Hi!

Just bought my first couple of leds to try out on my jackbot. Im happy with the result so far but i have a question.
I replaced some insert lamps with wedge lamps sitting on a lamp board in the game. I put in LEDs rated for 6VDC, direct current that is. And it worked like a charm.

Also had some green bayonett based 44/47 leds, also 6VDC. But those did not work in the sockets under the inserts, however they work when put in a GI socket on top of the PF. I noticed that the leds did shimmer with like half the strength when I held it against a bayonet socket under the PF. So, my theory is that those sockets have AC on them but the lamps are DC, so they wont work in the socket but when one "pole" of them touches the socket it only gets on wave of the AC and hence it lights up with half the strength in brightness.

Im new to ledding so I was just curious about this issue. If the inserts require AC bulbs how come the light boards does not, since they work with DC bulbs? Any general guidelines here?

Also noticed a very fast and tiny flickering from the GI lamps I put in the GI on top of the PF, kinda like a flourescent lamp pipe going bad. This caused the ball to leave a streak like the one from your cumputer mouse pointer. I got used to it after like one game but is this a general effect of leds? Or does it depend on the fact that I still had some old incandescent bulbs in the GI aswell, a component going bad on maybe the power driver board or maybe that I bought some cheap bulbs for a test?

Last question, do some games make use of 12V for lamps? I mean GI and or inserts, not flashers.

Thanks in advance

Hi again and thanks to both of you for your fast answers!

So, if I understand this correctly its best to always aim for AC leds when buying? What about the AC/DC leds that are available? Any particular use for DC only leds, or is it best to get all ACs?

Furthermore, just to wrap my head around this... the GI is AC (in most of the games), and there is also pulsed DC in most inserts and some less common GI circuits.

What I can do is to get AC LEDs to 1, get rid of the strobing since it will light through both directions and 2, it will probably also work in the insert bayonetts.

My conclusion is that I made a mistake buying the DC leds without thinking and that the bayonetts wont have any good use (wont light up or will strobe). The wedges though can be used if I find the right rotation for them. Still, they may to strobe a little even though I cant see it even if I look for it as it is now. The bayonetts though cant be rotated apparantly. (But will do a hack and see if I can isolate the bayonett with some tape and a wire to change the polarity just for fun..)

So, ill keep the wedges and let the bayonetts sit on a shelf for future needs.

Did I get it?

Allright, thanks for clarifying everything!

Its been a steep learning curve here to understand what kind of leds looks the best where and so on and now this AC/DC thing =)

Well, I will order some other and see if I can get it correctly. The strobe streak from the ball is pretty cool though i much rather prefer it not being there.

Testing these 6V LEDs with a 9V, battery is that really safe? Otherwise Ill just hook some 1.5V batteries to each other to get 6V.

/ Andy

Yeah I will try som high end LEDs and see if things gets better. I however managed to switch the polarity of my ba9s so they now work. Still think they only light up for half the AC current though = half brightness. Is that correct?

Allright, those under the pf (inserts) do however look good now even though it's pulsed DC. Guess it's only or more apparent in the AC circuit above the pf in the GI circuit.

Some more things, ghosting is that prevented in noghost LEDs by using a resistor to get the current below the leds "light up threshold"? Or do they use like a capacitor? Maybe both? I'm no expert here but I think a capacitor would smooth out the on/off states of the led so it would maybe dim better closer to an incandescent bulb. Anyway, the perfect led would probably need to include a rectifier, a resistor and a cap.

I've also heard about flickering (not to be confused with the strobing issue I have) which can be seen in older games and is caused by some hardware/software issue. There is a thread here on pinside that mentions it and shows how it can be fixed by adding a resistor in parallel with the led chip. Either in the led itself or on the socket lugs. Don't think that issue applies to Jackbot though since it was fixed in later games after like 1995.

Pretty interesting this, I tend to get dragged into stuff like this wanna know how stuff works and why =)

Alright thanks for pointing out the 60hz! I think mine is slightly worse though since I live in Sweden where we have 50hz =) good to know it relates to the AC cycles from the mains line.

Yeah, the more I read the more tricky issues I find. Not sure if I am to picky or not but I want it to be as good as possible. The bottom line here seem to be to buy some good anti flicker no ghost premium LEDs and test then out a bit to see what works the best. Will give it another shot and see what I can find. Thanks everyone for explaining! =)

To try and understand this a bit better I made some LED-hacks to try things hands on. (couldnt help it..)

Maybe the findings will help someone else understand too, so here it goes:

I disassembled a couple of the leds I bought, those were bayonet base/#44/47s, VDC ones with one SMD chip (Surface mounted Diode). Since they did not work under the PF in the inserts (where weve now learned there is pulsing DC) either the sockets or the leds were wired "wrong". At least their polarity did not match.

Inside the bulbs there are basically the SMD chip on top and then two poles. On one pole there is only a tiny wire that is bent around the plastic "cap" of the led so it touches the outside of the uhm.. bayonet base. The other pole has a small resistor wired to it. According to my assumption, which i do not know is correct, this should be connected to the + side of the DC in the socket because the resistor will do its thing before the current reaches the SMD chip. I dont know if its there to just reduce the current a bit or if it affects the color emitted from the SMD. (I have a led strip driven off 12V and you can change the color of the lights by turning a knob which reduces the voltage to the strip. Again im not sure but i think it works that way).

