Hantarex Polo 25 help needed

[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