Hantarex Polo 25 help needed

[jeff412]

Does anyone know where the test points are on the Polo and what the voltages should be at each test point?  I have a Polo with no neck glow and I've recapped it, replaced the flyback and HOT.  Any help would be greatly appreciated.

Jeff

[smartbomb2084]

Check Test Point 6.  This is the B+ voltage and should be 138 volts.
Also is the monitor making a 'ticking' sound?

[jeff412]

No, there is no ticking.  Can you give me an idea of where TP6 is?  I don't see it on the board.

Jeff

[grantspain]

check the voltage at R227,use frame as ground/set meter to dc volts 200v range/be careful

[jeff412]

Thanks,  I'll check it out tonight.

Jeff

[Karetaker]

No, there is no ticking.  Can you give me an idea of where TP6 is?  I don't see it on the board.

Jeff

About dead center at the very front of the board (front meaning closest to the tube). It's a jumper wire.

[arcadecup.com]

or check b+ on the middle wire of the yoke .. the jumper wire.. do not measure the yoke voltage or you will tickle your meter to death.
watch out for open traces.. mostly on the flyback pads.. they like to lift as the traces on this board are not th best.. cracks very easilty also in this area.

[jeff412]

At TP6 I measure 10 to 20 Volts and it bounces around all over the place.  The monitor is still in the cabinet and I can't get to the yoke very easily. But with nothing at TP 6 I assume I have nothing at the yoke either. Any ideas?  


Jeff

[smartbomb2084]

Unsolder and lift the deflection side of L103 ( near TP6 ) and connect a standard incandescent light bulb between it and chassis ground then power up the monitor.  If the bulb blinks you have a power supply problem.  If it is lit bright and steady you have a deflection problem.  Also, check the large color transisitors on the neck board, if one is shorted this monitor won't power up.

[jeff412]

Ok  I'll give it a shot.  I'll try here in a few minutes and see what it looks like.

Jeff

[jeff412]

I didn't have an incandesscent socket, so I'll have to try that later.  I tested all of the transistors on the neck board they appear to be good.  I did make a mistake before when I tested the voltage at TP6.  I had failed to plug in the yoke connector.  After plugging that in, I get 0 V at TP6.

Jeff

[jeff412]

or check b+ on the middle wire of the yoke .. the jumper wire.. do not measure the yoke voltage or you will tickle your meter to death.
watch out for open traces.. mostly on the flyback pads.. they like to lift as the traces on this board are not th best.. cracks very easilty also in this area.

I checked for open traces and I didn't see any.  The board is actually in very good condition.  I checked closely around the flyback and everything looks good.

Jeff

[smartbomb2084]

You don't have an  incandescant worklight?  Borrow the lamp from the living room end table and use alligator clipped jumper wires to connect the AC wall plug to the monitor.  Until you do this test you will likely just keep chasing your tail.

[jeff412]

Nope, no incandescent work light.  I'll pick one up tonight. They're cheap. What does the bulb do that a volt meter won't?  Should I not be able to do the same thing with a volt meter and lifting the leg of L103? Unless you are saying that the volt meter is just too slow to register the fluctuations.  Just curious.

Jeff

[smartbomb2084]

POLO monitors have a switching power supply and it needs an unshorted load to run properly.  A simple 60 watt light bulb works nicely to provide this load. If the light stays lit the power supply is good and a shorted component on the deflection side is causing the power supply to shut down. If the bulb blinks the power supply is at fault.  By performing this test we can narrow down our proplem to one side of the monitor or the other.

[jeff412]

Thanks for the explanation.  That makes sense.  I'll test it tonight.

Jeff

[jeff412]

I completed the test with the 60 W incandescent bulb.  The bulb did nothing.  I guess that means a power supply issue?

Jeff

[smartbomb2084]

You are sure it is hooked up correctly?  If that bulb doesn't light, then the monitor won't either. Lift the DEFLECTION end of L103 completeletly from the board so it is sticking up into the air. Hook one end of the bulb here and the other end to CHASSIS ground.

[smartbomb2084]

If you have no power supply switching activity then T101 and IC101, in that order, are suspect.

[jeff412]

Yes I'm sure I connected it correctly.  I did lift one leg of l103 right next to tp6.  Connected one alligator clip to l 103 and the other to ground.

