Hantarex Polo 25 help needed

[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