Author Topic: Kortek KT-2182 chassis - not turning on (worked fine a few days ago) (Read 15155 times)

ed12 · « **Reply #40 on:** March 10, 2013, 01:36:42 am »

i have a fast q here
did u notice a light blue glow in the neck of the tube ?

ed

Midcoastsurf · « **Reply #41 on:** March 10, 2013, 03:40:51 am »

There has never been a glow in the neck when the monitor was working. How do I check the heater voltage? Measure that pin on the solder side of the neck board?

Thanks

lilshawn · « **Reply #42 on:** March 10, 2013, 11:34:27 am »

you mentioned earlier that your voltage at D110 was 2.6vDC. this is your heaters power supply. it must be 6.2 volts.

you need to find out what's dragging down this voltage.

no heater = no picture. The heater supplies ions to the color guns in the neck. if there are no ions, there is no picture.

Midcoastsurf · « **Reply #43 on:** March 10, 2013, 01:26:38 pm »

I will re-measure D110 and post back.

Thanks

Midcoastsurf · « **Reply #44 on:** March 10, 2013, 03:31:51 pm »

The voltage at D110 is really high now...

D110 = 11.71 VDC

D107 = 10.87 VDC

Midcoastsurf · « **Reply #45 on:** March 12, 2013, 10:05:43 pm »

Hmm...almost double the voltage than why it should read at D110.

I have never seen a glow in the tube even when the tube did work.

Could I measure the heater pin voltage on the neck board? If so, do I just connect the other lead to ground?

lilshawn · « **Reply #46 on:** March 12, 2013, 10:26:52 pm »

sorry for late reply.

yes ground one lead and measure the lead marked "h" (the other heater pin will be connected to ground.)

Midcoastsurf · « **Reply #47 on:** March 12, 2013, 11:21:36 pm »

No worries lilshawn, I really appreciate all your help!

I get a 0.0 vDC reading at the heater pin solder joint on the neck board. Re-checked the voltages and get the following:

D107 = 13.3 vDC
D110 = 12.3 vDC
D120 = 87.7 vDC
D121 = 210 vDC

lilshawn · « **Reply #48 on:** March 13, 2013, 01:20:24 pm »

looks like your 6 volt has run away on you now... like there's no load.

check for a loose or broken connection between the neck card and the main board. continuity test the wires and connectors starting from the Heater pin on the neck card and working your way back to the connector and be sure there is continuity. then do the wire down from the neck card to the main board.

Midcoastsurf · « **Reply #49 on:** March 13, 2013, 04:40:07 pm »

OK, so the load on D110 comes from the heater receiving voltage and being powered, correct? I will trace the connection back to the main board starting at the heater pin and see if I can find a break in continuity.

lilshawn · « **Reply #50 on:** March 13, 2013, 06:41:07 pm »

yes.

the outputs are unregulated. IE: the output is going to vary up and down as the load increases and decreases.

power supplies like your computer power supply's 5 volts are going to push out more current as the load goes up and decrease as it goes down. this is so the voltage being "seen" by the computer stays a constant 5 volts. this is a regulated power supply.

the power supply in the monitor is set at a predetermined level...the voltage stays the same because the load never changes.

Midcoastsurf · « **Reply #51 on:** March 15, 2013, 01:41:30 am »

After working my way back from the heater pin socket to the chassis, everything was good until the resistor...

When taking the resistor in and out to test it earlier, the pad lifted

I was able to connect the leg of the resistor to the cleaned trace with a cut leg of a resistor. The result?

lilshawn · « **Reply #52 on:** March 15, 2013, 11:08:53 pm »

cool beans bro.

i'd let it run for a few days to stress test it, but I think you are in the clear.

Midcoastsurf · « **Reply #53 on:** March 29, 2013, 03:06:48 pm »

Ok, I left the game on for 12 hours without any issues.

Now, when playing a game, the monitor will turn off (you can see the image collapse into the center and everything goes black), but the game sounds can still be heard in the background. The screen then comes back on in 3-5 seconds. This happens about 1-2x per 9 holes. You can hear a "click" sound right before the monitor comes back on. I can't pinpoint this to a button being pressed or any action by the player. It can happen at any time (ball is in the air, moving the trackball, hitting the start button, etc.)

What is going on here?

