Ceronix 1492 Chirping

[frosty170]

I have a Ceronix #1492, that had no neck glow and was ticking, I did a full recap and still same problem, I have worked on a few monitor chassis with success, but this is a tough one, I used the light bulb test with the hot removed, connected one lead to the Collector on the HOT (PCB) and the other lead on chassis ground, what should happen when you have a good B+ is the light bulb should be solid, but it's flashing rapidly with chirping from the board, thinking it was the ICXRC584, i bought a kit with the following:
295     1N5348B  160V Zener Diode
292     1.2 Ohm 1/2 W Resistor
287     191K 1/4 W Resistor (Some boards used 169K so if you measure 169K no need to replace)
284     MPSA64 Transistor NOS obsolete item (These are also used in 065 & 098)
192     LA7830 Vertical IC
304     D1651 HOT
280     XRC5184 Power Transistor
I did find my HOT was bad, but with the Bulb test the HOT is removed. When I short pin 15 & 16 on the IC the bulb goes solid, also pin 11 to V- will cause the bulb to go solid. Something in the trigger circuit is not working, also have: B+ rail is intact (252 to filter cap = 0.1 Ω)
Feedback to pins 15, 16, and 11 is present
IC gets 16 V on pin 15
Pin 16 stays low at 3–4 V
Shorting 15 to 16 makes the supply run.
Thank you for any help.
Dave

[Chris-socal]

Hi Dave
Ceronix boards do not really work with traditional troubleshooting techniques. You are basically bypassing the XRC5284 safeguard in order to force a start. Not really useful other than to force HV into a system that is telling you there is a problem. Are you saying you are getting full image and start when you jump pins 15-16? If so be very careful, you officially ruled everything out except X-Ray.
However, I highly suspect you don’t have a proper image unless XRC 5184 itself is defective. The reason a regular lightbulb test doesn’t prove anything on these boards is because XRC5184 requires feedback coming from the flyback to tell it the flyback is working and awake. If not, it shuts down, restarts ( chirps), repeat, repeat.
The other thing XRC5184 is doing is checking load on the low voltage line. If it detects excessive load (HOT or Vertical IC, dead short diode, etc) it shuts down (chirp), repeat, repeat.
There is only one proper way to “force start” without making the inevitable happen and that is to use an independent low voltage power supply which forces start but at very low current that the components can absorb. This allows you to take readings on the board, even the HOT. This method is clearly outlined in the 1492 manual…..BUT it is rarely needed.

If you really blew out a HOT you have something else wrong, like diode 295 shorted or one of the diodes in the power supply section next to XRC5184 or the switching transformer…..or the flyback.

Not knowing the order of appearance I have a few possible theories.
1. You originally had a problem with the flyback and the HOT blew when you forced start.
2. Vertical IC LA7830. You can check this for shorts but it doesn’t prove it works, it just proves it didn’t short. Diode check pins 2-7 to pin 1, none should be shorted.
3. Problem inside of power supply section. 268 shorted, 292 out of tolerance, pins 12&13 on 272 burned open (should read 500 ohms range), open trace coming from Switching power supply.

When we have a board that we can’t find the source of chirp we will replace HOT to rule it out but they are rarely bad. These boards do not often blow them out because of multiple safeguards to prevent it.

For me, I can read a lot by looking at current draw as it is trying to start, but you need an adjustable Isolation AC power supply with a meter for that.

Lastly, Having no neck glow only verifies that the board is not being allowed to start. On these boards if everything isn’t right nothing is allowed to run.

I have several videos that can successfully put anyone to sleep unless you have a 1492 you are eager to learn about…. Then you are in luck! You might want to start with the one focused on 1492 power supply. When we say power supply We are referring to the onboard switching power supply, not the one in the game cabinet.

Keep me posted, and if you want to send me your board I can take a look.cross your fingers it isn’t flyback! Also, post a picture of the board from above, maybe I can spot something.

