Hantarex Polo

The Hantarex Polo. (25″ model displayed)

Schematics (NEW)
Cap Map (by mecha) (NEW)

Over the years I’ve had people tell me this disassembly guide helped them fix their Hantarex Polo monitors. I must admit that wasn’t my intention for creating this guide. It was just a step by step process I captured with one of my old phones while taking one apart back in 2011. I did so because I’ve actually broken the board part trying to remove the cage skipping a step. (oops) The thorough teardown was done with the intention of washing the chassis in the sink though, because 20 some odd years of filth even back then was something that concerned me. I’ve found a number of other points of failure since then, I’ll document them when I get one of these in front of me again someday.

The Hantarex Polo has a metal cage encasing the power supply section, I’m told it’s to prevent interference. I’ve run a number of these with the cage not reinstalled and they’re seemingly fine — it’s up to you if you want it to look aesthetically pleasing or not. This cage needs to be removed if ever you go to repair this chassis, these are the steps for removing it:

Step 1: Unscrew the cage. (don’t try removing it yet; you’ll see why soon)

Step 2: Remove under bracket.
This may use a little bit of finesse to get off, but it just pulls off. (I use a smaller flathead to pry up, just don’t dig into the board too much.) The bracket has small tabs that go into clips on the top of the chassis. The chassis I used for this demonstration actually had the clips bent sideways, so it was tricky to get out.

Once you get it out though, it might be a good time to straighten the tabs with needlenose pliers.

Step 3: Remove the power supply cage. The cage has tabs that stick through holes in the chassis and are rotated to lock the cage on. Failure to straighten these out first and attempting to pull the cage off may result in cracking the PCB; I would know, I’ve done it before, however it didn’t do a whole lot of damage. (The aforementioned oops at the beginning.) Since the cage is made out of aluminum I’m assuming, if you bend the tabs enough times they’ll probably break off eventually — you still have the bolt holes on the side to mount it in this case, it just might flop a bit.)

Sometimes the tabs have bends in them, if you grab them with needlenose pliers like this it can flatten them out, and twist to straighten them. The cage should come right off then.

Helpful tip: Don’t lose these parts. (Particularly the bolts.)

You will have free access now to replace the capacitors and do whatever else you like. I previously used this “guide” as a means for showing how to break down the chassis. I’ll retain those instructions for you to wash it or do whatever you like; this time around I will describe what the parts do too, as well as offer up some of the easier tips for fixing.

The fuse holder: This is the main fuse for the monitor; if ever it’s blown it will mean you have a short someplace, or in my case in the past, it meant that the T101 MOSFET on the power supply heatsink was bad. Also inspect the fuse holder with the power off (obviously) by removing the fuse and testing the rigidity of the clips — if they’re broken you will need to replace the fuse holder.

The power supply section: As I noted, the wall heatsink has the MOSFET mounted to it. There are two large filter capacitors, rated at 470 uf / 200V. Out of the many Polos I’ve seen, these are typically bulged or the outer covering of the cap peels downward; these conditions are symptomatic of capacitor failure, which may result in a wavy picture due to the irregular B+ voltage. Given that the AC voltage flows through these, you will probably develop AC in the DC voltage lines, or ripple. There are two large diodes near the filter capacitors, these are the rectifier diodes. I’m told that on American Polos there will only be 2 diodes here, and for international variants there will be 4. The American ones don’t have the extra two diodes because they’re not intended to be operated with 240V AC. The transformer for supplying various DC voltages to the chassis is on the other side of the power supply MOSFET wall. I’m finding these to develop cracks in the traces of the transformer due to the board being a flimsy fiberglass design and probably cracking under the weight of the heavy transformer assembly. If you desolder the transformer out you may notice the cracks better. For security and longevity purposes you may want to jumper the solder points of the transformer to their next points in circuit.

The flyback transformer: I’ve seen these fail a couple of different ways. In one instance I saw one put a 2 inch hole in the side; there were no fireworks in this instance, I just subbed it with one off another chassis and it was fine for a few more years until that one had issues. Another the anode “stem” part developed a crack in it; there were some fireworks that time. It was believed that if the flyback failed it would take out the HOT (Horizontal Output Transistor) too, but I found that not to be the case in either scenario mentioned. (The sparks imply the HOT still works and it’s trying to fire up the monitor!) I encourage never replacing any flyback unless it is definitively dead or shooting blue lightning.

