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4 channel lamp chaser board?


netdent
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Wondered if anyone could help me out? I have this 80's lamp controller it has 4 channels running 32 60volt lamps, it's mains fed, the lamps are staying on and not chasing as they should? Adjusting the pot does nothing I assume it's to alter the speed?

 

If not able to see the 2 chips at the top are 4011B and 4081B

 

The 3 further down are 4011B  4017B   4001B

 

I'm thinking one of the chips are bad, bit worried about probing anything as it's 240v!

 

THanks Ronnie

 

 

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Edited by netdent
correction
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Trying to get to the fault on this! I wrongly read the last digit on some of the chips as "8" when it was "B" so have updated that above.
 
So the 4017B is a decade counter so assume that does the flashing? Now I'm getting pulsing on it's enable but nothing on the outputs? To me that would look bad? but there may be much more to it, then all the lamps are on, if that was bad would they not be off?
 
The 2x 4011B left top and bottom seem to be regulators possibly 5v logic?
And then the 4001B some kind of buffer?
 
Any pointers would be great, I don't want to replace anything that's not needed!
 
Thanks Ronnie
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The 40xxB chips are doing the 4 channel chasing, they seem to be driving transistors that are then driving triacs or thyristors. Can you get the numbers/letters off of those and a picture of the back of the board. The 2 big resistors, big capacitor and bits are providing a power supply to the chips.

You are right to be careful, this thing is out to electrocute you lol.

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Thanks for that, I removed and tested the 4 small transistors 2N3704 they tested good and all lamps off with them removed, the bigger one's are TIC206's I will get a pic up of the reverese side

 

Cheers Ronnie

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If all the lamps are off with the transistors removed then the TIC206 triacs must be ok.

Check if the first four outputs of the 4017 are going high one at a time in sequence. If they are, the fault is between there and the transistors. 

Be very careful as the entire circuit is not isolated from the mains!

4017-1.jpg

Edited by CanonMan
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The power section of the circuit is the two large resistors at the top of the board, the capacitor and a few other components. It generates a DC supply of probably 12 to 15 volts which supplies all of the logic chips. As they are CMOS chips, a logic '1' is at least two thirds of supply voltage up to the actual supply voltage. A logic '0' is one-thirds supply voltage or lower. The supply voltage can be measured across the power pins (16 is +ve and 8 is ground) on the 4017 but it is not isolated from the mains and could kill you if you're not careful! Certainly don't go probing around using a mains-powered oscilloscope on it....

The 4011B in the bottom left-hand corner (next to the pot) is configured as a square-wave oscillator which generates clock pulses for the 4017B decade counter. The 4017B has ten outputs that go high one at time in sequence on receipt of a clock pulse on pin 14. As only four outputs are required, the fifth output is connected directly to the reset pin, so that the first output goes high directly after the fourth one and the sequence is repeated.

The outputs from the 4017B (pins 3, 2, 4 and 7, in that order) then go to the 4001B in the bottom right hand corner, which is a quad NOR gate chip. Each NOR gate has both input pins connected together and they come from the outputs of the 4017, so the NOR gates effectively invert the logic level of the outputs from the 4017B. This will eventually give three channels that are on and one that's off at any one time, which is going to look more impressive than having only one channel on and the other three off!

The other two chips on the circuit, The 4011B and the 4081B, will take a bit more explaining, so I'll do that in another post below.

Edited by CanonMan
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The 4081B that drives the transistors in the top right corner is a quad AND gate chip, and each gate receives an output from 4001B and another signal which comes from the 4011B in the top left corner (more on this later). Each output from the 4081B that is logic '1' turns on the appropriate transistor which fires the triac and turns on the output.

The mystery signal that goes to the AND gates in the 4081B is a zero crossing signal that is generated by the top-left 4011B from the incoming mains supply. The idea is that the zero-crossing signal is generated when the AC mains voltage is at it's lowest level. By switching the triacs on and off when the mains supply is a zero volts (or very close to it) the amount of interference generated is kept as low as possible.

The zero-crossing signal is only at logic '1' when the mains voltage is practically zero, which is 50 times a second, the rest of the time it's at logic '0' and when AND-ed with the outputs from the 4001B, ensure that the outputs can't be turned on. In other words, each output channel can only be on when it gets a logic '1' signal from the 4001B AND the mains voltage is at (well, near) zero.

As for what's wrong with this particular board, there are a couple of possibilities:

1) All of the outputs on the 4017B are stuck at logic '0',  which would leave all four outputs of the 4001B stuck at logic '1' and all fours output on all the time. This could be because the 4017B is faulty or because it's not getting a clock pulse on pin 14 from the 4011B next to it.

2) The outputs of the 4017B are sequencing properly but all outputs on the 4001B are stuck at logic '1' because it's faulty.

My money would be on the 4011B clock generator being faulty, but given the age of the chips on the board I'd be tempted to replace all five for the sake of future reliability. It is nice to be able to say what's causing the fault though :)

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CanonMan, what a gent you are, thanks so much for this explanation, that is sheer genious!

 

Right the 4017 is getting it's pulses which I can vary with the pot, but it's outputs do nothing on my probe neither state hi or lo, I see these 40XX series on ebay are cheap so I may just replace as you said but could try the 4017 first to see?

I have another one to test and get working if needs be but one of it's TIC206 is bad, well I had to rob it for this board as I shorted it by accident and killed it!

 

Thanks Ronnie

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You're welcome :)

It does sound like your 4017 has died if all the outputs are floating. Try replacing that first and you may be lucky!

I may have some NOS 4017 chips in my stash. I'll have a look next time I'm in the loft. If I have, I'll send you some. There seem to be a lot of people selling them on eBay but you never know whether you're getting fakes or not...

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1 hour ago, CanonMan said:

You're welcome :)

It does sound like your 4017 has died if all the outputs are floating. Try replacing that first and you may be lucky!

I may have some NOS 4017 chips in my stash. I'll have a look next time I'm in the loft. If I have, I'll send you some. There seem to be a lot of people selling them on eBay but you never know whether you're getting fakes or not...

Cheers I have ordered some of them on ebay likes of RS and CPC don't do that stuff these days! I will fit sockets in case they are duds!

Cheers Ronnie

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5 hours ago, netdent said:

UPDATE!

 

I replaced the 4017 decade counter and hey presto we have running lights again, nice one canonman will report on controller 2 when I get the new TIC206

 

Cheers Ronnie

That's a great result!

Hopefully the other one will be as easy to fix.

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1 minute ago, MikeB said:

They look amazing! Where did you find them? 

absolutely stunning 👌

Thanks mike, the other is same but says up to date games! I have had them for a few years part of a bulk buy but all vid games and 1 pinball

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