Thanks

lilshawn · « **Reply #54 on:** March 29, 2013, 03:54:18 pm »

Quote from: Midcoastsurf on March 29, 2013, 03:06:48 pm

you can see the image collapse into the center and everything goes black

what kind of collapse are we talking about here?

is it just powering off... or is the image ACTUALLY collapsing. (horizontally or vertically squashing down?)

sounds like you have an overheating component (HOT or the vertical IC (LC7832?)) or a broken solder joint on something that gets hot and being intermittent.

make sure your vert IC has good contact with it's heatsink. it should have some goop on there to help. make sure it's not dry. if it is dry and crusty, it's going to act like an insulator instead of a conductor of heat.

if it's actually POWERING OFF, then check your B+. while it runs. if it's all over the place you might have a bad feedback capacitor. when the power sags down (like when it's bright) it's not bringing it back up again properly and the system shuts down. check the heatsink on your FET for the B+ too.

Midcoastsurf · « **Reply #55 on:** March 29, 2013, 04:34:44 pm »

Collapse was probably the wrong term. The monitor is just turning off, then turning back on.

lilshawn · « **Reply #56 on:** March 29, 2013, 05:59:15 pm »

hook a volt meter to the B+ and watch it. if the B+ is dropping out when the monitor shuts down, then it's the power supply... if not, it's someplace else.

does your monitor size go wonky when the screen gets bright? (narrows up or changes size considerably when bright)

Midcoastsurf · « **Reply #57 on:** March 29, 2013, 06:21:38 pm »

If I increase the brightness on the monitor by turning the bottom dial on the flyback counter-clockwise (just a hair), I don't see any size changes to the monitor, the screen just gets brighter. The size also remains consistent if I increase the brightness from the remote PCB.

Where is the B+ measured at?

Thanks

lilshawn · « **Reply #58 on:** March 29, 2013, 07:07:04 pm »

Midcoastsurf · « **Reply #59 on:** March 30, 2013, 02:20:28 pm »

D121 measures a steady 209-210 vDC. I played three rounds of 9 holes keeping the meter hooked up and on top of the control panel, but of course the monitor decided to cooperate and did not shut off during the three games.

lilshawn · « **Reply #60 on:** March 30, 2013, 07:26:41 pm »

keep on it. it will glitch out when you least expect it.

that's why i like my fluke 87V, it has a logging function that will keep track of the high/low/avg voltage, it beeps when it sets a new high/low then i can recall it with a push of a button.

i just plunk it on the monitor and leave it for the day. then i can come back later and see if it dropped out.

Midcoastsurf · « **Reply #61 on:** April 05, 2013, 05:37:56 pm »

OK, the monitor only goes off every 1 in 3-4 games now. The range is: 198 - 220 vDC. The monitor turns off and comes back on much quicker than it used to, otherwise the voltage would probably continue to keep dropping. It's only 3-5 seconds between a blank screen and the image coming up again.

lilshawn · « **Reply #62 on:** April 05, 2013, 06:27:50 pm »

the operating volts look okay...what's the voltage while it's blank?

Midcoastsurf · « **Reply #63 on:** April 05, 2013, 07:46:04 pm »

When blank, the lowest was 198 and highest 220. When the monitor is on, it's a steady 209-210.

Midcoastsurf · « **Reply #64 on:** April 19, 2013, 06:38:27 pm »

I took a closer look at the HOT and noticed it had a piece of thin rubber between it and the heatsink it was screwed to. Some of the rubber had broken off, so I removed the rubber piece and put some heatsink compound between the back of the HOT and the heatsink. The monitor no longer powers up. My guess is that I created some cold solder joints when bending the HOT away from the heatsink to apply the compound. Any other thoughts?

Thanks

lilshawn · « **Reply #65 on:** April 19, 2013, 06:43:07 pm »

sorry for the lateness of my reply. i've been out of town. i read your post then forgot about it.

the tab of the HOT must be insulated from the heatsink by the silicone pad. the heatsink is grounded and the tab is high voltage. if the silicone pad is punctured and the tab grounded, it won't work.

Midcoastsurf · « **Reply #66 on:** April 19, 2013, 06:48:41 pm »

By tab, you are referring to the exposed metal on the back of the HOT, correct? My guess is I did not use enough compound, or I screwed the HOT down too tight and bridged the heatsink to the tab of the HOT. Good to know.

Is there a reason the HOT is connected to the heatsink in the first place if it is not using the surface area to dissipate the heat it generates? Why can't I just pull the HOT away from the heatsink 1/4 of an inch?

