a tale of 2 Polos (Ohmerone help!)

mecha

Well-known member
Joined
Apr 19, 2007
Messages
24,330
Reaction score
7,036
Location
MKE, Wisconsin
Polo #1:
symptom: HV present (the tube creates lightning when you discharge it), but no heater glow.

what I've tried so far:
all signs point to checking R35 on the neckboard and anywhere else there for bad solder joints. I went for the gusto and even removed the neck socket and resoldered it back in. there's no signs of any bad joints. resistance check on R35 yields 1.4 ohm, guessing that's within tolerance (it calls for 1 ohm). if you meter each side of R35 to the corresponding pins on the neck socket (5 and 6) continuity checks out between the resistor and the neck pins. HOWEVER, when you check between neck pins 5 and 6, it reads open. I'm guessing this is my problem. does this mean the neck socket is bad?

it's worth noting one of the 250V/100uF caps had a leg that came detached (replaced both 250V/100uF caps in each corner). there was also a trace along the back edge that was severed going to one of the big resistors on the other side of the HOT heatsink. I re-ran wire along the run of that trace.

just in case the replacement flyback I dropped in was no good, I took one of the old known-good flybacks I had and swapped it in. no change.

B+ was tested at 140VDC.

---

Polo #2:
symptom: no power at all. not even a click from the HOT.

what I know:
this chassis worked perfectly fine. after the other one lost heater glow I popped this one in my KI2 and it died on the spot... when I ran it on a loose tube about 20 minutes previous and it worked fine.

what I've tried:
fuse is good -- no solder joints look suspect. checked B+ at TP6, I'm getting 0.2VDC. the Fromm flowchart calls for replacement of ZD101 and check C112 in the event of "low B+".. but that was replaced in a cap kit. in the event of "0VDC B+" it calls for checking if R103 is open (it was not) and to test diodes D105-D112 (I tested all of them). the only other thing I haven't tried that it says is replacing IC101. how can I tell if IC101 is bad?


Polo 1 is pretty nasty with holding charges in the neckboard btw, so I don't like powering that one up too much. :) to my knowledge, that's the only one of my Polo chassis that does that. does that have anything to do with the heater circuit being flaky?
 
Test Points

Polo #1:
symptom: HV present (the tube creates lightning when you discharge it), but no heater glow.

what I've tried so far:
all signs point to checking R35 on the neckboard and anywhere else there for bad solder joints. I went for the gusto and even removed the neck socket and resoldered it back in. there's no signs of any bad joints. resistance check on R35 yields 1.4 ohm, guessing that's within tolerance (it calls for 1 ohm). if you meter each side of R35 to the corresponding pins on the neck socket (5 and 6) continuity checks out between the resistor and the neck pins. HOWEVER, when you check between neck pins 5 and 6, it reads open. I'm guessing this is my problem. does this mean the neck socket is bad?

Answer:
Pins 5 and 6 of fly should be low ohms compare with the other chassis.
does it show open too? odds are the path for the filament are open
not the windings of the flyback..keep checking..
you could have low voltage coming from the fly read the ac coming from the
flyback pins 5 and 6.
If you have low, high voltage then you may not have enough heater voltage
to see the glow.

the top two pins of crt are the heater pins should read low ohms.
without the socket on the crt, heater voltage comes from the fly.
Any 5-6 v ac or dc will lite up the heater at the crt or down the line
from the fly, without the fly running you can tap in external dc to see filament lite
or use crt checker to confirm your heater is good.A bad socket would be rare.
bent pins or not in the socket may be more likly.
Assuming you hv confirm you have the 200vs at tp33 or on c177..

it's worth noting one of the 250V/100uF caps had a leg that came detached (replaced both 250V/100uF caps in each corner). there was also a trace along the back edge that was severed going to one of the big resistors on the other side of the HOT heatsink. I re-ran wire along the run of that trace.

Those resistors step down the dc to the transformers and the path they ride on
odds are high for loosing connections to the resistor more then the resistors going bad
but they are easy enough to check in ciruit.you see how the pcb is over heated to
and from them.

just in case the replacement flyback I dropped in was no good, I took one of the old known-good flybacks I had and swapped it in. no change.

B+ was tested at 140VDC.



All secondary voltages are needed to drive the cicuits
TP6,7,8,9 should always note each one.

The ground that a tech uses is just as important as the Voltage TP's
the output voltages or secondary voltages use only cold grounds
the ground side of c123 should be common to the large heatsink
that the hot is on.

The Hot ground C107 neg side, is when your testing the primary side
of smps or power supply..



---

Polo #2:
symptom: no power at all. not even a click from the HOT.

what I know:
this chassis worked perfectly fine. after the other one lost heater glow I popped this one in my KI2 and it died on the spot... when I ran it on a loose tube about 20 minutes previous and it worked fine.

what I've tried:
fuse is good -- no solder joints look suspect. checked B+ at TP6, I'm getting 0.2VDC. the Fromm flowchart calls for replacement of ZD101 and check C112 in the event of "low B+".. but that was replaced in a cap kit. in the event of "0VDC B+" it calls for checking if R103 is open (it was not) and to test diodes D105-D112 (I tested all of them). the only other thing I haven't tried that it says is replacing IC101. how can I tell if IC101 is bad?