Chris
https://www.youtube.com/@Mymessyworkbench/videos

[frosty170]

Thank you for the fast reply, Just to clear up a few things, Monitor was dark and no neck glow when in the machine, I pulled it out to do a full recap, I pulled the HOT thinking I could do the bulb test, when pin 15/16 on the IC were shorted the bulb did light and flashing and chirping stopped, I had 127 vdc, so I'm guessing some part of the power supply worked. I checked the HOT since I had it out it showed shorted on the base to collector. I have not put the HOT or monitor back in the machine, I was thinking since I was getting the fast flashing bulb and chirping the problem was not corrected.

I will take a look at your videos.

Thank you

[Chris-socal]

Chirping probably stopped because the bulb was buffering the load. Im kinda surprised the bulb lit up. Probably when the power supply ramped up it sent enough voltage to feel the circuit but then didn’t get feedback from the flyback so it shut down. No chirp because the bulb absorbed the load not the switching transformer.

I haven’t heard of the classic light bulb test working on a Ceronix board. They discuss just about everything in the manual, even a troubleshooting section on the PS and that concept is never mentioned. Only powering it at low voltage and fooling XRC5184 into starting.

More and more there are signs that the flyback might be bad. The best way to check is to put a known-working flyback on. But you have to check those diodes and vertical IC.

Chris

[frosty170]

Thank you Chris, I watched your Ceronix 1492 power video and did more testing. Installed my new HOT back in, turned out my flyback was only giving me 50VDC on the B+, I have a parts board that had written "Bad" on it I was hoping that didn't mean Flyback, swapped flyback and removed my 20VDC, fired up and got 126.6 at the B+. no chirping. I will test 100% once I get my TPG. I want to get monitor at 100% before I plug the board in.
When I first powered on my IGT 701 fortune 1 video poker I did not hear the game or have video, If I have a bad game board do you repair those also ?

Thank you
Dave

[Chris-socal]

Just to clarify, the flyback doesn’t put out the B+, it is put out by the incoming power that is rectified by the diodes between the fuse and the switching transformer, it is governed by XRC5184. That means swapping the flyback released the hold that 5184 had on the other rails. If you don’t have chirping and you have B+ the board should be running.

Connect a black probe onto the big Vertical IC heatsink, clip or use red probe to read pin 8 of LM324, it should be reading something in the range of 1v to 6v. If so, the board is running. The correct setting is between 4.2v and 4.6v using the bottom knob of the flyback to adjust. If it is stuck at .6v you might have a problem…flyback runs but has no image.

Sometimes the bottom knob of the flyback is red locked so you have two options.
1. Leave it alone 
2. Grab it with regular pliers and try to pop it with one firm pop
Just hope the knob doesn’t break off. If it does break you have no choice but to leave it! LOL

Contrary to how other boards work the flyback doesn’t directly impact the base brightness on Ceronix boards, if you turn the lower flyback knob up the auto-bias circuit will turn the master gain down. If pin 8 is low, auto-bias will adjust the brightness up to where it is supposed to be. Setting at 4.6v simply keeps the supporting ICs in a healthy working range. The only brightness adjustment you can impact is the Gain knob on the remote board.

Without a signal source you should have a white/gray screen with some flickering.

Chris

[frosty170]

back again with some results. LM324 is stuck at 6.09 vdc, the bottom knob turns but does not change the voltage up or down. I powered on and had no neck glow, the neck board felt loose (it was on the old flyback), I swapped it with my old one and it fit tight, now I do have neck glow but no white/gray on screen turn the gain on the remote board but nothing. Ai had me check voltage on pin 6 on the neck board it was 87 vdc, Ai will send me down a rabbit hole so I stopped, except I did check the remote ribbon cable and its good.

