Meteor
Stern Electronics, 1979I have a Meteor with an Alltek lamp driver board it is fully led'ed however a few still flicker.
The rocket 1to7 and the specials on the left flicker.
If I put a resistor across them I can make them work normally.
My question is, is this acceptable with an Alltek board, am I likely to damage anything.
It would appear that this sequence of LED's needs a little more current to lock the scr's.
I wonder how low I can go with the resistors to achieve the required result.
Quoted from raysco:I have a Meteor with an Alltek lamp driver board it is fully led'ed however a few still flicker.
The rocket 1to7 and the specials on the left flicker.
If I put a resistor across them I can make them work normally.
My question is, is this acceptable with an Alltek board, am I likely to damage anything.
It would appear that this sequence of LED's needs a little more current to lock the scr's.
I wonder how low I can go with the resistors to achieve the required result.
With a DMM measure the voltage at the board where you ran the extra wire over to the lamp panel GI.
Thanks for your quick response.
I can measure the voltage in the morning, but can you tell me what I am looking for. All the rest of the lamps work fine except for these 9 lamps.
Would the wrong/ low voltage cause only a limited number of lamps to not work properly?
Yes, provided it’s the right amount of resistance. Too high and it will put to much load on the board.
The board was built to work with some resistance and in the form of light bulbs. Adding that back in allows it to latch on and off. It will be fine.
Quoted from raysco:My question is, is this acceptable with an Alltek board, am I likely to damage anything.
It would appear that this sequence of LED's needs a little more current to lock the scr's.
Since the Alltek will run regular incandescent bulbs as well, that are higher current... it should be fine to add a bit more load via resistor at the lamp socket.
Quoted from raysco:I wonder how low I can go with the resistors to achieve the required result.
The answer of course is to go only as low as necessary to stop the flickering, but also keeping in mind that at some point there is going "too low" (and you may need to then suspect a board issue).
With the extra resistor added to the lamp socket, you've got to do the parallel resistor calculation I think.
https://www.allaboutcircuits.com/tools/parallel-resistance-calculator/
Assuming the Alltek resistors are 1k ohm (just a guess, you'd have to check what it is if there's a schematic or via a mutlimeter).So let's say you went with 680 ohms on the resistor on the lamp socket. According to that calculator, it would bring the total resistance down to about 405 ohms. With a 470 ohm resistor at the lamp socket, it would be around 320 ohms.
I'd say keep the resistance above 350 ohms if not above 400 ohms. Excessively low total resistance values on the circuit will cause excess heat and part failure. Anything under 200 ohms total resistance for sure, but I wouldn't shoot for anything lower than 350 ohms total resistance (after doing the parallel resistor calculation) and would personally aim for a bit higher than that even.
This is just an example, I'm not 100% certain if the resistors the Alltek uses are 1k or a bit higher/lower.
Thanks for the replies, I tested with a 1k, and a 560 ohm, both work fine. Probably need to test and check how the board is running after a while. Wouldn't want to damage anything.
will try and measure the resistances on the Alltek board.
Is there a ground wire connected to the Alltek lamp driver board? I know without a ground, ghosting will still happen.
I have noticed on the LDB I make Stern MPU200 games may need a lower ohm load resistor than bally games or a couple lamps may flicker. I am using 560R. I assume it is the faster clock speed in MPU200 effects the latching nature of the SCRs. Changing nothing but the MPU software from Bally game to Stern MPU200 sometimes makes a previous 100% LDB have one or two positions flicker. Adding a parallel resistor to drop resistance 100R or so fixes them.
Also to consider is the feature lamp voltage. The more lamps turned on the higher the load will be. Which will lower the voltage so there is less current through the resistor keeping the SCR loaded. Making the LED feature lamps more likely to flicker.
I posted about this a few weeks back if you want to check it out.
Quoted from acebathound:Assuming the Alltek resistors are 1k ohm (just a guess, you'd have to check what it is if there's a schematic or via a mutlimeter).So let's say you went with 680 ohms on the resistor on the lamp socket.
What resistor are you talking about? There's nothing else on the SCR anode out to the playfield on the Bally LDB, but I am not familiar with the Alltek version. Is the SCR circuit dramatically different on those? I always considered 470 ohms for the resistor on Bally LDB games based on this post:
"Once upon a time there was a led that flickered when it was installed
in an older Bally or Stern pinball machine. The LEDS flickered on any
machine that used a Bally As2518-14, AS2518-23, or Stern LDB-100. These
lamp driver modules were used from 1977 thru 1989. These boards use SCRs
to switch # 44 Lamps on and off in pinball machines. This has worked
well for many years, until someone tried to use a led instead of a #44
lamp. The LED flickered. I discovered that the reason the led flickered
was that the LED drew no current below it’s forward bias point that it
would not hold an scr latched. If a resistor is added in parallel with
the led, it would draw enough current to keep the scr latched and there
was no flicker. (Life is Good). Through testing I found that a 470 olhm
resistor was more than enough to keep any of the scrs that I tested
latched. The 470 olhm resistor can be added in the socket of the led,
soldered across the lamp socket, or soldered on the lamp driver module.
The electrons don’t know or care where the resistor lives, as long as it
will cause a 1ma load to the anode of the scr. All 3 ways have been done
and they all work well." - text by Ron Googe.
Quoted from wayout440:What resistor are you talking about? There's nothing else on the SCR anode out to the playfield on the Bally LDB, but I am not familiar with the Alltek version. Is the SCR circuit dramatically different on those? I always considered 470 ohms for the resistor on Bally LDB games based on this post:
"Once upon a time there was a led that flickered when it was installed
in an older Bally or Stern pinball machine. The LEDS flickered on any
machine that used a Bally As2518-14, AS2518-23, or Stern LDB-100. These
lamp driver modules were used from 1977 thru 1989. These boards use SCRs
to switch # 44 Lamps on and off in pinball machines. This has worked
well for many years, until someone tried to use a led instead of a #44
lamp. The LED flickered. I discovered that the reason the led flickered
was that the LED drew no current below it’s forward bias point that it
would not hold an scr latched. If a resistor is added in parallel with
the led, it would draw enough current to keep the scr latched and there
was no flicker. (Life is Good). Through testing I found that a 470 olhm
resistor was more than enough to keep any of the scrs that I tested
latched. The 470 olhm resistor can be added in the socket of the led,
soldered across the lamp socket, or soldered on the lamp driver module.
The electrons don’t know or care where the resistor lives, as long as it
will cause a 1ma load to the anode of the scr. All 3 ways have been done
and they all work well." - text by Ron Googe.
feature lamp bus is brought to the LDB and the load resistor is there instead of across the lamp socket.
Quoted from KenLayton:You do know that the Alltek lamp driver board is configured for incandescent bulbs straight out of the box, don't you? If you want to run LED bulbs you have to configure the board for LEDs first.
Yep. OP did you attach the cable to a control lamp on the wire on the backbox?
My board is configured correctly to run LED's.
I queried with Alltek and Dave has kindly offered For me to return it for testing at postage cost only, so I could do that.
However As there are only 9 lamps flickering I might just take note of barakandl as posted above. 10x 560 ohm resistors cost 55c as There don't appear to be any "don't do this" comments.
Will test it out and keep an eye on the board. Will also report back if any issues occur.
Interesting. I recently added Led's to my Meteor and my Stars. I used the "Classic Ster/Bally Led Adapter Kit" on both of them. I had to swap out over 9 scr's on each of the factory lamp driver boards to get rid of the flicker. And some will still flicker even with new Scr's.
I will have to try adding the resistors on the lamp sockets.
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Westlake
Toronto, ON
Boston, MA