Author Topic: Hantarex polo - what happens when you turn the xray pot? (Read 11746 times)

crash41301 · « **Reply #40 on:** March 04, 2012, 02:50:31 pm »

I have
C177 = 47uf 250v
C14 = 4.7uf 250v

Both are new capacitors from a cap kit. I've tried swapping C177 out with another brand new 47uf 250v with no change. I suppose I could try swapping out C14 with another brand new one?

grantspain · « **Reply #41 on:** March 04, 2012, 02:58:11 pm »

i doubt you would have new faulty caps
whats the b+ measure at tp6?

crash41301 · « **Reply #42 on:** March 04, 2012, 06:13:55 pm »

131vDC @ tp6

grantspain · « **Reply #43 on:** March 04, 2012, 06:20:06 pm »

Quote from: crash41301 on March 04, 2012, 06:13:55 pm

131vDC @ tp6

its a touch low,should be 138vdc,adjusted by rv101 in the power supply section

has r234 blown again btw?

crash41301 · « **Reply #44 on:** March 04, 2012, 08:31:43 pm »

So I did some experimenting the last couple of hours.

When I hooked R40 back up, R234 blew again. I then removed all three RGB capacitors (R22, R25, R28) and transistors (T2, T4, T6) from the circuit. The only thing left hooked up was C14. I figured I would start adding stuff back in until R234 blew again and that would be my problematic component. I went ahead and powered the monitor back up just to have a base start knowing that power had returned to R40. *poof*. R234 blew again. ARGH! So, yet another R234 installed (Glad I bought 5 of these guys) and I lifted a leg on R40. Installed and powered up the monitor. ~175vDC at R40, then after a couple of seconds it dropped to ~130vDC. Ok, I'm at least back to what I had before.

Hmmm I thought to myself, the only thing in circuit after R40 is C14 and its brand new. I tested R40, its still holding good at 10.4ohm.(Schematic says 10.5, close enough) So I removed C14 from circuit, put R40 back in circuit, installed the chassis and powered up the monitor. There is literally nothing after R40 now since C14, R22, R25 and R28 all are removed. R234 survives and R40 has the same repeating pattern of 175vDC then a drop to 135vDC.

Is C14 grounding out or something? I whip out the multimeter and do a beep test for continuity on C14. It beeps between the legs. For comparison I pulled out some other capacitors and they do not beep between the legs. It appears that my BRAND NEW C14 is bad? Perhaps this is what killed my monitor after the cap install and the xray prot had nothing to do with it? I'm going to pick up a new 4.7uf 250v cap tomorrow (assuming the local electronics shop carries them anyway) and give it a try.

grantspain · « **Reply #45 on:** March 05, 2012, 02:44:02 am »

when you install the new cap lift one side of the following resistors
r32,r33,r34
then read the +200v

MonMotha · « **Reply #46 on:** March 05, 2012, 05:39:44 am »

FYI, metering continuity or resistance on a cap will initially read as a short circuit. As the cap charges up, the apparent resistance will climb towards infinite.

Of course, never test a charged cap. You could damage your meter and potentially yourself, especially if you've got a cheap meter.

crash41301 · « **Reply #47 on:** March 05, 2012, 07:21:37 pm »

Got the new 4.7uf 250v today. I installed it and left everything alone, fired up the monitor, and R234 lives.
So I added the resistors back in (R22, R25, R28), reinstalled and fired it up. It continues to live. I then put T2, T4, T6 back in, and it still continues to live.

Now for the bad part. With R22, R25, R28 not installed I was reading ~175vDC at R40. With them back in, and T2,T4, T6 back in, I read only 115vDC at R40.

I can see a picture, but its very faint and the horizontal and vertical hold on the picture is impossible to get. Hopefully its due to low voltage.

Any ideas?

grantspain · « **Reply #48 on:** March 05, 2012, 07:36:31 pm »

adjust the b+ up to 138vdc at tp6

crash41301 · « **Reply #49 on:** March 05, 2012, 08:01:40 pm »

Ok just got back from adjusting the B+ to 138vDC. My R40 is now at 136vDC or so.

I've got a bit of color in the screen now, but the picture is still flakey and acts as if V-Hold and H-Hold arent working correctly.

crash41301 · « **Reply #50 on:** March 05, 2012, 08:15:56 pm »

Couple of pictures of what I have on the screen now, perhaps they help better than my descriptions.

grantspain · « **Reply #51 on:** March 06, 2012, 02:44:07 am »

check +25 volts at tp31 and +12 at tp10

crash41301 · « **Reply #52 on:** March 06, 2012, 07:19:16 pm »

I've got:
11.7vDC @ TP10
26.1vDC @ TP31

Interestingly enough, when I started it up tonight to measure these voltages the image stayed sync'ed. I measured voltage at R40 and got 175vDC. After maybe 5-10 minutes the screen collapsed and I had 125vDC at R40 again. Something failing only when its hot perhaps?

grantspain · « **Reply #53 on:** March 06, 2012, 07:37:24 pm »

all those voltages are good,the b+ is fine

when you say the screen collapsed do you mean a vertical collapse?

crash41301 · « **Reply #54 on:** March 06, 2012, 08:06:40 pm »

