calling hantarex experts, no horizontal width control

[gazz292]

got a hantarex polo 2, 25 incher in my ex golden tee cab, in the uk so running on 240 volts.

bought the cab knowing the monitor had a fault.... it'll run fine for a random ammount of time, then shut off,

just before it shuts off, the screen flickers, kinda like when changing resolutions, if i remove power and reapply it, the monitor will come back up, and work fine for anything from a minute, to hours before doing the same again.
sometimes it'll run 8 hours with no hint of a problem at all.

i took the chassis board and neck board out, and re-flowed any solder joints that looked slightly suspect, and re-flowed all the lopt joints, but no differance.

last night i was trying to dial the monitor in to the best resolution to use with mala (feeding it with an arcadevga 3000 card (but it had the fault when running on the origional game pcb) and i needed to adjust the picture size and position.

i have the adjuster board in the socket on the back as i dont have an extension cable, and at first i was able to adjust everything.

Then i noticed that the horizontal width control was extremely jumpy... i.e. a small turn and it'd jump wider, then narrower, then that control stopped responding all together, and i guess i have the screen at full width now,

i pulled the control board off, re-flowed all the joints, tested the 4k7 pot for that particular control, it metered out fine, but i sprayed contact cleaner in all the pots anyway,

no differance,

so i swapped the horizontal width pot for the vertical hold pot which was the same value, absolutely no differance, i still have vertical hold control, but no horizontal width.

the pot meters fine right to the pins of the connector, i've tried wiggeling the socket on the main chassis, no differance to indicate a failed solder joint,

whilst i was fiddeling with the pots, the monitor began to do it's flicker before it shuts down, i noticed this time the bottom of the screen was pulled to the left, and if i hit the left hand side of the cab, it'd go back to normal, only to pull left again,

as long as i kept on hitting the cab and putting the bottom pull back to normal, the monitor stayed on, when i stopped hitting it, after a few seconds of pull to the left, it just down.

no ticking from the psu, heaters dead, as if the power was removed,

as usual, cycling the power brings it back up.

Any ideas what to look for??? is the failing and loss of horizontal width related?

with the hitting the cab side to 'fix' the pulling problem, that points to a dry joint, but i can hit the cab as much as i want when it's running fine, and never get it to display the fault, only when it's displaying the bottom picture pulling will hitting it do anything.

i'm thinking it's heat related, but am at a loss to where it's failing on the board.

[grantspain]

there is a common fault on polo 2 chassis whereby you lose width control and get pincushion
its caused by one or both east/west correction diodes at D47 and D44
other width issues are caused by T18 and T19

the monitor cutting out is a seperate issue,its most likely a bad solder joint on the flyback but it could be a bad joint anywhere with these-you will need to remove the primary psu protection cover and check under there

these chassis are also well known for leaky capacitors,especially in the psu section and hv section

[gazz292]

cheers for the reply,

i think my best bet is to get a cap kit of some sort (i'm in the uk, so not sure if anyone does them over here, or if i'm better off sourcing them localy)

and i'll also get a couple of the diodes and the transistors mentioned, then i can do all the work at once, ideally if i can get the capacitors and diodes and trannies from the same place, that'd be great.

[grantspain]

ebay is best bet for all-littlediode and dalbani have some of the stuff also
cpc is a good bet on everything
maplins have some of the caps

[gazz292]

kewl,

is there a list of the caps i need to get?? also, i had a quick look for the transistors, but couldent find them (well i found the BDX53A on ebay, but cant find the BC5588.. but i havent looked too hard... just tried RS components, but i dont want to use them as they are stupidly expensive, and they like to have silly minimum order quantities for components making one off jobs extremely expensive from them)

[grantspain]

T18-BC557b/BC558b (b not
T19-BDX53A/BDX53B/BDX53C
D44-BY228
D47-BYW95C
caps i change as a matter of course;
c17-220uf 50v
c18-22uf 50v
c25-22uf 50v
c31-470uf 35v
c32-220uf 25v
c106-47uf 250v
c92-47uf 250v
c1-100uf 200v
c11-100uf 250v
cpc will have all the caps and transistors-not sure with the diodes
imo change the two diodes first

[gazz292]

caught the chassis sparking tonight,

the past few days the monitor has been making a noise like you get when you feed it a resolution it dosent like, the picture would colapse both verticaly and horisontaly, going very fuzzy and mega interlaced.

then it shuts off, i do the usual, go round the back, unplug the power lead to the monitor from the distribution box, plug it back in,

first time i thought i heard a slight spark as the monitor came back up, 2nd time i looked at the flyback, it made the noise for a second but no spark....3rd time i saw it sparking, it's not the flyback, but behind the flyback, i.e. towards the front of the monitor, it looks to be coming from one of the transistors on the heat sink by the side of the flyback,

would one of those transistors on that heatsink be one of those you mentioned grant??

[grantspain]

yep thats probably t114 you mention
sparking is due to a bad solder joint or damage to the insulation sheet that is mounted behind the transistor

[gazz292]

i still havent take the chassis out yet (went out to get a cage mate for my pet rat, as she lost the last of her mates 5 days ago, and was becoming very withdrawn being alone, so been busy playing with a baby rat)

anyhoo, T114, i assume it controls something to do with the picture size? could that be the problem with my lack of horizontal size control... just seems weird that i had horizontal control, but jumpy, then it went, tho i guess if the transistor that works the horizontal control blew when i tried adjusting the pot, that's explain it.

another issue with this monitor, the picture is tilted to the right slightly, i.e. at the bottom, in the windowz desktop, the start button on the menu bar is on the bottom of the screen, and the clock and system tray are down off the bottom of the screen by 5 or 6 pixels,

is there a picture rotation control on this monitor, or is it yet another problem with the chasis i have to find and fix???

[grantspain]

T22(t114 is on polo 1 chassis) is the horizontal output transistor,it does not affect size as such as that is controlled by the bdx53 at T19
IF T22  shorts out then the chassis will go into trip and shutdown and you will get a chirp noise

the two diodes at d44 and d47 are the major problem that causes the jumpy width control,seen this issue many times

don't worry about HT on the anode with these monitors,they hold no charge after about 60 seconds-i would quite happily whip the anode cap off whilst standing in a bucket of water with these

I would suggest you replace diodes d44 and d47 and also replace T22 with a bu2530aw and make sure the insulation sheet is not damaged-also you will need some heat conductive grease(non metal based)

[gazz292]

finaly took the chassis out yesterday, after the monitor wouldent go more than a minute without arcing and shutting down,

i found a wire on the board with a broken solder joint, one of the thin red wires from the loom that goes with the flyback wires, so i imagine it's high-ish voltage, it was near the width control diodes,

no sign of arcing at the hot at all, solder joints were perfect, no continuity between the centre pin and the heat sink, but the circuit board around the D44 and D47 is blackened by heat,

i rekon the arcing was around the 2 diodes rather than the hot.

i havent ordered the diodes and caps yet, but i re-flowed a few joints, including the one wire i found loose, put it back in, and it hasnt arced since, or shut down, still no horizontal width control of course,

i measured the diodes in circuit, one was 0.450 and the other 0.530, this was on the diode setting of the multimeter, so i assume it's forward voltage drop it's reading or something, open circuit the other way round as expected, so the diodes arent flowing both directions,

but i'll replace t18 and 19, and D 44 and 47, as well as the list of caps when i get them ordered after xmas.