[Chris-socal]

Ok. This isn’t necessarily a bad thing but it will be difficult to proceed without a video source.
This likely means that the power side of the board is working but there is a problem in the auto-bias portion of the circuit. Its possible the board is hunting for an image and it’s ramping up the source.
I wouldn’t proceed without a source at this point. I might have mislead you in how I said those two statements. The white/gray screen is what you would get if the crt is powered on but the video source was not present.
The adjustments really need to be done with a source.
But I do think pin 8 being stuck at 8 v indicates a problem on the auto-bias. Possibly a shorted transistor, PRA-C is physically broken (rare, but I don’t know the history of the board), LA7851 or LM324 burned out, etc.
You can take readings of the pins of those ICs with a DVM, the expected range is shown on the schematic.
Oh, have you checked the 12v regulator? There is a diode with an arrow pointing to its lead with 12v printed on the board. 12v missing would starve the detection circuit of video and make them drive everything up. The regulator itself is mounted to the frame.

[frosty170]

Hi Chris, I had Ai keep track of the test here's what I have, im not sure why I lost the 6 vdc on pin 8.
Checked the 12 V regulator on the frame — 7812 OUT is 12 V. Diodes 101/102/103 good. Rail is not missing.
Pin 8 is stuck at 0.59 V with neck glow, anode on, no source, screen black. Earlier in this repair, with a different hookup, pin 8 did read about 6.1 V. After the spare flyback, 12 V confirmed, and the tube connected, it settled at 0.59 V and stays there.
IC readings: LM324 pin 4 = 10.7 V. CA3224 pin 22 = 10 V, pin 8 = 0.28 V, pin 10 = 6.92 V. Pin 11 (6 V ref) = 0.66 V. Pin 11 pad to ground is 3.3 MΩ with the chip out, so the board is not shorting that pin. Swapped CA3224E from a spare — pin 11 still 0.67 V, pin 8 still 0.62 V.
PRA-C not cracked. LA7851 pins 10 and 20 are 12 V. Grid-pulse transistor 153 tests good off board. Pull-up 154 is 2.66 kΩ. Powered, 153 base is 0.68 V and collector is 0.15 V.

Could you provide me with contact information so I can discuss my options.
Thank you

[Chris-socal]

When you are talking about pin 8 are you talking about LM324? Because .59 is a common number for flybacks to be stuck at when the secondary coil is burned out. Many times the flyback will start but have no image when at .59v…occasionally it will have an image but you cannot adjust the bottom knob.
You were talking about the neck board at one point and I don’t know what AI had you checking. I rarely ever look at neck board pins unless I have a color issue and I want to know what voltage each color is being driven at. AI might have been looking at a 1493 schematic where the color components are on the neck board.

I have noticed that when I ask AI questions about this board it has a tendency to revert to a wells Gardner schematic. I have to upload the 1492 page I am referring to every time I ask a question to keep it on track.

Without a video source it is really difficult to put any value on the readings because these boards are literally controlling everything other than vertical/horizontal position and post system-gain. It is going to ramp everything up trying to find those rgb bars at the top of the screen…its bias reference point.

If you want to send me your board you can PM here on NLG, Im happy to take a look. In fact, I will PM you some details.

Chris

[frosty170]

Thank you, board will be out to you today.

[frosty170]

Update…after further testing turned out I had 2 bad flybacks, both caused different issues, Thank you Chis for the fix and troubleshooting.

[Chris-socal]

The board looks very good overall, the flyback situation is unfortunate. At least you have a few options , none of which are cheap.

So in the end we think the flyback and the HOT were both taken out. Was the 160v zener diode shorted?

Chris

[frosty170]

The zener diode was good but I replaced it anyway.

[Chris-socal]

Great news, your board is up and running. I will send you a PM.
In the end, after swapping flybacks around to multiple boards, the main problem ended up being capacitor 421 or 423 on the neck board! One of them shorted internally when energized and pulled the bias line down to zero (which is pulled up to .6v by the flyback feed line that essentially wins the battle due to a protective resistor) but leaves the image blank.
There was also cracked solder joint on transistor 153 that was virtually invisible, it was possibly intermittent which would have caused bias control IC CA3224 to go on and off (flicker). Or just off!

Now the topic is solved!

Chris