Polo 25

mustang6771

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I've been commenting on an awesome Polo post by Mecha but didn't want to hijack it any longer - I need to keep track of my progress.
I guess I'll run down everything step by step and maybe someone can help me figure out what next to try out.

Hantarex Polo 25 Monitor - Blind. I have no game to try it out with currently, just a JPAC; however, turning the brightness up does nothing.

-When first received I could hear the high voltage. Disconnected the flyback and could then hear the HOT (I believe). Monitor got all static-y.
-B+ at TP6 tested out at about 138V
-No heater glow visible.
-R35 on neck board checks out fine.
-Solders on xfmr look good, traces look good and test out for continuity, and visual inspection of transformer shows no problems.
-I notice B+ filter caps are bulged out. Replace them with new like kind (330uf 200V - I have noticed other monitors of same model with larger size caps).
-Resoldered a cement resistor nearby as pad was lifting - fixed.
-Power up monitor to test it out, now there is only the OCP ticking coming from monitor.
-B+ measures between 0-5V cycling.
-Install new HOT.
-Test D116-119, 134, 135 - none are shorted.
-Test C174, 175, 172 - C172 test out as shorted, remove it from circuit and it does not test out as shorted any longer.
-Continuity test the xfmr - 5 pins plus the ground pin are all continuous to each other and thus ground - unsure if this is normal. Remove XFMR from board and test each pin - none are now continuous. Reinstalled the xfmr.

I'm sort of at a loss as to what to try next. I don't have a ton of spare parts lying around. I have a cap kit to install but don't want to do that work until I get something on screen.

Any help is appreciated.
 
I'm about to start working on my Polo 25 as well. I'll keep an eye on your thread. I'm definitely seeing a need to set up a test station, cause moving the tube on this this is some work.
 
Yeah I've picked over his thread & blog, super awesome. Mine is DOA right now, and looking at it I'm not sure if it's worth trying to fix. The prior owner did some stuff...I've got no neck glow, nada. I need to hook up a test bed and check voltages on the board...was way too dicey trying to reach into the Z-back it was in.

Here's a link to an album of pics I've started on it: https://plus.google.com/photos/109998847233395978455/albums/5789898288989920769
 
I had a chassis where the bigger of the 2 transformers (the one in the corner outside where the PS cage would be) just had a bad solder joint on it. I would just start going over solder joints just to be sure, especially if someone fucked with it before you.

they're not really bad as far as cold solder goes, I don't think... HOWEVER, I did have another one where, as stupid as it sounds, the AC connector needed to be resoldered. I mean you're probably looking at something incredibly obvious.

I assume you have absolutely nothing?

I find the filter cap ratings so unusual, cause I have so many of these that all had the 470/200V caps, but I've seen other people on here saying they have 330's. I would try upping those to what they're supposed to be first.
 
UPDATE - Progress!

O, Here's an update for those who feel like following. Please keep I am no expert at all so there are many things I don't know about monitors. Some simple solution I may be missing.

I replaced my B+filter caps with the 470uf version as well as a new HOT I ordered - same part number as the one that was on there, which is the correct one. So after doing that my monitor wouldn't fire up at all anymore. (It was blind, but still got HV before I did any work). After checking out everything on the flowchart and trying to do my best guess as to what was wrong I ended up putting back in the old HOT. Wallah, it worked. This bothers me a bit with the HOT because it has happened to me before from the same supplier. I don't know, maybe I'm not doing something right when I install the new one...
OK, so now the monitor fires up... after adjusting some i can see the screen, albeit very, very dim. The whole monitor is very dark. So I don't know what that means. Does that mean the tube needs to be rejuvenated or is it junked now?
I was working on adjusting all the pot switches to get a better picture but then I noticed that the neckboard was getting pretty hot. I even noticed a little smoke coming off of it. I don't know the average temperature of a warm monitor but it measured from 120-150 before I decided to seek help and turn it off. Maybe it was just burning off something, some old flux...

So that's where I am at.
-Dim Monitor
-Hot monitor, but it may actually supposed to be that hot - unknown

EDIT: I have a cap kit to install but don't know if that'll help. if someone gives me the green light that that may help I'll go ahead and try that out.
 
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Started poking into my polo today. 120v ac at the main input is my starting point. I trace voltage to R101 and C103 but past that I get nothing. F101 has no voltage to either end.

Then I shorted myself across both hands and yelled "GOD DAMN MOTHER FUCKER!!!!" and figured I'd take a short break and post.
 
Then I shorted myself across both hands and yelled "GOD DAMN MOTHER FUCKER!!!!" and figured I'd take a short break and post.

Working on it live huh? I'd way be careful but it's a little late now... good luck!
 
Yeah, live...trying to figure out where power is going and what's dead. Pulled the flyback off to check underneath it...it's a 7185, not sure if it works on there or not. Might spend some time with it again today exploring.
 
Hantarex (WORKING Moderately now)

OK! the good news is that I have a picture on the screen now. I capped the monitor, replaced the B+ filters, fixed a few traces and broken solders etc. Maybe something else that is minor.
Anyway where I am at right now looks like this... The monitor is dim, but not as dim as it was a week ago. I let it run for a few hours and it somehow brightened it self up a bit. It also doesn't take 30 mins to get brighter. I could probably play a game on it now but it's still dark. I checked the brightness POT as well as adjusted the crap out of the thing. I have a little screen burn from the fighter game that was using it before. The right and left screen edges are also fuzzy and I can't focus them in. I think whatever problem I am having right now isn't unique to the POLO but old monitors in general. I'm considering replacing the flyback transformer. I also suspect the tube may be weak but I can't really find anyone in my local area to test it out. I live in New Orleans BTW is anyone round here has a tester. Anyway, if anybody has any 2 cents about what to check or replace I'm most definitely willing to listen, I've learned a lot so far and this is becoming quite the hog of my time hobby. You all have been a great help so far!
 
I have read in a few places that a non-bright monitor and blurry edges can both be signs of a bad flyback. I mean, this things doesn't look brand new. I think I may try ordering a new one and seeing where that goes, does this train of thought sound right?
 
Success!

OK, Everything looks good to me now so I'd thought I'd share my success and say thanks to the guys who have helped me along the way.
The Polo looks good and is in the cab. After I got the heater working I did a cap kit and noticed that I couldn't get the monitor brightness up at all. Now, I think this monitor had been sitting for a long while and I still don't know all the mechanics of how they work but after running it for hours straight, it brightened itself up. I found this weird but went with it. It plateaued out and I decided to replace the flyback. This fixed some blurry edges a little but it was still a little dim. So.... I kept on running it and right now it's actually looking pretty good. So, I'm not sure what was going on there; maybe the tube needed to be run to burn off some crap off or just to get a good warm up in.

But the point is that everything is good and it looks fine and I'm happy.
Thanks, again guys.
 
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