hantarex polo ticking

[smartbomb2084]

Hello all,  I have a Hantarex Polo in a Revolution X that originally had a bad IC 104 (TDA 2593).  After replacing it and installing a cap kit the monitor now has the classic 'ticking' sound of the PS starting up and shutting down.  I lifted the deflection end of L103 and hooked a light bulb up to it.  The light bulb strobes with the starting and stopping of the PS.  I next lifted L106 and D118, the other secondary outputs to the deflection board  and the lightbulb STILL strobes.  There seem to be no obvious bad components on the primary or secondary side that I can find.  What am I missing here?  Could the transformer be bad?    THANKS in advance for any help.

[grantspain]

ic 104 going bad is very rare,did you have a horizontal frame collapse?
Check for cracks in the circuit board around R227
Check T114 BU508A

[smartbomb2084]

T114 is the HOT and it is fine.  Besides,  the entire deflection side of the monitor has been eliminated by lifting L103, L106, and D118, or hasn't it?  The monitor at first would not sync up horizontally and then the rolling picture would collapse into a red, green, and blue spot in the center of the screen ( No Horiz or Vert deflection) then shut off completely. Swapping out IC 104 got the picture rolling again.  I checked all the transistors in the sync circuit and even canged T110 just to be sure.  If the deflection side of the board is truly isolated from the PS then isn't my problem in the PS?

[grantspain]

and you have metered all the ps voltages?
could be the flyback

[grantspain]

TP6  +145V
TP7   +85V
TP8   +27V
TP9  +15V
those are the ps voltages

[smartbomb2084]

It is a little hard to check the PS voltages properly when the PS is turning on and shutting down continuously. Remember the strobing light bulb connected to L103?

[grantspain]

very obscure fault,not had that problem and i have worked on a fair few polo
if you have isolated the ps output and proved all the diodes and safety resistors on the transformer secondary output then i would advise to look at the fet t101 and ic 101

i can't help but think the flyback may have had a hand in this

[smartbomb2084]

 I forgot to mention (sorry) that I changed IC 101 on Saturday and still have a strobing light bulb.  As far as T101 FET is concerned, it has been my experience with enhanced MOSFETs in power supplies  that they usually short drain to gate and blow the main line fuse.  If T101 is bad how am I getting a strobing light bulb connected to L103 which is on the SECONDARY side of the PS transformer which is AFTER T101?

[qrz]

i don't have a print handy.......,
so for kicks , check the Vcc diode for the vert output ic. possibly shorted/leaky.
and the ic itself could be at fault.
removing pwr to that  chip might allow set to start .

qrz

[smartbomb2084]

Look, gentlemen, the ENTIRE deflection side of the board has been eliminated by lifting L103, L106, and D118.  If this is true, doesn't the problem lie in the PS.

[qrz]

have a model # , or a link for a schematic ?  i would sure like to see what ur working with......

most smps defects are caused by 'lytic fatigue. ( value changes , elevated ESR, leakage , ....)

however,                                         
semiconductors may short , open or leak.  sometimes , they will test good .  but, breakdown under
load/voltage .

resistors may also change values,  affecting biasing , feedback regulation, etc...

an increase of a few tenths of an ohm in the source resistor on the switching mosfet MAY render a
supply erratic , or inoperative .

qrz

[smartbomb2084]

Here you go,  in glorious PDf.               http://www.andysarcade.de/data/coinop/videogames/raster%20monitors/hantarex/polo_25/polo_25.pdf

[smartbomb2084]

This afternoon when I had a little time I removed the flyback from the board and the light bulb still strobes.  This should once and for all eliminate the flyback, at least for now.

[qrz]

tnx for the link ....that DOES help 
ok , lets lift one end of R187 (2.7 ohm) to remove vcc from the vert output ic ( tda1675 )
if still pulsing , lift one end of L106  (15v line )
still pulse ? then check  C121,C123, R130, C114, C111, C112   
also check D107-109  and   D116 -119
 R111,2,3 should total .5 ohms ( an R increase here may cause supply to fall out of regulation)
the PWM IC ( UC3842)  has the OVP supply sourced by L102/R119, D112 and filtered by C114
OCP via R127/C116
Run vcc supplied via D110/L112 and filtered by C112
start up B+ supplied via R105/6 - smoothed by C111, then rectified by D111 .....

qrz