[smartbomb2084]

Measure the voltage at the banded end of D101 and use the UNbanded end of D103 as ground-----BE CAREFUL.

[jeff412]

I pulled T101 and it tests open between pins 1 and 3.  Yes I tested both directions.  Are there any other parts I should test before ordering?

Jeff

[jeff412]

Since I know T101 is bad, do I need to do the voltage test between D101 and D103? 

Jeff

[smartbomb2084]

T101 is a MOSFET not a Bipolar and is tested differently.  Check out this link   http://www.utm.edu/staff/leeb/mostest.htm

[jeff412]

based on that test t 101 appears to be good

Jeff

[smartbomb2084]

Back to D101/D103.  We need to check for a source voltage to switch on an off.  T101 doesn't even need to be installed for this test. While you are at it check the voltage at the unbanded end of D105 (TP2).

[jeff412]

I have no voltage between D101 and D103.  I have 131 V AC on the negative side of D105.

Jeff

[smartbomb2084]

You should have DC VOLTAGE.  D101 banded end positve meter lead.  D103 UNbanded end negative meter lead, If your meter is not AUTORANGING you must set it for 500 volts DC not 200. If I remember correctly this should measure around 300 volts.  Again----BE CAREFUL.

For D105 positve meter lead Unbanded end.  Negative meter lead leave on the UNbanded end of D103 as above.

If you still have 0 volts DC R103 may be open. It is a disc shaped pinkish colored resistor connected to D101/D103 and  should be 10 Ohms.

On a side note, keep using the light bulb as a load until the power supply is good.

[jeff412]

I tested on 200.  I didn't realize I was looking for 500.  I'll test again.

Jeff

[jeff412]

D101 and 103 still have no voltage.  I measured across the pink resister and got 12 ohms in the circuit.  Do I need to remove it to test it?  Also, I noted that the heat sink for t101 has 131 volts ac on it.  Found that one the hard way.  Is that correct?

Jeff

[smartbomb2084]

The heatsink for T101 is connected to primary (power supply) ground.  I have to check on why you are getting shocked from it.  Hopefully some other memebers have a take on that one because I am not sure.

You are going to have to follow the power path from AC Line In up to D105.

My time for today is up as I will be gone from now until early tomorrow evening.

Good Luck and try not to get electrocuted.

[jeff412]

I greatly appreciate your help.  This is going to be an awesome troubleshooting thread if we can get it fixed.  I will see if I can find the cause of the ac on the heat sink.

Jeff

[grantspain]

t101 should have an insulation sheet between it and the heat shield

[jeff412]

It does.  I have the connector hooked up wrong.  I have to back up and regroup.

Jeff

[jeff412]

Ok.  Here's the deal.   As much as I hate to admit it.  I screwed up.  Somehow I ended up connecting the hot leg to the center pin of the 3 pin connector instead of ground.  That is why I was getting 131 V on the heat sink.  I now have it connected properly.  This monitor wasn't working before in another cabinet, so I know that wasn't my issue.  Hopefully I didn't toast something else because of this error.  After reconnecting it properly, I now have 171 V DC at TP6 and 338 V DC between D101 and D103.  Where should I go from here?

Jeff

[smartbomb2084]

I found out that you should not have AC on the heatsink of T101.  I measured for voltage on it saturday and found none.  Then I bravely (read foolishly) touched it with my bare hand and... nothing.  So I am glad you found the cause. One thing about working on monitors is that mistakes generally are not tolerated.

We need to  redo the light bulb test with the deflection end of L103 lifted.  We still have not officially narrowed the problem down to the power supply or the deflection circuits.  171 volts at TP6 is high,  it should be about 138 volts.

[jeff412]

The light bulb stays lit with L103 lifted.

Jeff

[smartbomb2084]

Excellent.  One step closer.  What did we learn?  Has the monitor been powered up completely assembled since our bulb has been burning bright?

[jeff412]

Yes.   It is currently fully assembled.  I am reading 171 V at TP6 with it assembled.

Jeff

[smartbomb2084]

I assume you have the drawings for this monitor. Have you checked for all the other power supply voltages at their test points as shown in the power supply drawing.  Are you sure the HOT is good?

