If there's a number of feature lamps not working you might have a comms issue between the MPU board and the lamp driver board.
Any chance you can make a video showing all playfield lamps in lamp test mode?

Thanks, the video tells the story. You have an open circuit on the signal between the MPU board connector J1 pin 15 and the lamp driver board connector J4 pin 14 (Yellow-Blue wire).

Yes it might be related - the tilt switch is on the same signal as the one having problems between the MPU board and the lamp driver board. Try what radium mentioned a few posts ago and disconnect J2 (playfield switch harness) and J3 (cabinet switch harness) from the MPU board.

Great find!
BTW, depending on the height of the plumb bob do you notice when you move it to the left it doesn't reach the ring? I find the bottom of the plumb bob hits the wood panel preventing contact with the metal ring. I usually put a 3mm spacer at the top and bottom of the plumb bob assembly to correct it.

It was more a general question of whether you have good connectivity of power to the LDB.
What DC voltages do you measure at TP5 on the MPU board, TP1 on the LDB and TP1 on the SDB with your multimeter? These are all the 5V logic power rail.

Where are you connecting the earth lead of the oscilloscope probe? I presume it's the same place you connect the black lead of your multimeter when measuring voltages? Do you read zero volts between the ground points on all the boards and chassis earth braids?

BTW, thanks for the considered response in the other thread about moving your issue back here.

Noted, I was going to ask you to take waveforms of those yesterday, but the last scans you did are showing the SCR is being selected but for whatever reason not latching. So we can presume that the lamp data, address and strobe signals from the MPU board are ok.

Let's backtrack for a moment. On the other thread you mentioned this:

What do you mean about your noise getting lower? There shouldn't be any to begin with.
I see you're using an Alltek Solenoid driver board. I believe their 5 volt power is a switch mode power supply (SMPS) which operates at high frequency and can generate noise.
So, have you got a Bally solenoid driver board you can try - their 5 volts is generated by a "linear" regulator which doesn't generate any high frequency noise.

Isn't this telling us something? When you say "free floating", do you mean not screwed down?

I don't imagine so.

One other thing, I think you mentioned earlier at some point that when the game gets warm less lamps flicker. Have you tried using a hair drier to work out what item being heated is affecting the flicker?

Sorry which board J2 and J3 you're referring to?

She looks truly amazing, beautiful job!

The ground braid running in front of the transformer cage looks like it's insulated from the cage in some clear blueish tube - or is the braid connected to lugs there? I can't quite tell from the angle.

Yes, please do.

Hold off on the raygun, erm I mean hair drier until there are results on the SDB swap.

J4 upper left has ground, 5 volts, the lamp address, data and strobe signals.
J2 lower left has lamp drives only - no logic signals coming in.

Get the hair dryer out and start heating stuff to see what improves the situation. Heat the boards one by one to try and isolate it. Don't cook them, just speed up the boards getting warm to see what reduces the flickering.

Have you got an EPROM programmer?

Incandescents lamps are very low resistance. When they're being switched on by the SCR, there is greater current flow going through the SCR which it needs to latch and stay on.
LEDs are very high resistance. The current they draw when lit is low and causes the SCRs to have difficulty latching on. This is the reason for using resistor solutions with LEDs to increase the current flow which helps the SCRs to latch on. However the resistors being used are nowhere near as low as the resistance of an incandescent lamp. The resistor value we use is "good enough" to solve the issue while keeping power consumption low.
At 6.3 volts, the current through #44 lamps are generally 300ma, while LEDs are generally 20ma - 60ma depending on the type.

Please if you can stay with incandescents for now. The system was designed around them. LEDs practically switch on and off instantly. Incandescents have persistence. Your eyes are not going to notice a brief instant power loss on an incandescent where you will with LEDs.
It's also not uncommon for people who have installed LEDs throughout their game that some of them flicker in lamp test mode but work ok in game/attract mode.
The factory design using incandescents that are flickering right now is the primary issue.