You can alway sub the ic101 with the other chassis a good know ic.

Its important to learn from what you already know!!
Like you said you have 140vs b+ on one chassis and the other you don't that
means you have a working primary circuit on one chassis there are the working voltage
on Ic101 so you should know what the voltages are on every pin of ic101.
Any dc coming from the bridge goes to the Mosfet or tp2
even if no drive for the power supply transformer you should have dc at tp2.

Polo 1 is pretty nasty with holding charges in the neckboard btw, so I don't like powering that one up too much. :) to my knowledge, that's the only one of my Polo chassis that does that. does that have anything to do with the heater circuit being flaky?



I hear ya i get shock too. Try discharging c177 with a 10k ohm resistor
untill no snap from the recharge..discharge let go discharge untill its discharged
with the set off ofcoarse and then reach for the neck board.
trying to touch the pcb only the voltage is riding on those 3 large watt resistors..
if you loose you video b+ at any point check R234 for 10 ohms..during the discharge
of c177.really this only helps when you want to handle the neck board for any reason.
 
Well I don't mind getting zapped. How do I fix the 2 monitors? Thats all I really want to do. :) I need them badly for other games.
 
Haha I thought I saw some other text in my quote lol. Hard to tell on a cell phone screen I guess. Thanks

I compared the neck pins on the neckboard from the chassis with no heater against 2 other ones and I am getting an open between the heater neck pins, while I have continuity on the heater pins on my other 2 neckboards.
 
Last edited:
well, this is rich..

I found SEVEN broken traces around the flyback, on, you guessed it, the heater pins. did my patchwork on those and I got heater again, but with an all-white screen. I had a blanking problem and replaced R40 and it's all good again.

I'm running the monitor now with Tekken Tag and it's looking beautiful. :D

now onto the next chassis.

Polo 1 broken traces! glad I could just scrape and solder patch them instead of using wires.
IMAG0868.jpg


Polo 1 then had a blanking issue (not pictured).. replaced R40 and we were back in it..

Polo 1 alive:
IMAG0867.jpg


Polo 2 had some poorly soldered parts in the power supply. real easy fix after all.
IMAG0869.jpg


yep, got both of them working. if I never stressed the importance of checking your traces... well, check your traces. :p
 
Last edited:
silly me, thinking I had this conquered...

Polo #1:
I left the old flyback on cause it worked and I didn't want to do anything further that could mess this up (key words), but the anode would just fall off on its own... clips seemed fine, but I found this as an excuse to put the new flyback back in. upon reinstallation of the chassis to the tube, I apparently touched the color drive heatsinks together since they bend so easy, which pops the blanking resistors R35 and R40. replaced those, wound up breaking the brown wire off the neckboard somehow (part of that cluster of brown, orange, yellow and black wires by the flyback, what do those do?), so I resoldered that back in the hole. now I'm left with a chassis that no longer powers on at all and just emits a buzzing from the neckboard.

Polo #2:
this one kind of frightens me too, albeit not as much. I'm particularly concerned that turning the brightness and screen pots all the way down still presents a very bright picture on the screen. I even sometimes get a line on the left side of the screen. then other times it gets "snowy" with blue dots. before this chassis took a shit, I don't ever recall this being a problem before. I'm leaning towards it being a bad resistor somewhere or perhaps I'm sitting on 2 BAD new flybacks between the two chassis.
 
FFS

ok, I admit, I resoldered the ribbon cable to the neckboard backwards. so since I shot 12V onto the ground line (guessing based on the pin descriptions) what does this mean? I have HV again, replaced R40, but I'm getting a cycling all-white screen that changes from blue, to green, to red, and repeats. I replaced the LM chip with no change.

I played it smart this time and bent the outer legs of the color transistors in opposite directions so I can't accidentally touch the bastards together again.

EDIT: one component I overlooked was T1. can it be that easy? we'll find out. :p
 
Last edited:
I told Ohmerone that there was some user error at stake... after that, I don't know what happened, so I had to figure it out myself.

the Polo #2 had a whining flyback, the sound would go away if you tinkered with the Screen control. the part that was bad however was if you tapped the monitor frame, the whole picture would flip out. I was ready to throw another flyback at it thinking the one on it was bad when I discovered that pesky pin that KLOV users insist shouldn't be soldered in and just leave it tucked underneath was in fact touching another pin. I moved it away and reinstalled.

then guess what happened? it flashed the same white screen with the rotating colors as Polo #1. so I threw a hail mary and pulled the flyback again and just soldered the pin that everyone on KLOV claims shouldn't be soldered and...

I got a black screen. ran the Test pattern, I saw vertical lines. I couldn't wait to try it on the other chassis and guess what...

I fixed that too.

so that pin that you're supposed to just ignore and leave tucked underneath the flyback? solder that bizarch, cause apparently you need it.

reason Polo #1 suddenly developed this problem was because I had an ORIGINAL flyback on it before (in the Tekken Tag screen). so... that is all.

fuck it.

happy gaming, my Killer Instinct 2 is happy.
 
Back
Top Bottom