[jeff412]

No I haven't checked but I will.  The hot appears to be good.   It doesn't say bu508a on it.  The one that I believe is the hot has 9440 on it.
Jeff

[smartbomb2084]

That number just doesn't sound good to me for the HOT. I would like to see us have an actual bu508a. Take it out and test it.  I don't think its shorted but if you get a meter reading with a zero as a first digit using any direction and any polarity then the transistor is junk.

[jeff412]

I removed it and tested it and it appears to be good

[smartbomb2084]

Do you still have 171 volts at TP6 with T114 removed?

[jeff412]

I will check.  I have a Bu508a here.  Should I go ahead and install it?

Jeff

[smartbomb2084]

Absolutely

[jeff412]

After closer inspection, the hot was a BU508af.  It just wasn't very visible.  The 9440 was silkscreened below the Bu508af lettering.  With the hot removed I am getting 176.5 V at TP6.

Jeff

[jeff412]

With the new HOT installed I am getting 175 V DC at TP6.

Jeff

[smartbomb2084]

We still need to check the other power upply voltages.  This 175 volts you are getting is a solid steady reading?  If there was a short somewhere why doesn't the power supply shut down?   Maybe our little wiring mishap has had some effect. Reinstall the HOT and hook the light bulb up to L103 while it is still fully connected to the board. That's all I have for now. If the power supply isn't shutting down then there must be some other lower power circuit causing a problem. It is hard to say sometimes when you aren't there in person.

[jeff412]

The voltage at TP6 fluctuates slightly, but ony a couple volts.  It moves between 174 and 176.  With L103 in the circuit and the bulb connected, the bulb doesn't burn and I get the ticking sound.  I assume that is the PS shutting down?

Jeff

[jeff412]

Thanks for the help.

Jeff

[jeff412]

The voltage at TP6 fluctuates slightly, but ony a couple volts.  It moves between 174 and 176.  With L103 in the circuit and the bulb connected, the bulb doesn't burn and I get the ticking sound.  I assume that is the PS shutting down? 

Jeff

edit 4/26/2010:  Afte thinking about this a little while, it is possible that the my clip was touching the frame when it was connected to L103.  I will redo the test tonight.

[smartbomb2084]

That makes sense because the bulb should have blinked with the ticking of the PS. Check to see that you have 138 volts at L103 with it out of circuit and just the light bulb connected.  Don't forget to check the other PS voltages.  I will see what we can find out during the course of the day and post back later on.

[smartbomb2084]

I dug out an old POLO chassis from a couple of years back that I became frustrated with because I was unable to get it going.  On this monitor I have 205 volts at TP6.  When L103 is lifted and the light bulb hooked to it I have a sweet 140 volts form the PS.  When you first power it up you can hear the familiar 'spit' sound that the monitor makes when charging up the tube but then nothing.  I figure the x-ray protection cicuit is shutting it down. Hopefully I will get some time today to work on it and get even more frustrated.

How are you making out with yours?

[jeff412]

Had Scouts last night with my boy.  I wasn't able to work on it.  I have a board meeting at work tonight, but I should be home early enough to do a little testing.

Jeff

[grantspain]

i will be working a a couple of polo chassis this week,one is polo 1 and the other polo 2-the polo 2 is blowing the HOT constantly whilst the polo 1 remains in trip but i know the HOT is fine.
I will post up what i find if it helps-got a feeling the flyback is the problem on the polo 1 and one of the high voltage caps is causing the HOT to blow on the polo 2

[jeff412]

I'm finally in from work.  I went out to the shop and lifted one leg of L103.  With the bulb connected and shining constantly I am measuring 132 V DC.    I just wanted to post these results.  I am going to go test the other PS test points. 

Jeff

[jeff412]

At the unbanded end of D105 (TP2) I am getting overvoltage on my meter with it set to 600V. 

Jeff

[jeff412]

The schematic I have for the Polo shows waveforms for tp2 tp3 tp21 tp23 tp27 tp29 tp32 tp35 tp36 tp37 tp38 and r32/33/34.  I don't have an O-scope, so I can't verify these waveforms.  My meter doesn't want to give me any good data either.  Are these the test points I should be testing and if so, what should I expect to get at each one?  I can bring an O-scope home from work tomorrow if that is necessary.

