebuildable chassis for this thing?
 
Replace both C112 and C114. Also after the +B is ok you might have a problem with the frame circuit.

Here are my repair logs

Hantarex Repair Logs

1. Monitor Power Supply output high and not regulating. C112 and C114 (22uf 50V Electrolytic Caps) replaced. This can also cause the Monitor to trip.
2. East –West not adjusting. Check D134 and D135 for leakage. Also check the Horizontal size adjustment as this also effects the E/W
3. Tripping (Ticking Sound). Scoped output of Line Output Transistor. Very small Square wave low volts pulses. Flyback faulty. In this condition R227 was getting extremely hot
4. Shading on side of screen and streaking on picture. Check R36
5. Not starting up. Check C181 (4.7uf 250v Cap)
6. Picture Shimmering, Ripples and line pulling, Check Caps on secondary of Power Supply. C123/C129/C166
7. Lines on top of picture. Power supply set too low
8. Tripping, Check Line output transistor. Remove Transistor and connect globe to power supply. If output Ok. Transistor could be leaky or Flyback is faulty
9. Power Supply oscillates with no load but does not run with a load. Check R111,R112,R113 (1.5Ohm Resistors)
10. Power Supply dead. Check D105
11. Picture severely distorted on sides. Check R250 6.8k Resistor (Open Circuit)
12. Power Supply dead. Check ZD101 18v Zener Between transformer and Fet heatsink
13. Can use IRF 840 for Chopper FET
14. No brightness control, R240 (180K resistor O/C)
15. Keeps tripping, Scan coil plug cold solder joints
16. Monitor comes on but frame collapse. Fusible frame IC supply resistor burnt and Frame IC blown. Power supply was not regulating. Replaced C112 and C114. replaced Frame IC and Resistor. Fitted cap kit
 
Replace both C112 and C114. Also after the +B is ok you might have a problem with the frame circuit.

Thank you kind sir for the tip. I replaced them and it still has a B+ of 179 rather than the expected 138. :(

In fact, I went ahead and ordered and installed a full cap kit.

Anyone else have ideas on what could cause the B+ to be so high?

BUMP, I'M STUMPED! :(
 
Maybe your missing Horizontal Drive current.
what ground are you using for your meter,the dc is real high..

Check those large watt resistors connections to pcb ,R218 are being used
to lower the voltage to the Horiz_drive transformer @TP27,voltage? Its just as important
to Hv is The Horiz-Output stage to work.check R227 is soldered in good.


Do you have your 15vs to Ic105 and No 12v's out?
You need 15vs at TP9 coming out of the powersupply.
All the other secondary voltages coming out of the smps are good to know
what they are running at too.check TP6,7,8
Did you test the powersupply yet with a incandescent bulb 95watt to sub the load?
If the dc volts drop to normal then the problem is not in the smps @ the B+ to cold ground.
Let us know what you find.
 
Maybe your missing Horizontal Drive current.
what ground are you using for your meter,the dc is real high..

Check those large watt resistors connections to pcb ,R218 are being used
to lower the voltage to the Horiz_drive transformer @TP27,voltage? Its just as important
to Hv is The Horiz-Output stage to work.check R227 is soldered in good.


Do you have your 15vs to Ic105 and No 12v's out?
You need 15vs at TP9 coming out of the powersupply.
All the other secondary voltages coming out of the smps are good to know
what they are running at too.check TP6,7,8
Did you test the powersupply yet with a incandescent bulb 95watt to sub the load?
If the dc volts drop to normal then the problem is not in the smps @ the B+ to cold ground.
Let us know what you find.

Thank you for the help kind sir. I followed your sage advice to the extent that I was able. I checked that both of those big resistors is good and re-soldered them to the board and tried it again with the same result.

I checked the voltage at TP9 and got a solid 15v. Checked TP8 and got 27.9. Is that good? I checked TP6 and TP7 and got a goose egg. Nada. Nothing at all. I'm assuming I was looking for DC, correct? What does that indicate?

As for the lightbulb trick....I don't follow what I'm supposed to do there.