If you look at the waveforms of the lamp power we took (example below), they are what we call rectified but unregulated DC. They basically look like mountains that start from zero volts, rise to a peak around 10 -13 volts then fall back to zero volts and repeats 120 or 100 times per second depending on country.
Bally cleverly designed the system to switch feature lamps on early in the DC phase while the voltage is low (but rising), in order to gently power on the lamps. When the voltage has then dropped back to zero volts at the end of the DC power phase, the current through the SCRs drops to zero and the SCRs switch off. This process resulted in extending the life of the lamps. When the DC voltage has hit zero, this is what we call Zero Crossing. The Zero Crossing detector on the MPU board interrupts the CPU so it can take care of critical system functions which includes refreshing the lamp SCRs.
Lamps are refreshed starting from address 0 through to 16. The problem all along appears to be lamps that are being switched on earliest in the DC lamp power phase with address 0 lamps being worst affected. Why your game is suffering from this is the big question.

FeatureLamp_DC (resized).jpg

You can leave the higher addressed lights as LEDs.

Hang on, I thought incandescents (the low addressed ones) were also flickering in lamp test mode?? The video of the single incandescent lamp you hooked up directly between the rectifier board and lamp driver board was flickering and it was in lamp test mode right?

When we did this, was the game in attract mode, lamp test mode?

barakandl and vid1900 the video here shows the single lamp test wired directly from the rectifier board to the lamp board (playfield is disconnected). Lamp is an incandescent. Normally in attract mode this lamp flashes exactly the same way it does in lamp test mode but you can see it's also flickering.

https://pinside.com/pinball/forum/topic/bally-as-2518-club/page/26#post-4620922

So this eliminates lamp power connectors from the rectifier board or playfield wiring as the issue.

jsa I have to agree with barakandl and vid1900 though, at this point you need to try swapping some of those SCRs. Put aside the fact that two lamp boards are doing it. Maybe those SCRs have been shocked by something you did on the playfield.
I would swap Q14 on the Bally lamp board, disconnect the playfield and then try the single incandescent lamp test directly between the lamp board and rectifier board again in whatever mode has been inducing the flicker.

I know, we've gone in depth through this issue when it was being discussed in the "Bally/Stern AS-2518 Club" thread before it got moved back here. There are plenty of oscilloscope waveforms taken while we were trying to determine what was happening. Everything apart from the SCRs failing to latch about 2 out of 3 times seems normal.

Quickly scroll through these:
https://pinside.com/pinball/forum/topic/bally-as-2518-club/page/26
https://pinside.com/pinball/forum/topic/bally-as-2518-club/page/27

Yes, we've almost exhausted everything so this is why we're suggesting to swap the SCRs just incase both lamp boards have the same issue.

It's truly bizarre...

A short at the lamp socket usually.

When I took the waveforms on my lamp board in the other thread, the next day one of the LEDs I was nowhere near tampering with on that game started flickering ON when it was supposed to be OFF. After an hour or two that SCR eventually got stuck on. There was no short and it happened out of the blue - the SCR just died a natural death.

The job of a rectifier is to convert AC to DC. It does not remove ripple - that's the job of a filter capacitor/regulator.

The lamp DC supply was already measured here with a scope (second image):
https://pinside.com/pinball/forum/topic/bally-as-2518-club/page/26#post-4620933
As you can see it is rectified but unregulated DC (full of ripple). The whole design of this lamp circuit relies on the ripple dropping to zero volts in order for the SCRs to switch off. If the lamp voltage was flat regulated DC the lamps would never switch off.

It's unregulated DC so ripple is going to be full scale. The only thing that can affect the peak is the voltage out of the transformer and load. The DC voltage in the waveform jsa took looks a little high, but if anything that should have made things better, not worse since the SCRs would have more current flow to cause them to latch.

We already tested connecting a lamp directly to the rectifier board - same issue.
I think we measured ground voltages earlier (can't remember what they were) - there is probably merit in running a jumper wire directly from the rectifier board ground to the lamp driver board ground.