Jeff

[jeff412]

I think I found the test points you were referring to.  All of these are tested with one leg of L103 pulled and the light bulb for load.

TP6:  132-134 V
TP7:  79.9 V
TP8:  26 V
TP9:  16 V

Is L106 supposed to look like a resistor?

Jeff

[jeff412]

i will be working a a couple of polo chassis this week,one is polo 1 and the other polo 2-the polo 2 is blowing the HOT constantly whilst the polo 1 remains in trip but i know the HOT is fine.
I will post up what i find if it helps-got a feeling the flyback is the problem on the polo 1 and one of the high voltage caps is causing the HOT to blow on the polo 2

Any and all help would be greatly appreciated.

Jeff

[smartbomb2084]

Yes TP6-7-8-9 were the PS test points I was referring to. Yours are a little low but should be well enough in range. You can adjust the B+ using RV101 which will affect all of these voltages simultaneously. I suppose using an O-scope is the way to go.  If you know how to use one why do you need help from the forum?

I assume you have checked all the obvious diodes and transisitors in the deflection circuit like T113-T117-T118 for example.  R219, the large 7W standup resisitor on the edge of the board is easily broken loose from handling. If you have recapped this monitor already be sure there are no solder splashes or broken traces around your cap replacements.

I managed to get mine lit yesterday C14 on the neck board was bad. I don't know why I didn't catch that before when I worked on it but back then I didn't have my trusty BK PRECISION CAPANALYZER 881. Although It is lit I still have no video and so far all I know is that I have 11.5 volts at IC401.

The adventure continues...

[jeff412]

I do know how to use an O-scope, but I am new to monitors.  The one I have at work is typically used for our microwave radio system.

I have tested all of the diodes in the circuit and they appear to be good, but I really need to lift one end and test them that way.  R219 seems to be good.  I will test T113-T118 as you suggested and see how those look.

I have recapped the monitor and everything looks good there.

If the voltage at TP6 is high, does that indicate a short somewhere in the deflection circuit?

Jeff

[jeff412]

I managed to get mine lit yesterday C14 on the neck board was bad. I don't know why I didn't catch that before when I worked on it but back then I didn't have my trusty BK PRECISION CAPANALYZER 881. Although It is lit I still have no video and so far all I know is that I have 11.5 volts at IC401.

The adventure continues...

How does the capanalyzer work?  Do you remove the cap and test it or does it magically test them in the circuit?

[jeff412]

Is there anything special about T118 or T117?  With T118 I get a reading between all legs and all combinations.  Pretty certain it's bad.  With T117 I show it open between the outside legs.  I assume it's a BJT and not a MOSFET?   T113 looks to be good.  And I have a 10 ohm resister in L106 instead of a coil.  Is that correct?

Jeff

[smartbomb2084]

I wouldn't say that T118 is 'special' but it is necessary.  Sounds llike you may be on to something here. I wish I could say for sure.  On T118  I read on 'open' between the BASE (neg lead) and the EMITTER (Pos lead) in circuit on the board I have.  Did you test this BDX 53A out of circuit?

L106 is an inductor even though it resembles a resistor.  Some inductors are color coded like resistors.

[jeff412]

I did test the BDX53A out of the circuit as well as the c558B. I've attached a pic of the L106.  Perhaps it is a coil, but I wouldn't have guessed it.  It does kinda have a funny shape.

Jeff

[smartbomb2084]

Yes it IS an inductor.  The very same one is on both boards I have.  So it sounds as if T118 (BDX 53A) is toast?

The Capanalyzer checks the caps 'magically' in circuit --- for the most part.  I have had to remove one here and there to get a true reading.      http://www.mcmelectronics.com/product/B-K-PRECISION-881-/73-1000

[jeff412]

Yes it IS an inductor.  The very same one is on both boards I have.  So it sounds as if T118 (BDX 53A) is toast?

The Capanalyzer checks the caps 'magically' in circuit --- for the most part.  I have had to remove one here and there to get a true reading.      http://www.mcmelectronics.com/product/B-K-PRECISION-881-/73-1000

Great!  More stuff to buy.  The wife will be very happy.