All the other stuff: This is where all the real action is at. Starting with the middle heatsink, there are two ICs: the larger multi-legged one is the vertical deflection IC; the smaller is for horizontal width control. Directly next to the smaller transistor is the width coil; under no circumstance should you ever adjust this, as the width control is fully electronic. Between the width transistor and coil is another smaller triacs transistor, this is (I’m assuming) the amplifier for the width transistor. Thus if you have a chassis that has no width control, focus on these transistors first; if replacing these doesn’t fix it, you can check D134 and D135. The tall black part in the corner is the horizontal linearity coil; it’s magnetic, so metal things will stick to it. To its right is a transistor mounted on the outer heatsink wall; this is the horizontal output transistor (HOT), part number BU508A. If ever your monitor doesn’t turn on and it makes a faint ticking sound, chances are the HOT has failed.

If you need to replace the flyback, you’ll need to desolder the old focus wire off and solder the new one in. There are two types of neck sockets: the one pictured, and another one that the entire plastic part of the socket lifts off (and is very difficult to open). For the picture style, there’s two tabs holding the door shut, simply pull them outward and lift up. To the right of the neck socket in the picture are three transistors: these are the drive transistors for the primary colors Red, Green, and Blue. When handling the chassis and reinstalling it on the tube, make sure that the heatsinks for the transistors aren’t touching each other, as this can create a blanking problem and you will need to replace T1 on the neckboard to fix it.

I suppose if you dismantled all the removable stuff, you’ll have a pile of parts like this. With the parts removed now is a good time to inspect the PCB for cracks. This typically happens below the flyback and transformer near the power supply cage; if any traces appear to be “scratched” on the solder side, I suggest measuring for continuity on all the flyback or transformer traces. From the component side, you may visually see cracks like in the bottom picture.

On the outer edge of the chassis behind the HOT heatsink are two ceramic resistors. Your B+ is carried through these (very important if you want the monitor to work) and like many ceramic resistors they will get very hot and it can damage the solder pads they’re connected to. The solder pads will typically break off from the traces. In the past I tried to lay new wire over the existing traces, but now I just run 18 gauge wire between points. Also notable, there’s a plastic trim piece under this side of the chassis (not seen); if you take it out, make sure to reinstall it when you’re done. (It’s for stabilizing the fragile board, without it could make the cracking worse.)

The solder pads for the B+ ceramics may potentially look like this. I used to hook the legs 90 degrees and resolder, but I found through my experiences this isn’t the best way to restore connections to these.

Hantarex Polo tips and tricks:

Vertical Linearity: A common problem with Polos is the top and bottom of the picture are not even heights. Sometimes the top will be stretched, and the bottom squished, and vice versa. Pictured below (stolen from another KLOV user) is what it looks like.

There’s an adjustment pot near the vertical IC (the one with a ton of legs) labeled “V. Lin.”, I can’t remember exactly which direction changes it, so you’ll have to experiment with it. It’s also worth noting that the adjustment pot does not have a knob, you’ll have to use a small flathead screwdriver or preferably a plastic TV alignment tool; so if you use a metal tool and don’t have steady hands, be extra careful you don’t touch places that you’re not supposed to with it. (It may not damage you, but it may damage the monitor… or perhaps both.)

High voltage shutdown: Do you hear a pulsing ticking sound? Shutdown can be caused by a shorted Horizontal Output Transistor (HOT, T114). The part # is Philips BU508A. Another place to check is the flyback, inspect for cracks. If the flyback is bad you will have to replace it. Another spot to check is R103.

B+ testing and adjustment: If you have any strange anomalies with width adjustment, waviness, or the monitor just seems a little odd, your B+ voltage may need to be adjusted. TP6 (pictured below) is the designated test point for B+; alternatively you can use the leg on L104 facing TP6 instead for better grip with an alligator clip; use the HOT heatsink wall for ground, and set your multimeter to 200V DC range. You want this to be 137V DC; is it too high or too low? (scroll down)

The B+ adjustment is contained inside the power supply cage, so you’ll need to remove the cage first if it hasn’t been already. The adjustment is labeled as V. Adj. Turn it very slowly until you reach 138V. This process of course assumes that you have a working monitor with functional horizontal deflection. There may also be a hole that’s covered up with a sticker to get at this without taking it apart.

Blooming: Ever notice a transition between a dark screen to a bright white one and the whole picture expands and contracts? This is “blooming”. It’s caused by filter caps (the largest capacitors) on their way out. They’re rated at 470 uF / 200V. If you intend on keeping your Polo for awhile it’s probably a good idea to change these anyway. As noted above, these seem to fail a lot, probably from the increased ambient heat from the cage being installed.

Yoke: The Polo has a unique connector for the deflection yoke. You’ll notice it has 5 wires: one set for horizontal deflection, another set for vertical deflection, and then there’s a black jumper wire in the middle. This black jumper wire is a very handy feature, as it will prevent the monitor from powering on with the yoke unplugged (running any monitor with the yoke connections not plugged in can potentially damage the chassis). It’s worth noting that the yoke on the Polo, unlike most other monitors, has no adjustable convergence or purity rings. Unlike traditional monitors there’s no real way to flip the horizontal or vertical pairs of the yoke plug, instead Hantarex has 2 headers for normal orientation and another for mirrored. In the picture, the left header is normal and right header is mirrored.