Thanks again!

ed12 · « **Reply #67 on:** April 19, 2013, 07:20:45 pm »

yes it will and no u do not remove it from the heatsink unless to replace

ed

lilshawn · « **Reply #68 on:** April 19, 2013, 07:43:58 pm »

the HOT well... runs hot. in all the infinite wisdom of the engineers, the "output" leg of the HOT is attached to the tab (the die is soldered to the tab) and is all attached together. this would make the heatsink charged to high voltages.

as such the tab needs to be isolated, but it also has to have heat drawn away from it...but they also have to conform with certain safety rules to become certified. (underwriters, electrical code, etc.) and it's not so safe to have a large piece of metal charged to several hundred volts. so, what they do is insulate the tab from the heatsink using a silicone pad or a mica sheet. that way, the heat is drawn away, and the heatsink is insulated from high voltage.

BUT, they also say that all exposed metal be grounded. so the heatsink is grounded.

whew.

so if you attach the HOT to the heatsink without protection, it's effectively grounded out.

Midcoastsurf · « **Reply #69 on:** April 19, 2013, 07:48:50 pm »

Nice explanation, thanks! So will heatsink compound work in this case, or do I need to find a replacement mica/silicone pad? If I need the pad, then is there a DIY solution, or do I need to buy from an electronics supplier?

lilshawn · « **Reply #70 on:** April 20, 2013, 03:31:59 pm »

you need to either:

good:

replace the pad with a new one. silicone / mica doesn't matter....heatsink grease is fine to put on there too if you like as long as it's not conductive.

BAD/UNSAFE:

screw the HOT directly to the heatsink and isolate the heatsink by cutting the traces attaching it to ground AND THEN DON'T EVER TOUCH IT OR HAVE ANYTHING COME IN CONTACT WITH IT EVER EVER EVER EVER EVUR EVAR EHVAR!!!!!!1111!!oneoneoneeleven

although it will work, isolating the heatsink creates a HUGE electrocution hazard. poking you finger in and touching a tab is not easy to do accidentally ...brushing you arm by a HUGE ASS heatsink is.

as long as the pad doesn't have any holes or is torn in such a way as to allow the tab to ground out it should be fine. you can test this by mounting the HOT then testing for continuity with a meter between the metal tab (or center leg) and the heatsink. way high resistance (1000's of ohms (kilo ohms)) or open is fine a short (0 ohms) or low ohms is bad.

Midcoastsurf · « **Reply #71 on:** May 01, 2013, 02:21:59 am »

OK, I put a piece of Sil-Pad 1200 between the heat sink and the HOT. Hooked everything on the chassis back up and nothing. The fuse is good and I measured 121 vAC at the fuse holder (both sides), but no voltages at the big diodes in the power supply section on the chassis. Where should I look next?

Thanks

lilshawn · « **Reply #72 on:** May 01, 2013, 09:51:59 am »

Measure the output between the cathode side (banded leg side) of D120 and ground.
there should be 80V DC.

check for voltage at L108 (either side) and ground (could be up to 200 volts DC so prepare yourself and your meter for it.)

something is not quite right.

Midcoastsurf · « **Reply #73 on:** May 01, 2013, 10:26:48 am »

No voltage at D120. I will check the other spot tonight. Maybe the HOT went bad when I accidentally mounted it straight to the heatsink?

lilshawn · « **Reply #74 on:** May 01, 2013, 10:32:04 am »

that's a possibility. you can test that theory by removing the HOT and seeing if the voltage at D120 and L108 returns.

grantspain · « **Reply #75 on:** May 01, 2013, 04:48:32 pm »

pretty sure you would have killed that transistor by mounting without insulation sheet
just meter the transistor

Midcoastsurf · « **Reply #76 on:** May 04, 2013, 05:13:47 pm »

Did some testing on the HOT with my DMM set to diode setting. It starts out at 400 and here are the results:

Is the HOT bad?

grantspain · « **Reply #77 on:** May 04, 2013, 05:31:53 pm »

i guess it depends if 1=dead short,if so then yes its knackered

Midcoastsurf · « **Reply #78 on:** May 04, 2013, 06:07:11 pm »

It actually drops down from 400 to 001. A fuse that is good will read the same on my DMM. Is the only other test to pull the HOT and see if I get voltage at D120 as lilshawn suggests?

Thanks

grantspain · « **Reply #79 on:** May 04, 2013, 07:26:54 pm »

a good hot will read something like 0.400 certainly not 000


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