Attaching pictures of what it looks like when the voltage at R40 drops. Before the voltage dropped I had enough time to sit and adjust the screen to fit the monitor perfectly. I also had a perfect picture. (Besides the colors being out of whack, but adjusting would probably fix that)

Seems like it all comes down to that 200vDC (In my case 175vDC) dropping. I just dont understand what could be causing it to drop like that?

grantspain · « **Reply #55 on:** March 07, 2012, 02:30:37 am »

puely guess work now-try changing ic1 lm1203n and possibly ic104 TDA2593

check r189,r198,t110,t112

crash41301 · « **Reply #56 on:** March 07, 2012, 02:59:13 pm »

Ah crap on guess work

Already have a new LM1203 in there. I'll try swapping for the other new LM1203 I had just to see.
I'll check R189, 198, t110, 112 tonight
If all is good there I'll order a TDA2593 I guess

grantspain · « **Reply #57 on:** March 07, 2012, 04:42:42 pm »

i would have thought the resistor would have cured the problem but there is no knowing what damage has been done to the chassis and how far it goes-this will be a real labour of love to repair

grantspain · « **Reply #58 on:** March 07, 2012, 06:11:49 pm »

have you checked -190v at tp30

crash41301 · « **Reply #59 on:** March 10, 2012, 08:49:40 pm »

Been a couple of days. I got sick and didnt feel like doing much besides sleeping and laying around. Here is what I got though.

R189 = 10.2
R198 = 10.3

T110 T112 measure the same resistance across each leg combination. So either both are bad, or both are good I guess?

Tp30 = 172.2vDC - Turning the monitor on, again the screen showed up full screen. My son was so excited to play the NBA Jam again that we sat and played an entire game. Occasionally the screen would shake like it was going to go out, but didnt. I'll turn it back on and let it sit for a while later. I suspect the voltage will drop at TP30 when the screen collapses. We'll see.

crash41301 · « **Reply #60 on:** March 11, 2012, 01:42:31 am »

I pulled the DC side of D137 out of circuit, hooked up the chassis and measured it. My thinking was that something might be shorting out or getting hot on the way from D137 to the color drive transistors, thus shorting my 200V down to 135v. I figured I would start as far back as I could - where AC becomes DC. I only measured like 112vDC after unhooking. crud! It was a steady 112vDC though, it never dropped from its peak like the 200v did. I was really hoping for 200v there, so that kind of spoiled my plans. I put the Diode back in circuit.

I also happened to get the color drive transistors I ordered in the mail while sick. I figured I might as well pop them in. I had a bad green one, figured while I was doing it I might as well change them all out since they are cheap. I swapped them, fired up the monitor fully wired up and expected it to work for a few seconds until the 200v dropped. Well... the 200v hasnt dropped yet? I dont think it could have been the color transistor shorting because the 200v dropped when all of the transistors were out of circuit. A bad solder joint on D137 perhaps? Whatever it was, I dont really care so long as it works!

I played a couple of games. I've noticed that occasionally the picture will jump for a split second, but it mostly seems ok. I'm leaving it on for several hours to do a test to see. If the picture barely jumps like that on occasion I'll be happy enough, at least for a while. Attaching pictures to show my somewhat victory over this thing. This was my first attempt at repairing a monitor chassis (or any PCB for that matter) When I started this I didnt even know what a capacitor, resistor, or transistor did. I'm pretty happy

Thanks a TON Grant for all your help!

grantspain · « **Reply #61 on:** March 11, 2012, 05:19:02 am »

quite possible there is a bad pcb track or pad which would have caused the issue,the jump may be down to a couple of caps on the sync circuit-unlikely they woulod have been included in any kit

picture looks very good,well done

crash41301 · « **Reply #62 on:** March 11, 2012, 12:41:37 pm »

Quote from: grantspain on March 11, 2012, 05:19:02 am

quite possible there is a bad pcb track or pad which would have caused the issue,the jump may be down to a couple of caps on the sync circuit-unlikely they woulod have been included in any kit

picture looks very good,well done

Eff... screen just whacked back out.

crash41301 · « **Reply #63 on:** March 11, 2012, 04:19:59 pm »

Back to square 1 I guess. I turned it off and let it sit for a couple of hours and then came back. The screen is full size again, but begins to get shakey after a few minutes. Something heat related I'm thinking? Any thoughts?

grantspain · « **Reply #64 on:** March 11, 2012, 05:06:52 pm »

only suggestion i can make is to get some electronic component freezer spray and start elimating the ic's one by one
have you tried tapping the chassis to see if its solder joint related?

crash41301 · « **Reply #65 on:** March 11, 2012, 09:05:35 pm »

I think I might have found the short. Tapping around with the plastic side of a screw driver I was able to get the screen to shake at the neck card. Upon closer inspection I believe the neck socket had loose solder joints. Possibly from me taking it on / off a million times. I re-heated them and installed. So far so good, we'll see what happens...

Paradroid · « **Reply #66 on:** March 12, 2012, 03:10:11 am »

Great story so far... I hope you end up winning!

crash41301 · « **Reply #67 on:** April 07, 2012, 12:29:17 am »

I always hated reading these types of epicly long repair threads only for it to end suddenly with no resolution. So... Its been however long now and the Polo still seems to be working well

So a BIG thanks to Grant, and to everyone else: stick with it, it CAN be done


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