The lamp diver board doesn't get ground from the cabinet/head braid. It gets it from the rectifier board.
Actually there are already three ground wires running from the rectifier board to the lamp driver board:
Rectifier J3-4 to LDB J1-1
Rectifier J3-3 to LDB J1-2
Rectifier J3-14 to LDB J1-11

What's the likelihood all three of those wires have poor connections after you've re-terminated them all?
Try running a jumper wire from the lower leg of either white ceramic resistor on the rectifier board directly to the ground test point on the lamp driver board and see what happens. Be careful you don't jumper to the wrong spot and blow stuff up.

The curious thing about your SCR waveforms is there is always two missed latches in a row..

I wouldn't bother but if you really want to isolate the ground for test you could try it.

Is the transformer still wired for 115VAC or did you change it to 120VAC during the resto?

Can you post some pictures of the wires soldered to the transformer?

I don't see any transformer pics in your gallery showing which lugs the wires are soldered to.
Though I can vaguely see from one of the pictures with the cage in front of the transformer that it looks like it's wired for 115VAC.

The beginning of the manual shows how to wire the input voltage at the transformer.

Transformer3 (resized).jpg

Change it to 120VAC. In all honesty it might make the issue worse, but there's enough weirdness in this that who knows. If it's not obvious cut the link between lug 9 and 11 when you move the yellow wire.

I actually expected it might make the lamp issue worse since you now have slightly lower voltages out of the transformer compared to before.

Have you run the hair dryer test yet? Alternatively using freeze spray to cool components down to see what's thermally affecting the flickering?

This is pointing to the solenoid power as the potential area of issue. The zero crossing signal to the MPU board is basically solenoid power from the rectifier board. Sounds like the point which the MPU board is detecting "zero crossing" on that power rail is varying depending on solenoid/coil load.
Is the larger ceramic resistor on the rectifier board getting hot? i.e. is it dissipating power or is it open circuit?

Took some waveform snapshots from an early Bally with my old dual input oscilloscope. These are incandescent lamp based.

The following picture shows when the zero crossing detector on the MPU board falls and activates the CPU interrupt in reference to zero crossing source (43V solenoid power).

IMG_0027b.jpg

As above but below is zoomed in on the 43V solenoid power voltage. Zero crossing interrupt triggers on the rise of the 43V solenoid power when it's around 6 volts.

IMG_0052b.jpg

Below shows when the Q14 SCR on the lamp driver board is activated on the gate leg after zero crossing detector has triggered and the CPU zero crossing interrupt service routine refreshes that SCR. Note below sometimes the time before activating the SCR drifts.

IMG_0066b.jpg

As above but below is zoomed in time wise to show the Q14 SCR is usually triggered/activated around 0.49ms after the zero crossing interrupt triggers.

IMG_0062b.jpg

Since the lamp flashing is worse when the gate coil is active, we can presume something is potentially going on with the 43V line since it's used as the reference for when the zero crossing service occurs (which handles the lamp board SCR refresh).

If your scope is dual input, you could try and take similar readings to compare.

Interesting... Now we're finally onto something.
Your waveforms are showing extra skinny pulses on the zero crossing detector output because of noise on the 43V line. Those extra zero crossing detector pulses are causing the CPU to run the zero crossing service too early and is why you are getting the lamp flickering (because the lamps are being refreshed earlier than they should be, i.e. before there is enough lamp current for the SCRs to latch).

The question is what's causing all that noise on the 43V line.
Disconnect J3 and J1 from the rectifier board. This disconnects everything past the rectifier board.
With your oscilloscope, take a snapshot of ground and another snapshot of the 43V line.
For ground hookup the oscilloscope probe to the bottom leg of the large ceramic resistor on the rectifier board.
For 43V hook up the oscilloscope probe to the top leg of the large ceramic resistor on the rectifier board.
Also, take a snapshot of the ground braid somewhere.
BTW if you can, try to offset the signals on your oscilloscope so the voltage starts near the bottom of the image (not the middle) so you can fit more detail in.