[jeff412]

Is there anything else that could be bad due to the bad T118 and T117?

[smartbomb2084]

I would check the resistors in the circuit near T118 like R250, R251, and R253. Anything is possible.

[jeff412]

Off to Mouser I go.  Hopefully this thing will be up and going soon.  Thanks for all of the great help.


Jeff

[smartbomb2084]

I'd like to see this thing lit before we open the champagne.  BDX 53A may be hard to find.  You will probably end up using an NTE cross.

Good luck and keep us posted.

[jeff412]

I think Mouser has it.  They have a BDX53ATU that the datasheet shows to be a BDX53A.  Do you know if the TU means anything?

Jeff

[smartbomb2084]

Don't know what it means.  If MOUSER's data sheet says it will work we can trust it.

[jeff412]

Ordered it this morning.  Going to pick up the champaign after work.

Jeff

[jeff412]

Parts are "Out for Delivery".  Hopefully I will have it up an running tonight. 

[jeff412]

Got the transistors installed today.  No Glory   I poured out the champaign and just turned it off and walked away.  I'll try to get back out there tonight and do some more testing.

Jeff

[smartbomb2084]

That is unfortunate.  I didn't even get a sip of my champagne.

Is there any change?  Do you even get the slightest static charged 'spit' sound when you first turn it on?  Did you test the new BDX53A against the original one before it was installed to be sure it is bad?

How does R167, R255, and T119 test?  Is pin one of IC 103 shorted to ground?

[jeff412]

No I didn't test the BDX53A, but I bought 5 of them in anticipation of failure.  I had no indication of improvement at all.  I'll get started testing again as soon as I play a game of chess with my son.

Jef

[jeff412]

Chess lasted too long.  I'll have to work on it tomorrow.

Jeff

[jeff412]

I tested R167 and R255 and T119.  They are good.  Pin 1 of IC103 is not shorted to ground.  I began checking everything and in the process found that I had a bad solder joint on the center leg of the HOT.  I removed it and tested it.  IT was still good.  I resoldered and tested the chassis.  Now I am getting PS shutdown with everything connected. (Tick Tick).  I'm very frustrated with this thing.  Any more suggestions?

Jeff

[smartbomb2084]

Sorry for the late reply but I've been busy with MEGATOUCH woes and haven't had much computer time.

I think I once read on this forum that the HANTAREX POLO was the easiest monitor to work on.  I think the truth is the exact opposite.  I lost the high voltage on the monitor I'm working on and now I have the dreaded "Tick Tick'  too. Like you I have tested and changed various parts and still have not found the problem.  POLO must mean frustration in Italian.

The bulb test proved your PS to be good and the 'Tick Tick' is definitely a short some where or a broken trace in the high voltage section.  Sometimes when we take the 'shotgun approach' and change all the caps and the flyback we actually create more problems than we had when we started. You see lots of posts here on the forum about how a working monitor was recapped and now has problems.  I am not questioning your soldering skills but changing 20 or so parts before doing any troubleshooting isn't always the best idea.

You said you have tested "everything" and still not found the problem.  Does this include D118, D119, D134,and D135?  Check if C172, C174, and C175 are shorted.  Thanks to the Arcade Repair God's flowchart for those last suggestions.


I am as stumped as you are at this point.  I'll bet there are people lurking out there who could help us.  ANYBODY?

[jeff412]

I don't know where I am either.  I am going to start over.  I tested everything with them installed in the circuit, just looking for shorts.  I have pull a few diodes and tested them, not all.  I haven't tested the caps,  but I did go back and verify they were all installed in the right direction.  I have replaced the flyback and caps, HOT, bdx53a, bc558B,  I have resoldered everything that even hinted at a poor solder joint whether I soldered it or not.


Jeff

[grantspain]

i told you earlier where to test the B+,this most likely a flyback problem or shorted high voltage cap

[jeff412]

Ok.  I'll try to get in there.  I guess I could pull the monitor and do it that way.  My meter isn't fast enough to see the voltage changes since the PS is going into shutdown.  Do you have any suggestions on how to prevent shutdown long enough to test B+ or am I just looking for any voltage at the jumper on the yoke?

