Build Your Own Arcade Controls Forum

Main => Monitor/Video Forum => Topic started by: menace on October 23, 2005, 02:28:53 pm

Title: Need some input on hantarex Polo problem
Post by: menace on October 23, 2005, 02:28:53 pm

I posted this awhile back but that I would have another go at it.  here's the situation--when i power it on the screen  has retrace lines and makes a very rapid ticking sound for about 10-15 seconds (see picture 1)  (there is no game attached at this point)

Then the monitor switches into the second picture and from there it stays until powered down.  When you re-power the process repeats.  I have checked the tube and it reads as excellent with no shorts and good strength on the color guns.  I have also looked at randy fromm's chart but this lies somewhere in the middle of working and non.

Any thoughts?  Its a nice big 27" so I'm hoping to salvage it.

Title: Re: Need some input on hantarex Polo problem
Post by: Ken Layton on October 23, 2005, 07:02:35 pm

Has it been capkitted yet?

Have you measured the screen voltage? Typical screen voltages vary between 400 to 800 volts. It should change as you turn the screen control. If not then the flyback is shot.

Has the neckboard gotten wet? Is there moisture inside the tube socket on the neckboard?

Title: Re: Need some input on hantarex Polo problem
Post by: menace on October 24, 2005, 06:47:35 am

It has been cap kitted and the only voltage I have checked was at Tp6 which oddly enough goes from 136-138 V in picture one down to 126V in picture 2.  I will check the screen voltage but its a new flyback so I'm hoping to the arcade gawds that this isn't the problem.  I will also swap out the neckboard since yes it has been exposed to moisture (long time ago though) but if you're thinking there may be corrosion in there causing troubles then this is a definite possibility.

Title: Re: Need some input on hantarex Polo problem
Post by: menace on October 25, 2005, 07:49:39 pm

Ok checked the voltage at pin 7 (g2) and it read a solid 642VDC--i then adjusted the screen pot on the flyback and it varied by 20V or so.  Interesting thing is that with the DMM attached there wasn't  the tell tale fast click and it stayed looking like picture one--when the meter was disconnected it went to picture 2.  if i hooked the DMM back up it would return to picture 1.  Not sure what this tells me though. 

Title: Re: Need some input on hantarex Polo problem
Post by: Ken Layton on October 26, 2005, 01:38:28 am

When you turn the screen control all the way through it's range you should get a much greater voltage swing. I wonder if there's either a short in the tube or the tube socket?

Title: Re: Need some input on hantarex Polo problem
Post by: menace on October 26, 2005, 06:46:00 am

Thanks ken--I will check out the tube socket and neckboard and have a look there--all readings on the B&K 470 indicate its a good tube with no shorts.  Can you think of any situation where I would get a "false negative" from a rejuvenator?

Title: Re: Need some input on hantarex Polo problem
Post by: Ken Layton on October 26, 2005, 10:12:32 am

I'd double check for a possible open or way off value resistor on the neckboard as well as any shorted transistors.

Title: Re: Need some input on hantarex Polo problem
Post by: menace on October 27, 2005, 07:24:49 am

In hopes of narrowing down which section of the board i need to start pulling and checking parts from I did some voltage probing last night.  On the LM1203N I should have +12v at pins 1,13,23,28--I had 11.77V.

TP        should have                  did have
6                138                               127.6
8                  27                                 24.47
9                  15                                 13.65
10               12                                  11.78
7                  85(?)                              .23 (this one has got to be wrong)
3                                                       -50 (I measured DC--should this still be AC)
5                                                       -51.1(again measured in DC)
25                                                      5.57
26                                                      126

So I'm thinking I have a power supply problem based on the low B+  Any ideas on how to track it further?  I'm going to investigate that TP7 voltage and see what I read wrong on the schematics