0e79fb3f3835827ee041572492b2ade55b7553f6.jpg
06ba9531772953ac971149fd02b475a4ae11a45e.jpg
0ce9043105c03b3bbf9094956a5a2328905fc7f0.jpg

Can you take a snapshot with the - leg on the bottom of the large ceramic resistor and the + leg on the top of the large ceramic resistor?

Yes, with power on.

Ok, disconnect the line cord from the wall socket.
Remove J2 from the rectifier board and pull out the thin green solenoid power wire at pin 2 and tape up the end and leave it hanging.
Carefully reconnect J2, plugin the line cord, power up and remeasure across that large ceramic resistor.

Hmm, with the machine off, can you check with your multimeter on resistance mode that you have zero ohm continuity from a ground braid to the lower leg of the large ceramic resistor?
Disconnect the line cord from the wall socket and check that you have zero ohm continuity from the earth pin on the line cord plug to the lower leg of the large ceramic resistor.

Leave the line cord from the wall socket disconnected.
Remove J2 from the rectifier board and pull out wires at pins 1, 2, 5 and 9. Tape them up separately and leave them hanging.
Carefully reconnect J2, plugin the line cord, power up and remeasure across that large ceramic resistor.
We are now removing everything to the rectifier board except line ground and line power to power the transformer.

Can you take snapshots of test points TP1 and TP3 on the rectifier board? Want to see if that noise is appearing on the other DC voltage rails (6.5V and 12V respectively).

So on TP1 when the lamp voltage reaches zero, the ringing noise stops.
On TP3 however, the 12V line is not dropping to zero volts - it's dropping to 3.5V which coincidentally is the size of the peak to peak ringing noise on the 43V line (just freak luck). Does your oscilloscope allow you to go greater than 1V/div so you can fit the full height of that TP3 waveform? Also adjust the time scale so we can see at least two repetitions of the wave.

If you remove fuses F1, F2, F3 and F5 - leave F4 and F6 (do this with the line cord disconnected since F6 may have live power to prevent any accidental shocks), do you still get the ringing noise on the 43V line (top of the large ceramic resistor) after powering back on.

If you have a spare line cord we might hook it up direct to the rectifier board to bypass cabinet wiring and the EMI filter.

When you power on, can you hear the transformer hum? If yes, is it barely noticeable or fairly noticeable? Either way can you make sure the 4 screws on each corner of the transformer that hold it together are nice and tight.

By any chance is there an online manual for your oscilloscope? I'd like to see what's going in and out of the transformer but want to make sure we don't damage your oscilloscope.

Looks like a neat little unit. I wanted to check that the "-" lead on the probe wasn't internally connected to ground which it isn't. This means we can measure AC with it.

It supports max +/- 25V for measurement. We want to measure more than this. I think I asked before, does the probe have a X1 and X10 switch? Switching to X10 will allow you to measure 10 times higher voltages so you can read up to +/- 250V.

Looks to me like it's in the 20kHz range. Everything is disconnected from the rectifier board except power and the ripple is still there. There is no high frequency ripple in my waveforms above.

See the picture below with the red switch: Did your oscilloscope came with alligator clip leads, or a proper oscilloscope probe like below? Did your scope come with the "Analog Discovery BNC Adapter"? If you have the BNC adapter but the unit came with alligator clip leads, consider getting some oscilloscope probes from ebay (they're cheap).

Can you remove fuse F4 from the rectifier board so the only fuse left is F6. Set up you oscilloscope so the offset is back on zero so the wave is in the middle of the image. Connect the negative lead to solder point E4 and the positive lead to E3. Lets see what the AC waveform looks like out of the transformer for the 43V supply.

Do the same with the positive lead on point E11 and the negative lead on E12. This is the AC output for the 12V supply.