Jeff

[grantspain]

you have to desolder pins 1 and 3 so that they are completely seperated from the trace,then with the lightbulb connected you have a stable b+

[jeff412]

Are you referring to pins 1 and 3 on the connector that goes to the yoke?    Then where do I connect the bulb?  Between the jumper and ground?

Jeff

[grantspain]

Are you referring to pins 1 and 3 on the connector that goes to the yoke?    Then where do I connect the bulb?  Between the jumper and ground?

Jeff

no,pins 1 and 3 of the flyback transformer
connect the bulb to frame and resistor 227(flyback side)

[jeff412]

Ok.  Will do.  I'll try it tonight.

Jeff

[smartbomb2084]

Does this flyback bulb test between pins 1 and 3 test just the primary side of the flyback or does it prove the secondary side bad somehow too?

[jeff412]

With pin 1 and 3 desoldered and verified with continuity test, I am still getting PS shutdown.  I went back and lifted one leg of L103 again and I the ps doesn't shut down.  I guess this means that my problem is somewhere between L103 and the primary coil of the flyback?

Jeff 

[jeff412]

Looks like the only thing it could be is a bad C168.  I've tested and it doesn't appear to be bad, but maybe it's shorting out after it gets high voltage on it.  The largest 100uf I have is 200V.  Since the voltage is only 138V on that line do you think it would be ok to put in the 200V to test?

Jeff

[smartbomb2084]

I would try it. It should be okay for testing purposes but I don't think it is your problem.

Sorry.

[jeff412]

What do you think it is? The only components between l103 and the flyback are r227 and c168,  unless I missed something.  The cap is new so I would expect it to be good.  R227 tests good as well.  There are no shorts to ground on that circuit either.  


edit:  never mind.  I see that it goes through the jumper on the yoke

[jeff412]

Looking at the schematic, it looks like I can eliminate everything around the HOT by lifting R219.  Is that correct?  I have a question about the schematic though.  Near the right side of the schematic is W101.  Does that go into the Video amplifier circuit anywhere?  Does that go anywhere?

Jeff

[smartbomb2084]

If you lift R219, you would still have to lift R228 and L109, then the PS probably won't run because of no load.  W101 doesn't go to the neck board directly but the B+ does go to R240 and R239 and then to G1 of the picture tube.

[jeff412]

I stuck.  I don't know where to go from here.

Jeff

[jeff412]

I'm starting over yet again.   The BU508A that I installed had a metal tab, so it was shorting to the heat sink.  I reinstalled the original one, which I believe to be good, and I'm still getting PS shutdown.  I wasn't getting PS shutdown before I installed the HOT.  I probably toasted something with the shorted base.  I will desolder pins 1 and 3 of the flyback again tomorrow and see if I can get a good B+ on the yoke jumper.

Jeff

[grantspain]

if you are willing to wait until next friday then I will confirm that the load on pins 1 and 3 proves the deflection and power supply is fine and the fault lies with the flyback transformer-i will be fixing one with an almost identical issue

if you want to prove the bu508a then compare readings of each out of circuit

[jeff412]

I don't mind waiting.  I have desoldered pins 1 and 3 and I am still getting PS shutdown.  The two hots measure the same out of the circuit.

[grantspain]

well if you have desoldered the pins so they do not touch then most likely the fault is on deflection circuit
look at d134,d135

[jeff412]

OK I'll check it out.  At the zoo with the kids right now. I'll test when I get home.

[jeff412]

D134 and D135 are good.  I also removed R219 and tested it and it is good.

Jeff

[grantspain]

just to let you know the chassis i was working on,which shows good b+ with flyback isolated(pins 1 and 3 desoldered) is indeed the flyback at fault-unfortunately I have been sent a polo 2 auto flyback and not a polo 1 flyback-it works but you get no control over brightness and the vertical scan is too low

[jeff412]

I've just about given up.  I had a U2000 sitting on a shelf and have decided to get it going instead of the Polo.  If you have any more suggestions, I'd love to get it going.

Jeff

[grantspain]

a photo of the pins you have desoldered on the flyback please,with the flyback out of circuit and a load from chassis ground to r 227 there is no reason for ps shutdown

[jeff412]

Ok.  I'll do that this evening.

Jeff