Hantarex Polo 28" issues

[Rattanee]

Hey folks

Got a bunch of these monitors and I seem to be having truoble with most of them.

Monitor 1:
Did a full lytic job on it, powers up and works fine, aside from both horizontal and vertical linearity being out of whack. Adjusting the horizontal linearity coil pretty much changes width. (Or is that a size coil and I'm missing something? L109) Adjusting vert linearity works, but I can't get it to be perfect either. In both directions the edges are squished while the middle seems fine.

Like so:||| |  |  |  |  | | |||


Monitor 2: Vert linearity is fine on this one, but it has the same issue with horizontal linearity. and in addition, there's a small "pinch" in the image width near the top, about 1 cm in height, where the width is about 1 cm smaller then anywhere else...

Monitor 3:
This one has me baffled... looks like a powersupply thing... but I can't seem to find any problems in the smps. It had a crack in the pcb at c120 but that's been fixed.
Here's what it does:


All three  had all the lytics replaced with brand new caps.

Thanks for any and all help folks!
(Also having some Wells issues but i'll get there  when I order the parts that are obviously blown...like a whole upgrade  kit set for an U5000  -shudder-)

[Rattanee]

Well looks like I'm alone in this, but I've got a hunch C170 (mylar cap) is on it's way out causing the distortion. I'll see if I can get up in time to catch the local electronics store and score a few caps tomorrow and post the results. Got to wonder if this has to do with the linearity coil acting like a width coil though....

[grantspain]

impossible to say if those problems are actually monitor related unless you have either a 15khz pcb or a colour bar generator connected
as for that wierd interference I have never seen anything like that on a polo before-do you get that with no signal connected and the screen volts turned up to a white raster?

[Rattanee]

100% sure they are monitor related. Does the same with arcade pcbs, be it MK2 or C&D or whatever that I hook up. I hope my hunch is on the money with the horizontal linearity. Just got to wait till tomorrow till I can get some new caps and see if they fix the problem.

As for the interference, the "diagonally rolling blackouts" are just the camera, that's not visible with the naked eye. Look at the 'cover image" of the youtube video, that's the actual interference pattern that is visible. It's just some 'torn' darker areas that keep rolling vertically. I'll check tomorrow morning but I think I'm getting the pattern regardless of whether there's anything hooked up.

[grantspain]

I have never seen any compression issues on hanty monitors and I have worked on hundreds,only way you will compression is if yoke is not matched to chassis or a very oddball issue with chassis-for you to have all of them doing this is very strange
maybe someone has modified the high voltage caps,only way to tell is download the schems and reference all the poly cap values

[Rattanee]

Well we'll see soon.... I'm guessing it's a problem with the scan-speed correction cap... it's possible there were a series of bad caps, as all these monitors were manufactured at the same time. (Got over 50 cabinets with these in it that were made at the same time.)

I'm off to get fresh caps right now... going to buy a few different values up and down from what the schematics say just in case. We'll see how this goes.

The tubes/yokes definitely belong to these chassies.

[Rattanee]

Okay I'm baffled...

Schematics say 390n for C170 which is supposed tobethe s correction cap. All the chassiesI pulled have 820nf caps there. I pulled one to test, and it's at 830nf, so that should be good.
As I understand it, the higher the value of the s cap, the slower the electron beams scan at the edges.
The tubes are Videocolor a66ecy13x01. Is that right for a 28" polo?(I'dassume they are the factory tubes but then again at this point I'm not certain.
Will I fry anything if I go higher with the value of this cap?

[Rattanee]

well... one 2.2uf 250v MKT cap later horizontal is as linear as it should be!

Hopefully it'll last... Monitor's been up and running a while now so hopefully there won't be any problems.

Now all that's left is the interference, and that smallpinch at the top of the picture on one.

[Rattanee]

Okay I thought the cap just threw my adjustments off, but now apparently E-W correction doesn't adjust properly. Whatever I do there's always a small dimple in the middle of the image.

[grantspain]

i need to check the schems

[Rattanee]

Thanks.