Oscilloscope_Probe1 (resized).jpg

In that case you better not do it on the 43VAC supply. The AC side of the 43V supply is going to be near 130V peak to peak. Note the 43V DC supply you've been measuring so far has been nearly 65V peak to peak - you can see it in the first waveform image from my post #557.

You should be safe to do it on the 12VAC points (E11 and E12). Peak to peak it will be around 34V peak to peak. Remember to remove fuse F4.

Do you have resistors on hand? If yes, what values do you have? We may need to make up a voltage divider with them to measure the 43VAC supply.

For now, just measure between E11 and E12 on the rectifier board and post the waveform.

This is just getting too weird. You had the power on at the machine right? We should be seeing a sine wave - it's clipping badly with the flat spots on top and bottom of the wave.

Looks to me like the noise is still there. Can you redo it with the voltage on 5V/Div and time on 2ms/Div then at 200us/Div ?

It seems like when you change the time base it zooms in on the stored recording which is ok. If you still have the recording can you change the voltage to 1V/Div so we can zoom in to see the noise? In any case it looks like it's still there.

Are you currently powering the rectifier board directly with the line cord cable you made up or did you reconnect the rectifier board back to the cabinet power wiring/EMI filter?

I've gotta head out, won't be back for another day or so.

I mean it looks like the noise is coming in on the transformer - it might sound like an odd question but you did move the machine from one site to another when you completed it right?

It would be good to get an oscilloscope measurement from another machine - what else have you got? If you can't work out where, hopefully someone can chime in where to measure on your other machine a similar AC or DC voltage that's unfiltered/unregulated from it's power supply.

Something is actively generating that noise, your soldering is not at fault.

To me, this noise we're seeing is coming in from your wall socket probably from a bad switch mode power supply or inverter in the house. Do you have solar panels?

Have you still got the original EMI filter from the game? It might have been doing a better job at rejecting the noise. Maybe you could hook it inline with the direct line cord you've got.
Are you friendly with either of your neighbors? Maybe you could run a long extension cord from their house to power the machine and see what happens.
Or what's the chance you have a UPS (uninterruptible power supply) you could hook the machine up to?
.

You'd need to hook up a couple of very high value resistors in series to create a divider circuit. See below:
Of course I need to stress that you exercise extreme caution to prevent shock. The line peak to peak voltage is near 340V.
If you don't have these value resistors tell us what you have that's in the vicinity.

MeasuringLine.jpg

Have you got an old fashioned AC power pack you could measure the output with your scope? Something like a 9VAC, 12VAC or 15VAC power pack? If you haven't got an AC unit what about a DC unit? Will save you messing around with hooking resistors to your line cord for measurements.

I didn't see that coming when asking the solar panel question..

I'm glad the game was effectively disconnected after the transformer. We might otherwise be looking at some damage.

We might be counting our chickens too early.

If you've got something like a 15VAC transformer power pack, plug it in and hook up your oscilloscope to its 15VAC output and see if there's any of that noise.

So it's still there. Got a pic of the wave repeating twice? The voltage is going under zero so something isn't right for DC. Can you post a picture of the transformer label?

Your oscilloscope can't scale the image so you're missing the peaks. You might want to invest in some oscilloscope probes so you can X10 the input. They're pretty cheap on ebay. You'll just need to get some BNC connectors to mate them to the oscilloscope or get the official BNC adapter.

Yeah the issue looks about the same to me. The switching interference is about 2V peak to peak on that 25VAC output. On your 43VAC output at the pinball transformer is was about 3.5V peak to peak. With the stretched sample in picture 2 it calculates more accurately to around 24.5kHz.

Feel like reconnecting everything in the game and see what happens?

Before with Inverter on:

Before.png

After with Inverter off:
After.png

Wow, what a most unique problem. Your oscilloscope was invaluable in diagnosing this..

I was looking up switch mode power supply frequencies earlier and some web sites mentioned inverters in the conversation and well inverters are used with solar panels. To be honest I almost didn't bother asking the solar panel question because I was expecting the answer to be no.
All good.

Gotta like a plug'n'play solution