The resistor is not there to correct the flicker effect that can be seen when using leds in older machines since such a resistor needs to be mounted parallel to the SMD (across the poles) to draw a bit more current and trick the hardware/software in those machines. Absolutely no expert on that but thats what ive read.

Experiment 1 - Getting the DC bulbs to work for inserts (with bayonet base)
My first experiment was to switch the polarity of the bayonet bulbs. So, i took one apart and just flipped the chip. Did that by desoldering the bottom tip and pull out the resistor wire. Next I soldered the other pole straight down to the bottom tip and bent the resistor leg around the LED plastic cap so it had contact with the bayonet case.
When I tried the bulb it now worked! No flicker whatsoever, at least not that I can see, so it now works with the pulsing DC under the PF. Maybe if one would add a capacitor it would look smoother but i dont know what cap to use so i skipped that part. This is the same thing as when you flip a wedge base LED that does not light up, its just that some soldering is required here to rearrange the wires inside the bayonet base.

Experiment 2 - Getting rid of the strobing in the GI LEDs on top of the PF.
Now, since i bought DC LEDs because I was unexperienced, they worked in the sockets above the PF, the GI sockets. But, there was a horrible strobing from them which is most likely at 50Hz since i live in Sweden where we have that Hertz in the electric system.
So, as described above in the thread the strobing occurs because the LED is a DC one and the current in the sockets is AC. The LED is only lighting up during one of the "waves/phases" of current, the one on the right side of the LED, the + side. Then it goes out when the current comes at the other pole since the LED SMD chip is a diode and wont let current through in both directions. Like a standard diode used at switches etc but this is a light emitting one. This is not visible with a standard incandescent bulb since it will let the current through from both directions and just do its thing, glow.

Had I bought AC LEDs there would not be any strobing. And thats because those AC leds contains a rectifier made from diodes (some fancy small ones probably, or some other fancy stuff I dont know the name of). I wont dig into exactly how a rectifier works but the bottom line is, it will direct the two AC waves towards on point and that point would be the + side of the LED.

I digged up 4 diodes and soldered them together to make a rectifier and then hooked up the LED to it. Its not pretty but it worked! The LED worked in the GI circuit and the strobing was gone! yay!

rectifier.jpg

Experiment 3 - Making a home made Flex LED
While was at it I took apart one bayonet base LED and just soldered some harder wires to it (legs from a standard diode), kept them fairly long and soldered them to the bayonet socket together with some shring tubing to make it look better and to keep it from shorting. Now I had my home made Flex. Not really worth the job if you want flex LEDs but since I have allready bought some cheap ones I could at least try it instead of just letting them sit on the shelf.
homeflex.jpg

Experiment 4 - Converting a frosted warm white LED to a wedge based one
I did not buy any white wedges for my inserts since I just got some samples to start the journey of ledding. However I have a shit load of frosted warm whites that strobes like crazy in the GI so I had to try to convert one to a wedge socket so I can at least make use of some of the strobing frosteds.
Again, i ripped one apart and put it in a wedge socket from another LED I trashed. Worked like a sharm too. The polarity issue was easily overcome since it was a wedge base.
wedgie.jpg

Something else to try is to reduce or cure ghosting in the LEDS. Not sure what to add to make that but maybe some resistor could do it. Reduce the threshold of the LED so it wont light up from the small current that is on the circuit even though standard bulbs are off. Ive read its there to keep the incandescent bulbs slightly warm so they can react faster when its time to switch on. They are not as sensitive as the LEDs and will not glow. The LEDs however will light up from the small "warming" current since they are more sensitive.

Understanding how LEDs work really got a lot easier now that I tried some hacks. Of course its better to buy the right stuff from the beginning, it was fun never the less!

Feel free to correct the stuff i probably misunderstood above

Thanks for chiming in CactusJack! Interesting info there. Especially the 100Hz thing! It seems there will be new and better LEDs emerging during the next few years, so I think stocking up would not be wise (whatever LED you decide on buying) but rather be effective and buy what you need for each game and invest a little more to get the best available at the moment. Basically this was exactly one of the possible conclusions I was looking for when buying the samples so the whole expriment thing and the testing of the cheaper leds from china was successfull =)

I think, if youre on a budget, buying some AC LEDs from the east could suffice for inserts (as long as they have the correct polarity, and maybe even for the GI. Still, these will ghost like I think any "normal" LED would do but the strobing will probably be gone. Dunno if there are any cheapo non ghosting ones to test but I will get some AC ones at least to try before I hit the more expensive ones. (would remove the polarity issue as well as the strobing). If youre not concerned about ghosting or smooth transitions between on and off it could probably work. Will look into that board thing later too (Hergs LED OCD stuff), that will enhance the LED experience.

I will read up on it! But while slightly browsing it, it looked nice. Especially if it's possible to have smoother transitions between the on off states of the LEDs.

Thanks! =)