Any more tips before I give up and buy a rebuilt chassis for this beast?

Thanks again!
 
antarex

Heres a out of focus picture of the jumpers or test points.
Thats where the bulb would go on right side
of the black coil and the other wire from the bulb would go to ground.
To confirm the smps is working correctly.Odds are the problem is outside
the powersupply,because some of your secondary voltages are correct.

That should be TP6 the 145v line Or B+
Confirm all the supply voltages are there like TP7 if not check r130 for open.
You need 12vs coming from Ic105 the 12v regulator to the drive ic also.

If you can get good chassis do it or repair the one you have.
They all need to be rebuilt sooner or later.
Check your PM for more details about repair.
Good Luck!
 

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Thanks again. I checked the test point (I think it was TP10) next to the VR and it wasn't getting any voltage out. The voltage in was 15v though so I thought perhaps the regulator was bad. But then I remembered I had already changed that out with a new one. So I went and bought another one just in case and swapped it in. In doing so, I noticed a bad trace leading up to the VR so I repaired that.

Put it all back together and, unfortunately, i'm still not getting the 12v out. So....I'm guessing I have another bad trace/connection along in there somewhere. I had to get up early to try this since this whole weekend has been crammed and busy. Now it looks like I won't be able to look at it again until tonight at the earliest.

Could the missing +12 actually cause the high B+?

But...thanks again for the tips!
 
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Missing 12v's

Yes,
If the traces are good. And you have a good 12v ic.
Check the ohms on the output of the 12v Ic to ground.
C166 needs to be good. A short can be on the output side
to ground a suspect would be d401 on the control board or the
Tda2593 the way to check is remove the solder from pin 1
and see if the 12vs comes up, any component tied in with the 12v line
would be a suspect,lifting a part one at a time to see if the 12vs shows up.
Another way would be apply external 12vs to 12v line. for TS only
to check Ic and other parts using the 12vs.
Some more things to check when you get time.
 
Thank you for all your help. I made some good progress but this game has moved along to someone else. It is now Paul Olson's problem. :)

Good luck paul!
 
Thank you for all your help. I made some good progress but this game has moved along to someone else. It is now Paul Olson's problem. :)

Good luck paul!

Thanks. Now that the Pinbot is working, I am going to try to start on this tomorrow night.


Ohmerone, thanks for all of the pre purchase help. :)
 
I'm going through the exact same symptoms right now, Hantarex Polo, the 7812 at IC105 is getting 15 volts in but outputting 0. Swapping the regulator doesn't fix it, so like Ohmerone is saying something on the output must be bogging it down. I'm getting like 600 ohms resistance between the output and ground so I think whatever it is, is probably failing under load. I'm swapping IC104 first to rule that out, then I'll start disabling other things :)
 
I'm going through the exact same symptoms right now, Hantarex Polo, the 7812 at IC105 is getting 15 volts in but outputting 0. Swapping the regulator doesn't fix it, so like Ohmerone is saying something on the output must be bogging it down. I'm getting like 600 ohms resistance between the output and ground so I think whatever it is, is probably failing under load. I'm swapping IC104 first to rule that out, then I'll start disabling other things :)

Need to measure the ohms between the 12 v out pin to

It's ground pin. What's the ohms?

Or is the 600 ohms on the trace only


The 12 goes to the ic 104. Just remove the ic

And if the 12 vs go up then the ic is at fault

Otherwise check d401 on remote board.

Luk
 
Alright, figured it out. I was plugging the damn ground wire from the frame into the pin on the front of the chassis, that pin is directly connected to the 12 volt. So no matter how many times I disconnected things and checked it out of the frame, nothing was shorted, there was 600ohms or so of resistance between the 12v line and the ground line going into that IC105.

The ground line plugs into the neck board up right by the bottom of the socket. Plugging it in where it goes I now have my 12 volts I need.... but now my flyback is bad so I'm swapping that to see what's next :)

If you don't measure 12 volts at TP10 make sure you don't have the ground wire plugged into J117 on the front of the chassis that is connected directly to 12 volt!

Edit: Swapped in a new flyback and now i'm up and running.
 
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