I did manage to get a pretty acceptable geometry out of it as it is, but there's still a small dimple in the middle... I'll have to shop around for some other caps (not as easy to get them locally as I would've hoped) and I guess I'll try going lower and lower in value until I get an acceptable balance between the pin cushion effect and the overly high scan-speed near the edges.

It's strange that the h-lin coil only adjusts width and not actual linearity though... would that be a fault, or is it like that on all polos? (Never had to touch it so far.)

As for the one with the interference, I hooked it up again, and got a completely different interference pattern this time. I'm suspecting it's not going to be a powersupply issue afterall, rather something in the RGB section.

[grantspain]

that h.lin coil does affect the width in a way,is the horizontal size adjustment working?


that other issue could be down to lm1203 ic

[Rattanee]

Yeah the h-size is working, as a matter of fact every control is working fine, but the coil does nothing but change the width of the image. Just to be on the safe side... that coil is adjusted with a sqare shaped key on it's smaller half, the taller half with the glue atop is permanently glued... right?


As for the other... Well... I'll try swapping to a known good neckboard, but what I also noticed was that it had excessive breathing despite having had a recap. It's getting somewhat confusing...

[grantspain]

that coil is correct with the glue on top

have you checked the b+ at pin 3 of the flyback,should be about 105 volts

[Rattanee]

I'll pull a tube onto my bench and measure it there. (Kinda hard to do inside the machine

[Rattanee]

B+ according to the schematics should be +138vdc, I have 136,7vdc coming from the smps, and 137.2 vdc on the other end of the 10w resistor that connects b+ to the flyback.

[Rattanee]

Okay the interference went away after swapping neckboards so that's a plus, however that chassis still has quite an excessive breathing problem.

Summary:
Monitor 1: Swapped C170 to a 2.2uf 250v mkt cap, compression on the sides stopped, however pin-cushion can't beadjuted to a "perfect" straight (I'm a maximalist,most people wouldn't notice the problem.)

There is still the problem of a faint "pinch" about 1 cm from the top of the picture. Any ideas?

Monitor 2: Same as above, no pinch there.

Monitor 3: Swapped neckboards, now works fine, but there is excessive breathing. Image expands almost 2 cms in either direction depending on what is shown. This is where I wish there was a block diagram withthechematics... any ideas?
B+ is 139vdc stable.

[grantspain]

where are you reading the b+
at pin 3 of flyback it should be 105-110vdc no more
you can get width jumping issues with faulty east/west correction diodes D134/D135

[grantspain]

the vertical problem if you have changed the caps c137,139,142,144 could be the tda1675 ic

[Rattanee]

Read B+ on R227. It's directly connected to the B+ rail and pin 3 of the flyback. Getting about 1.5vdc difference in the reading between the two legs.

Vertical problem? Vertical deflection works okay on all three. One has a faint linearity problem but that's just an adjustment issue (the pot is flaky and the picture keeps jumping if I leave it at the position where linearity is even.)

I'll check those diodes, though if they're dead I've no idea where I'll get them... these type of diodes are proving to be a pain to source here.

[princess prin prin]

Schematics say 390n for C170

I see that value only in the American schematics (where a different tube type is also indicated) but the original Hantarex schematics have 330nF(0.33uF)/250V and so do all my chassis.

The tubes are Videocolor a66ecy13x01. Is that right for a 28" polo?(I'dassume they are the factory tubes but then again at this point I'm not certain.

Yes, correct tube (replaced the older A66EAS00X01 used in the 80's). Also possible is A66EAS13X01. All Thomson (Videocolor) tubes.

[Rattanee]

Well the chassies originally had a 820nf cap there. I haven't the foggiest idea why they started to act as if the cap was dieing.

[grantspain]

I have seen them with various value caps,most certainly 820nf
almost all have a 320nf that I have worked on though

you are aware there is also a horizontal size coil on the polo,maybe its just an adjustment issue between that,the h.amp pot and the linearity coil

[Rattanee]

These do not have a size coil, they have a fixed winding inductivity in place of it. (My 33" chassis does have a width coil tho so I know what you mean.)