Flyback replacement (old intelligence with Bob Roberts replacement flybacks): I unfortunately have no more “new” flybacks for this demonstration, but I wanted to say that contrary to what a lot of users on KLOV and other video game message boards may say, you do have to solder all the flyback pins. The pin that’s offset from the ring of pins does NOT get tucked underneath. I had a chassis once where I followed KLOV’s advice and tucked the pin underneath and it produced an all-white screen that cycled between red, green and blue. So after tinkering with it enough, I reproduced the same problem on another chassis and figured out that it was that one lone pin that caused the problem. (The leftmost pin on the same side as the Focus and Screen adjustments). New intelligence: There are actually 2 holes for that wire appendage to solder into, if in the event you burn a solder pad off.

Vertical Collapse:
While most would be inclined to replace the TDA1675 vertical IC to fix vertical collapse, give R167 and sometimes also R177 a look. These parts are R167 2.7 ohm 1/2W flameproof and R177 1 ohm 1/2W resistors. Also related to the chassis cracking beneath TH101, there is a possibility the +27V output here can have a break. I’ve tested for voltage at either side of R167 and found the resistor open that way (voltage in, nothing out). You can likewise remove the resistors from circuit to test. A flameproof resistor is also known as a fusible resistor, where if there’s a presence of a short the resistor will go open to cut the power supply. I’ve seen these resistors bad without the need for replacing the vertical IC, so I’m at something of a loss for why R167 would go open, but maybe it’s from stress.

Color Drive Transistors (more old intelligence from 2012 that’s still relevant today): The transistors on the neckboard (that drive Red, Green and Blue) are fitted with heatsinks that should solder to the bottom of the neckboard but unfortunately are either very fragile and break off, or they just don’t stay soldered in very well. This means that the transistors bend very freely and are prone to actually touching one another, which can likely take out T1 on the neckboard and potentially IC1. Here’s something you can do to help prevent this:

The transistors are typically plastered in flux. Desolder the transistors out first, use a pair of needlenose pliers to flatten and straighten the transistor legs. Use a soft bristle toothbrush and some 91% isopropyl rubbing alcohol to clean the flux off. If you have a fiberglass brush or a pick you can really get the goo off.

Squeaky clean.

Before reinstalling the transistors, use a piece of sandpaper to sand the tips of the heatsinks. (Or I prefer a sanding bit on a rotary tool for more effectiveness.) I’ve found that the reasons the anchors on the heatsinks didn’t stick in the past is because these tips are corroded; sanding will (hopefully) allow solder to stick to them again. Upon doing so, now reinstall the transistors, ensure the heatsinks are low enough that they stick through the through holes, cause typically they aren’t in far enough to solder properly.

**(The following 90 degree method is an optional step, and a method I no longer use given the anchor cleanup method I use now, permitting you want the transistors to never move again/make your life difficult later if you ever want to desolder them out later.)** Then bend the legs flat 90 degrees like pictured. This will enable the transistors to grip against the back of the neckboard very tight and they won’t be able to bend freely anymore. Note the leftmost transistor, part of that one leg is overhanging the trace, you can snip that. When you’re all done bending and adjusting you can solder the legs in.

Cracking: Here’s a variety of repairs I had to do to just ONE chassis. This particular one had high voltage, but no heater glow. It was very confusing cause I checked the neckboard over about 800 times and found nothing wrong with the neck socket or R103. As I was running out of ideas I noticed some scratch marks on the under side of the chassis and had a hunch that I should probably check continuity between the points and found that those weren’t scratches: they were cracks! You can see plain as day how many cracks there were in the flyback area.

Underneath you can see that I had to patch about 7 traces. This was the reason the heater circuit wasn’t working. (Update: I wound up having to fix all of this again, now I think every flyback trace is jumpered.)

Something else unusual happened to this chassis. The outer frame trim is held together with screws running through the PCB. It developed a huge crack where the metal frame border screws the deflection board in. This particular trace actually goes to the B+ resistors outside the flyback, with that circuit broken I’m sure there would be no B+. (This break must have happened when I pulled the chassis to fix the “no heater” issue, as I had high voltage previous to the repair) **This further demonstrates how fragile these things are, and why if you ever ship them off for repair you need to ensure they’re very well padded and ideally packed in a box inside of a larger box.**

Also, be careful with those corner capacitors. Use 105 degree Nichicons instead of Bob Roberts Richey caps from 1985 too.

I will include new intel when I get it.